2 /* pngrtran.c - transforms the data in a row for PNG readers
4 * Last changed in libpng 1.6.19 [November 12, 2015]
5 * Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains functions optionally called by an application
14 * in order to tell libpng how to handle data when reading a PNG.
15 * Transformations that are used in both reading and writing are
21 #ifdef PNG_READ_SUPPORTED
23 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
25 png_set_crc_action(png_structrp png_ptr
, int crit_action
, int ancil_action
)
27 png_debug(1, "in png_set_crc_action");
32 /* Tell libpng how we react to CRC errors in critical chunks */
35 case PNG_CRC_NO_CHANGE
: /* Leave setting as is */
38 case PNG_CRC_WARN_USE
: /* Warn/use data */
39 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
40 png_ptr
->flags
|= PNG_FLAG_CRC_CRITICAL_USE
;
43 case PNG_CRC_QUIET_USE
: /* Quiet/use data */
44 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
45 png_ptr
->flags
|= PNG_FLAG_CRC_CRITICAL_USE
|
46 PNG_FLAG_CRC_CRITICAL_IGNORE
;
49 case PNG_CRC_WARN_DISCARD
: /* Not a valid action for critical data */
51 "Can't discard critical data on CRC error");
52 case PNG_CRC_ERROR_QUIT
: /* Error/quit */
56 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
60 /* Tell libpng how we react to CRC errors in ancillary chunks */
63 case PNG_CRC_NO_CHANGE
: /* Leave setting as is */
66 case PNG_CRC_WARN_USE
: /* Warn/use data */
67 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
68 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_USE
;
71 case PNG_CRC_QUIET_USE
: /* Quiet/use data */
72 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
73 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_USE
|
74 PNG_FLAG_CRC_ANCILLARY_NOWARN
;
77 case PNG_CRC_ERROR_QUIT
: /* Error/quit */
78 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
79 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_NOWARN
;
82 case PNG_CRC_WARN_DISCARD
: /* Warn/discard data */
86 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
91 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
92 /* Is it OK to set a transformation now? Only if png_start_read_image or
93 * png_read_update_info have not been called. It is not necessary for the IHDR
94 * to have been read in all cases; the need_IHDR parameter allows for this
98 png_rtran_ok(png_structrp png_ptr
, int need_IHDR
)
102 if ((png_ptr
->flags
& PNG_FLAG_ROW_INIT
) != 0)
103 png_app_error(png_ptr
,
104 "invalid after png_start_read_image or png_read_update_info");
106 else if (need_IHDR
&& (png_ptr
->mode
& PNG_HAVE_IHDR
) == 0)
107 png_app_error(png_ptr
, "invalid before the PNG header has been read");
111 /* Turn on failure to initialize correctly for all transforms. */
112 png_ptr
->flags
|= PNG_FLAG_DETECT_UNINITIALIZED
;
118 return 0; /* no png_error possible! */
122 #ifdef PNG_READ_BACKGROUND_SUPPORTED
123 /* Handle alpha and tRNS via a background color */
125 png_set_background_fixed(png_structrp png_ptr
,
126 png_const_color_16p background_color
, int background_gamma_code
,
127 int need_expand
, png_fixed_point background_gamma
)
129 png_debug(1, "in png_set_background_fixed");
131 if (png_rtran_ok(png_ptr
, 0) == 0 || background_color
== NULL
)
134 if (background_gamma_code
== PNG_BACKGROUND_GAMMA_UNKNOWN
)
136 png_warning(png_ptr
, "Application must supply a known background gamma");
140 png_ptr
->transformations
|= PNG_COMPOSE
| PNG_STRIP_ALPHA
;
141 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
142 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
144 png_ptr
->background
= *background_color
;
145 png_ptr
->background_gamma
= background_gamma
;
146 png_ptr
->background_gamma_type
= (png_byte
)(background_gamma_code
);
147 if (need_expand
!= 0)
148 png_ptr
->transformations
|= PNG_BACKGROUND_EXPAND
;
150 png_ptr
->transformations
&= ~PNG_BACKGROUND_EXPAND
;
153 # ifdef PNG_FLOATING_POINT_SUPPORTED
155 png_set_background(png_structrp png_ptr
,
156 png_const_color_16p background_color
, int background_gamma_code
,
157 int need_expand
, double background_gamma
)
159 png_set_background_fixed(png_ptr
, background_color
, background_gamma_code
,
160 need_expand
, png_fixed(png_ptr
, background_gamma
, "png_set_background"));
162 # endif /* FLOATING_POINT */
163 #endif /* READ_BACKGROUND */
165 /* Scale 16-bit depth files to 8-bit depth. If both of these are set then the
166 * one that pngrtran does first (scale) happens. This is necessary to allow the
167 * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
169 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
171 png_set_scale_16(png_structrp png_ptr
)
173 png_debug(1, "in png_set_scale_16");
175 if (png_rtran_ok(png_ptr
, 0) == 0)
178 png_ptr
->transformations
|= PNG_SCALE_16_TO_8
;
182 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
183 /* Chop 16-bit depth files to 8-bit depth */
185 png_set_strip_16(png_structrp png_ptr
)
187 png_debug(1, "in png_set_strip_16");
189 if (png_rtran_ok(png_ptr
, 0) == 0)
192 png_ptr
->transformations
|= PNG_16_TO_8
;
196 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
198 png_set_strip_alpha(png_structrp png_ptr
)
200 png_debug(1, "in png_set_strip_alpha");
202 if (png_rtran_ok(png_ptr
, 0) == 0)
205 png_ptr
->transformations
|= PNG_STRIP_ALPHA
;
209 #if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
210 static png_fixed_point
211 translate_gamma_flags(png_structrp png_ptr
, png_fixed_point output_gamma
,
214 /* Check for flag values. The main reason for having the old Mac value as a
215 * flag is that it is pretty near impossible to work out what the correct
216 * value is from Apple documentation - a working Mac system is needed to
217 * discover the value!
219 if (output_gamma
== PNG_DEFAULT_sRGB
||
220 output_gamma
== PNG_FP_1
/ PNG_DEFAULT_sRGB
)
222 /* If there is no sRGB support this just sets the gamma to the standard
223 * sRGB value. (This is a side effect of using this function!)
225 # ifdef PNG_READ_sRGB_SUPPORTED
226 png_ptr
->flags
|= PNG_FLAG_ASSUME_sRGB
;
231 output_gamma
= PNG_GAMMA_sRGB
;
233 output_gamma
= PNG_GAMMA_sRGB_INVERSE
;
236 else if (output_gamma
== PNG_GAMMA_MAC_18
||
237 output_gamma
== PNG_FP_1
/ PNG_GAMMA_MAC_18
)
240 output_gamma
= PNG_GAMMA_MAC_OLD
;
242 output_gamma
= PNG_GAMMA_MAC_INVERSE
;
248 # ifdef PNG_FLOATING_POINT_SUPPORTED
249 static png_fixed_point
250 convert_gamma_value(png_structrp png_ptr
, double output_gamma
)
252 /* The following silently ignores cases where fixed point (times 100,000)
253 * gamma values are passed to the floating point API. This is safe and it
254 * means the fixed point constants work just fine with the floating point
255 * API. The alternative would just lead to undetected errors and spurious
256 * bug reports. Negative values fail inside the _fixed API unless they
257 * correspond to the flag values.
259 if (output_gamma
> 0 && output_gamma
< 128)
260 output_gamma
*= PNG_FP_1
;
262 /* This preserves -1 and -2 exactly: */
263 output_gamma
= floor(output_gamma
+ .5);
265 if (output_gamma
> PNG_FP_MAX
|| output_gamma
< PNG_FP_MIN
)
266 png_fixed_error(png_ptr
, "gamma value");
268 return (png_fixed_point
)output_gamma
;
271 #endif /* READ_ALPHA_MODE || READ_GAMMA */
273 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
275 png_set_alpha_mode_fixed(png_structrp png_ptr
, int mode
,
276 png_fixed_point output_gamma
)
279 png_fixed_point file_gamma
;
281 png_debug(1, "in png_set_alpha_mode");
283 if (png_rtran_ok(png_ptr
, 0) == 0)
286 output_gamma
= translate_gamma_flags(png_ptr
, output_gamma
, 1/*screen*/);
288 /* Validate the value to ensure it is in a reasonable range. The value
289 * is expected to be 1 or greater, but this range test allows for some
290 * viewing correction values. The intent is to weed out users of this API
291 * who use the inverse of the gamma value accidentally! Since some of these
292 * values are reasonable this may have to be changed.
294 if (output_gamma
< 70000 || output_gamma
> 300000)
295 png_error(png_ptr
, "output gamma out of expected range");
297 /* The default file gamma is the inverse of the output gamma; the output
298 * gamma may be changed below so get the file value first:
300 file_gamma
= png_reciprocal(output_gamma
);
302 /* There are really 8 possibilities here, composed of any combination
305 * premultiply the color channels
306 * do not encode non-opaque pixels
307 * encode the alpha as well as the color channels
309 * The differences disappear if the input/output ('screen') gamma is 1.0,
310 * because then the encoding is a no-op and there is only the choice of
311 * premultiplying the color channels or not.
313 * png_set_alpha_mode and png_set_background interact because both use
314 * png_compose to do the work. Calling both is only useful when
315 * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
316 * with a default gamma value. Otherwise PNG_COMPOSE must not be set.
320 case PNG_ALPHA_PNG
: /* default: png standard */
321 /* No compose, but it may be set by png_set_background! */
322 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
323 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
326 case PNG_ALPHA_ASSOCIATED
: /* color channels premultiplied */
328 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
329 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
330 /* The output is linear: */
331 output_gamma
= PNG_FP_1
;
334 case PNG_ALPHA_OPTIMIZED
: /* associated, non-opaque pixels linear */
336 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
337 png_ptr
->flags
|= PNG_FLAG_OPTIMIZE_ALPHA
;
338 /* output_gamma records the encoding of opaque pixels! */
341 case PNG_ALPHA_BROKEN
: /* associated, non-linear, alpha encoded */
343 png_ptr
->transformations
|= PNG_ENCODE_ALPHA
;
344 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
348 png_error(png_ptr
, "invalid alpha mode");
351 /* Only set the default gamma if the file gamma has not been set (this has
352 * the side effect that the gamma in a second call to png_set_alpha_mode will
355 if (png_ptr
->colorspace
.gamma
== 0)
357 png_ptr
->colorspace
.gamma
= file_gamma
;
358 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
361 /* But always set the output gamma: */
362 png_ptr
->screen_gamma
= output_gamma
;
364 /* Finally, if pre-multiplying, set the background fields to achieve the
369 /* And obtain alpha pre-multiplication by composing on black: */
370 memset(&png_ptr
->background
, 0, (sizeof png_ptr
->background
));
371 png_ptr
->background_gamma
= png_ptr
->colorspace
.gamma
; /* just in case */
372 png_ptr
->background_gamma_type
= PNG_BACKGROUND_GAMMA_FILE
;
373 png_ptr
->transformations
&= ~PNG_BACKGROUND_EXPAND
;
375 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
377 "conflicting calls to set alpha mode and background");
379 png_ptr
->transformations
|= PNG_COMPOSE
;
383 # ifdef PNG_FLOATING_POINT_SUPPORTED
385 png_set_alpha_mode(png_structrp png_ptr
, int mode
, double output_gamma
)
387 png_set_alpha_mode_fixed(png_ptr
, mode
, convert_gamma_value(png_ptr
,
393 #ifdef PNG_READ_QUANTIZE_SUPPORTED
394 /* Dither file to 8-bit. Supply a palette, the current number
395 * of elements in the palette, the maximum number of elements
396 * allowed, and a histogram if possible. If the current number
397 * of colors is greater than the maximum number, the palette will be
398 * modified to fit in the maximum number. "full_quantize" indicates
399 * whether we need a quantizing cube set up for RGB images, or if we
400 * simply are reducing the number of colors in a paletted image.
403 typedef struct png_dsort_struct
405 struct png_dsort_struct
* next
;
409 typedef png_dsort
* png_dsortp
;
410 typedef png_dsort
* * png_dsortpp
;
413 png_set_quantize(png_structrp png_ptr
, png_colorp palette
,
414 int num_palette
, int maximum_colors
, png_const_uint_16p histogram
,
417 png_debug(1, "in png_set_quantize");
419 if (png_rtran_ok(png_ptr
, 0) == 0)
422 png_ptr
->transformations
|= PNG_QUANTIZE
;
424 if (full_quantize
== 0)
428 png_ptr
->quantize_index
= (png_bytep
)png_malloc(png_ptr
,
429 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
430 for (i
= 0; i
< num_palette
; i
++)
431 png_ptr
->quantize_index
[i
] = (png_byte
)i
;
434 if (num_palette
> maximum_colors
)
436 if (histogram
!= NULL
)
438 /* This is easy enough, just throw out the least used colors.
439 * Perhaps not the best solution, but good enough.
444 /* Initialize an array to sort colors */
445 png_ptr
->quantize_sort
= (png_bytep
)png_malloc(png_ptr
,
446 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
448 /* Initialize the quantize_sort array */
449 for (i
= 0; i
< num_palette
; i
++)
450 png_ptr
->quantize_sort
[i
] = (png_byte
)i
;
452 /* Find the least used palette entries by starting a
453 * bubble sort, and running it until we have sorted
454 * out enough colors. Note that we don't care about
455 * sorting all the colors, just finding which are
459 for (i
= num_palette
- 1; i
>= maximum_colors
; i
--)
461 int done
; /* To stop early if the list is pre-sorted */
465 for (j
= 0; j
< i
; j
++)
467 if (histogram
[png_ptr
->quantize_sort
[j
]]
468 < histogram
[png_ptr
->quantize_sort
[j
+ 1]])
472 t
= png_ptr
->quantize_sort
[j
];
473 png_ptr
->quantize_sort
[j
] = png_ptr
->quantize_sort
[j
+ 1];
474 png_ptr
->quantize_sort
[j
+ 1] = t
;
483 /* Swap the palette around, and set up a table, if necessary */
484 if (full_quantize
!= 0)
488 /* Put all the useful colors within the max, but don't
491 for (i
= 0; i
< maximum_colors
; i
++)
493 if ((int)png_ptr
->quantize_sort
[i
] >= maximum_colors
)
497 while ((int)png_ptr
->quantize_sort
[j
] >= maximum_colors
);
499 palette
[i
] = palette
[j
];
507 /* Move all the used colors inside the max limit, and
508 * develop a translation table.
510 for (i
= 0; i
< maximum_colors
; i
++)
512 /* Only move the colors we need to */
513 if ((int)png_ptr
->quantize_sort
[i
] >= maximum_colors
)
519 while ((int)png_ptr
->quantize_sort
[j
] >= maximum_colors
);
521 tmp_color
= palette
[j
];
522 palette
[j
] = palette
[i
];
523 palette
[i
] = tmp_color
;
524 /* Indicate where the color went */
525 png_ptr
->quantize_index
[j
] = (png_byte
)i
;
526 png_ptr
->quantize_index
[i
] = (png_byte
)j
;
530 /* Find closest color for those colors we are not using */
531 for (i
= 0; i
< num_palette
; i
++)
533 if ((int)png_ptr
->quantize_index
[i
] >= maximum_colors
)
535 int min_d
, k
, min_k
, d_index
;
537 /* Find the closest color to one we threw out */
538 d_index
= png_ptr
->quantize_index
[i
];
539 min_d
= PNG_COLOR_DIST(palette
[d_index
], palette
[0]);
540 for (k
= 1, min_k
= 0; k
< maximum_colors
; k
++)
544 d
= PNG_COLOR_DIST(palette
[d_index
], palette
[k
]);
552 /* Point to closest color */
553 png_ptr
->quantize_index
[i
] = (png_byte
)min_k
;
557 png_free(png_ptr
, png_ptr
->quantize_sort
);
558 png_ptr
->quantize_sort
= NULL
;
562 /* This is much harder to do simply (and quickly). Perhaps
563 * we need to go through a median cut routine, but those
564 * don't always behave themselves with only a few colors
565 * as input. So we will just find the closest two colors,
566 * and throw out one of them (chosen somewhat randomly).
567 * [We don't understand this at all, so if someone wants to
568 * work on improving it, be our guest - AED, GRP]
578 /* Initialize palette index arrays */
579 png_ptr
->index_to_palette
= (png_bytep
)png_malloc(png_ptr
,
580 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
581 png_ptr
->palette_to_index
= (png_bytep
)png_malloc(png_ptr
,
582 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
584 /* Initialize the sort array */
585 for (i
= 0; i
< num_palette
; i
++)
587 png_ptr
->index_to_palette
[i
] = (png_byte
)i
;
588 png_ptr
->palette_to_index
[i
] = (png_byte
)i
;
591 hash
= (png_dsortpp
)png_calloc(png_ptr
, (png_uint_32
)(769 *
592 (sizeof (png_dsortp
))));
594 num_new_palette
= num_palette
;
596 /* Initial wild guess at how far apart the farthest pixel
597 * pair we will be eliminating will be. Larger
598 * numbers mean more areas will be allocated, Smaller
599 * numbers run the risk of not saving enough data, and
600 * having to do this all over again.
602 * I have not done extensive checking on this number.
606 while (num_new_palette
> maximum_colors
)
608 for (i
= 0; i
< num_new_palette
- 1; i
++)
612 for (j
= i
+ 1; j
< num_new_palette
; j
++)
616 d
= PNG_COLOR_DIST(palette
[i
], palette
[j
]);
621 t
= (png_dsortp
)png_malloc_warn(png_ptr
,
622 (png_uint_32
)(sizeof (png_dsort
)));
628 t
->left
= (png_byte
)i
;
629 t
->right
= (png_byte
)j
;
638 for (i
= 0; i
<= max_d
; i
++)
644 for (p
= hash
[i
]; p
; p
= p
->next
)
646 if ((int)png_ptr
->index_to_palette
[p
->left
]
648 (int)png_ptr
->index_to_palette
[p
->right
]
653 if (num_new_palette
& 0x01)
665 palette
[png_ptr
->index_to_palette
[j
]]
666 = palette
[num_new_palette
];
667 if (full_quantize
== 0)
671 for (k
= 0; k
< num_palette
; k
++)
673 if (png_ptr
->quantize_index
[k
] ==
674 png_ptr
->index_to_palette
[j
])
675 png_ptr
->quantize_index
[k
] =
676 png_ptr
->index_to_palette
[next_j
];
678 if ((int)png_ptr
->quantize_index
[k
] ==
680 png_ptr
->quantize_index
[k
] =
681 png_ptr
->index_to_palette
[j
];
685 png_ptr
->index_to_palette
[png_ptr
->palette_to_index
686 [num_new_palette
]] = png_ptr
->index_to_palette
[j
];
688 png_ptr
->palette_to_index
[png_ptr
->index_to_palette
[j
]]
689 = png_ptr
->palette_to_index
[num_new_palette
];
691 png_ptr
->index_to_palette
[j
] =
692 (png_byte
)num_new_palette
;
694 png_ptr
->palette_to_index
[num_new_palette
] =
697 if (num_new_palette
<= maximum_colors
)
700 if (num_new_palette
<= maximum_colors
)
705 for (i
= 0; i
< 769; i
++)
709 png_dsortp p
= hash
[i
];
713 png_free(png_ptr
, p
);
721 png_free(png_ptr
, hash
);
722 png_free(png_ptr
, png_ptr
->palette_to_index
);
723 png_free(png_ptr
, png_ptr
->index_to_palette
);
724 png_ptr
->palette_to_index
= NULL
;
725 png_ptr
->index_to_palette
= NULL
;
727 num_palette
= maximum_colors
;
729 if (png_ptr
->palette
== NULL
)
731 png_ptr
->palette
= palette
;
733 png_ptr
->num_palette
= (png_uint_16
)num_palette
;
735 if (full_quantize
!= 0)
739 int total_bits
= PNG_QUANTIZE_RED_BITS
+ PNG_QUANTIZE_GREEN_BITS
+
740 PNG_QUANTIZE_BLUE_BITS
;
741 int num_red
= (1 << PNG_QUANTIZE_RED_BITS
);
742 int num_green
= (1 << PNG_QUANTIZE_GREEN_BITS
);
743 int num_blue
= (1 << PNG_QUANTIZE_BLUE_BITS
);
744 png_size_t num_entries
= ((png_size_t
)1 << total_bits
);
746 png_ptr
->palette_lookup
= (png_bytep
)png_calloc(png_ptr
,
747 (png_uint_32
)(num_entries
* (sizeof (png_byte
))));
749 distance
= (png_bytep
)png_malloc(png_ptr
, (png_uint_32
)(num_entries
*
750 (sizeof (png_byte
))));
752 memset(distance
, 0xff, num_entries
* (sizeof (png_byte
)));
754 for (i
= 0; i
< num_palette
; i
++)
757 int r
= (palette
[i
].red
>> (8 - PNG_QUANTIZE_RED_BITS
));
758 int g
= (palette
[i
].green
>> (8 - PNG_QUANTIZE_GREEN_BITS
));
759 int b
= (palette
[i
].blue
>> (8 - PNG_QUANTIZE_BLUE_BITS
));
761 for (ir
= 0; ir
< num_red
; ir
++)
763 /* int dr = abs(ir - r); */
764 int dr
= ((ir
> r
) ? ir
- r
: r
- ir
);
765 int index_r
= (ir
<< (PNG_QUANTIZE_BLUE_BITS
+
766 PNG_QUANTIZE_GREEN_BITS
));
768 for (ig
= 0; ig
< num_green
; ig
++)
770 /* int dg = abs(ig - g); */
771 int dg
= ((ig
> g
) ? ig
- g
: g
- ig
);
773 int dm
= ((dr
> dg
) ? dr
: dg
);
774 int index_g
= index_r
| (ig
<< PNG_QUANTIZE_BLUE_BITS
);
776 for (ib
= 0; ib
< num_blue
; ib
++)
778 int d_index
= index_g
| ib
;
779 /* int db = abs(ib - b); */
780 int db
= ((ib
> b
) ? ib
- b
: b
- ib
);
781 int dmax
= ((dm
> db
) ? dm
: db
);
782 int d
= dmax
+ dt
+ db
;
784 if (d
< (int)distance
[d_index
])
786 distance
[d_index
] = (png_byte
)d
;
787 png_ptr
->palette_lookup
[d_index
] = (png_byte
)i
;
794 png_free(png_ptr
, distance
);
797 #endif /* READ_QUANTIZE */
799 #ifdef PNG_READ_GAMMA_SUPPORTED
801 png_set_gamma_fixed(png_structrp png_ptr
, png_fixed_point scrn_gamma
,
802 png_fixed_point file_gamma
)
804 png_debug(1, "in png_set_gamma_fixed");
806 if (png_rtran_ok(png_ptr
, 0) == 0)
809 /* New in libpng-1.5.4 - reserve particular negative values as flags. */
810 scrn_gamma
= translate_gamma_flags(png_ptr
, scrn_gamma
, 1/*screen*/);
811 file_gamma
= translate_gamma_flags(png_ptr
, file_gamma
, 0/*file*/);
813 /* Checking the gamma values for being >0 was added in 1.5.4 along with the
814 * premultiplied alpha support; this actually hides an undocumented feature
815 * of the previous implementation which allowed gamma processing to be
816 * disabled in background handling. There is no evidence (so far) that this
817 * was being used; however, png_set_background itself accepted and must still
818 * accept '0' for the gamma value it takes, because it isn't always used.
820 * Since this is an API change (albeit a very minor one that removes an
821 * undocumented API feature) the following checks were only enabled in
825 png_error(png_ptr
, "invalid file gamma in png_set_gamma");
828 png_error(png_ptr
, "invalid screen gamma in png_set_gamma");
830 /* Set the gamma values unconditionally - this overrides the value in the PNG
831 * file if a gAMA chunk was present. png_set_alpha_mode provides a
832 * different, easier, way to default the file gamma.
834 png_ptr
->colorspace
.gamma
= file_gamma
;
835 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
836 png_ptr
->screen_gamma
= scrn_gamma
;
839 # ifdef PNG_FLOATING_POINT_SUPPORTED
841 png_set_gamma(png_structrp png_ptr
, double scrn_gamma
, double file_gamma
)
843 png_set_gamma_fixed(png_ptr
, convert_gamma_value(png_ptr
, scrn_gamma
),
844 convert_gamma_value(png_ptr
, file_gamma
));
846 # endif /* FLOATING_POINT */
847 #endif /* READ_GAMMA */
849 #ifdef PNG_READ_EXPAND_SUPPORTED
850 /* Expand paletted images to RGB, expand grayscale images of
851 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
855 png_set_expand(png_structrp png_ptr
)
857 png_debug(1, "in png_set_expand");
859 if (png_rtran_ok(png_ptr
, 0) == 0)
862 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
865 /* GRR 19990627: the following three functions currently are identical
866 * to png_set_expand(). However, it is entirely reasonable that someone
867 * might wish to expand an indexed image to RGB but *not* expand a single,
868 * fully transparent palette entry to a full alpha channel--perhaps instead
869 * convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
870 * the transparent color with a particular RGB value, or drop tRNS entirely.
871 * IOW, a future version of the library may make the transformations flag
872 * a bit more fine-grained, with separate bits for each of these three
875 * More to the point, these functions make it obvious what libpng will be
876 * doing, whereas "expand" can (and does) mean any number of things.
878 * GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
879 * to expand only the sample depth but not to expand the tRNS to alpha
880 * and its name was changed to png_set_expand_gray_1_2_4_to_8().
883 /* Expand paletted images to RGB. */
885 png_set_palette_to_rgb(png_structrp png_ptr
)
887 png_debug(1, "in png_set_palette_to_rgb");
889 if (png_rtran_ok(png_ptr
, 0) == 0)
892 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
895 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
897 png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr
)
899 png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
901 if (png_rtran_ok(png_ptr
, 0) == 0)
904 png_ptr
->transformations
|= PNG_EXPAND
;
907 /* Expand tRNS chunks to alpha channels. */
909 png_set_tRNS_to_alpha(png_structrp png_ptr
)
911 png_debug(1, "in png_set_tRNS_to_alpha");
913 if (png_rtran_ok(png_ptr
, 0) == 0)
916 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
918 #endif /* READ_EXPAND */
920 #ifdef PNG_READ_EXPAND_16_SUPPORTED
921 /* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
922 * it may not work correctly.)
925 png_set_expand_16(png_structrp png_ptr
)
927 png_debug(1, "in png_set_expand_16");
929 if (png_rtran_ok(png_ptr
, 0) == 0)
932 png_ptr
->transformations
|= (PNG_EXPAND_16
| PNG_EXPAND
| PNG_EXPAND_tRNS
);
936 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
938 png_set_gray_to_rgb(png_structrp png_ptr
)
940 png_debug(1, "in png_set_gray_to_rgb");
942 if (png_rtran_ok(png_ptr
, 0) == 0)
945 /* Because rgb must be 8 bits or more: */
946 png_set_expand_gray_1_2_4_to_8(png_ptr
);
947 png_ptr
->transformations
|= PNG_GRAY_TO_RGB
;
951 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
953 png_set_rgb_to_gray_fixed(png_structrp png_ptr
, int error_action
,
954 png_fixed_point red
, png_fixed_point green
)
956 png_debug(1, "in png_set_rgb_to_gray");
958 /* Need the IHDR here because of the check on color_type below. */
960 if (png_rtran_ok(png_ptr
, 1) == 0)
963 switch (error_action
)
965 case PNG_ERROR_ACTION_NONE
:
966 png_ptr
->transformations
|= PNG_RGB_TO_GRAY
;
969 case PNG_ERROR_ACTION_WARN
:
970 png_ptr
->transformations
|= PNG_RGB_TO_GRAY_WARN
;
973 case PNG_ERROR_ACTION_ERROR
:
974 png_ptr
->transformations
|= PNG_RGB_TO_GRAY_ERR
;
978 png_error(png_ptr
, "invalid error action to rgb_to_gray");
981 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
982 #ifdef PNG_READ_EXPAND_SUPPORTED
983 png_ptr
->transformations
|= PNG_EXPAND
;
986 /* Make this an error in 1.6 because otherwise the application may assume
987 * that it just worked and get a memory overwrite.
990 "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
992 /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
996 if (red
>= 0 && green
>= 0 && red
+ green
<= PNG_FP_1
)
998 png_uint_16 red_int
, green_int
;
1000 /* NOTE: this calculation does not round, but this behavior is retained
1001 * for consistency; the inaccuracy is very small. The code here always
1002 * overwrites the coefficients, regardless of whether they have been
1003 * defaulted or set already.
1005 red_int
= (png_uint_16
)(((png_uint_32
)red
*32768)/100000);
1006 green_int
= (png_uint_16
)(((png_uint_32
)green
*32768)/100000);
1008 png_ptr
->rgb_to_gray_red_coeff
= red_int
;
1009 png_ptr
->rgb_to_gray_green_coeff
= green_int
;
1010 png_ptr
->rgb_to_gray_coefficients_set
= 1;
1015 if (red
>= 0 && green
>= 0)
1016 png_app_warning(png_ptr
,
1017 "ignoring out of range rgb_to_gray coefficients");
1019 /* Use the defaults, from the cHRM chunk if set, else the historical
1020 * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
1021 * png_do_rgb_to_gray for more discussion of the values. In this case
1022 * the coefficients are not marked as 'set' and are not overwritten if
1023 * something has already provided a default.
1025 if (png_ptr
->rgb_to_gray_red_coeff
== 0 &&
1026 png_ptr
->rgb_to_gray_green_coeff
== 0)
1028 png_ptr
->rgb_to_gray_red_coeff
= 6968;
1029 png_ptr
->rgb_to_gray_green_coeff
= 23434;
1030 /* png_ptr->rgb_to_gray_blue_coeff = 2366; */
1036 #ifdef PNG_FLOATING_POINT_SUPPORTED
1037 /* Convert a RGB image to a grayscale of the same width. This allows us,
1038 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
1042 png_set_rgb_to_gray(png_structrp png_ptr
, int error_action
, double red
,
1045 png_set_rgb_to_gray_fixed(png_ptr
, error_action
,
1046 png_fixed(png_ptr
, red
, "rgb to gray red coefficient"),
1047 png_fixed(png_ptr
, green
, "rgb to gray green coefficient"));
1049 #endif /* FLOATING POINT */
1051 #endif /* RGB_TO_GRAY */
1053 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
1054 defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
1056 png_set_read_user_transform_fn(png_structrp png_ptr
, png_user_transform_ptr
1057 read_user_transform_fn
)
1059 png_debug(1, "in png_set_read_user_transform_fn");
1061 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
1062 png_ptr
->transformations
|= PNG_USER_TRANSFORM
;
1063 png_ptr
->read_user_transform_fn
= read_user_transform_fn
;
1068 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
1069 #ifdef PNG_READ_GAMMA_SUPPORTED
1070 /* In the case of gamma transformations only do transformations on images where
1071 * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
1072 * slows things down slightly, and also needlessly introduces small errors.
1074 static int /* PRIVATE */
1075 png_gamma_threshold(png_fixed_point screen_gamma
, png_fixed_point file_gamma
)
1077 /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
1078 * correction as a difference of the overall transform from 1.0
1080 * We want to compare the threshold with s*f - 1, if we get
1081 * overflow here it is because of wacky gamma values so we
1082 * turn on processing anyway.
1084 png_fixed_point gtest
;
1085 return !png_muldiv(>est
, screen_gamma
, file_gamma
, PNG_FP_1
) ||
1086 png_gamma_significant(gtest
);
1090 /* Initialize everything needed for the read. This includes modifying
1094 /* For the moment 'png_init_palette_transformations' and
1095 * 'png_init_rgb_transformations' only do some flag canceling optimizations.
1096 * The intent is that these two routines should have palette or rgb operations
1097 * extracted from 'png_init_read_transformations'.
1099 static void /* PRIVATE */
1100 png_init_palette_transformations(png_structrp png_ptr
)
1102 /* Called to handle the (input) palette case. In png_do_read_transformations
1103 * the first step is to expand the palette if requested, so this code must
1104 * take care to only make changes that are invariant with respect to the
1105 * palette expansion, or only do them if there is no expansion.
1107 * STRIP_ALPHA has already been handled in the caller (by setting num_trans
1110 int input_has_alpha
= 0;
1111 int input_has_transparency
= 0;
1113 if (png_ptr
->num_trans
> 0)
1117 /* Ignore if all the entries are opaque (unlikely!) */
1118 for (i
=0; i
<png_ptr
->num_trans
; ++i
)
1120 if (png_ptr
->trans_alpha
[i
] == 255)
1122 else if (png_ptr
->trans_alpha
[i
] == 0)
1123 input_has_transparency
= 1;
1126 input_has_transparency
= 1;
1127 input_has_alpha
= 1;
1133 /* If no alpha we can optimize. */
1134 if (input_has_alpha
== 0)
1136 /* Any alpha means background and associative alpha processing is
1137 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1138 * and ENCODE_ALPHA are irrelevant.
1140 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1141 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1143 if (input_has_transparency
== 0)
1144 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_BACKGROUND_EXPAND
);
1147 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1148 /* png_set_background handling - deals with the complexity of whether the
1149 * background color is in the file format or the screen format in the case
1150 * where an 'expand' will happen.
1153 /* The following code cannot be entered in the alpha pre-multiplication case
1154 * because PNG_BACKGROUND_EXPAND is cancelled below.
1156 if ((png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) != 0 &&
1157 (png_ptr
->transformations
& PNG_EXPAND
) != 0)
1160 png_ptr
->background
.red
=
1161 png_ptr
->palette
[png_ptr
->background
.index
].red
;
1162 png_ptr
->background
.green
=
1163 png_ptr
->palette
[png_ptr
->background
.index
].green
;
1164 png_ptr
->background
.blue
=
1165 png_ptr
->palette
[png_ptr
->background
.index
].blue
;
1167 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1168 if ((png_ptr
->transformations
& PNG_INVERT_ALPHA
) != 0)
1170 if ((png_ptr
->transformations
& PNG_EXPAND_tRNS
) == 0)
1172 /* Invert the alpha channel (in tRNS) unless the pixels are
1173 * going to be expanded, in which case leave it for later
1175 int i
, istop
= png_ptr
->num_trans
;
1177 for (i
=0; i
<istop
; i
++)
1178 png_ptr
->trans_alpha
[i
] = (png_byte
)(255 -
1179 png_ptr
->trans_alpha
[i
]);
1182 #endif /* READ_INVERT_ALPHA */
1184 } /* background expand and (therefore) no alpha association. */
1185 #endif /* READ_EXPAND && READ_BACKGROUND */
1188 static void /* PRIVATE */
1189 png_init_rgb_transformations(png_structrp png_ptr
)
1191 /* Added to libpng-1.5.4: check the color type to determine whether there
1192 * is any alpha or transparency in the image and simply cancel the
1193 * background and alpha mode stuff if there isn't.
1195 int input_has_alpha
= (png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0;
1196 int input_has_transparency
= png_ptr
->num_trans
> 0;
1198 /* If no alpha we can optimize. */
1199 if (input_has_alpha
== 0)
1201 /* Any alpha means background and associative alpha processing is
1202 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1203 * and ENCODE_ALPHA are irrelevant.
1205 # ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1206 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1207 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1210 if (input_has_transparency
== 0)
1211 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_BACKGROUND_EXPAND
);
1214 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1215 /* png_set_background handling - deals with the complexity of whether the
1216 * background color is in the file format or the screen format in the case
1217 * where an 'expand' will happen.
1220 /* The following code cannot be entered in the alpha pre-multiplication case
1221 * because PNG_BACKGROUND_EXPAND is cancelled below.
1223 if ((png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) != 0 &&
1224 (png_ptr
->transformations
& PNG_EXPAND
) != 0 &&
1225 (png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) == 0)
1226 /* i.e., GRAY or GRAY_ALPHA */
1229 /* Expand background and tRNS chunks */
1230 int gray
= png_ptr
->background
.gray
;
1231 int trans_gray
= png_ptr
->trans_color
.gray
;
1233 switch (png_ptr
->bit_depth
)
1253 /* FALL THROUGH (Already 8 bits) */
1256 /* Already a full 16 bits */
1260 png_ptr
->background
.red
= png_ptr
->background
.green
=
1261 png_ptr
->background
.blue
= (png_uint_16
)gray
;
1263 if ((png_ptr
->transformations
& PNG_EXPAND_tRNS
) == 0)
1265 png_ptr
->trans_color
.red
= png_ptr
->trans_color
.green
=
1266 png_ptr
->trans_color
.blue
= (png_uint_16
)trans_gray
;
1269 } /* background expand and (therefore) no alpha association. */
1270 #endif /* READ_EXPAND && READ_BACKGROUND */
1274 png_init_read_transformations(png_structrp png_ptr
)
1276 png_debug(1, "in png_init_read_transformations");
1278 /* This internal function is called from png_read_start_row in pngrutil.c
1279 * and it is called before the 'rowbytes' calculation is done, so the code
1280 * in here can change or update the transformations flags.
1282 * First do updates that do not depend on the details of the PNG image data
1286 #ifdef PNG_READ_GAMMA_SUPPORTED
1287 /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
1288 * png_set_alpha_mode and this is another source for a default file gamma so
1289 * the test needs to be performed later - here. In addition prior to 1.5.4
1290 * the tests were repeated for the PALETTE color type here - this is no
1291 * longer necessary (and doesn't seem to have been necessary before.)
1294 /* The following temporary indicates if overall gamma correction is
1297 int gamma_correction
= 0;
1299 if (png_ptr
->colorspace
.gamma
!= 0) /* has been set */
1301 if (png_ptr
->screen_gamma
!= 0) /* screen set too */
1302 gamma_correction
= png_gamma_threshold(png_ptr
->colorspace
.gamma
,
1303 png_ptr
->screen_gamma
);
1306 /* Assume the output matches the input; a long time default behavior
1307 * of libpng, although the standard has nothing to say about this.
1309 png_ptr
->screen_gamma
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1312 else if (png_ptr
->screen_gamma
!= 0)
1313 /* The converse - assume the file matches the screen, note that this
1314 * perhaps undesireable default can (from 1.5.4) be changed by calling
1315 * png_set_alpha_mode (even if the alpha handling mode isn't required
1316 * or isn't changed from the default.)
1318 png_ptr
->colorspace
.gamma
= png_reciprocal(png_ptr
->screen_gamma
);
1320 else /* neither are set */
1321 /* Just in case the following prevents any processing - file and screen
1322 * are both assumed to be linear and there is no way to introduce a
1323 * third gamma value other than png_set_background with 'UNIQUE', and,
1326 png_ptr
->screen_gamma
= png_ptr
->colorspace
.gamma
= PNG_FP_1
;
1328 /* We have a gamma value now. */
1329 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
1331 /* Now turn the gamma transformation on or off as appropriate. Notice
1332 * that PNG_GAMMA just refers to the file->screen correction. Alpha
1333 * composition may independently cause gamma correction because it needs
1334 * linear data (e.g. if the file has a gAMA chunk but the screen gamma
1335 * hasn't been specified.) In any case this flag may get turned off in
1336 * the code immediately below if the transform can be handled outside the
1339 if (gamma_correction
!= 0)
1340 png_ptr
->transformations
|= PNG_GAMMA
;
1343 png_ptr
->transformations
&= ~PNG_GAMMA
;
1347 /* Certain transformations have the effect of preventing other
1348 * transformations that happen afterward in png_do_read_transformations;
1349 * resolve the interdependencies here. From the code of
1350 * png_do_read_transformations the order is:
1352 * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
1353 * 2) PNG_STRIP_ALPHA (if no compose)
1354 * 3) PNG_RGB_TO_GRAY
1355 * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
1358 * 7) PNG_STRIP_ALPHA (if compose)
1359 * 8) PNG_ENCODE_ALPHA
1360 * 9) PNG_SCALE_16_TO_8
1362 * 11) PNG_QUANTIZE (converts to palette)
1364 * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
1365 * 14) PNG_INVERT_MONO
1366 * 15) PNG_INVERT_ALPHA
1371 * 20) PNG_FILLER (includes PNG_ADD_ALPHA)
1372 * 21) PNG_SWAP_ALPHA
1373 * 22) PNG_SWAP_BYTES
1374 * 23) PNG_USER_TRANSFORM [must be last]
1376 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1377 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) != 0 &&
1378 (png_ptr
->transformations
& PNG_COMPOSE
) == 0)
1380 /* Stripping the alpha channel happens immediately after the 'expand'
1381 * transformations, before all other transformation, so it cancels out
1382 * the alpha handling. It has the side effect negating the effect of
1383 * PNG_EXPAND_tRNS too:
1385 png_ptr
->transformations
&= ~(PNG_BACKGROUND_EXPAND
| PNG_ENCODE_ALPHA
|
1387 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1389 /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
1390 * so transparency information would remain just so long as it wasn't
1391 * expanded. This produces unexpected API changes if the set of things
1392 * that do PNG_EXPAND_tRNS changes (perfectly possible given the
1393 * documentation - which says ask for what you want, accept what you
1394 * get.) This makes the behavior consistent from 1.5.4:
1396 png_ptr
->num_trans
= 0;
1398 #endif /* STRIP_ALPHA supported, no COMPOSE */
1400 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1401 /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
1402 * settings will have no effect.
1404 if (png_gamma_significant(png_ptr
->screen_gamma
) == 0)
1406 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1407 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1411 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1412 /* Make sure the coefficients for the rgb to gray conversion are set
1415 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) != 0)
1416 png_colorspace_set_rgb_coefficients(png_ptr
);
1419 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1420 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1421 /* Detect gray background and attempt to enable optimization for
1422 * gray --> RGB case.
1424 * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
1425 * RGB_ALPHA (in which case need_expand is superfluous anyway), the
1426 * background color might actually be gray yet not be flagged as such.
1427 * This is not a problem for the current code, which uses
1428 * PNG_BACKGROUND_IS_GRAY only to decide when to do the
1429 * png_do_gray_to_rgb() transformation.
1431 * TODO: this code needs to be revised to avoid the complexity and
1432 * interdependencies. The color type of the background should be recorded in
1433 * png_set_background, along with the bit depth, then the code has a record
1434 * of exactly what color space the background is currently in.
1436 if ((png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) != 0)
1438 /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
1439 * the file was grayscale the background value is gray.
1441 if ((png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) == 0)
1442 png_ptr
->mode
|= PNG_BACKGROUND_IS_GRAY
;
1445 else if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
1447 /* PNG_COMPOSE: png_set_background was called with need_expand false,
1448 * so the color is in the color space of the output or png_set_alpha_mode
1449 * was called and the color is black. Ignore RGB_TO_GRAY because that
1450 * happens before GRAY_TO_RGB.
1452 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) != 0)
1454 if (png_ptr
->background
.red
== png_ptr
->background
.green
&&
1455 png_ptr
->background
.red
== png_ptr
->background
.blue
)
1457 png_ptr
->mode
|= PNG_BACKGROUND_IS_GRAY
;
1458 png_ptr
->background
.gray
= png_ptr
->background
.red
;
1462 #endif /* READ_EXPAND && READ_BACKGROUND */
1463 #endif /* READ_GRAY_TO_RGB */
1465 /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
1466 * can be performed directly on the palette, and some (such as rgb to gray)
1467 * can be optimized inside the palette. This is particularly true of the
1468 * composite (background and alpha) stuff, which can be pretty much all done
1469 * in the palette even if the result is expanded to RGB or gray afterward.
1471 * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
1472 * earlier and the palette stuff is actually handled on the first row. This
1473 * leads to the reported bug that the palette returned by png_get_PLTE is not
1476 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
1477 png_init_palette_transformations(png_ptr
);
1480 png_init_rgb_transformations(png_ptr
);
1482 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1483 defined(PNG_READ_EXPAND_16_SUPPORTED)
1484 if ((png_ptr
->transformations
& PNG_EXPAND_16
) != 0 &&
1485 (png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
1486 (png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) == 0 &&
1487 png_ptr
->bit_depth
!= 16)
1489 /* TODO: fix this. Because the expand_16 operation is after the compose
1490 * handling the background color must be 8, not 16, bits deep, but the
1491 * application will supply a 16-bit value so reduce it here.
1493 * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
1494 * present, so that case is ok (until do_expand_16 is moved.)
1496 * NOTE: this discards the low 16 bits of the user supplied background
1497 * color, but until expand_16 works properly there is no choice!
1499 # define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
1500 CHOP(png_ptr
->background
.red
);
1501 CHOP(png_ptr
->background
.green
);
1502 CHOP(png_ptr
->background
.blue
);
1503 CHOP(png_ptr
->background
.gray
);
1506 #endif /* READ_BACKGROUND && READ_EXPAND_16 */
1508 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1509 (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
1510 defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
1511 if ((png_ptr
->transformations
& (PNG_16_TO_8
|PNG_SCALE_16_TO_8
)) != 0 &&
1512 (png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
1513 (png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) == 0 &&
1514 png_ptr
->bit_depth
== 16)
1516 /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
1517 * component this will also happen after PNG_COMPOSE and so the background
1518 * color must be pre-expanded here.
1520 * TODO: fix this too.
1522 png_ptr
->background
.red
= (png_uint_16
)(png_ptr
->background
.red
* 257);
1523 png_ptr
->background
.green
=
1524 (png_uint_16
)(png_ptr
->background
.green
* 257);
1525 png_ptr
->background
.blue
= (png_uint_16
)(png_ptr
->background
.blue
* 257);
1526 png_ptr
->background
.gray
= (png_uint_16
)(png_ptr
->background
.gray
* 257);
1530 /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
1531 * background support (see the comments in scripts/pnglibconf.dfa), this
1532 * allows pre-multiplication of the alpha channel to be implemented as
1533 * compositing on black. This is probably sub-optimal and has been done in
1534 * 1.5.4 betas simply to enable external critique and testing (i.e. to
1535 * implement the new API quickly, without lots of internal changes.)
1538 #ifdef PNG_READ_GAMMA_SUPPORTED
1539 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1540 /* Includes ALPHA_MODE */
1541 png_ptr
->background_1
= png_ptr
->background
;
1544 /* This needs to change - in the palette image case a whole set of tables are
1545 * built when it would be quicker to just calculate the correct value for
1546 * each palette entry directly. Also, the test is too tricky - why check
1547 * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
1548 * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
1549 * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
1550 * the gamma tables will not be built even if composition is required on a
1551 * gamma encoded value.
1553 * In 1.5.4 this is addressed below by an additional check on the individual
1554 * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
1557 if ((png_ptr
->transformations
& PNG_GAMMA
) != 0 ||
1558 ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) != 0 &&
1559 (png_gamma_significant(png_ptr
->colorspace
.gamma
) != 0 ||
1560 png_gamma_significant(png_ptr
->screen_gamma
) != 0)) ||
1561 ((png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
1562 (png_gamma_significant(png_ptr
->colorspace
.gamma
) != 0 ||
1563 png_gamma_significant(png_ptr
->screen_gamma
) != 0
1564 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1565 || (png_ptr
->background_gamma_type
== PNG_BACKGROUND_GAMMA_UNIQUE
&&
1566 png_gamma_significant(png_ptr
->background_gamma
) != 0)
1568 )) || ((png_ptr
->transformations
& PNG_ENCODE_ALPHA
) != 0 &&
1569 png_gamma_significant(png_ptr
->screen_gamma
) != 0))
1571 png_build_gamma_table(png_ptr
, png_ptr
->bit_depth
);
1573 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1574 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
1576 /* Issue a warning about this combination: because RGB_TO_GRAY is
1577 * optimized to do the gamma transform if present yet do_background has
1578 * to do the same thing if both options are set a
1579 * double-gamma-correction happens. This is true in all versions of
1582 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) != 0)
1583 png_warning(png_ptr
,
1584 "libpng does not support gamma+background+rgb_to_gray");
1586 if ((png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
) != 0)
1588 /* We don't get to here unless there is a tRNS chunk with non-opaque
1589 * entries - see the checking code at the start of this function.
1591 png_color back
, back_1
;
1592 png_colorp palette
= png_ptr
->palette
;
1593 int num_palette
= png_ptr
->num_palette
;
1595 if (png_ptr
->background_gamma_type
== PNG_BACKGROUND_GAMMA_FILE
)
1598 back
.red
= png_ptr
->gamma_table
[png_ptr
->background
.red
];
1599 back
.green
= png_ptr
->gamma_table
[png_ptr
->background
.green
];
1600 back
.blue
= png_ptr
->gamma_table
[png_ptr
->background
.blue
];
1602 back_1
.red
= png_ptr
->gamma_to_1
[png_ptr
->background
.red
];
1603 back_1
.green
= png_ptr
->gamma_to_1
[png_ptr
->background
.green
];
1604 back_1
.blue
= png_ptr
->gamma_to_1
[png_ptr
->background
.blue
];
1608 png_fixed_point g
, gs
;
1610 switch (png_ptr
->background_gamma_type
)
1612 case PNG_BACKGROUND_GAMMA_SCREEN
:
1613 g
= (png_ptr
->screen_gamma
);
1617 case PNG_BACKGROUND_GAMMA_FILE
:
1618 g
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1619 gs
= png_reciprocal2(png_ptr
->colorspace
.gamma
,
1620 png_ptr
->screen_gamma
);
1623 case PNG_BACKGROUND_GAMMA_UNIQUE
:
1624 g
= png_reciprocal(png_ptr
->background_gamma
);
1625 gs
= png_reciprocal2(png_ptr
->background_gamma
,
1626 png_ptr
->screen_gamma
);
1629 g
= PNG_FP_1
; /* back_1 */
1630 gs
= PNG_FP_1
; /* back */
1634 if (png_gamma_significant(gs
) != 0)
1636 back
.red
= png_gamma_8bit_correct(png_ptr
->background
.red
,
1638 back
.green
= png_gamma_8bit_correct(png_ptr
->background
.green
,
1640 back
.blue
= png_gamma_8bit_correct(png_ptr
->background
.blue
,
1646 back
.red
= (png_byte
)png_ptr
->background
.red
;
1647 back
.green
= (png_byte
)png_ptr
->background
.green
;
1648 back
.blue
= (png_byte
)png_ptr
->background
.blue
;
1651 if (png_gamma_significant(g
) != 0)
1653 back_1
.red
= png_gamma_8bit_correct(png_ptr
->background
.red
,
1655 back_1
.green
= png_gamma_8bit_correct(
1656 png_ptr
->background
.green
, g
);
1657 back_1
.blue
= png_gamma_8bit_correct(png_ptr
->background
.blue
,
1663 back_1
.red
= (png_byte
)png_ptr
->background
.red
;
1664 back_1
.green
= (png_byte
)png_ptr
->background
.green
;
1665 back_1
.blue
= (png_byte
)png_ptr
->background
.blue
;
1669 for (i
= 0; i
< num_palette
; i
++)
1671 if (i
< (int)png_ptr
->num_trans
&&
1672 png_ptr
->trans_alpha
[i
] != 0xff)
1674 if (png_ptr
->trans_alpha
[i
] == 0)
1678 else /* if (png_ptr->trans_alpha[i] != 0xff) */
1682 v
= png_ptr
->gamma_to_1
[palette
[i
].red
];
1683 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.red
);
1684 palette
[i
].red
= png_ptr
->gamma_from_1
[w
];
1686 v
= png_ptr
->gamma_to_1
[palette
[i
].green
];
1687 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.green
);
1688 palette
[i
].green
= png_ptr
->gamma_from_1
[w
];
1690 v
= png_ptr
->gamma_to_1
[palette
[i
].blue
];
1691 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.blue
);
1692 palette
[i
].blue
= png_ptr
->gamma_from_1
[w
];
1697 palette
[i
].red
= png_ptr
->gamma_table
[palette
[i
].red
];
1698 palette
[i
].green
= png_ptr
->gamma_table
[palette
[i
].green
];
1699 palette
[i
].blue
= png_ptr
->gamma_table
[palette
[i
].blue
];
1703 /* Prevent the transformations being done again.
1705 * NOTE: this is highly dubious; it removes the transformations in
1706 * place. This seems inconsistent with the general treatment of the
1707 * transformations elsewhere.
1709 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_GAMMA
);
1710 } /* color_type == PNG_COLOR_TYPE_PALETTE */
1712 /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
1713 else /* color_type != PNG_COLOR_TYPE_PALETTE */
1716 png_fixed_point g
= PNG_FP_1
; /* Correction to linear */
1717 png_fixed_point gs
= PNG_FP_1
; /* Correction to screen */
1719 switch (png_ptr
->background_gamma_type
)
1721 case PNG_BACKGROUND_GAMMA_SCREEN
:
1722 g
= png_ptr
->screen_gamma
;
1723 /* gs = PNG_FP_1; */
1726 case PNG_BACKGROUND_GAMMA_FILE
:
1727 g
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1728 gs
= png_reciprocal2(png_ptr
->colorspace
.gamma
,
1729 png_ptr
->screen_gamma
);
1732 case PNG_BACKGROUND_GAMMA_UNIQUE
:
1733 g
= png_reciprocal(png_ptr
->background_gamma
);
1734 gs
= png_reciprocal2(png_ptr
->background_gamma
,
1735 png_ptr
->screen_gamma
);
1739 png_error(png_ptr
, "invalid background gamma type");
1742 g_sig
= png_gamma_significant(g
);
1743 gs_sig
= png_gamma_significant(gs
);
1746 png_ptr
->background_1
.gray
= png_gamma_correct(png_ptr
,
1747 png_ptr
->background
.gray
, g
);
1750 png_ptr
->background
.gray
= png_gamma_correct(png_ptr
,
1751 png_ptr
->background
.gray
, gs
);
1753 if ((png_ptr
->background
.red
!= png_ptr
->background
.green
) ||
1754 (png_ptr
->background
.red
!= png_ptr
->background
.blue
) ||
1755 (png_ptr
->background
.red
!= png_ptr
->background
.gray
))
1757 /* RGB or RGBA with color background */
1760 png_ptr
->background_1
.red
= png_gamma_correct(png_ptr
,
1761 png_ptr
->background
.red
, g
);
1763 png_ptr
->background_1
.green
= png_gamma_correct(png_ptr
,
1764 png_ptr
->background
.green
, g
);
1766 png_ptr
->background_1
.blue
= png_gamma_correct(png_ptr
,
1767 png_ptr
->background
.blue
, g
);
1772 png_ptr
->background
.red
= png_gamma_correct(png_ptr
,
1773 png_ptr
->background
.red
, gs
);
1775 png_ptr
->background
.green
= png_gamma_correct(png_ptr
,
1776 png_ptr
->background
.green
, gs
);
1778 png_ptr
->background
.blue
= png_gamma_correct(png_ptr
,
1779 png_ptr
->background
.blue
, gs
);
1785 /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
1786 png_ptr
->background_1
.red
= png_ptr
->background_1
.green
1787 = png_ptr
->background_1
.blue
= png_ptr
->background_1
.gray
;
1789 png_ptr
->background
.red
= png_ptr
->background
.green
1790 = png_ptr
->background
.blue
= png_ptr
->background
.gray
;
1793 /* The background is now in screen gamma: */
1794 png_ptr
->background_gamma_type
= PNG_BACKGROUND_GAMMA_SCREEN
;
1795 } /* color_type != PNG_COLOR_TYPE_PALETTE */
1796 }/* png_ptr->transformations & PNG_BACKGROUND */
1799 /* Transformation does not include PNG_BACKGROUND */
1800 #endif /* READ_BACKGROUND */
1801 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
1802 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1803 /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
1804 && ((png_ptr
->transformations
& PNG_EXPAND
) == 0 ||
1805 (png_ptr
->transformations
& PNG_RGB_TO_GRAY
) == 0)
1809 png_colorp palette
= png_ptr
->palette
;
1810 int num_palette
= png_ptr
->num_palette
;
1813 /* NOTE: there are other transformations that should probably be in
1816 for (i
= 0; i
< num_palette
; i
++)
1818 palette
[i
].red
= png_ptr
->gamma_table
[palette
[i
].red
];
1819 palette
[i
].green
= png_ptr
->gamma_table
[palette
[i
].green
];
1820 palette
[i
].blue
= png_ptr
->gamma_table
[palette
[i
].blue
];
1823 /* Done the gamma correction. */
1824 png_ptr
->transformations
&= ~PNG_GAMMA
;
1825 } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
1827 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1830 #endif /* READ_GAMMA */
1832 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1833 /* No GAMMA transformation (see the hanging else 4 lines above) */
1834 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
1835 (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
))
1838 int istop
= (int)png_ptr
->num_trans
;
1840 png_colorp palette
= png_ptr
->palette
;
1842 back
.red
= (png_byte
)png_ptr
->background
.red
;
1843 back
.green
= (png_byte
)png_ptr
->background
.green
;
1844 back
.blue
= (png_byte
)png_ptr
->background
.blue
;
1846 for (i
= 0; i
< istop
; i
++)
1848 if (png_ptr
->trans_alpha
[i
] == 0)
1853 else if (png_ptr
->trans_alpha
[i
] != 0xff)
1855 /* The png_composite() macro is defined in png.h */
1856 png_composite(palette
[i
].red
, palette
[i
].red
,
1857 png_ptr
->trans_alpha
[i
], back
.red
);
1859 png_composite(palette
[i
].green
, palette
[i
].green
,
1860 png_ptr
->trans_alpha
[i
], back
.green
);
1862 png_composite(palette
[i
].blue
, palette
[i
].blue
,
1863 png_ptr
->trans_alpha
[i
], back
.blue
);
1867 png_ptr
->transformations
&= ~PNG_COMPOSE
;
1869 #endif /* READ_BACKGROUND */
1871 #ifdef PNG_READ_SHIFT_SUPPORTED
1872 if ((png_ptr
->transformations
& PNG_SHIFT
) != 0 &&
1873 (png_ptr
->transformations
& PNG_EXPAND
) == 0 &&
1874 (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
))
1877 int istop
= png_ptr
->num_palette
;
1878 int shift
= 8 - png_ptr
->sig_bit
.red
;
1880 png_ptr
->transformations
&= ~PNG_SHIFT
;
1882 /* significant bits can be in the range 1 to 7 for a meaninful result, if
1883 * the number of significant bits is 0 then no shift is done (this is an
1884 * error condition which is silently ignored.)
1886 if (shift
> 0 && shift
< 8)
1887 for (i
=0; i
<istop
; ++i
)
1889 int component
= png_ptr
->palette
[i
].red
;
1891 component
>>= shift
;
1892 png_ptr
->palette
[i
].red
= (png_byte
)component
;
1895 shift
= 8 - png_ptr
->sig_bit
.green
;
1896 if (shift
> 0 && shift
< 8)
1897 for (i
=0; i
<istop
; ++i
)
1899 int component
= png_ptr
->palette
[i
].green
;
1901 component
>>= shift
;
1902 png_ptr
->palette
[i
].green
= (png_byte
)component
;
1905 shift
= 8 - png_ptr
->sig_bit
.blue
;
1906 if (shift
> 0 && shift
< 8)
1907 for (i
=0; i
<istop
; ++i
)
1909 int component
= png_ptr
->palette
[i
].blue
;
1911 component
>>= shift
;
1912 png_ptr
->palette
[i
].blue
= (png_byte
)component
;
1915 #endif /* READ_SHIFT */
1918 /* Modify the info structure to reflect the transformations. The
1919 * info should be updated so a PNG file could be written with it,
1920 * assuming the transformations result in valid PNG data.
1923 png_read_transform_info(png_structrp png_ptr
, png_inforp info_ptr
)
1925 png_debug(1, "in png_read_transform_info");
1927 #ifdef PNG_READ_EXPAND_SUPPORTED
1928 if ((png_ptr
->transformations
& PNG_EXPAND
) != 0)
1930 if (info_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
1932 /* This check must match what actually happens in
1933 * png_do_expand_palette; if it ever checks the tRNS chunk to see if
1934 * it is all opaque we must do the same (at present it does not.)
1936 if (png_ptr
->num_trans
> 0)
1937 info_ptr
->color_type
= PNG_COLOR_TYPE_RGB_ALPHA
;
1940 info_ptr
->color_type
= PNG_COLOR_TYPE_RGB
;
1942 info_ptr
->bit_depth
= 8;
1943 info_ptr
->num_trans
= 0;
1945 if (png_ptr
->palette
== NULL
)
1946 png_error (png_ptr
, "Palette is NULL in indexed image");
1950 if (png_ptr
->num_trans
!= 0)
1952 if ((png_ptr
->transformations
& PNG_EXPAND_tRNS
) != 0)
1953 info_ptr
->color_type
|= PNG_COLOR_MASK_ALPHA
;
1955 if (info_ptr
->bit_depth
< 8)
1956 info_ptr
->bit_depth
= 8;
1958 info_ptr
->num_trans
= 0;
1963 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
1964 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
1965 /* The following is almost certainly wrong unless the background value is in
1968 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
1969 info_ptr
->background
= png_ptr
->background
;
1972 #ifdef PNG_READ_GAMMA_SUPPORTED
1973 /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
1974 * however it seems that the code in png_init_read_transformations, which has
1975 * been called before this from png_read_update_info->png_read_start_row
1976 * sometimes does the gamma transform and cancels the flag.
1978 * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
1979 * the screen_gamma value. The following probably results in weirdness if
1980 * the info_ptr is used by the app after the rows have been read.
1982 info_ptr
->colorspace
.gamma
= png_ptr
->colorspace
.gamma
;
1985 if (info_ptr
->bit_depth
== 16)
1987 # ifdef PNG_READ_16BIT_SUPPORTED
1988 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1989 if ((png_ptr
->transformations
& PNG_SCALE_16_TO_8
) != 0)
1990 info_ptr
->bit_depth
= 8;
1993 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1994 if ((png_ptr
->transformations
& PNG_16_TO_8
) != 0)
1995 info_ptr
->bit_depth
= 8;
1999 /* No 16-bit support: force chopping 16-bit input down to 8, in this case
2000 * the app program can chose if both APIs are available by setting the
2001 * correct scaling to use.
2003 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2004 /* For compatibility with previous versions use the strip method by
2005 * default. This code works because if PNG_SCALE_16_TO_8 is already
2006 * set the code below will do that in preference to the chop.
2008 png_ptr
->transformations
|= PNG_16_TO_8
;
2009 info_ptr
->bit_depth
= 8;
2012 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2013 png_ptr
->transformations
|= PNG_SCALE_16_TO_8
;
2014 info_ptr
->bit_depth
= 8;
2017 CONFIGURATION ERROR
: you must enable at least one
16 to
8 method
2020 #endif /* !READ_16BIT */
2023 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2024 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) != 0)
2025 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
|
2026 PNG_COLOR_MASK_COLOR
);
2029 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2030 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) != 0)
2031 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
&
2032 ~PNG_COLOR_MASK_COLOR
);
2035 #ifdef PNG_READ_QUANTIZE_SUPPORTED
2036 if ((png_ptr
->transformations
& PNG_QUANTIZE
) != 0)
2038 if (((info_ptr
->color_type
== PNG_COLOR_TYPE_RGB
) ||
2039 (info_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)) &&
2040 png_ptr
->palette_lookup
!= 0 && info_ptr
->bit_depth
== 8)
2042 info_ptr
->color_type
= PNG_COLOR_TYPE_PALETTE
;
2047 #ifdef PNG_READ_EXPAND_16_SUPPORTED
2048 if ((png_ptr
->transformations
& PNG_EXPAND_16
) != 0 &&
2049 info_ptr
->bit_depth
== 8 &&
2050 info_ptr
->color_type
!= PNG_COLOR_TYPE_PALETTE
)
2052 info_ptr
->bit_depth
= 16;
2056 #ifdef PNG_READ_PACK_SUPPORTED
2057 if ((png_ptr
->transformations
& PNG_PACK
) != 0 &&
2058 (info_ptr
->bit_depth
< 8))
2059 info_ptr
->bit_depth
= 8;
2062 if (info_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
2063 info_ptr
->channels
= 1;
2065 else if ((info_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
2066 info_ptr
->channels
= 3;
2069 info_ptr
->channels
= 1;
2071 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2072 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) != 0)
2074 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
&
2075 ~PNG_COLOR_MASK_ALPHA
);
2076 info_ptr
->num_trans
= 0;
2080 if ((info_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
2081 info_ptr
->channels
++;
2083 #ifdef PNG_READ_FILLER_SUPPORTED
2084 /* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
2085 if ((png_ptr
->transformations
& PNG_FILLER
) != 0 &&
2086 (info_ptr
->color_type
== PNG_COLOR_TYPE_RGB
||
2087 info_ptr
->color_type
== PNG_COLOR_TYPE_GRAY
))
2089 info_ptr
->channels
++;
2090 /* If adding a true alpha channel not just filler */
2091 if ((png_ptr
->transformations
& PNG_ADD_ALPHA
) != 0)
2092 info_ptr
->color_type
|= PNG_COLOR_MASK_ALPHA
;
2096 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
2097 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
2098 if ((png_ptr
->transformations
& PNG_USER_TRANSFORM
) != 0)
2100 if (png_ptr
->user_transform_depth
!= 0)
2101 info_ptr
->bit_depth
= png_ptr
->user_transform_depth
;
2103 if (png_ptr
->user_transform_channels
!= 0)
2104 info_ptr
->channels
= png_ptr
->user_transform_channels
;
2108 info_ptr
->pixel_depth
= (png_byte
)(info_ptr
->channels
*
2109 info_ptr
->bit_depth
);
2111 info_ptr
->rowbytes
= PNG_ROWBYTES(info_ptr
->pixel_depth
, info_ptr
->width
);
2113 /* Adding in 1.5.4: cache the above value in png_struct so that we can later
2114 * check in png_rowbytes that the user buffer won't get overwritten. Note
2115 * that the field is not always set - if png_read_update_info isn't called
2116 * the application has to either not do any transforms or get the calculation
2119 png_ptr
->info_rowbytes
= info_ptr
->rowbytes
;
2121 #ifndef PNG_READ_EXPAND_SUPPORTED
2122 if (png_ptr
!= NULL
)
2127 #ifdef PNG_READ_PACK_SUPPORTED
2128 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
2129 * without changing the actual values. Thus, if you had a row with
2130 * a bit depth of 1, you would end up with bytes that only contained
2131 * the numbers 0 or 1. If you would rather they contain 0 and 255, use
2132 * png_do_shift() after this.
2135 png_do_unpack(png_row_infop row_info
, png_bytep row
)
2137 png_debug(1, "in png_do_unpack");
2139 if (row_info
->bit_depth
< 8)
2142 png_uint_32 row_width
=row_info
->width
;
2144 switch (row_info
->bit_depth
)
2148 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
2149 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2150 png_uint_32 shift
= 7 - (int)((row_width
+ 7) & 0x07);
2151 for (i
= 0; i
< row_width
; i
++)
2153 *dp
= (png_byte
)((*sp
>> shift
) & 0x01);
2172 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
2173 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2174 png_uint_32 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
2175 for (i
= 0; i
< row_width
; i
++)
2177 *dp
= (png_byte
)((*sp
>> shift
) & 0x03);
2195 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
2196 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2197 png_uint_32 shift
= (int)((1 - ((row_width
+ 1) & 0x01)) << 2);
2198 for (i
= 0; i
< row_width
; i
++)
2200 *dp
= (png_byte
)((*sp
>> shift
) & 0x0f);
2219 row_info
->bit_depth
= 8;
2220 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2221 row_info
->rowbytes
= row_width
* row_info
->channels
;
2226 #ifdef PNG_READ_SHIFT_SUPPORTED
2227 /* Reverse the effects of png_do_shift. This routine merely shifts the
2228 * pixels back to their significant bits values. Thus, if you have
2229 * a row of bit depth 8, but only 5 are significant, this will shift
2230 * the values back to 0 through 31.
2233 png_do_unshift(png_row_infop row_info
, png_bytep row
,
2234 png_const_color_8p sig_bits
)
2238 png_debug(1, "in png_do_unshift");
2240 /* The palette case has already been handled in the _init routine. */
2241 color_type
= row_info
->color_type
;
2243 if (color_type
!= PNG_COLOR_TYPE_PALETTE
)
2247 int bit_depth
= row_info
->bit_depth
;
2249 if ((color_type
& PNG_COLOR_MASK_COLOR
) != 0)
2251 shift
[channels
++] = bit_depth
- sig_bits
->red
;
2252 shift
[channels
++] = bit_depth
- sig_bits
->green
;
2253 shift
[channels
++] = bit_depth
- sig_bits
->blue
;
2258 shift
[channels
++] = bit_depth
- sig_bits
->gray
;
2261 if ((color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
2263 shift
[channels
++] = bit_depth
- sig_bits
->alpha
;
2269 for (c
= have_shift
= 0; c
< channels
; ++c
)
2271 /* A shift of more than the bit depth is an error condition but it
2272 * gets ignored here.
2274 if (shift
[c
] <= 0 || shift
[c
] >= bit_depth
)
2281 if (have_shift
== 0)
2288 /* Must be 1bpp gray: should not be here! */
2293 /* Must be 2bpp gray */
2294 /* assert(channels == 1 && shift[0] == 1) */
2297 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2301 int b
= (*bp
>> 1) & 0x55;
2302 *bp
++ = (png_byte
)b
;
2308 /* Must be 4bpp gray */
2309 /* assert(channels == 1) */
2312 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2313 int gray_shift
= shift
[0];
2314 int mask
= 0xf >> gray_shift
;
2320 int b
= (*bp
>> gray_shift
) & mask
;
2321 *bp
++ = (png_byte
)b
;
2327 /* Single byte components, G, GA, RGB, RGBA */
2330 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2335 int b
= *bp
>> shift
[channel
];
2336 if (++channel
>= channels
)
2338 *bp
++ = (png_byte
)b
;
2343 #ifdef PNG_READ_16BIT_SUPPORTED
2345 /* Double byte components, G, GA, RGB, RGBA */
2348 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2353 int value
= (bp
[0] << 8) + bp
[1];
2355 value
>>= shift
[channel
];
2356 if (++channel
>= channels
)
2358 *bp
++ = (png_byte
)(value
>> 8);
2359 *bp
++ = (png_byte
)value
;
2369 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2370 /* Scale rows of bit depth 16 down to 8 accurately */
2372 png_do_scale_16_to_8(png_row_infop row_info
, png_bytep row
)
2374 png_debug(1, "in png_do_scale_16_to_8");
2376 if (row_info
->bit_depth
== 16)
2378 png_bytep sp
= row
; /* source */
2379 png_bytep dp
= row
; /* destination */
2380 png_bytep ep
= sp
+ row_info
->rowbytes
; /* end+1 */
2384 /* The input is an array of 16-bit components, these must be scaled to
2385 * 8 bits each. For a 16-bit value V the required value (from the PNG
2386 * specification) is:
2390 * This reduces to round(V / 257), or floor((V + 128.5)/257)
2392 * Represent V as the two byte value vhi.vlo. Make a guess that the
2393 * result is the top byte of V, vhi, then the correction to this value
2396 * error = floor(((V-vhi.vhi) + 128.5) / 257)
2397 * = floor(((vlo-vhi) + 128.5) / 257)
2399 * This can be approximated using integer arithmetic (and a signed
2402 * error = (vlo-vhi+128) >> 8;
2404 * The approximate differs from the exact answer only when (vlo-vhi) is
2405 * 128; it then gives a correction of +1 when the exact correction is
2406 * 0. This gives 128 errors. The exact answer (correct for all 16-bit
2409 * error = (vlo-vhi+128)*65535 >> 24;
2411 * An alternative arithmetic calculation which also gives no errors is:
2413 * (V * 255 + 32895) >> 16
2416 png_int_32 tmp
= *sp
++; /* must be signed! */
2417 tmp
+= (((int)*sp
++ - tmp
+ 128) * 65535) >> 24;
2418 *dp
++ = (png_byte
)tmp
;
2421 row_info
->bit_depth
= 8;
2422 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2423 row_info
->rowbytes
= row_info
->width
* row_info
->channels
;
2428 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2430 /* Simply discard the low byte. This was the default behavior prior
2433 png_do_chop(png_row_infop row_info
, png_bytep row
)
2435 png_debug(1, "in png_do_chop");
2437 if (row_info
->bit_depth
== 16)
2439 png_bytep sp
= row
; /* source */
2440 png_bytep dp
= row
; /* destination */
2441 png_bytep ep
= sp
+ row_info
->rowbytes
; /* end+1 */
2446 sp
+= 2; /* skip low byte */
2449 row_info
->bit_depth
= 8;
2450 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2451 row_info
->rowbytes
= row_info
->width
* row_info
->channels
;
2456 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2458 png_do_read_swap_alpha(png_row_infop row_info
, png_bytep row
)
2460 png_debug(1, "in png_do_read_swap_alpha");
2463 png_uint_32 row_width
= row_info
->width
;
2464 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
2466 /* This converts from RGBA to ARGB */
2467 if (row_info
->bit_depth
== 8)
2469 png_bytep sp
= row
+ row_info
->rowbytes
;
2474 for (i
= 0; i
< row_width
; i
++)
2484 #ifdef PNG_READ_16BIT_SUPPORTED
2485 /* This converts from RRGGBBAA to AARRGGBB */
2488 png_bytep sp
= row
+ row_info
->rowbytes
;
2493 for (i
= 0; i
< row_width
; i
++)
2510 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2512 /* This converts from GA to AG */
2513 if (row_info
->bit_depth
== 8)
2515 png_bytep sp
= row
+ row_info
->rowbytes
;
2520 for (i
= 0; i
< row_width
; i
++)
2528 #ifdef PNG_READ_16BIT_SUPPORTED
2529 /* This converts from GGAA to AAGG */
2532 png_bytep sp
= row
+ row_info
->rowbytes
;
2537 for (i
= 0; i
< row_width
; i
++)
2553 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2555 png_do_read_invert_alpha(png_row_infop row_info
, png_bytep row
)
2557 png_uint_32 row_width
;
2558 png_debug(1, "in png_do_read_invert_alpha");
2560 row_width
= row_info
->width
;
2561 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
2563 if (row_info
->bit_depth
== 8)
2565 /* This inverts the alpha channel in RGBA */
2566 png_bytep sp
= row
+ row_info
->rowbytes
;
2570 for (i
= 0; i
< row_width
; i
++)
2572 *(--dp
) = (png_byte
)(255 - *(--sp
));
2574 /* This does nothing:
2578 We can replace it with:
2585 #ifdef PNG_READ_16BIT_SUPPORTED
2586 /* This inverts the alpha channel in RRGGBBAA */
2589 png_bytep sp
= row
+ row_info
->rowbytes
;
2593 for (i
= 0; i
< row_width
; i
++)
2595 *(--dp
) = (png_byte
)(255 - *(--sp
));
2596 *(--dp
) = (png_byte
)(255 - *(--sp
));
2598 /* This does nothing:
2605 We can replace it with:
2613 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2615 if (row_info
->bit_depth
== 8)
2617 /* This inverts the alpha channel in GA */
2618 png_bytep sp
= row
+ row_info
->rowbytes
;
2622 for (i
= 0; i
< row_width
; i
++)
2624 *(--dp
) = (png_byte
)(255 - *(--sp
));
2629 #ifdef PNG_READ_16BIT_SUPPORTED
2632 /* This inverts the alpha channel in GGAA */
2633 png_bytep sp
= row
+ row_info
->rowbytes
;
2637 for (i
= 0; i
< row_width
; i
++)
2639 *(--dp
) = (png_byte
)(255 - *(--sp
));
2640 *(--dp
) = (png_byte
)(255 - *(--sp
));
2654 #ifdef PNG_READ_FILLER_SUPPORTED
2655 /* Add filler channel if we have RGB color */
2657 png_do_read_filler(png_row_infop row_info
, png_bytep row
,
2658 png_uint_32 filler
, png_uint_32 flags
)
2661 png_uint_32 row_width
= row_info
->width
;
2663 #ifdef PNG_READ_16BIT_SUPPORTED
2664 png_byte hi_filler
= (png_byte
)(filler
>>8);
2666 png_byte lo_filler
= (png_byte
)filler
;
2668 png_debug(1, "in png_do_read_filler");
2671 row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
2673 if (row_info
->bit_depth
== 8)
2675 if ((flags
& PNG_FLAG_FILLER_AFTER
) != 0)
2677 /* This changes the data from G to GX */
2678 png_bytep sp
= row
+ (png_size_t
)row_width
;
2679 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2680 for (i
= 1; i
< row_width
; i
++)
2682 *(--dp
) = lo_filler
;
2685 *(--dp
) = lo_filler
;
2686 row_info
->channels
= 2;
2687 row_info
->pixel_depth
= 16;
2688 row_info
->rowbytes
= row_width
* 2;
2693 /* This changes the data from G to XG */
2694 png_bytep sp
= row
+ (png_size_t
)row_width
;
2695 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2696 for (i
= 0; i
< row_width
; i
++)
2699 *(--dp
) = lo_filler
;
2701 row_info
->channels
= 2;
2702 row_info
->pixel_depth
= 16;
2703 row_info
->rowbytes
= row_width
* 2;
2707 #ifdef PNG_READ_16BIT_SUPPORTED
2708 else if (row_info
->bit_depth
== 16)
2710 if ((flags
& PNG_FLAG_FILLER_AFTER
) != 0)
2712 /* This changes the data from GG to GGXX */
2713 png_bytep sp
= row
+ (png_size_t
)row_width
* 2;
2714 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2715 for (i
= 1; i
< row_width
; i
++)
2717 *(--dp
) = lo_filler
;
2718 *(--dp
) = hi_filler
;
2722 *(--dp
) = lo_filler
;
2723 *(--dp
) = hi_filler
;
2724 row_info
->channels
= 2;
2725 row_info
->pixel_depth
= 32;
2726 row_info
->rowbytes
= row_width
* 4;
2731 /* This changes the data from GG to XXGG */
2732 png_bytep sp
= row
+ (png_size_t
)row_width
* 2;
2733 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2734 for (i
= 0; i
< row_width
; i
++)
2738 *(--dp
) = lo_filler
;
2739 *(--dp
) = hi_filler
;
2741 row_info
->channels
= 2;
2742 row_info
->pixel_depth
= 32;
2743 row_info
->rowbytes
= row_width
* 4;
2747 } /* COLOR_TYPE == GRAY */
2748 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
)
2750 if (row_info
->bit_depth
== 8)
2752 if ((flags
& PNG_FLAG_FILLER_AFTER
) != 0)
2754 /* This changes the data from RGB to RGBX */
2755 png_bytep sp
= row
+ (png_size_t
)row_width
* 3;
2756 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2757 for (i
= 1; i
< row_width
; i
++)
2759 *(--dp
) = lo_filler
;
2764 *(--dp
) = lo_filler
;
2765 row_info
->channels
= 4;
2766 row_info
->pixel_depth
= 32;
2767 row_info
->rowbytes
= row_width
* 4;
2772 /* This changes the data from RGB to XRGB */
2773 png_bytep sp
= row
+ (png_size_t
)row_width
* 3;
2774 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2775 for (i
= 0; i
< row_width
; i
++)
2780 *(--dp
) = lo_filler
;
2782 row_info
->channels
= 4;
2783 row_info
->pixel_depth
= 32;
2784 row_info
->rowbytes
= row_width
* 4;
2788 #ifdef PNG_READ_16BIT_SUPPORTED
2789 else if (row_info
->bit_depth
== 16)
2791 if ((flags
& PNG_FLAG_FILLER_AFTER
) != 0)
2793 /* This changes the data from RRGGBB to RRGGBBXX */
2794 png_bytep sp
= row
+ (png_size_t
)row_width
* 6;
2795 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2796 for (i
= 1; i
< row_width
; i
++)
2798 *(--dp
) = lo_filler
;
2799 *(--dp
) = hi_filler
;
2807 *(--dp
) = lo_filler
;
2808 *(--dp
) = hi_filler
;
2809 row_info
->channels
= 4;
2810 row_info
->pixel_depth
= 64;
2811 row_info
->rowbytes
= row_width
* 8;
2816 /* This changes the data from RRGGBB to XXRRGGBB */
2817 png_bytep sp
= row
+ (png_size_t
)row_width
* 6;
2818 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2819 for (i
= 0; i
< row_width
; i
++)
2827 *(--dp
) = lo_filler
;
2828 *(--dp
) = hi_filler
;
2831 row_info
->channels
= 4;
2832 row_info
->pixel_depth
= 64;
2833 row_info
->rowbytes
= row_width
* 8;
2837 } /* COLOR_TYPE == RGB */
2841 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2842 /* Expand grayscale files to RGB, with or without alpha */
2844 png_do_gray_to_rgb(png_row_infop row_info
, png_bytep row
)
2847 png_uint_32 row_width
= row_info
->width
;
2849 png_debug(1, "in png_do_gray_to_rgb");
2851 if (row_info
->bit_depth
>= 8 &&
2852 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) == 0)
2854 if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
2856 if (row_info
->bit_depth
== 8)
2858 /* This changes G to RGB */
2859 png_bytep sp
= row
+ (png_size_t
)row_width
- 1;
2860 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2861 for (i
= 0; i
< row_width
; i
++)
2871 /* This changes GG to RRGGBB */
2872 png_bytep sp
= row
+ (png_size_t
)row_width
* 2 - 1;
2873 png_bytep dp
= sp
+ (png_size_t
)row_width
* 4;
2874 for (i
= 0; i
< row_width
; i
++)
2877 *(dp
--) = *(sp
- 1);
2879 *(dp
--) = *(sp
- 1);
2886 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2888 if (row_info
->bit_depth
== 8)
2890 /* This changes GA to RGBA */
2891 png_bytep sp
= row
+ (png_size_t
)row_width
* 2 - 1;
2892 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2893 for (i
= 0; i
< row_width
; i
++)
2904 /* This changes GGAA to RRGGBBAA */
2905 png_bytep sp
= row
+ (png_size_t
)row_width
* 4 - 1;
2906 png_bytep dp
= sp
+ (png_size_t
)row_width
* 4;
2907 for (i
= 0; i
< row_width
; i
++)
2912 *(dp
--) = *(sp
- 1);
2914 *(dp
--) = *(sp
- 1);
2920 row_info
->channels
= (png_byte
)(row_info
->channels
+ 2);
2921 row_info
->color_type
|= PNG_COLOR_MASK_COLOR
;
2922 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
*
2923 row_info
->bit_depth
);
2924 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
2929 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2930 /* Reduce RGB files to grayscale, with or without alpha
2931 * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
2932 * <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
2933 * versions dated 1998 through November 2002 have been archived at
2934 * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
2935 * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
2936 * Charles Poynton poynton at poynton.com
2938 * Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2940 * which can be expressed with integers as
2942 * Y = (6969 * R + 23434 * G + 2365 * B)/32768
2944 * Poynton's current link (as of January 2003 through July 2011):
2945 * <http://www.poynton.com/notes/colour_and_gamma/>
2946 * has changed the numbers slightly:
2948 * Y = 0.2126*R + 0.7152*G + 0.0722*B
2950 * which can be expressed with integers as
2952 * Y = (6966 * R + 23436 * G + 2366 * B)/32768
2954 * Historically, however, libpng uses numbers derived from the ITU-R Rec 709
2955 * end point chromaticities and the D65 white point. Depending on the
2956 * precision used for the D65 white point this produces a variety of different
2957 * numbers, however if the four decimal place value used in ITU-R Rec 709 is
2958 * used (0.3127,0.3290) the Y calculation would be:
2960 * Y = (6968 * R + 23435 * G + 2366 * B)/32768
2962 * While this is correct the rounding results in an overflow for white, because
2963 * the sum of the rounded coefficients is 32769, not 32768. Consequently
2964 * libpng uses, instead, the closest non-overflowing approximation:
2966 * Y = (6968 * R + 23434 * G + 2366 * B)/32768
2968 * Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
2969 * (including an sRGB chunk) then the chromaticities are used to calculate the
2970 * coefficients. See the chunk handling in pngrutil.c for more information.
2972 * In all cases the calculation is to be done in a linear colorspace. If no
2973 * gamma information is available to correct the encoding of the original RGB
2974 * values this results in an implicit assumption that the original PNG RGB
2975 * values were linear.
2977 * Other integer coefficents can be used via png_set_rgb_to_gray(). Because
2978 * the API takes just red and green coefficients the blue coefficient is
2979 * calculated to make the sum 32768. This will result in different rounding
2980 * to that used above.
2983 png_do_rgb_to_gray(png_structrp png_ptr
, png_row_infop row_info
, png_bytep row
)
2988 png_debug(1, "in png_do_rgb_to_gray");
2990 if ((row_info
->color_type
& PNG_COLOR_MASK_PALETTE
) == 0 &&
2991 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
2993 PNG_CONST png_uint_32 rc
= png_ptr
->rgb_to_gray_red_coeff
;
2994 PNG_CONST png_uint_32 gc
= png_ptr
->rgb_to_gray_green_coeff
;
2995 PNG_CONST png_uint_32 bc
= 32768 - rc
- gc
;
2996 PNG_CONST png_uint_32 row_width
= row_info
->width
;
2997 PNG_CONST
int have_alpha
=
2998 (row_info
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0;
3000 if (row_info
->bit_depth
== 8)
3002 #ifdef PNG_READ_GAMMA_SUPPORTED
3003 /* Notice that gamma to/from 1 are not necessarily inverses (if
3004 * there is an overall gamma correction). Prior to 1.5.5 this code
3005 * checked the linearized values for equality; this doesn't match
3006 * the documentation, the original values must be checked.
3008 if (png_ptr
->gamma_from_1
!= NULL
&& png_ptr
->gamma_to_1
!= NULL
)
3014 for (i
= 0; i
< row_width
; i
++)
3016 png_byte red
= *(sp
++);
3017 png_byte green
= *(sp
++);
3018 png_byte blue
= *(sp
++);
3020 if (red
!= green
|| red
!= blue
)
3022 red
= png_ptr
->gamma_to_1
[red
];
3023 green
= png_ptr
->gamma_to_1
[green
];
3024 blue
= png_ptr
->gamma_to_1
[blue
];
3027 *(dp
++) = png_ptr
->gamma_from_1
[
3028 (rc
*red
+ gc
*green
+ bc
*blue
+ 16384)>>15];
3033 /* If there is no overall correction the table will not be
3036 if (png_ptr
->gamma_table
!= NULL
)
3037 red
= png_ptr
->gamma_table
[red
];
3042 if (have_alpha
!= 0)
3053 for (i
= 0; i
< row_width
; i
++)
3055 png_byte red
= *(sp
++);
3056 png_byte green
= *(sp
++);
3057 png_byte blue
= *(sp
++);
3059 if (red
!= green
|| red
!= blue
)
3062 /* NOTE: this is the historical approach which simply
3063 * truncates the results.
3065 *(dp
++) = (png_byte
)((rc
*red
+ gc
*green
+ bc
*blue
)>>15);
3071 if (have_alpha
!= 0)
3077 else /* RGB bit_depth == 16 */
3079 #ifdef PNG_READ_GAMMA_SUPPORTED
3080 if (png_ptr
->gamma_16_to_1
!= NULL
&& png_ptr
->gamma_16_from_1
!= NULL
)
3086 for (i
= 0; i
< row_width
; i
++)
3088 png_uint_16 red
, green
, blue
, w
;
3091 hi
=*(sp
)++; lo
=*(sp
)++; red
= (png_uint_16
)((hi
<< 8) | (lo
));
3092 hi
=*(sp
)++; lo
=*(sp
)++; green
= (png_uint_16
)((hi
<< 8) | (lo
));
3093 hi
=*(sp
)++; lo
=*(sp
)++; blue
= (png_uint_16
)((hi
<< 8) | (lo
));
3095 if (red
== green
&& red
== blue
)
3097 if (png_ptr
->gamma_16_table
!= NULL
)
3098 w
= png_ptr
->gamma_16_table
[(red
& 0xff)
3099 >> png_ptr
->gamma_shift
][red
>> 8];
3107 png_uint_16 red_1
= png_ptr
->gamma_16_to_1
[(red
& 0xff)
3108 >> png_ptr
->gamma_shift
][red
>>8];
3109 png_uint_16 green_1
=
3110 png_ptr
->gamma_16_to_1
[(green
& 0xff) >>
3111 png_ptr
->gamma_shift
][green
>>8];
3112 png_uint_16 blue_1
= png_ptr
->gamma_16_to_1
[(blue
& 0xff)
3113 >> png_ptr
->gamma_shift
][blue
>>8];
3114 png_uint_16 gray16
= (png_uint_16
)((rc
*red_1
+ gc
*green_1
3115 + bc
*blue_1
+ 16384)>>15);
3116 w
= png_ptr
->gamma_16_from_1
[(gray16
& 0xff) >>
3117 png_ptr
->gamma_shift
][gray16
>> 8];
3121 *(dp
++) = (png_byte
)((w
>>8) & 0xff);
3122 *(dp
++) = (png_byte
)(w
& 0xff);
3124 if (have_alpha
!= 0)
3138 for (i
= 0; i
< row_width
; i
++)
3140 png_uint_16 red
, green
, blue
, gray16
;
3143 hi
=*(sp
)++; lo
=*(sp
)++; red
= (png_uint_16
)((hi
<< 8) | (lo
));
3144 hi
=*(sp
)++; lo
=*(sp
)++; green
= (png_uint_16
)((hi
<< 8) | (lo
));
3145 hi
=*(sp
)++; lo
=*(sp
)++; blue
= (png_uint_16
)((hi
<< 8) | (lo
));
3147 if (red
!= green
|| red
!= blue
)
3150 /* From 1.5.5 in the 16-bit case do the accurate conversion even
3151 * in the 'fast' case - this is because this is where the code
3152 * ends up when handling linear 16-bit data.
3154 gray16
= (png_uint_16
)((rc
*red
+ gc
*green
+ bc
*blue
+ 16384) >>
3156 *(dp
++) = (png_byte
)((gray16
>> 8) & 0xff);
3157 *(dp
++) = (png_byte
)(gray16
& 0xff);
3159 if (have_alpha
!= 0)
3168 row_info
->channels
= (png_byte
)(row_info
->channels
- 2);
3169 row_info
->color_type
= (png_byte
)(row_info
->color_type
&
3170 ~PNG_COLOR_MASK_COLOR
);
3171 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
*
3172 row_info
->bit_depth
);
3173 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
3179 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
3180 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
3181 /* Replace any alpha or transparency with the supplied background color.
3182 * "background" is already in the screen gamma, while "background_1" is
3183 * at a gamma of 1.0. Paletted files have already been taken care of.
3186 png_do_compose(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
3188 #ifdef PNG_READ_GAMMA_SUPPORTED
3189 png_const_bytep gamma_table
= png_ptr
->gamma_table
;
3190 png_const_bytep gamma_from_1
= png_ptr
->gamma_from_1
;
3191 png_const_bytep gamma_to_1
= png_ptr
->gamma_to_1
;
3192 png_const_uint_16pp gamma_16
= png_ptr
->gamma_16_table
;
3193 png_const_uint_16pp gamma_16_from_1
= png_ptr
->gamma_16_from_1
;
3194 png_const_uint_16pp gamma_16_to_1
= png_ptr
->gamma_16_to_1
;
3195 int gamma_shift
= png_ptr
->gamma_shift
;
3196 int optimize
= (png_ptr
->flags
& PNG_FLAG_OPTIMIZE_ALPHA
) != 0;
3201 png_uint_32 row_width
= row_info
->width
;
3204 png_debug(1, "in png_do_compose");
3207 switch (row_info
->color_type
)
3209 case PNG_COLOR_TYPE_GRAY
:
3211 switch (row_info
->bit_depth
)
3217 for (i
= 0; i
< row_width
; i
++)
3219 if ((png_uint_16
)((*sp
>> shift
) & 0x01)
3220 == png_ptr
->trans_color
.gray
)
3222 unsigned int tmp
= *sp
& (0x7f7f >> (7 - shift
));
3223 tmp
|= png_ptr
->background
.gray
<< shift
;
3224 *sp
= (png_byte
)(tmp
& 0xff);
3241 #ifdef PNG_READ_GAMMA_SUPPORTED
3242 if (gamma_table
!= NULL
)
3246 for (i
= 0; i
< row_width
; i
++)
3248 if ((png_uint_16
)((*sp
>> shift
) & 0x03)
3249 == png_ptr
->trans_color
.gray
)
3251 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3252 tmp
|= png_ptr
->background
.gray
<< shift
;
3253 *sp
= (png_byte
)(tmp
& 0xff);
3258 unsigned int p
= (*sp
>> shift
) & 0x03;
3259 unsigned int g
= (gamma_table
[p
| (p
<< 2) |
3260 (p
<< 4) | (p
<< 6)] >> 6) & 0x03;
3261 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3263 *sp
= (png_byte
)(tmp
& 0xff);
3282 for (i
= 0; i
< row_width
; i
++)
3284 if ((png_uint_16
)((*sp
>> shift
) & 0x03)
3285 == png_ptr
->trans_color
.gray
)
3287 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3288 tmp
|= png_ptr
->background
.gray
<< shift
;
3289 *sp
= (png_byte
)(tmp
& 0xff);
3307 #ifdef PNG_READ_GAMMA_SUPPORTED
3308 if (gamma_table
!= NULL
)
3312 for (i
= 0; i
< row_width
; i
++)
3314 if ((png_uint_16
)((*sp
>> shift
) & 0x0f)
3315 == png_ptr
->trans_color
.gray
)
3317 unsigned int tmp
= *sp
& (0x0f0f >> (4 - shift
));
3318 tmp
|= png_ptr
->background
.gray
<< shift
;
3319 *sp
= (png_byte
)(tmp
& 0xff);
3324 unsigned int p
= (*sp
>> shift
) & 0x0f;
3325 unsigned int g
= (gamma_table
[p
| (p
<< 4)] >> 4) &
3327 unsigned int tmp
= *sp
& (0x0f0f >> (4 - shift
));
3329 *sp
= (png_byte
)(tmp
& 0xff);
3348 for (i
= 0; i
< row_width
; i
++)
3350 if ((png_uint_16
)((*sp
>> shift
) & 0x0f)
3351 == png_ptr
->trans_color
.gray
)
3353 unsigned int tmp
= *sp
& (0x0f0f >> (4 - shift
));
3354 tmp
|= png_ptr
->background
.gray
<< shift
;
3355 *sp
= (png_byte
)(tmp
& 0xff);
3373 #ifdef PNG_READ_GAMMA_SUPPORTED
3374 if (gamma_table
!= NULL
)
3377 for (i
= 0; i
< row_width
; i
++, sp
++)
3379 if (*sp
== png_ptr
->trans_color
.gray
)
3380 *sp
= (png_byte
)png_ptr
->background
.gray
;
3383 *sp
= gamma_table
[*sp
];
3390 for (i
= 0; i
< row_width
; i
++, sp
++)
3392 if (*sp
== png_ptr
->trans_color
.gray
)
3393 *sp
= (png_byte
)png_ptr
->background
.gray
;
3401 #ifdef PNG_READ_GAMMA_SUPPORTED
3402 if (gamma_16
!= NULL
)
3405 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3409 v
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3411 if (v
== png_ptr
->trans_color
.gray
)
3413 /* Background is already in screen gamma */
3414 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3416 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
3422 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3423 *sp
= (png_byte
)((v
>> 8) & 0xff);
3424 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3432 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3436 v
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3438 if (v
== png_ptr
->trans_color
.gray
)
3440 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3442 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
3456 case PNG_COLOR_TYPE_RGB
:
3458 if (row_info
->bit_depth
== 8)
3460 #ifdef PNG_READ_GAMMA_SUPPORTED
3461 if (gamma_table
!= NULL
)
3464 for (i
= 0; i
< row_width
; i
++, sp
+= 3)
3466 if (*sp
== png_ptr
->trans_color
.red
&&
3467 *(sp
+ 1) == png_ptr
->trans_color
.green
&&
3468 *(sp
+ 2) == png_ptr
->trans_color
.blue
)
3470 *sp
= (png_byte
)png_ptr
->background
.red
;
3471 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3472 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3477 *sp
= gamma_table
[*sp
];
3478 *(sp
+ 1) = gamma_table
[*(sp
+ 1)];
3479 *(sp
+ 2) = gamma_table
[*(sp
+ 2)];
3487 for (i
= 0; i
< row_width
; i
++, sp
+= 3)
3489 if (*sp
== png_ptr
->trans_color
.red
&&
3490 *(sp
+ 1) == png_ptr
->trans_color
.green
&&
3491 *(sp
+ 2) == png_ptr
->trans_color
.blue
)
3493 *sp
= (png_byte
)png_ptr
->background
.red
;
3494 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3495 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3500 else /* if (row_info->bit_depth == 16) */
3502 #ifdef PNG_READ_GAMMA_SUPPORTED
3503 if (gamma_16
!= NULL
)
3506 for (i
= 0; i
< row_width
; i
++, sp
+= 6)
3508 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3510 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3513 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3516 if (r
== png_ptr
->trans_color
.red
&&
3517 g
== png_ptr
->trans_color
.green
&&
3518 b
== png_ptr
->trans_color
.blue
)
3520 /* Background is already in screen gamma */
3521 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3522 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3523 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3525 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3527 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3529 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3534 png_uint_16 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3535 *sp
= (png_byte
)((v
>> 8) & 0xff);
3536 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3538 v
= gamma_16
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3539 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3540 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3542 v
= gamma_16
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3543 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3544 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3553 for (i
= 0; i
< row_width
; i
++, sp
+= 6)
3555 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3557 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3560 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3563 if (r
== png_ptr
->trans_color
.red
&&
3564 g
== png_ptr
->trans_color
.green
&&
3565 b
== png_ptr
->trans_color
.blue
)
3567 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3568 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3569 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3571 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3573 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3575 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3583 case PNG_COLOR_TYPE_GRAY_ALPHA
:
3585 if (row_info
->bit_depth
== 8)
3587 #ifdef PNG_READ_GAMMA_SUPPORTED
3588 if (gamma_to_1
!= NULL
&& gamma_from_1
!= NULL
&&
3589 gamma_table
!= NULL
)
3592 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3594 png_uint_16 a
= *(sp
+ 1);
3597 *sp
= gamma_table
[*sp
];
3601 /* Background is already in screen gamma */
3602 *sp
= (png_byte
)png_ptr
->background
.gray
;
3609 v
= gamma_to_1
[*sp
];
3610 png_composite(w
, v
, a
, png_ptr
->background_1
.gray
);
3612 w
= gamma_from_1
[w
];
3621 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3623 png_byte a
= *(sp
+ 1);
3626 *sp
= (png_byte
)png_ptr
->background
.gray
;
3629 png_composite(*sp
, *sp
, a
, png_ptr
->background
.gray
);
3633 else /* if (png_ptr->bit_depth == 16) */
3635 #ifdef PNG_READ_GAMMA_SUPPORTED
3636 if (gamma_16
!= NULL
&& gamma_16_from_1
!= NULL
&&
3637 gamma_16_to_1
!= NULL
)
3640 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3642 png_uint_16 a
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3645 if (a
== (png_uint_16
)0xffff)
3649 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3650 *sp
= (png_byte
)((v
>> 8) & 0xff);
3651 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3656 /* Background is already in screen gamma */
3657 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3659 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
& 0xff);
3664 png_uint_16 g
, v
, w
;
3666 g
= gamma_16_to_1
[*(sp
+ 1) >> gamma_shift
][*sp
];
3667 png_composite_16(v
, g
, a
, png_ptr
->background_1
.gray
);
3671 w
= gamma_16_from_1
[(v
& 0xff) >>
3672 gamma_shift
][v
>> 8];
3673 *sp
= (png_byte
)((w
>> 8) & 0xff);
3674 *(sp
+ 1) = (png_byte
)(w
& 0xff);
3682 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3684 png_uint_16 a
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3689 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3691 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
& 0xff);
3694 else if (a
< 0xffff)
3698 g
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3699 png_composite_16(v
, g
, a
, png_ptr
->background
.gray
);
3700 *sp
= (png_byte
)((v
>> 8) & 0xff);
3701 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3709 case PNG_COLOR_TYPE_RGB_ALPHA
:
3711 if (row_info
->bit_depth
== 8)
3713 #ifdef PNG_READ_GAMMA_SUPPORTED
3714 if (gamma_to_1
!= NULL
&& gamma_from_1
!= NULL
&&
3715 gamma_table
!= NULL
)
3718 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3720 png_byte a
= *(sp
+ 3);
3724 *sp
= gamma_table
[*sp
];
3725 *(sp
+ 1) = gamma_table
[*(sp
+ 1)];
3726 *(sp
+ 2) = gamma_table
[*(sp
+ 2)];
3731 /* Background is already in screen gamma */
3732 *sp
= (png_byte
)png_ptr
->background
.red
;
3733 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3734 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3741 v
= gamma_to_1
[*sp
];
3742 png_composite(w
, v
, a
, png_ptr
->background_1
.red
);
3743 if (optimize
== 0) w
= gamma_from_1
[w
];
3746 v
= gamma_to_1
[*(sp
+ 1)];
3747 png_composite(w
, v
, a
, png_ptr
->background_1
.green
);
3748 if (optimize
== 0) w
= gamma_from_1
[w
];
3751 v
= gamma_to_1
[*(sp
+ 2)];
3752 png_composite(w
, v
, a
, png_ptr
->background_1
.blue
);
3753 if (optimize
== 0) w
= gamma_from_1
[w
];
3762 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3764 png_byte a
= *(sp
+ 3);
3768 *sp
= (png_byte
)png_ptr
->background
.red
;
3769 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3770 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3775 png_composite(*sp
, *sp
, a
, png_ptr
->background
.red
);
3777 png_composite(*(sp
+ 1), *(sp
+ 1), a
,
3778 png_ptr
->background
.green
);
3780 png_composite(*(sp
+ 2), *(sp
+ 2), a
,
3781 png_ptr
->background
.blue
);
3786 else /* if (row_info->bit_depth == 16) */
3788 #ifdef PNG_READ_GAMMA_SUPPORTED
3789 if (gamma_16
!= NULL
&& gamma_16_from_1
!= NULL
&&
3790 gamma_16_to_1
!= NULL
)
3793 for (i
= 0; i
< row_width
; i
++, sp
+= 8)
3795 png_uint_16 a
= (png_uint_16
)(((png_uint_16
)(*(sp
+ 6))
3796 << 8) + (png_uint_16
)(*(sp
+ 7)));
3798 if (a
== (png_uint_16
)0xffff)
3802 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3803 *sp
= (png_byte
)((v
>> 8) & 0xff);
3804 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3806 v
= gamma_16
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3807 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3808 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3810 v
= gamma_16
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3811 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3812 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3817 /* Background is already in screen gamma */
3818 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3819 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3820 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3822 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3824 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3826 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3833 v
= gamma_16_to_1
[*(sp
+ 1) >> gamma_shift
][*sp
];
3834 png_composite_16(w
, v
, a
, png_ptr
->background_1
.red
);
3836 w
= gamma_16_from_1
[((w
& 0xff) >> gamma_shift
)][w
>>
3838 *sp
= (png_byte
)((w
>> 8) & 0xff);
3839 *(sp
+ 1) = (png_byte
)(w
& 0xff);
3841 v
= gamma_16_to_1
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3842 png_composite_16(w
, v
, a
, png_ptr
->background_1
.green
);
3844 w
= gamma_16_from_1
[((w
& 0xff) >> gamma_shift
)][w
>>
3847 *(sp
+ 2) = (png_byte
)((w
>> 8) & 0xff);
3848 *(sp
+ 3) = (png_byte
)(w
& 0xff);
3850 v
= gamma_16_to_1
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3851 png_composite_16(w
, v
, a
, png_ptr
->background_1
.blue
);
3853 w
= gamma_16_from_1
[((w
& 0xff) >> gamma_shift
)][w
>>
3856 *(sp
+ 4) = (png_byte
)((w
>> 8) & 0xff);
3857 *(sp
+ 5) = (png_byte
)(w
& 0xff);
3866 for (i
= 0; i
< row_width
; i
++, sp
+= 8)
3868 png_uint_16 a
= (png_uint_16
)(((png_uint_16
)(*(sp
+ 6))
3869 << 8) + (png_uint_16
)(*(sp
+ 7)));
3873 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3874 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3875 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3877 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3879 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3881 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3884 else if (a
< 0xffff)
3888 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3889 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3891 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3894 png_composite_16(v
, r
, a
, png_ptr
->background
.red
);
3895 *sp
= (png_byte
)((v
>> 8) & 0xff);
3896 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3898 png_composite_16(v
, g
, a
, png_ptr
->background
.green
);
3899 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3900 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3902 png_composite_16(v
, b
, a
, png_ptr
->background
.blue
);
3903 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3904 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3917 #endif /* READ_BACKGROUND || READ_ALPHA_MODE */
3919 #ifdef PNG_READ_GAMMA_SUPPORTED
3920 /* Gamma correct the image, avoiding the alpha channel. Make sure
3921 * you do this after you deal with the transparency issue on grayscale
3922 * or RGB images. If your bit depth is 8, use gamma_table, if it
3923 * is 16, use gamma_16_table and gamma_shift. Build these with
3924 * build_gamma_table().
3927 png_do_gamma(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
3929 png_const_bytep gamma_table
= png_ptr
->gamma_table
;
3930 png_const_uint_16pp gamma_16_table
= png_ptr
->gamma_16_table
;
3931 int gamma_shift
= png_ptr
->gamma_shift
;
3935 png_uint_32 row_width
=row_info
->width
;
3937 png_debug(1, "in png_do_gamma");
3939 if (((row_info
->bit_depth
<= 8 && gamma_table
!= NULL
) ||
3940 (row_info
->bit_depth
== 16 && gamma_16_table
!= NULL
)))
3942 switch (row_info
->color_type
)
3944 case PNG_COLOR_TYPE_RGB
:
3946 if (row_info
->bit_depth
== 8)
3949 for (i
= 0; i
< row_width
; i
++)
3951 *sp
= gamma_table
[*sp
];
3953 *sp
= gamma_table
[*sp
];
3955 *sp
= gamma_table
[*sp
];
3960 else /* if (row_info->bit_depth == 16) */
3963 for (i
= 0; i
< row_width
; i
++)
3967 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3968 *sp
= (png_byte
)((v
>> 8) & 0xff);
3969 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3972 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3973 *sp
= (png_byte
)((v
>> 8) & 0xff);
3974 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3977 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3978 *sp
= (png_byte
)((v
>> 8) & 0xff);
3979 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3986 case PNG_COLOR_TYPE_RGB_ALPHA
:
3988 if (row_info
->bit_depth
== 8)
3991 for (i
= 0; i
< row_width
; i
++)
3993 *sp
= gamma_table
[*sp
];
3996 *sp
= gamma_table
[*sp
];
3999 *sp
= gamma_table
[*sp
];
4006 else /* if (row_info->bit_depth == 16) */
4009 for (i
= 0; i
< row_width
; i
++)
4011 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4012 *sp
= (png_byte
)((v
>> 8) & 0xff);
4013 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4016 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4017 *sp
= (png_byte
)((v
>> 8) & 0xff);
4018 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4021 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4022 *sp
= (png_byte
)((v
>> 8) & 0xff);
4023 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4030 case PNG_COLOR_TYPE_GRAY_ALPHA
:
4032 if (row_info
->bit_depth
== 8)
4035 for (i
= 0; i
< row_width
; i
++)
4037 *sp
= gamma_table
[*sp
];
4042 else /* if (row_info->bit_depth == 16) */
4045 for (i
= 0; i
< row_width
; i
++)
4047 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4048 *sp
= (png_byte
)((v
>> 8) & 0xff);
4049 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4056 case PNG_COLOR_TYPE_GRAY
:
4058 if (row_info
->bit_depth
== 2)
4061 for (i
= 0; i
< row_width
; i
+= 4)
4069 ((((int)gamma_table
[a
|(a
>>2)|(a
>>4)|(a
>>6)]) ) & 0xc0)|
4070 ((((int)gamma_table
[(b
<<2)|b
|(b
>>2)|(b
>>4)])>>2) & 0x30)|
4071 ((((int)gamma_table
[(c
<<4)|(c
<<2)|c
|(c
>>2)])>>4) & 0x0c)|
4072 ((((int)gamma_table
[(d
<<6)|(d
<<4)|(d
<<2)|d
])>>6) ));
4077 if (row_info
->bit_depth
== 4)
4080 for (i
= 0; i
< row_width
; i
+= 2)
4082 int msb
= *sp
& 0xf0;
4083 int lsb
= *sp
& 0x0f;
4085 *sp
= (png_byte
)((((int)gamma_table
[msb
| (msb
>> 4)]) & 0xf0)
4086 | (((int)gamma_table
[(lsb
<< 4) | lsb
]) >> 4));
4091 else if (row_info
->bit_depth
== 8)
4094 for (i
= 0; i
< row_width
; i
++)
4096 *sp
= gamma_table
[*sp
];
4101 else if (row_info
->bit_depth
== 16)
4104 for (i
= 0; i
< row_width
; i
++)
4106 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4107 *sp
= (png_byte
)((v
>> 8) & 0xff);
4108 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4122 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
4123 /* Encode the alpha channel to the output gamma (the input channel is always
4124 * linear.) Called only with color types that have an alpha channel. Needs the
4128 png_do_encode_alpha(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
4130 png_uint_32 row_width
= row_info
->width
;
4132 png_debug(1, "in png_do_encode_alpha");
4134 if ((row_info
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
4136 if (row_info
->bit_depth
== 8)
4138 PNG_CONST png_bytep table
= png_ptr
->gamma_from_1
;
4142 PNG_CONST
int step
=
4143 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) ? 4 : 2;
4145 /* The alpha channel is the last component: */
4148 for (; row_width
> 0; --row_width
, row
+= step
)
4155 else if (row_info
->bit_depth
== 16)
4157 PNG_CONST png_uint_16pp table
= png_ptr
->gamma_16_from_1
;
4158 PNG_CONST
int gamma_shift
= png_ptr
->gamma_shift
;
4162 PNG_CONST
int step
=
4163 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) ? 8 : 4;
4165 /* The alpha channel is the last component: */
4168 for (; row_width
> 0; --row_width
, row
+= step
)
4172 v
= table
[*(row
+ 1) >> gamma_shift
][*row
];
4173 *row
= (png_byte
)((v
>> 8) & 0xff);
4174 *(row
+ 1) = (png_byte
)(v
& 0xff);
4182 /* Only get to here if called with a weird row_info; no harm has been done,
4183 * so just issue a warning.
4185 png_warning(png_ptr
, "png_do_encode_alpha: unexpected call");
4189 #ifdef PNG_READ_EXPAND_SUPPORTED
4190 /* Expands a palette row to an RGB or RGBA row depending
4191 * upon whether you supply trans and num_trans.
4194 png_do_expand_palette(png_row_infop row_info
, png_bytep row
,
4195 png_const_colorp palette
, png_const_bytep trans_alpha
, int num_trans
)
4200 png_uint_32 row_width
=row_info
->width
;
4202 png_debug(1, "in png_do_expand_palette");
4204 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
)
4206 if (row_info
->bit_depth
< 8)
4208 switch (row_info
->bit_depth
)
4212 sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
4213 dp
= row
+ (png_size_t
)row_width
- 1;
4214 shift
= 7 - (int)((row_width
+ 7) & 0x07);
4215 for (i
= 0; i
< row_width
; i
++)
4217 if ((*sp
>> shift
) & 0x01)
4239 sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
4240 dp
= row
+ (png_size_t
)row_width
- 1;
4241 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
4242 for (i
= 0; i
< row_width
; i
++)
4244 value
= (*sp
>> shift
) & 0x03;
4245 *dp
= (png_byte
)value
;
4262 sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
4263 dp
= row
+ (png_size_t
)row_width
- 1;
4264 shift
= (int)((row_width
& 0x01) << 2);
4265 for (i
= 0; i
< row_width
; i
++)
4267 value
= (*sp
>> shift
) & 0x0f;
4268 *dp
= (png_byte
)value
;
4286 row_info
->bit_depth
= 8;
4287 row_info
->pixel_depth
= 8;
4288 row_info
->rowbytes
= row_width
;
4291 if (row_info
->bit_depth
== 8)
4296 sp
= row
+ (png_size_t
)row_width
- 1;
4297 dp
= row
+ (png_size_t
)(row_width
<< 2) - 1;
4299 for (i
= 0; i
< row_width
; i
++)
4301 if ((int)(*sp
) >= num_trans
)
4305 *dp
-- = trans_alpha
[*sp
];
4307 *dp
-- = palette
[*sp
].blue
;
4308 *dp
-- = palette
[*sp
].green
;
4309 *dp
-- = palette
[*sp
].red
;
4312 row_info
->bit_depth
= 8;
4313 row_info
->pixel_depth
= 32;
4314 row_info
->rowbytes
= row_width
* 4;
4315 row_info
->color_type
= 6;
4316 row_info
->channels
= 4;
4321 sp
= row
+ (png_size_t
)row_width
- 1;
4322 dp
= row
+ (png_size_t
)(row_width
* 3) - 1;
4324 for (i
= 0; i
< row_width
; i
++)
4326 *dp
-- = palette
[*sp
].blue
;
4327 *dp
-- = palette
[*sp
].green
;
4328 *dp
-- = palette
[*sp
].red
;
4332 row_info
->bit_depth
= 8;
4333 row_info
->pixel_depth
= 24;
4334 row_info
->rowbytes
= row_width
* 3;
4335 row_info
->color_type
= 2;
4336 row_info
->channels
= 3;
4343 /* If the bit depth < 8, it is expanded to 8. Also, if the already
4344 * expanded transparency value is supplied, an alpha channel is built.
4347 png_do_expand(png_row_infop row_info
, png_bytep row
,
4348 png_const_color_16p trans_color
)
4353 png_uint_32 row_width
=row_info
->width
;
4355 png_debug(1, "in png_do_expand");
4358 if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
4360 unsigned int gray
= trans_color
!= NULL
? trans_color
->gray
: 0;
4362 if (row_info
->bit_depth
< 8)
4364 switch (row_info
->bit_depth
)
4368 gray
= (gray
& 0x01) * 0xff;
4369 sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
4370 dp
= row
+ (png_size_t
)row_width
- 1;
4371 shift
= 7 - (int)((row_width
+ 7) & 0x07);
4372 for (i
= 0; i
< row_width
; i
++)
4374 if ((*sp
>> shift
) & 0x01)
4396 gray
= (gray
& 0x03) * 0x55;
4397 sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
4398 dp
= row
+ (png_size_t
)row_width
- 1;
4399 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
4400 for (i
= 0; i
< row_width
; i
++)
4402 value
= (*sp
>> shift
) & 0x03;
4403 *dp
= (png_byte
)(value
| (value
<< 2) | (value
<< 4) |
4421 gray
= (gray
& 0x0f) * 0x11;
4422 sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
4423 dp
= row
+ (png_size_t
)row_width
- 1;
4424 shift
= (int)((1 - ((row_width
+ 1) & 0x01)) << 2);
4425 for (i
= 0; i
< row_width
; i
++)
4427 value
= (*sp
>> shift
) & 0x0f;
4428 *dp
= (png_byte
)(value
| (value
<< 4));
4447 row_info
->bit_depth
= 8;
4448 row_info
->pixel_depth
= 8;
4449 row_info
->rowbytes
= row_width
;
4452 if (trans_color
!= NULL
)
4454 if (row_info
->bit_depth
== 8)
4457 sp
= row
+ (png_size_t
)row_width
- 1;
4458 dp
= row
+ (png_size_t
)(row_width
<< 1) - 1;
4460 for (i
= 0; i
< row_width
; i
++)
4462 if ((*sp
& 0xffU
) == gray
)
4472 else if (row_info
->bit_depth
== 16)
4474 unsigned int gray_high
= (gray
>> 8) & 0xff;
4475 unsigned int gray_low
= gray
& 0xff;
4476 sp
= row
+ row_info
->rowbytes
- 1;
4477 dp
= row
+ (row_info
->rowbytes
<< 1) - 1;
4478 for (i
= 0; i
< row_width
; i
++)
4480 if ((*(sp
- 1) & 0xffU
) == gray_high
&&
4481 (*(sp
) & 0xffU
) == gray_low
)
4498 row_info
->color_type
= PNG_COLOR_TYPE_GRAY_ALPHA
;
4499 row_info
->channels
= 2;
4500 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
<< 1);
4501 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
,
4505 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
&&
4506 trans_color
!= NULL
)
4508 if (row_info
->bit_depth
== 8)
4510 png_byte red
= (png_byte
)(trans_color
->red
& 0xff);
4511 png_byte green
= (png_byte
)(trans_color
->green
& 0xff);
4512 png_byte blue
= (png_byte
)(trans_color
->blue
& 0xff);
4513 sp
= row
+ (png_size_t
)row_info
->rowbytes
- 1;
4514 dp
= row
+ (png_size_t
)(row_width
<< 2) - 1;
4515 for (i
= 0; i
< row_width
; i
++)
4517 if (*(sp
- 2) == red
&& *(sp
- 1) == green
&& *(sp
) == blue
)
4528 else if (row_info
->bit_depth
== 16)
4530 png_byte red_high
= (png_byte
)((trans_color
->red
>> 8) & 0xff);
4531 png_byte green_high
= (png_byte
)((trans_color
->green
>> 8) & 0xff);
4532 png_byte blue_high
= (png_byte
)((trans_color
->blue
>> 8) & 0xff);
4533 png_byte red_low
= (png_byte
)(trans_color
->red
& 0xff);
4534 png_byte green_low
= (png_byte
)(trans_color
->green
& 0xff);
4535 png_byte blue_low
= (png_byte
)(trans_color
->blue
& 0xff);
4536 sp
= row
+ row_info
->rowbytes
- 1;
4537 dp
= row
+ (png_size_t
)(row_width
<< 3) - 1;
4538 for (i
= 0; i
< row_width
; i
++)
4540 if (*(sp
- 5) == red_high
&&
4541 *(sp
- 4) == red_low
&&
4542 *(sp
- 3) == green_high
&&
4543 *(sp
- 2) == green_low
&&
4544 *(sp
- 1) == blue_high
&&
4565 row_info
->color_type
= PNG_COLOR_TYPE_RGB_ALPHA
;
4566 row_info
->channels
= 4;
4567 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
<< 2);
4568 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4574 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4575 /* If the bit depth is 8 and the color type is not a palette type expand the
4576 * whole row to 16 bits. Has no effect otherwise.
4579 png_do_expand_16(png_row_infop row_info
, png_bytep row
)
4581 if (row_info
->bit_depth
== 8 &&
4582 row_info
->color_type
!= PNG_COLOR_TYPE_PALETTE
)
4584 /* The row have a sequence of bytes containing [0..255] and we need
4585 * to turn it into another row containing [0..65535], to do this we
4588 * (input / 255) * 65535
4590 * Which happens to be exactly input * 257 and this can be achieved
4591 * simply by byte replication in place (copying backwards).
4593 png_byte
*sp
= row
+ row_info
->rowbytes
; /* source, last byte + 1 */
4594 png_byte
*dp
= sp
+ row_info
->rowbytes
; /* destination, end + 1 */
4596 dp
[-2] = dp
[-1] = *--sp
, dp
-= 2;
4598 row_info
->rowbytes
*= 2;
4599 row_info
->bit_depth
= 16;
4600 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
* 16);
4605 #ifdef PNG_READ_QUANTIZE_SUPPORTED
4607 png_do_quantize(png_row_infop row_info
, png_bytep row
,
4608 png_const_bytep palette_lookup
, png_const_bytep quantize_lookup
)
4612 png_uint_32 row_width
=row_info
->width
;
4614 png_debug(1, "in png_do_quantize");
4616 if (row_info
->bit_depth
== 8)
4618 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
&& palette_lookup
)
4623 for (i
= 0; i
< row_width
; i
++)
4629 /* This looks real messy, but the compiler will reduce
4630 * it down to a reasonable formula. For example, with
4631 * 5 bits per color, we get:
4632 * p = (((r >> 3) & 0x1f) << 10) |
4633 * (((g >> 3) & 0x1f) << 5) |
4634 * ((b >> 3) & 0x1f);
4636 p
= (((r
>> (8 - PNG_QUANTIZE_RED_BITS
)) &
4637 ((1 << PNG_QUANTIZE_RED_BITS
) - 1)) <<
4638 (PNG_QUANTIZE_GREEN_BITS
+ PNG_QUANTIZE_BLUE_BITS
)) |
4639 (((g
>> (8 - PNG_QUANTIZE_GREEN_BITS
)) &
4640 ((1 << PNG_QUANTIZE_GREEN_BITS
) - 1)) <<
4641 (PNG_QUANTIZE_BLUE_BITS
)) |
4642 ((b
>> (8 - PNG_QUANTIZE_BLUE_BITS
)) &
4643 ((1 << PNG_QUANTIZE_BLUE_BITS
) - 1));
4645 *dp
++ = palette_lookup
[p
];
4648 row_info
->color_type
= PNG_COLOR_TYPE_PALETTE
;
4649 row_info
->channels
= 1;
4650 row_info
->pixel_depth
= row_info
->bit_depth
;
4651 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4654 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
&&
4655 palette_lookup
!= NULL
)
4660 for (i
= 0; i
< row_width
; i
++)
4667 p
= (((r
>> (8 - PNG_QUANTIZE_RED_BITS
)) &
4668 ((1 << PNG_QUANTIZE_RED_BITS
) - 1)) <<
4669 (PNG_QUANTIZE_GREEN_BITS
+ PNG_QUANTIZE_BLUE_BITS
)) |
4670 (((g
>> (8 - PNG_QUANTIZE_GREEN_BITS
)) &
4671 ((1 << PNG_QUANTIZE_GREEN_BITS
) - 1)) <<
4672 (PNG_QUANTIZE_BLUE_BITS
)) |
4673 ((b
>> (8 - PNG_QUANTIZE_BLUE_BITS
)) &
4674 ((1 << PNG_QUANTIZE_BLUE_BITS
) - 1));
4676 *dp
++ = palette_lookup
[p
];
4679 row_info
->color_type
= PNG_COLOR_TYPE_PALETTE
;
4680 row_info
->channels
= 1;
4681 row_info
->pixel_depth
= row_info
->bit_depth
;
4682 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4685 else if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
4690 for (i
= 0; i
< row_width
; i
++, sp
++)
4692 *sp
= quantize_lookup
[*sp
];
4697 #endif /* READ_QUANTIZE */
4699 /* Transform the row. The order of transformations is significant,
4700 * and is very touchy. If you add a transformation, take care to
4701 * decide how it fits in with the other transformations here.
4704 png_do_read_transformations(png_structrp png_ptr
, png_row_infop row_info
)
4706 png_debug(1, "in png_do_read_transformations");
4708 if (png_ptr
->row_buf
== NULL
)
4710 /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
4711 * error is incredibly rare and incredibly easy to debug without this
4714 png_error(png_ptr
, "NULL row buffer");
4717 /* The following is debugging; prior to 1.5.4 the code was never compiled in;
4718 * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
4719 * PNG_WARN_UNINITIALIZED_ROW removed. In 1.6 the new flag is set only for
4720 * all transformations, however in practice the ROW_INIT always gets done on
4721 * demand, if necessary.
4723 if ((png_ptr
->flags
& PNG_FLAG_DETECT_UNINITIALIZED
) != 0 &&
4724 (png_ptr
->flags
& PNG_FLAG_ROW_INIT
) == 0)
4726 /* Application has failed to call either png_read_start_image() or
4727 * png_read_update_info() after setting transforms that expand pixels.
4728 * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
4730 png_error(png_ptr
, "Uninitialized row");
4733 #ifdef PNG_READ_EXPAND_SUPPORTED
4734 if ((png_ptr
->transformations
& PNG_EXPAND
) != 0)
4736 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
)
4738 png_do_expand_palette(row_info
, png_ptr
->row_buf
+ 1,
4739 png_ptr
->palette
, png_ptr
->trans_alpha
, png_ptr
->num_trans
);
4744 if (png_ptr
->num_trans
!= 0 &&
4745 (png_ptr
->transformations
& PNG_EXPAND_tRNS
) != 0)
4746 png_do_expand(row_info
, png_ptr
->row_buf
+ 1,
4747 &(png_ptr
->trans_color
));
4750 png_do_expand(row_info
, png_ptr
->row_buf
+ 1,
4756 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
4757 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) != 0 &&
4758 (png_ptr
->transformations
& PNG_COMPOSE
) == 0 &&
4759 (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
4760 row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
))
4761 png_do_strip_channel(row_info
, png_ptr
->row_buf
+ 1,
4762 0 /* at_start == false, because SWAP_ALPHA happens later */);
4765 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
4766 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) != 0)
4769 png_do_rgb_to_gray(png_ptr
, row_info
,
4770 png_ptr
->row_buf
+ 1);
4774 png_ptr
->rgb_to_gray_status
=1;
4775 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) ==
4776 PNG_RGB_TO_GRAY_WARN
)
4777 png_warning(png_ptr
, "png_do_rgb_to_gray found nongray pixel");
4779 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) ==
4780 PNG_RGB_TO_GRAY_ERR
)
4781 png_error(png_ptr
, "png_do_rgb_to_gray found nongray pixel");
4786 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
4788 * In most cases, the "simple transparency" should be done prior to doing
4789 * gray-to-RGB, or you will have to test 3x as many bytes to check if a
4790 * pixel is transparent. You would also need to make sure that the
4791 * transparency information is upgraded to RGB.
4793 * To summarize, the current flow is:
4794 * - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
4795 * with background "in place" if transparent,
4796 * convert to RGB if necessary
4797 * - Gray + alpha -> composite with gray background and remove alpha bytes,
4798 * convert to RGB if necessary
4800 * To support RGB backgrounds for gray images we need:
4801 * - Gray + simple transparency -> convert to RGB + simple transparency,
4802 * compare 3 or 6 bytes and composite with
4803 * background "in place" if transparent
4804 * (3x compare/pixel compared to doing
4805 * composite with gray bkgrnd)
4806 * - Gray + alpha -> convert to RGB + alpha, composite with background and
4807 * remove alpha bytes (3x float
4808 * operations/pixel compared with composite
4809 * on gray background)
4811 * Greg's change will do this. The reason it wasn't done before is for
4812 * performance, as this increases the per-pixel operations. If we would check
4813 * in advance if the background was gray or RGB, and position the gray-to-RGB
4814 * transform appropriately, then it would save a lot of work/time.
4817 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4818 /* If gray -> RGB, do so now only if background is non-gray; else do later
4819 * for performance reasons
4821 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) != 0 &&
4822 (png_ptr
->mode
& PNG_BACKGROUND_IS_GRAY
) == 0)
4823 png_do_gray_to_rgb(row_info
, png_ptr
->row_buf
+ 1);
4826 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
4827 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
4828 if ((png_ptr
->transformations
& PNG_COMPOSE
) != 0)
4829 png_do_compose(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4832 #ifdef PNG_READ_GAMMA_SUPPORTED
4833 if ((png_ptr
->transformations
& PNG_GAMMA
) != 0 &&
4834 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
4835 /* Because RGB_TO_GRAY does the gamma transform. */
4836 (png_ptr
->transformations
& PNG_RGB_TO_GRAY
) == 0 &&
4838 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
4839 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
4840 /* Because PNG_COMPOSE does the gamma transform if there is something to
4841 * do (if there is an alpha channel or transparency.)
4843 !((png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
4844 ((png_ptr
->num_trans
!= 0) ||
4845 (png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)) &&
4847 /* Because png_init_read_transformations transforms the palette, unless
4848 * RGB_TO_GRAY will do the transform.
4850 (png_ptr
->color_type
!= PNG_COLOR_TYPE_PALETTE
))
4851 png_do_gamma(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4854 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
4855 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) != 0 &&
4856 (png_ptr
->transformations
& PNG_COMPOSE
) != 0 &&
4857 (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
4858 row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
))
4859 png_do_strip_channel(row_info
, png_ptr
->row_buf
+ 1,
4860 0 /* at_start == false, because SWAP_ALPHA happens later */);
4863 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
4864 if ((png_ptr
->transformations
& PNG_ENCODE_ALPHA
) != 0 &&
4865 (row_info
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0)
4866 png_do_encode_alpha(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4869 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
4870 if ((png_ptr
->transformations
& PNG_SCALE_16_TO_8
) != 0)
4871 png_do_scale_16_to_8(row_info
, png_ptr
->row_buf
+ 1);
4874 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
4875 /* There is no harm in doing both of these because only one has any effect,
4876 * by putting the 'scale' option first if the app asks for scale (either by
4877 * calling the API or in a TRANSFORM flag) this is what happens.
4879 if ((png_ptr
->transformations
& PNG_16_TO_8
) != 0)
4880 png_do_chop(row_info
, png_ptr
->row_buf
+ 1);
4883 #ifdef PNG_READ_QUANTIZE_SUPPORTED
4884 if ((png_ptr
->transformations
& PNG_QUANTIZE
) != 0)
4886 png_do_quantize(row_info
, png_ptr
->row_buf
+ 1,
4887 png_ptr
->palette_lookup
, png_ptr
->quantize_index
);
4889 if (row_info
->rowbytes
== 0)
4890 png_error(png_ptr
, "png_do_quantize returned rowbytes=0");
4892 #endif /* READ_QUANTIZE */
4894 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4895 /* Do the expansion now, after all the arithmetic has been done. Notice
4896 * that previous transformations can handle the PNG_EXPAND_16 flag if this
4897 * is efficient (particularly true in the case of gamma correction, where
4898 * better accuracy results faster!)
4900 if ((png_ptr
->transformations
& PNG_EXPAND_16
) != 0)
4901 png_do_expand_16(row_info
, png_ptr
->row_buf
+ 1);
4904 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4905 /* NOTE: moved here in 1.5.4 (from much later in this list.) */
4906 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) != 0 &&
4907 (png_ptr
->mode
& PNG_BACKGROUND_IS_GRAY
) != 0)
4908 png_do_gray_to_rgb(row_info
, png_ptr
->row_buf
+ 1);
4911 #ifdef PNG_READ_INVERT_SUPPORTED
4912 if ((png_ptr
->transformations
& PNG_INVERT_MONO
) != 0)
4913 png_do_invert(row_info
, png_ptr
->row_buf
+ 1);
4916 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
4917 if ((png_ptr
->transformations
& PNG_INVERT_ALPHA
) != 0)
4918 png_do_read_invert_alpha(row_info
, png_ptr
->row_buf
+ 1);
4921 #ifdef PNG_READ_SHIFT_SUPPORTED
4922 if ((png_ptr
->transformations
& PNG_SHIFT
) != 0)
4923 png_do_unshift(row_info
, png_ptr
->row_buf
+ 1,
4927 #ifdef PNG_READ_PACK_SUPPORTED
4928 if ((png_ptr
->transformations
& PNG_PACK
) != 0)
4929 png_do_unpack(row_info
, png_ptr
->row_buf
+ 1);
4932 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
4933 /* Added at libpng-1.5.10 */
4934 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
4935 png_ptr
->num_palette_max
>= 0)
4936 png_do_check_palette_indexes(png_ptr
, row_info
);
4939 #ifdef PNG_READ_BGR_SUPPORTED
4940 if ((png_ptr
->transformations
& PNG_BGR
) != 0)
4941 png_do_bgr(row_info
, png_ptr
->row_buf
+ 1);
4944 #ifdef PNG_READ_PACKSWAP_SUPPORTED
4945 if ((png_ptr
->transformations
& PNG_PACKSWAP
) != 0)
4946 png_do_packswap(row_info
, png_ptr
->row_buf
+ 1);
4949 #ifdef PNG_READ_FILLER_SUPPORTED
4950 if ((png_ptr
->transformations
& PNG_FILLER
) != 0)
4951 png_do_read_filler(row_info
, png_ptr
->row_buf
+ 1,
4952 (png_uint_32
)png_ptr
->filler
, png_ptr
->flags
);
4955 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
4956 if ((png_ptr
->transformations
& PNG_SWAP_ALPHA
) != 0)
4957 png_do_read_swap_alpha(row_info
, png_ptr
->row_buf
+ 1);
4960 #ifdef PNG_READ_16BIT_SUPPORTED
4961 #ifdef PNG_READ_SWAP_SUPPORTED
4962 if ((png_ptr
->transformations
& PNG_SWAP_BYTES
) != 0)
4963 png_do_swap(row_info
, png_ptr
->row_buf
+ 1);
4967 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
4968 if ((png_ptr
->transformations
& PNG_USER_TRANSFORM
) != 0)
4970 if (png_ptr
->read_user_transform_fn
!= NULL
)
4971 (*(png_ptr
->read_user_transform_fn
)) /* User read transform function */
4972 (png_ptr
, /* png_ptr */
4973 row_info
, /* row_info: */
4974 /* png_uint_32 width; width of row */
4975 /* png_size_t rowbytes; number of bytes in row */
4976 /* png_byte color_type; color type of pixels */
4977 /* png_byte bit_depth; bit depth of samples */
4978 /* png_byte channels; number of channels (1-4) */
4979 /* png_byte pixel_depth; bits per pixel (depth*channels) */
4980 png_ptr
->row_buf
+ 1); /* start of pixel data for row */
4981 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
4982 if (png_ptr
->user_transform_depth
!= 0)
4983 row_info
->bit_depth
= png_ptr
->user_transform_depth
;
4985 if (png_ptr
->user_transform_channels
!= 0)
4986 row_info
->channels
= png_ptr
->user_transform_channels
;
4988 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
*
4989 row_info
->channels
);
4991 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_info
->width
);
4996 #endif /* READ_TRANSFORMS */