[LIBPNG]
[reactos.git] / reactos / dll / 3rdparty / libpng / pngrtran.c
1
2 /* pngrtran.c - transforms the data in a row for PNG readers
3 *
4 * Last changed in libpng 1.6.24 [August 4, 2016]
5 * Copyright (c) 1998-2002,2004,2006-2016 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.)
8 *
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
12 *
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
16 * in pngtrans.c.
17 */
18
19 #include "pngpriv.h"
20
21 #ifdef PNG_READ_SUPPORTED
22
23 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
24 void PNGAPI
25 png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
26 {
27 png_debug(1, "in png_set_crc_action");
28
29 if (png_ptr == NULL)
30 return;
31
32 /* Tell libpng how we react to CRC errors in critical chunks */
33 switch (crit_action)
34 {
35 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
36 break;
37
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;
41 break;
42
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;
47 break;
48
49 case PNG_CRC_WARN_DISCARD: /* Not a valid action for critical data */
50 png_warning(png_ptr,
51 "Can't discard critical data on CRC error");
52 case PNG_CRC_ERROR_QUIT: /* Error/quit */
53
54 case PNG_CRC_DEFAULT:
55 default:
56 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
57 break;
58 }
59
60 /* Tell libpng how we react to CRC errors in ancillary chunks */
61 switch (ancil_action)
62 {
63 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
64 break;
65
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;
69 break;
70
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;
75 break;
76
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;
80 break;
81
82 case PNG_CRC_WARN_DISCARD: /* Warn/discard data */
83
84 case PNG_CRC_DEFAULT:
85 default:
86 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
87 break;
88 }
89 }
90
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
95 * check too.
96 */
97 static int
98 png_rtran_ok(png_structrp png_ptr, int need_IHDR)
99 {
100 if (png_ptr != NULL)
101 {
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");
105
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");
108
109 else
110 {
111 /* Turn on failure to initialize correctly for all transforms. */
112 png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
113
114 return 1; /* Ok */
115 }
116 }
117
118 return 0; /* no png_error possible! */
119 }
120 #endif
121
122 #ifdef PNG_READ_BACKGROUND_SUPPORTED
123 /* Handle alpha and tRNS via a background color */
124 void PNGFAPI
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)
128 {
129 png_debug(1, "in png_set_background_fixed");
130
131 if (png_rtran_ok(png_ptr, 0) == 0 || background_color == NULL)
132 return;
133
134 if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
135 {
136 png_warning(png_ptr, "Application must supply a known background gamma");
137 return;
138 }
139
140 png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
141 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
142 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
143
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;
149 else
150 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
151 }
152
153 # ifdef PNG_FLOATING_POINT_SUPPORTED
154 void PNGAPI
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)
158 {
159 png_set_background_fixed(png_ptr, background_color, background_gamma_code,
160 need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
161 }
162 # endif /* FLOATING_POINT */
163 #endif /* READ_BACKGROUND */
164
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.
168 */
169 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
170 void PNGAPI
171 png_set_scale_16(png_structrp png_ptr)
172 {
173 png_debug(1, "in png_set_scale_16");
174
175 if (png_rtran_ok(png_ptr, 0) == 0)
176 return;
177
178 png_ptr->transformations |= PNG_SCALE_16_TO_8;
179 }
180 #endif
181
182 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
183 /* Chop 16-bit depth files to 8-bit depth */
184 void PNGAPI
185 png_set_strip_16(png_structrp png_ptr)
186 {
187 png_debug(1, "in png_set_strip_16");
188
189 if (png_rtran_ok(png_ptr, 0) == 0)
190 return;
191
192 png_ptr->transformations |= PNG_16_TO_8;
193 }
194 #endif
195
196 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
197 void PNGAPI
198 png_set_strip_alpha(png_structrp png_ptr)
199 {
200 png_debug(1, "in png_set_strip_alpha");
201
202 if (png_rtran_ok(png_ptr, 0) == 0)
203 return;
204
205 png_ptr->transformations |= PNG_STRIP_ALPHA;
206 }
207 #endif
208
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,
212 int is_screen)
213 {
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!
218 */
219 if (output_gamma == PNG_DEFAULT_sRGB ||
220 output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
221 {
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!)
224 */
225 # ifdef PNG_READ_sRGB_SUPPORTED
226 png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
227 # else
228 PNG_UNUSED(png_ptr)
229 # endif
230 if (is_screen != 0)
231 output_gamma = PNG_GAMMA_sRGB;
232 else
233 output_gamma = PNG_GAMMA_sRGB_INVERSE;
234 }
235
236 else if (output_gamma == PNG_GAMMA_MAC_18 ||
237 output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
238 {
239 if (is_screen != 0)
240 output_gamma = PNG_GAMMA_MAC_OLD;
241 else
242 output_gamma = PNG_GAMMA_MAC_INVERSE;
243 }
244
245 return output_gamma;
246 }
247
248 # ifdef PNG_FLOATING_POINT_SUPPORTED
249 static png_fixed_point
250 convert_gamma_value(png_structrp png_ptr, double output_gamma)
251 {
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.
258 */
259 if (output_gamma > 0 && output_gamma < 128)
260 output_gamma *= PNG_FP_1;
261
262 /* This preserves -1 and -2 exactly: */
263 output_gamma = floor(output_gamma + .5);
264
265 if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
266 png_fixed_error(png_ptr, "gamma value");
267
268 return (png_fixed_point)output_gamma;
269 }
270 # endif
271 #endif /* READ_ALPHA_MODE || READ_GAMMA */
272
273 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
274 void PNGFAPI
275 png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
276 png_fixed_point output_gamma)
277 {
278 int compose = 0;
279 png_fixed_point file_gamma;
280
281 png_debug(1, "in png_set_alpha_mode");
282
283 if (png_rtran_ok(png_ptr, 0) == 0)
284 return;
285
286 output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
287
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:
293 *
294 * 1.6.x: changed from 0.07..3 to 0.01..100 (to accomodate the optimal 16-bit
295 * gamma of 36, and its reciprocal.)
296 */
297 if (output_gamma < 1000 || output_gamma > 10000000)
298 png_error(png_ptr, "output gamma out of expected range");
299
300 /* The default file gamma is the inverse of the output gamma; the output
301 * gamma may be changed below so get the file value first:
302 */
303 file_gamma = png_reciprocal(output_gamma);
304
305 /* There are really 8 possibilities here, composed of any combination
306 * of:
307 *
308 * premultiply the color channels
309 * do not encode non-opaque pixels
310 * encode the alpha as well as the color channels
311 *
312 * The differences disappear if the input/output ('screen') gamma is 1.0,
313 * because then the encoding is a no-op and there is only the choice of
314 * premultiplying the color channels or not.
315 *
316 * png_set_alpha_mode and png_set_background interact because both use
317 * png_compose to do the work. Calling both is only useful when
318 * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
319 * with a default gamma value. Otherwise PNG_COMPOSE must not be set.
320 */
321 switch (mode)
322 {
323 case PNG_ALPHA_PNG: /* default: png standard */
324 /* No compose, but it may be set by png_set_background! */
325 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
326 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
327 break;
328
329 case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
330 compose = 1;
331 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
332 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
333 /* The output is linear: */
334 output_gamma = PNG_FP_1;
335 break;
336
337 case PNG_ALPHA_OPTIMIZED: /* associated, non-opaque pixels linear */
338 compose = 1;
339 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
340 png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
341 /* output_gamma records the encoding of opaque pixels! */
342 break;
343
344 case PNG_ALPHA_BROKEN: /* associated, non-linear, alpha encoded */
345 compose = 1;
346 png_ptr->transformations |= PNG_ENCODE_ALPHA;
347 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
348 break;
349
350 default:
351 png_error(png_ptr, "invalid alpha mode");
352 }
353
354 /* Only set the default gamma if the file gamma has not been set (this has
355 * the side effect that the gamma in a second call to png_set_alpha_mode will
356 * be ignored.)
357 */
358 if (png_ptr->colorspace.gamma == 0)
359 {
360 png_ptr->colorspace.gamma = file_gamma;
361 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
362 }
363
364 /* But always set the output gamma: */
365 png_ptr->screen_gamma = output_gamma;
366
367 /* Finally, if pre-multiplying, set the background fields to achieve the
368 * desired result.
369 */
370 if (compose != 0)
371 {
372 /* And obtain alpha pre-multiplication by composing on black: */
373 memset(&png_ptr->background, 0, (sizeof png_ptr->background));
374 png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */
375 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
376 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
377
378 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
379 png_error(png_ptr,
380 "conflicting calls to set alpha mode and background");
381
382 png_ptr->transformations |= PNG_COMPOSE;
383 }
384 }
385
386 # ifdef PNG_FLOATING_POINT_SUPPORTED
387 void PNGAPI
388 png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
389 {
390 png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
391 output_gamma));
392 }
393 # endif
394 #endif
395
396 #ifdef PNG_READ_QUANTIZE_SUPPORTED
397 /* Dither file to 8-bit. Supply a palette, the current number
398 * of elements in the palette, the maximum number of elements
399 * allowed, and a histogram if possible. If the current number
400 * of colors is greater than the maximum number, the palette will be
401 * modified to fit in the maximum number. "full_quantize" indicates
402 * whether we need a quantizing cube set up for RGB images, or if we
403 * simply are reducing the number of colors in a paletted image.
404 */
405
406 typedef struct png_dsort_struct
407 {
408 struct png_dsort_struct * next;
409 png_byte left;
410 png_byte right;
411 } png_dsort;
412 typedef png_dsort * png_dsortp;
413 typedef png_dsort * * png_dsortpp;
414
415 void PNGAPI
416 png_set_quantize(png_structrp png_ptr, png_colorp palette,
417 int num_palette, int maximum_colors, png_const_uint_16p histogram,
418 int full_quantize)
419 {
420 png_debug(1, "in png_set_quantize");
421
422 if (png_rtran_ok(png_ptr, 0) == 0)
423 return;
424
425 png_ptr->transformations |= PNG_QUANTIZE;
426
427 if (full_quantize == 0)
428 {
429 int i;
430
431 png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
432 (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
433 for (i = 0; i < num_palette; i++)
434 png_ptr->quantize_index[i] = (png_byte)i;
435 }
436
437 if (num_palette > maximum_colors)
438 {
439 if (histogram != NULL)
440 {
441 /* This is easy enough, just throw out the least used colors.
442 * Perhaps not the best solution, but good enough.
443 */
444
445 int i;
446
447 /* Initialize an array to sort colors */
448 png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
449 (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
450
451 /* Initialize the quantize_sort array */
452 for (i = 0; i < num_palette; i++)
453 png_ptr->quantize_sort[i] = (png_byte)i;
454
455 /* Find the least used palette entries by starting a
456 * bubble sort, and running it until we have sorted
457 * out enough colors. Note that we don't care about
458 * sorting all the colors, just finding which are
459 * least used.
460 */
461
462 for (i = num_palette - 1; i >= maximum_colors; i--)
463 {
464 int done; /* To stop early if the list is pre-sorted */
465 int j;
466
467 done = 1;
468 for (j = 0; j < i; j++)
469 {
470 if (histogram[png_ptr->quantize_sort[j]]
471 < histogram[png_ptr->quantize_sort[j + 1]])
472 {
473 png_byte t;
474
475 t = png_ptr->quantize_sort[j];
476 png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
477 png_ptr->quantize_sort[j + 1] = t;
478 done = 0;
479 }
480 }
481
482 if (done != 0)
483 break;
484 }
485
486 /* Swap the palette around, and set up a table, if necessary */
487 if (full_quantize != 0)
488 {
489 int j = num_palette;
490
491 /* Put all the useful colors within the max, but don't
492 * move the others.
493 */
494 for (i = 0; i < maximum_colors; i++)
495 {
496 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
497 {
498 do
499 j--;
500 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
501
502 palette[i] = palette[j];
503 }
504 }
505 }
506 else
507 {
508 int j = num_palette;
509
510 /* Move all the used colors inside the max limit, and
511 * develop a translation table.
512 */
513 for (i = 0; i < maximum_colors; i++)
514 {
515 /* Only move the colors we need to */
516 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
517 {
518 png_color tmp_color;
519
520 do
521 j--;
522 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
523
524 tmp_color = palette[j];
525 palette[j] = palette[i];
526 palette[i] = tmp_color;
527 /* Indicate where the color went */
528 png_ptr->quantize_index[j] = (png_byte)i;
529 png_ptr->quantize_index[i] = (png_byte)j;
530 }
531 }
532
533 /* Find closest color for those colors we are not using */
534 for (i = 0; i < num_palette; i++)
535 {
536 if ((int)png_ptr->quantize_index[i] >= maximum_colors)
537 {
538 int min_d, k, min_k, d_index;
539
540 /* Find the closest color to one we threw out */
541 d_index = png_ptr->quantize_index[i];
542 min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
543 for (k = 1, min_k = 0; k < maximum_colors; k++)
544 {
545 int d;
546
547 d = PNG_COLOR_DIST(palette[d_index], palette[k]);
548
549 if (d < min_d)
550 {
551 min_d = d;
552 min_k = k;
553 }
554 }
555 /* Point to closest color */
556 png_ptr->quantize_index[i] = (png_byte)min_k;
557 }
558 }
559 }
560 png_free(png_ptr, png_ptr->quantize_sort);
561 png_ptr->quantize_sort = NULL;
562 }
563 else
564 {
565 /* This is much harder to do simply (and quickly). Perhaps
566 * we need to go through a median cut routine, but those
567 * don't always behave themselves with only a few colors
568 * as input. So we will just find the closest two colors,
569 * and throw out one of them (chosen somewhat randomly).
570 * [We don't understand this at all, so if someone wants to
571 * work on improving it, be our guest - AED, GRP]
572 */
573 int i;
574 int max_d;
575 int num_new_palette;
576 png_dsortp t;
577 png_dsortpp hash;
578
579 t = NULL;
580
581 /* Initialize palette index arrays */
582 png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
583 (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
584 png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
585 (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
586
587 /* Initialize the sort array */
588 for (i = 0; i < num_palette; i++)
589 {
590 png_ptr->index_to_palette[i] = (png_byte)i;
591 png_ptr->palette_to_index[i] = (png_byte)i;
592 }
593
594 hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
595 (sizeof (png_dsortp))));
596
597 num_new_palette = num_palette;
598
599 /* Initial wild guess at how far apart the farthest pixel
600 * pair we will be eliminating will be. Larger
601 * numbers mean more areas will be allocated, Smaller
602 * numbers run the risk of not saving enough data, and
603 * having to do this all over again.
604 *
605 * I have not done extensive checking on this number.
606 */
607 max_d = 96;
608
609 while (num_new_palette > maximum_colors)
610 {
611 for (i = 0; i < num_new_palette - 1; i++)
612 {
613 int j;
614
615 for (j = i + 1; j < num_new_palette; j++)
616 {
617 int d;
618
619 d = PNG_COLOR_DIST(palette[i], palette[j]);
620
621 if (d <= max_d)
622 {
623
624 t = (png_dsortp)png_malloc_warn(png_ptr,
625 (png_uint_32)(sizeof (png_dsort)));
626
627 if (t == NULL)
628 break;
629
630 t->next = hash[d];
631 t->left = (png_byte)i;
632 t->right = (png_byte)j;
633 hash[d] = t;
634 }
635 }
636 if (t == NULL)
637 break;
638 }
639
640 if (t != NULL)
641 for (i = 0; i <= max_d; i++)
642 {
643 if (hash[i] != NULL)
644 {
645 png_dsortp p;
646
647 for (p = hash[i]; p; p = p->next)
648 {
649 if ((int)png_ptr->index_to_palette[p->left]
650 < num_new_palette &&
651 (int)png_ptr->index_to_palette[p->right]
652 < num_new_palette)
653 {
654 int j, next_j;
655
656 if (num_new_palette & 0x01)
657 {
658 j = p->left;
659 next_j = p->right;
660 }
661 else
662 {
663 j = p->right;
664 next_j = p->left;
665 }
666
667 num_new_palette--;
668 palette[png_ptr->index_to_palette[j]]
669 = palette[num_new_palette];
670 if (full_quantize == 0)
671 {
672 int k;
673
674 for (k = 0; k < num_palette; k++)
675 {
676 if (png_ptr->quantize_index[k] ==
677 png_ptr->index_to_palette[j])
678 png_ptr->quantize_index[k] =
679 png_ptr->index_to_palette[next_j];
680
681 if ((int)png_ptr->quantize_index[k] ==
682 num_new_palette)
683 png_ptr->quantize_index[k] =
684 png_ptr->index_to_palette[j];
685 }
686 }
687
688 png_ptr->index_to_palette[png_ptr->palette_to_index
689 [num_new_palette]] = png_ptr->index_to_palette[j];
690
691 png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
692 = png_ptr->palette_to_index[num_new_palette];
693
694 png_ptr->index_to_palette[j] =
695 (png_byte)num_new_palette;
696
697 png_ptr->palette_to_index[num_new_palette] =
698 (png_byte)j;
699 }
700 if (num_new_palette <= maximum_colors)
701 break;
702 }
703 if (num_new_palette <= maximum_colors)
704 break;
705 }
706 }
707
708 for (i = 0; i < 769; i++)
709 {
710 if (hash[i] != NULL)
711 {
712 png_dsortp p = hash[i];
713 while (p)
714 {
715 t = p->next;
716 png_free(png_ptr, p);
717 p = t;
718 }
719 }
720 hash[i] = 0;
721 }
722 max_d += 96;
723 }
724 png_free(png_ptr, hash);
725 png_free(png_ptr, png_ptr->palette_to_index);
726 png_free(png_ptr, png_ptr->index_to_palette);
727 png_ptr->palette_to_index = NULL;
728 png_ptr->index_to_palette = NULL;
729 }
730 num_palette = maximum_colors;
731 }
732 if (png_ptr->palette == NULL)
733 {
734 png_ptr->palette = palette;
735 }
736 png_ptr->num_palette = (png_uint_16)num_palette;
737
738 if (full_quantize != 0)
739 {
740 int i;
741 png_bytep distance;
742 int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
743 PNG_QUANTIZE_BLUE_BITS;
744 int num_red = (1 << PNG_QUANTIZE_RED_BITS);
745 int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
746 int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
747 png_size_t num_entries = ((png_size_t)1 << total_bits);
748
749 png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
750 (png_uint_32)(num_entries * (sizeof (png_byte))));
751
752 distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
753 (sizeof (png_byte))));
754
755 memset(distance, 0xff, num_entries * (sizeof (png_byte)));
756
757 for (i = 0; i < num_palette; i++)
758 {
759 int ir, ig, ib;
760 int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
761 int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
762 int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
763
764 for (ir = 0; ir < num_red; ir++)
765 {
766 /* int dr = abs(ir - r); */
767 int dr = ((ir > r) ? ir - r : r - ir);
768 int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
769 PNG_QUANTIZE_GREEN_BITS));
770
771 for (ig = 0; ig < num_green; ig++)
772 {
773 /* int dg = abs(ig - g); */
774 int dg = ((ig > g) ? ig - g : g - ig);
775 int dt = dr + dg;
776 int dm = ((dr > dg) ? dr : dg);
777 int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
778
779 for (ib = 0; ib < num_blue; ib++)
780 {
781 int d_index = index_g | ib;
782 /* int db = abs(ib - b); */
783 int db = ((ib > b) ? ib - b : b - ib);
784 int dmax = ((dm > db) ? dm : db);
785 int d = dmax + dt + db;
786
787 if (d < (int)distance[d_index])
788 {
789 distance[d_index] = (png_byte)d;
790 png_ptr->palette_lookup[d_index] = (png_byte)i;
791 }
792 }
793 }
794 }
795 }
796
797 png_free(png_ptr, distance);
798 }
799 }
800 #endif /* READ_QUANTIZE */
801
802 #ifdef PNG_READ_GAMMA_SUPPORTED
803 void PNGFAPI
804 png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
805 png_fixed_point file_gamma)
806 {
807 png_debug(1, "in png_set_gamma_fixed");
808
809 if (png_rtran_ok(png_ptr, 0) == 0)
810 return;
811
812 /* New in libpng-1.5.4 - reserve particular negative values as flags. */
813 scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
814 file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
815
816 /* Checking the gamma values for being >0 was added in 1.5.4 along with the
817 * premultiplied alpha support; this actually hides an undocumented feature
818 * of the previous implementation which allowed gamma processing to be
819 * disabled in background handling. There is no evidence (so far) that this
820 * was being used; however, png_set_background itself accepted and must still
821 * accept '0' for the gamma value it takes, because it isn't always used.
822 *
823 * Since this is an API change (albeit a very minor one that removes an
824 * undocumented API feature) the following checks were only enabled in
825 * libpng-1.6.0.
826 */
827 if (file_gamma <= 0)
828 png_error(png_ptr, "invalid file gamma in png_set_gamma");
829
830 if (scrn_gamma <= 0)
831 png_error(png_ptr, "invalid screen gamma in png_set_gamma");
832
833 /* Set the gamma values unconditionally - this overrides the value in the PNG
834 * file if a gAMA chunk was present. png_set_alpha_mode provides a
835 * different, easier, way to default the file gamma.
836 */
837 png_ptr->colorspace.gamma = file_gamma;
838 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
839 png_ptr->screen_gamma = scrn_gamma;
840 }
841
842 # ifdef PNG_FLOATING_POINT_SUPPORTED
843 void PNGAPI
844 png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
845 {
846 png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
847 convert_gamma_value(png_ptr, file_gamma));
848 }
849 # endif /* FLOATING_POINT */
850 #endif /* READ_GAMMA */
851
852 #ifdef PNG_READ_EXPAND_SUPPORTED
853 /* Expand paletted images to RGB, expand grayscale images of
854 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
855 * to alpha channels.
856 */
857 void PNGAPI
858 png_set_expand(png_structrp png_ptr)
859 {
860 png_debug(1, "in png_set_expand");
861
862 if (png_rtran_ok(png_ptr, 0) == 0)
863 return;
864
865 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
866 }
867
868 /* GRR 19990627: the following three functions currently are identical
869 * to png_set_expand(). However, it is entirely reasonable that someone
870 * might wish to expand an indexed image to RGB but *not* expand a single,
871 * fully transparent palette entry to a full alpha channel--perhaps instead
872 * convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
873 * the transparent color with a particular RGB value, or drop tRNS entirely.
874 * IOW, a future version of the library may make the transformations flag
875 * a bit more fine-grained, with separate bits for each of these three
876 * functions.
877 *
878 * More to the point, these functions make it obvious what libpng will be
879 * doing, whereas "expand" can (and does) mean any number of things.
880 *
881 * GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
882 * to expand only the sample depth but not to expand the tRNS to alpha
883 * and its name was changed to png_set_expand_gray_1_2_4_to_8().
884 */
885
886 /* Expand paletted images to RGB. */
887 void PNGAPI
888 png_set_palette_to_rgb(png_structrp png_ptr)
889 {
890 png_debug(1, "in png_set_palette_to_rgb");
891
892 if (png_rtran_ok(png_ptr, 0) == 0)
893 return;
894
895 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
896 }
897
898 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
899 void PNGAPI
900 png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
901 {
902 png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
903
904 if (png_rtran_ok(png_ptr, 0) == 0)
905 return;
906
907 png_ptr->transformations |= PNG_EXPAND;
908 }
909
910 /* Expand tRNS chunks to alpha channels. */
911 void PNGAPI
912 png_set_tRNS_to_alpha(png_structrp png_ptr)
913 {
914 png_debug(1, "in png_set_tRNS_to_alpha");
915
916 if (png_rtran_ok(png_ptr, 0) == 0)
917 return;
918
919 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
920 }
921 #endif /* READ_EXPAND */
922
923 #ifdef PNG_READ_EXPAND_16_SUPPORTED
924 /* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
925 * it may not work correctly.)
926 */
927 void PNGAPI
928 png_set_expand_16(png_structrp png_ptr)
929 {
930 png_debug(1, "in png_set_expand_16");
931
932 if (png_rtran_ok(png_ptr, 0) == 0)
933 return;
934
935 png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
936 }
937 #endif
938
939 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
940 void PNGAPI
941 png_set_gray_to_rgb(png_structrp png_ptr)
942 {
943 png_debug(1, "in png_set_gray_to_rgb");
944
945 if (png_rtran_ok(png_ptr, 0) == 0)
946 return;
947
948 /* Because rgb must be 8 bits or more: */
949 png_set_expand_gray_1_2_4_to_8(png_ptr);
950 png_ptr->transformations |= PNG_GRAY_TO_RGB;
951 }
952 #endif
953
954 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
955 void PNGFAPI
956 png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
957 png_fixed_point red, png_fixed_point green)
958 {
959 png_debug(1, "in png_set_rgb_to_gray");
960
961 /* Need the IHDR here because of the check on color_type below. */
962 /* TODO: fix this */
963 if (png_rtran_ok(png_ptr, 1) == 0)
964 return;
965
966 switch (error_action)
967 {
968 case PNG_ERROR_ACTION_NONE:
969 png_ptr->transformations |= PNG_RGB_TO_GRAY;
970 break;
971
972 case PNG_ERROR_ACTION_WARN:
973 png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
974 break;
975
976 case PNG_ERROR_ACTION_ERROR:
977 png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
978 break;
979
980 default:
981 png_error(png_ptr, "invalid error action to rgb_to_gray");
982 }
983
984 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
985 #ifdef PNG_READ_EXPAND_SUPPORTED
986 png_ptr->transformations |= PNG_EXPAND;
987 #else
988 {
989 /* Make this an error in 1.6 because otherwise the application may assume
990 * that it just worked and get a memory overwrite.
991 */
992 png_error(png_ptr,
993 "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
994
995 /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
996 }
997 #endif
998 {
999 if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
1000 {
1001 png_uint_16 red_int, green_int;
1002
1003 /* NOTE: this calculation does not round, but this behavior is retained
1004 * for consistency; the inaccuracy is very small. The code here always
1005 * overwrites the coefficients, regardless of whether they have been
1006 * defaulted or set already.
1007 */
1008 red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
1009 green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
1010
1011 png_ptr->rgb_to_gray_red_coeff = red_int;
1012 png_ptr->rgb_to_gray_green_coeff = green_int;
1013 png_ptr->rgb_to_gray_coefficients_set = 1;
1014 }
1015
1016 else
1017 {
1018 if (red >= 0 && green >= 0)
1019 png_app_warning(png_ptr,
1020 "ignoring out of range rgb_to_gray coefficients");
1021
1022 /* Use the defaults, from the cHRM chunk if set, else the historical
1023 * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
1024 * png_do_rgb_to_gray for more discussion of the values. In this case
1025 * the coefficients are not marked as 'set' and are not overwritten if
1026 * something has already provided a default.
1027 */
1028 if (png_ptr->rgb_to_gray_red_coeff == 0 &&
1029 png_ptr->rgb_to_gray_green_coeff == 0)
1030 {
1031 png_ptr->rgb_to_gray_red_coeff = 6968;
1032 png_ptr->rgb_to_gray_green_coeff = 23434;
1033 /* png_ptr->rgb_to_gray_blue_coeff = 2366; */
1034 }
1035 }
1036 }
1037 }
1038
1039 #ifdef PNG_FLOATING_POINT_SUPPORTED
1040 /* Convert a RGB image to a grayscale of the same width. This allows us,
1041 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
1042 */
1043
1044 void PNGAPI
1045 png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
1046 double green)
1047 {
1048 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1049 png_fixed(png_ptr, red, "rgb to gray red coefficient"),
1050 png_fixed(png_ptr, green, "rgb to gray green coefficient"));
1051 }
1052 #endif /* FLOATING POINT */
1053
1054 #endif /* RGB_TO_GRAY */
1055
1056 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
1057 defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
1058 void PNGAPI
1059 png_set_read_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
1060 read_user_transform_fn)
1061 {
1062 png_debug(1, "in png_set_read_user_transform_fn");
1063
1064 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
1065 png_ptr->transformations |= PNG_USER_TRANSFORM;
1066 png_ptr->read_user_transform_fn = read_user_transform_fn;
1067 #endif
1068 }
1069 #endif
1070
1071 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
1072 #ifdef PNG_READ_GAMMA_SUPPORTED
1073 /* In the case of gamma transformations only do transformations on images where
1074 * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
1075 * slows things down slightly, and also needlessly introduces small errors.
1076 */
1077 static int /* PRIVATE */
1078 png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
1079 {
1080 /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
1081 * correction as a difference of the overall transform from 1.0
1082 *
1083 * We want to compare the threshold with s*f - 1, if we get
1084 * overflow here it is because of wacky gamma values so we
1085 * turn on processing anyway.
1086 */
1087 png_fixed_point gtest;
1088 return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
1089 png_gamma_significant(gtest);
1090 }
1091 #endif
1092
1093 /* Initialize everything needed for the read. This includes modifying
1094 * the palette.
1095 */
1096
1097 /* For the moment 'png_init_palette_transformations' and
1098 * 'png_init_rgb_transformations' only do some flag canceling optimizations.
1099 * The intent is that these two routines should have palette or rgb operations
1100 * extracted from 'png_init_read_transformations'.
1101 */
1102 static void /* PRIVATE */
1103 png_init_palette_transformations(png_structrp png_ptr)
1104 {
1105 /* Called to handle the (input) palette case. In png_do_read_transformations
1106 * the first step is to expand the palette if requested, so this code must
1107 * take care to only make changes that are invariant with respect to the
1108 * palette expansion, or only do them if there is no expansion.
1109 *
1110 * STRIP_ALPHA has already been handled in the caller (by setting num_trans
1111 * to 0.)
1112 */
1113 int input_has_alpha = 0;
1114 int input_has_transparency = 0;
1115
1116 if (png_ptr->num_trans > 0)
1117 {
1118 int i;
1119
1120 /* Ignore if all the entries are opaque (unlikely!) */
1121 for (i=0; i<png_ptr->num_trans; ++i)
1122 {
1123 if (png_ptr->trans_alpha[i] == 255)
1124 continue;
1125 else if (png_ptr->trans_alpha[i] == 0)
1126 input_has_transparency = 1;
1127 else
1128 {
1129 input_has_transparency = 1;
1130 input_has_alpha = 1;
1131 break;
1132 }
1133 }
1134 }
1135
1136 /* If no alpha we can optimize. */
1137 if (input_has_alpha == 0)
1138 {
1139 /* Any alpha means background and associative alpha processing is
1140 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1141 * and ENCODE_ALPHA are irrelevant.
1142 */
1143 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1144 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1145
1146 if (input_has_transparency == 0)
1147 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1148 }
1149
1150 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1151 /* png_set_background handling - deals with the complexity of whether the
1152 * background color is in the file format or the screen format in the case
1153 * where an 'expand' will happen.
1154 */
1155
1156 /* The following code cannot be entered in the alpha pre-multiplication case
1157 * because PNG_BACKGROUND_EXPAND is cancelled below.
1158 */
1159 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0 &&
1160 (png_ptr->transformations & PNG_EXPAND) != 0)
1161 {
1162 {
1163 png_ptr->background.red =
1164 png_ptr->palette[png_ptr->background.index].red;
1165 png_ptr->background.green =
1166 png_ptr->palette[png_ptr->background.index].green;
1167 png_ptr->background.blue =
1168 png_ptr->palette[png_ptr->background.index].blue;
1169
1170 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1171 if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0)
1172 {
1173 if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
1174 {
1175 /* Invert the alpha channel (in tRNS) unless the pixels are
1176 * going to be expanded, in which case leave it for later
1177 */
1178 int i, istop = png_ptr->num_trans;
1179
1180 for (i=0; i<istop; i++)
1181 png_ptr->trans_alpha[i] = (png_byte)(255 -
1182 png_ptr->trans_alpha[i]);
1183 }
1184 }
1185 #endif /* READ_INVERT_ALPHA */
1186 }
1187 } /* background expand and (therefore) no alpha association. */
1188 #endif /* READ_EXPAND && READ_BACKGROUND */
1189 }
1190
1191 static void /* PRIVATE */
1192 png_init_rgb_transformations(png_structrp png_ptr)
1193 {
1194 /* Added to libpng-1.5.4: check the color type to determine whether there
1195 * is any alpha or transparency in the image and simply cancel the
1196 * background and alpha mode stuff if there isn't.
1197 */
1198 int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
1199 int input_has_transparency = png_ptr->num_trans > 0;
1200
1201 /* If no alpha we can optimize. */
1202 if (input_has_alpha == 0)
1203 {
1204 /* Any alpha means background and associative alpha processing is
1205 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1206 * and ENCODE_ALPHA are irrelevant.
1207 */
1208 # ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1209 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1210 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1211 # endif
1212
1213 if (input_has_transparency == 0)
1214 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1215 }
1216
1217 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1218 /* png_set_background handling - deals with the complexity of whether the
1219 * background color is in the file format or the screen format in the case
1220 * where an 'expand' will happen.
1221 */
1222
1223 /* The following code cannot be entered in the alpha pre-multiplication case
1224 * because PNG_BACKGROUND_EXPAND is cancelled below.
1225 */
1226 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0 &&
1227 (png_ptr->transformations & PNG_EXPAND) != 0 &&
1228 (png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
1229 /* i.e., GRAY or GRAY_ALPHA */
1230 {
1231 {
1232 /* Expand background and tRNS chunks */
1233 int gray = png_ptr->background.gray;
1234 int trans_gray = png_ptr->trans_color.gray;
1235
1236 switch (png_ptr->bit_depth)
1237 {
1238 case 1:
1239 gray *= 0xff;
1240 trans_gray *= 0xff;
1241 break;
1242
1243 case 2:
1244 gray *= 0x55;
1245 trans_gray *= 0x55;
1246 break;
1247
1248 case 4:
1249 gray *= 0x11;
1250 trans_gray *= 0x11;
1251 break;
1252
1253 default:
1254
1255 case 8:
1256 /* FALL THROUGH (Already 8 bits) */
1257
1258 case 16:
1259 /* Already a full 16 bits */
1260 break;
1261 }
1262
1263 png_ptr->background.red = png_ptr->background.green =
1264 png_ptr->background.blue = (png_uint_16)gray;
1265
1266 if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
1267 {
1268 png_ptr->trans_color.red = png_ptr->trans_color.green =
1269 png_ptr->trans_color.blue = (png_uint_16)trans_gray;
1270 }
1271 }
1272 } /* background expand and (therefore) no alpha association. */
1273 #endif /* READ_EXPAND && READ_BACKGROUND */
1274 }
1275
1276 void /* PRIVATE */
1277 png_init_read_transformations(png_structrp png_ptr)
1278 {
1279 png_debug(1, "in png_init_read_transformations");
1280
1281 /* This internal function is called from png_read_start_row in pngrutil.c
1282 * and it is called before the 'rowbytes' calculation is done, so the code
1283 * in here can change or update the transformations flags.
1284 *
1285 * First do updates that do not depend on the details of the PNG image data
1286 * being processed.
1287 */
1288
1289 #ifdef PNG_READ_GAMMA_SUPPORTED
1290 /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
1291 * png_set_alpha_mode and this is another source for a default file gamma so
1292 * the test needs to be performed later - here. In addition prior to 1.5.4
1293 * the tests were repeated for the PALETTE color type here - this is no
1294 * longer necessary (and doesn't seem to have been necessary before.)
1295 */
1296 {
1297 /* The following temporary indicates if overall gamma correction is
1298 * required.
1299 */
1300 int gamma_correction = 0;
1301
1302 if (png_ptr->colorspace.gamma != 0) /* has been set */
1303 {
1304 if (png_ptr->screen_gamma != 0) /* screen set too */
1305 gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
1306 png_ptr->screen_gamma);
1307
1308 else
1309 /* Assume the output matches the input; a long time default behavior
1310 * of libpng, although the standard has nothing to say about this.
1311 */
1312 png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma);
1313 }
1314
1315 else if (png_ptr->screen_gamma != 0)
1316 /* The converse - assume the file matches the screen, note that this
1317 * perhaps undesireable default can (from 1.5.4) be changed by calling
1318 * png_set_alpha_mode (even if the alpha handling mode isn't required
1319 * or isn't changed from the default.)
1320 */
1321 png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma);
1322
1323 else /* neither are set */
1324 /* Just in case the following prevents any processing - file and screen
1325 * are both assumed to be linear and there is no way to introduce a
1326 * third gamma value other than png_set_background with 'UNIQUE', and,
1327 * prior to 1.5.4
1328 */
1329 png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1;
1330
1331 /* We have a gamma value now. */
1332 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
1333
1334 /* Now turn the gamma transformation on or off as appropriate. Notice
1335 * that PNG_GAMMA just refers to the file->screen correction. Alpha
1336 * composition may independently cause gamma correction because it needs
1337 * linear data (e.g. if the file has a gAMA chunk but the screen gamma
1338 * hasn't been specified.) In any case this flag may get turned off in
1339 * the code immediately below if the transform can be handled outside the
1340 * row loop.
1341 */
1342 if (gamma_correction != 0)
1343 png_ptr->transformations |= PNG_GAMMA;
1344
1345 else
1346 png_ptr->transformations &= ~PNG_GAMMA;
1347 }
1348 #endif
1349
1350 /* Certain transformations have the effect of preventing other
1351 * transformations that happen afterward in png_do_read_transformations;
1352 * resolve the interdependencies here. From the code of
1353 * png_do_read_transformations the order is:
1354 *
1355 * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
1356 * 2) PNG_STRIP_ALPHA (if no compose)
1357 * 3) PNG_RGB_TO_GRAY
1358 * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
1359 * 5) PNG_COMPOSE
1360 * 6) PNG_GAMMA
1361 * 7) PNG_STRIP_ALPHA (if compose)
1362 * 8) PNG_ENCODE_ALPHA
1363 * 9) PNG_SCALE_16_TO_8
1364 * 10) PNG_16_TO_8
1365 * 11) PNG_QUANTIZE (converts to palette)
1366 * 12) PNG_EXPAND_16
1367 * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
1368 * 14) PNG_INVERT_MONO
1369 * 15) PNG_INVERT_ALPHA
1370 * 16) PNG_SHIFT
1371 * 17) PNG_PACK
1372 * 18) PNG_BGR
1373 * 19) PNG_PACKSWAP
1374 * 20) PNG_FILLER (includes PNG_ADD_ALPHA)
1375 * 21) PNG_SWAP_ALPHA
1376 * 22) PNG_SWAP_BYTES
1377 * 23) PNG_USER_TRANSFORM [must be last]
1378 */
1379 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1380 if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0 &&
1381 (png_ptr->transformations & PNG_COMPOSE) == 0)
1382 {
1383 /* Stripping the alpha channel happens immediately after the 'expand'
1384 * transformations, before all other transformation, so it cancels out
1385 * the alpha handling. It has the side effect negating the effect of
1386 * PNG_EXPAND_tRNS too:
1387 */
1388 png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
1389 PNG_EXPAND_tRNS);
1390 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1391
1392 /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
1393 * so transparency information would remain just so long as it wasn't
1394 * expanded. This produces unexpected API changes if the set of things
1395 * that do PNG_EXPAND_tRNS changes (perfectly possible given the
1396 * documentation - which says ask for what you want, accept what you
1397 * get.) This makes the behavior consistent from 1.5.4:
1398 */
1399 png_ptr->num_trans = 0;
1400 }
1401 #endif /* STRIP_ALPHA supported, no COMPOSE */
1402
1403 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1404 /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
1405 * settings will have no effect.
1406 */
1407 if (png_gamma_significant(png_ptr->screen_gamma) == 0)
1408 {
1409 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1410 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1411 }
1412 #endif
1413
1414 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1415 /* Make sure the coefficients for the rgb to gray conversion are set
1416 * appropriately.
1417 */
1418 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
1419 png_colorspace_set_rgb_coefficients(png_ptr);
1420 #endif
1421
1422 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1423 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1424 /* Detect gray background and attempt to enable optimization for
1425 * gray --> RGB case.
1426 *
1427 * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
1428 * RGB_ALPHA (in which case need_expand is superfluous anyway), the
1429 * background color might actually be gray yet not be flagged as such.
1430 * This is not a problem for the current code, which uses
1431 * PNG_BACKGROUND_IS_GRAY only to decide when to do the
1432 * png_do_gray_to_rgb() transformation.
1433 *
1434 * TODO: this code needs to be revised to avoid the complexity and
1435 * interdependencies. The color type of the background should be recorded in
1436 * png_set_background, along with the bit depth, then the code has a record
1437 * of exactly what color space the background is currently in.
1438 */
1439 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0)
1440 {
1441 /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
1442 * the file was grayscale the background value is gray.
1443 */
1444 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
1445 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1446 }
1447
1448 else if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1449 {
1450 /* PNG_COMPOSE: png_set_background was called with need_expand false,
1451 * so the color is in the color space of the output or png_set_alpha_mode
1452 * was called and the color is black. Ignore RGB_TO_GRAY because that
1453 * happens before GRAY_TO_RGB.
1454 */
1455 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
1456 {
1457 if (png_ptr->background.red == png_ptr->background.green &&
1458 png_ptr->background.red == png_ptr->background.blue)
1459 {
1460 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1461 png_ptr->background.gray = png_ptr->background.red;
1462 }
1463 }
1464 }
1465 #endif /* READ_EXPAND && READ_BACKGROUND */
1466 #endif /* READ_GRAY_TO_RGB */
1467
1468 /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
1469 * can be performed directly on the palette, and some (such as rgb to gray)
1470 * can be optimized inside the palette. This is particularly true of the
1471 * composite (background and alpha) stuff, which can be pretty much all done
1472 * in the palette even if the result is expanded to RGB or gray afterward.
1473 *
1474 * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
1475 * earlier and the palette stuff is actually handled on the first row. This
1476 * leads to the reported bug that the palette returned by png_get_PLTE is not
1477 * updated.
1478 */
1479 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1480 png_init_palette_transformations(png_ptr);
1481
1482 else
1483 png_init_rgb_transformations(png_ptr);
1484
1485 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1486 defined(PNG_READ_EXPAND_16_SUPPORTED)
1487 if ((png_ptr->transformations & PNG_EXPAND_16) != 0 &&
1488 (png_ptr->transformations & PNG_COMPOSE) != 0 &&
1489 (png_ptr->transformations & PNG_BACKGROUND_EXPAND) == 0 &&
1490 png_ptr->bit_depth != 16)
1491 {
1492 /* TODO: fix this. Because the expand_16 operation is after the compose
1493 * handling the background color must be 8, not 16, bits deep, but the
1494 * application will supply a 16-bit value so reduce it here.
1495 *
1496 * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
1497 * present, so that case is ok (until do_expand_16 is moved.)
1498 *
1499 * NOTE: this discards the low 16 bits of the user supplied background
1500 * color, but until expand_16 works properly there is no choice!
1501 */
1502 # define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
1503 CHOP(png_ptr->background.red);
1504 CHOP(png_ptr->background.green);
1505 CHOP(png_ptr->background.blue);
1506 CHOP(png_ptr->background.gray);
1507 # undef CHOP
1508 }
1509 #endif /* READ_BACKGROUND && READ_EXPAND_16 */
1510
1511 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1512 (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
1513 defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
1514 if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) != 0 &&
1515 (png_ptr->transformations & PNG_COMPOSE) != 0 &&
1516 (png_ptr->transformations & PNG_BACKGROUND_EXPAND) == 0 &&
1517 png_ptr->bit_depth == 16)
1518 {
1519 /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
1520 * component this will also happen after PNG_COMPOSE and so the background
1521 * color must be pre-expanded here.
1522 *
1523 * TODO: fix this too.
1524 */
1525 png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
1526 png_ptr->background.green =
1527 (png_uint_16)(png_ptr->background.green * 257);
1528 png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
1529 png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
1530 }
1531 #endif
1532
1533 /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
1534 * background support (see the comments in scripts/pnglibconf.dfa), this
1535 * allows pre-multiplication of the alpha channel to be implemented as
1536 * compositing on black. This is probably sub-optimal and has been done in
1537 * 1.5.4 betas simply to enable external critique and testing (i.e. to
1538 * implement the new API quickly, without lots of internal changes.)
1539 */
1540
1541 #ifdef PNG_READ_GAMMA_SUPPORTED
1542 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1543 /* Includes ALPHA_MODE */
1544 png_ptr->background_1 = png_ptr->background;
1545 # endif
1546
1547 /* This needs to change - in the palette image case a whole set of tables are
1548 * built when it would be quicker to just calculate the correct value for
1549 * each palette entry directly. Also, the test is too tricky - why check
1550 * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
1551 * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
1552 * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
1553 * the gamma tables will not be built even if composition is required on a
1554 * gamma encoded value.
1555 *
1556 * In 1.5.4 this is addressed below by an additional check on the individual
1557 * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
1558 * tables.
1559 */
1560 if ((png_ptr->transformations & PNG_GAMMA) != 0 ||
1561 ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0 &&
1562 (png_gamma_significant(png_ptr->colorspace.gamma) != 0 ||
1563 png_gamma_significant(png_ptr->screen_gamma) != 0)) ||
1564 ((png_ptr->transformations & PNG_COMPOSE) != 0 &&
1565 (png_gamma_significant(png_ptr->colorspace.gamma) != 0 ||
1566 png_gamma_significant(png_ptr->screen_gamma) != 0
1567 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1568 || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE &&
1569 png_gamma_significant(png_ptr->background_gamma) != 0)
1570 # endif
1571 )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA) != 0 &&
1572 png_gamma_significant(png_ptr->screen_gamma) != 0))
1573 {
1574 png_build_gamma_table(png_ptr, png_ptr->bit_depth);
1575
1576 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1577 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1578 {
1579 /* Issue a warning about this combination: because RGB_TO_GRAY is
1580 * optimized to do the gamma transform if present yet do_background has
1581 * to do the same thing if both options are set a
1582 * double-gamma-correction happens. This is true in all versions of
1583 * libpng to date.
1584 */
1585 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
1586 png_warning(png_ptr,
1587 "libpng does not support gamma+background+rgb_to_gray");
1588
1589 if ((png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) != 0)
1590 {
1591 /* We don't get to here unless there is a tRNS chunk with non-opaque
1592 * entries - see the checking code at the start of this function.
1593 */
1594 png_color back, back_1;
1595 png_colorp palette = png_ptr->palette;
1596 int num_palette = png_ptr->num_palette;
1597 int i;
1598 if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
1599 {
1600
1601 back.red = png_ptr->gamma_table[png_ptr->background.red];
1602 back.green = png_ptr->gamma_table[png_ptr->background.green];
1603 back.blue = png_ptr->gamma_table[png_ptr->background.blue];
1604
1605 back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
1606 back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
1607 back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
1608 }
1609 else
1610 {
1611 png_fixed_point g, gs;
1612
1613 switch (png_ptr->background_gamma_type)
1614 {
1615 case PNG_BACKGROUND_GAMMA_SCREEN:
1616 g = (png_ptr->screen_gamma);
1617 gs = PNG_FP_1;
1618 break;
1619
1620 case PNG_BACKGROUND_GAMMA_FILE:
1621 g = png_reciprocal(png_ptr->colorspace.gamma);
1622 gs = png_reciprocal2(png_ptr->colorspace.gamma,
1623 png_ptr->screen_gamma);
1624 break;
1625
1626 case PNG_BACKGROUND_GAMMA_UNIQUE:
1627 g = png_reciprocal(png_ptr->background_gamma);
1628 gs = png_reciprocal2(png_ptr->background_gamma,
1629 png_ptr->screen_gamma);
1630 break;
1631 default:
1632 g = PNG_FP_1; /* back_1 */
1633 gs = PNG_FP_1; /* back */
1634 break;
1635 }
1636
1637 if (png_gamma_significant(gs) != 0)
1638 {
1639 back.red = png_gamma_8bit_correct(png_ptr->background.red,
1640 gs);
1641 back.green = png_gamma_8bit_correct(png_ptr->background.green,
1642 gs);
1643 back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1644 gs);
1645 }
1646
1647 else
1648 {
1649 back.red = (png_byte)png_ptr->background.red;
1650 back.green = (png_byte)png_ptr->background.green;
1651 back.blue = (png_byte)png_ptr->background.blue;
1652 }
1653
1654 if (png_gamma_significant(g) != 0)
1655 {
1656 back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
1657 g);
1658 back_1.green = png_gamma_8bit_correct(
1659 png_ptr->background.green, g);
1660 back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1661 g);
1662 }
1663
1664 else
1665 {
1666 back_1.red = (png_byte)png_ptr->background.red;
1667 back_1.green = (png_byte)png_ptr->background.green;
1668 back_1.blue = (png_byte)png_ptr->background.blue;
1669 }
1670 }
1671
1672 for (i = 0; i < num_palette; i++)
1673 {
1674 if (i < (int)png_ptr->num_trans &&
1675 png_ptr->trans_alpha[i] != 0xff)
1676 {
1677 if (png_ptr->trans_alpha[i] == 0)
1678 {
1679 palette[i] = back;
1680 }
1681 else /* if (png_ptr->trans_alpha[i] != 0xff) */
1682 {
1683 png_byte v, w;
1684
1685 v = png_ptr->gamma_to_1[palette[i].red];
1686 png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
1687 palette[i].red = png_ptr->gamma_from_1[w];
1688
1689 v = png_ptr->gamma_to_1[palette[i].green];
1690 png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
1691 palette[i].green = png_ptr->gamma_from_1[w];
1692
1693 v = png_ptr->gamma_to_1[palette[i].blue];
1694 png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
1695 palette[i].blue = png_ptr->gamma_from_1[w];
1696 }
1697 }
1698 else
1699 {
1700 palette[i].red = png_ptr->gamma_table[palette[i].red];
1701 palette[i].green = png_ptr->gamma_table[palette[i].green];
1702 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1703 }
1704 }
1705
1706 /* Prevent the transformations being done again.
1707 *
1708 * NOTE: this is highly dubious; it removes the transformations in
1709 * place. This seems inconsistent with the general treatment of the
1710 * transformations elsewhere.
1711 */
1712 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
1713 } /* color_type == PNG_COLOR_TYPE_PALETTE */
1714
1715 /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
1716 else /* color_type != PNG_COLOR_TYPE_PALETTE */
1717 {
1718 int gs_sig, g_sig;
1719 png_fixed_point g = PNG_FP_1; /* Correction to linear */
1720 png_fixed_point gs = PNG_FP_1; /* Correction to screen */
1721
1722 switch (png_ptr->background_gamma_type)
1723 {
1724 case PNG_BACKGROUND_GAMMA_SCREEN:
1725 g = png_ptr->screen_gamma;
1726 /* gs = PNG_FP_1; */
1727 break;
1728
1729 case PNG_BACKGROUND_GAMMA_FILE:
1730 g = png_reciprocal(png_ptr->colorspace.gamma);
1731 gs = png_reciprocal2(png_ptr->colorspace.gamma,
1732 png_ptr->screen_gamma);
1733 break;
1734
1735 case PNG_BACKGROUND_GAMMA_UNIQUE:
1736 g = png_reciprocal(png_ptr->background_gamma);
1737 gs = png_reciprocal2(png_ptr->background_gamma,
1738 png_ptr->screen_gamma);
1739 break;
1740
1741 default:
1742 png_error(png_ptr, "invalid background gamma type");
1743 }
1744
1745 g_sig = png_gamma_significant(g);
1746 gs_sig = png_gamma_significant(gs);
1747
1748 if (g_sig != 0)
1749 png_ptr->background_1.gray = png_gamma_correct(png_ptr,
1750 png_ptr->background.gray, g);
1751
1752 if (gs_sig != 0)
1753 png_ptr->background.gray = png_gamma_correct(png_ptr,
1754 png_ptr->background.gray, gs);
1755
1756 if ((png_ptr->background.red != png_ptr->background.green) ||
1757 (png_ptr->background.red != png_ptr->background.blue) ||
1758 (png_ptr->background.red != png_ptr->background.gray))
1759 {
1760 /* RGB or RGBA with color background */
1761 if (g_sig != 0)
1762 {
1763 png_ptr->background_1.red = png_gamma_correct(png_ptr,
1764 png_ptr->background.red, g);
1765
1766 png_ptr->background_1.green = png_gamma_correct(png_ptr,
1767 png_ptr->background.green, g);
1768
1769 png_ptr->background_1.blue = png_gamma_correct(png_ptr,
1770 png_ptr->background.blue, g);
1771 }
1772
1773 if (gs_sig != 0)
1774 {
1775 png_ptr->background.red = png_gamma_correct(png_ptr,
1776 png_ptr->background.red, gs);
1777
1778 png_ptr->background.green = png_gamma_correct(png_ptr,
1779 png_ptr->background.green, gs);
1780
1781 png_ptr->background.blue = png_gamma_correct(png_ptr,
1782 png_ptr->background.blue, gs);
1783 }
1784 }
1785
1786 else
1787 {
1788 /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
1789 png_ptr->background_1.red = png_ptr->background_1.green
1790 = png_ptr->background_1.blue = png_ptr->background_1.gray;
1791
1792 png_ptr->background.red = png_ptr->background.green
1793 = png_ptr->background.blue = png_ptr->background.gray;
1794 }
1795
1796 /* The background is now in screen gamma: */
1797 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
1798 } /* color_type != PNG_COLOR_TYPE_PALETTE */
1799 }/* png_ptr->transformations & PNG_BACKGROUND */
1800
1801 else
1802 /* Transformation does not include PNG_BACKGROUND */
1803 #endif /* READ_BACKGROUND */
1804 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
1805 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1806 /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
1807 && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
1808 (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
1809 #endif
1810 )
1811 {
1812 png_colorp palette = png_ptr->palette;
1813 int num_palette = png_ptr->num_palette;
1814 int i;
1815
1816 /* NOTE: there are other transformations that should probably be in
1817 * here too.
1818 */
1819 for (i = 0; i < num_palette; i++)
1820 {
1821 palette[i].red = png_ptr->gamma_table[palette[i].red];
1822 palette[i].green = png_ptr->gamma_table[palette[i].green];
1823 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1824 }
1825
1826 /* Done the gamma correction. */
1827 png_ptr->transformations &= ~PNG_GAMMA;
1828 } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
1829 }
1830 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1831 else
1832 #endif
1833 #endif /* READ_GAMMA */
1834
1835 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1836 /* No GAMMA transformation (see the hanging else 4 lines above) */
1837 if ((png_ptr->transformations & PNG_COMPOSE) != 0 &&
1838 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1839 {
1840 int i;
1841 int istop = (int)png_ptr->num_trans;
1842 png_color back;
1843 png_colorp palette = png_ptr->palette;
1844
1845 back.red = (png_byte)png_ptr->background.red;
1846 back.green = (png_byte)png_ptr->background.green;
1847 back.blue = (png_byte)png_ptr->background.blue;
1848
1849 for (i = 0; i < istop; i++)
1850 {
1851 if (png_ptr->trans_alpha[i] == 0)
1852 {
1853 palette[i] = back;
1854 }
1855
1856 else if (png_ptr->trans_alpha[i] != 0xff)
1857 {
1858 /* The png_composite() macro is defined in png.h */
1859 png_composite(palette[i].red, palette[i].red,
1860 png_ptr->trans_alpha[i], back.red);
1861
1862 png_composite(palette[i].green, palette[i].green,
1863 png_ptr->trans_alpha[i], back.green);
1864
1865 png_composite(palette[i].blue, palette[i].blue,
1866 png_ptr->trans_alpha[i], back.blue);
1867 }
1868 }
1869
1870 png_ptr->transformations &= ~PNG_COMPOSE;
1871 }
1872 #endif /* READ_BACKGROUND */
1873
1874 #ifdef PNG_READ_SHIFT_SUPPORTED
1875 if ((png_ptr->transformations & PNG_SHIFT) != 0 &&
1876 (png_ptr->transformations & PNG_EXPAND) == 0 &&
1877 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1878 {
1879 int i;
1880 int istop = png_ptr->num_palette;
1881 int shift = 8 - png_ptr->sig_bit.red;
1882
1883 png_ptr->transformations &= ~PNG_SHIFT;
1884
1885 /* significant bits can be in the range 1 to 7 for a meaninful result, if
1886 * the number of significant bits is 0 then no shift is done (this is an
1887 * error condition which is silently ignored.)
1888 */
1889 if (shift > 0 && shift < 8)
1890 for (i=0; i<istop; ++i)
1891 {
1892 int component = png_ptr->palette[i].red;
1893
1894 component >>= shift;
1895 png_ptr->palette[i].red = (png_byte)component;
1896 }
1897
1898 shift = 8 - png_ptr->sig_bit.green;
1899 if (shift > 0 && shift < 8)
1900 for (i=0; i<istop; ++i)
1901 {
1902 int component = png_ptr->palette[i].green;
1903
1904 component >>= shift;
1905 png_ptr->palette[i].green = (png_byte)component;
1906 }
1907
1908 shift = 8 - png_ptr->sig_bit.blue;
1909 if (shift > 0 && shift < 8)
1910 for (i=0; i<istop; ++i)
1911 {
1912 int component = png_ptr->palette[i].blue;
1913
1914 component >>= shift;
1915 png_ptr->palette[i].blue = (png_byte)component;
1916 }
1917 }
1918 #endif /* READ_SHIFT */
1919 }
1920
1921 /* Modify the info structure to reflect the transformations. The
1922 * info should be updated so a PNG file could be written with it,
1923 * assuming the transformations result in valid PNG data.
1924 */
1925 void /* PRIVATE */
1926 png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
1927 {
1928 png_debug(1, "in png_read_transform_info");
1929
1930 #ifdef PNG_READ_EXPAND_SUPPORTED
1931 if ((png_ptr->transformations & PNG_EXPAND) != 0)
1932 {
1933 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1934 {
1935 /* This check must match what actually happens in
1936 * png_do_expand_palette; if it ever checks the tRNS chunk to see if
1937 * it is all opaque we must do the same (at present it does not.)
1938 */
1939 if (png_ptr->num_trans > 0)
1940 info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
1941
1942 else
1943 info_ptr->color_type = PNG_COLOR_TYPE_RGB;
1944
1945 info_ptr->bit_depth = 8;
1946 info_ptr->num_trans = 0;
1947
1948 if (png_ptr->palette == NULL)
1949 png_error (png_ptr, "Palette is NULL in indexed image");
1950 }
1951 else
1952 {
1953 if (png_ptr->num_trans != 0)
1954 {
1955 if ((png_ptr->transformations & PNG_EXPAND_tRNS) != 0)
1956 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
1957 }
1958 if (info_ptr->bit_depth < 8)
1959 info_ptr->bit_depth = 8;
1960
1961 info_ptr->num_trans = 0;
1962 }
1963 }
1964 #endif
1965
1966 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
1967 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
1968 /* The following is almost certainly wrong unless the background value is in
1969 * the screen space!
1970 */
1971 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1972 info_ptr->background = png_ptr->background;
1973 #endif
1974
1975 #ifdef PNG_READ_GAMMA_SUPPORTED
1976 /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
1977 * however it seems that the code in png_init_read_transformations, which has
1978 * been called before this from png_read_update_info->png_read_start_row
1979 * sometimes does the gamma transform and cancels the flag.
1980 *
1981 * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
1982 * the screen_gamma value. The following probably results in weirdness if
1983 * the info_ptr is used by the app after the rows have been read.
1984 */
1985 info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
1986 #endif
1987
1988 if (info_ptr->bit_depth == 16)
1989 {
1990 # ifdef PNG_READ_16BIT_SUPPORTED
1991 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1992 if ((png_ptr->transformations & PNG_SCALE_16_TO_8) != 0)
1993 info_ptr->bit_depth = 8;
1994 # endif
1995
1996 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1997 if ((png_ptr->transformations & PNG_16_TO_8) != 0)
1998 info_ptr->bit_depth = 8;
1999 # endif
2000
2001 # else
2002 /* No 16-bit support: force chopping 16-bit input down to 8, in this case
2003 * the app program can chose if both APIs are available by setting the
2004 * correct scaling to use.
2005 */
2006 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2007 /* For compatibility with previous versions use the strip method by
2008 * default. This code works because if PNG_SCALE_16_TO_8 is already
2009 * set the code below will do that in preference to the chop.
2010 */
2011 png_ptr->transformations |= PNG_16_TO_8;
2012 info_ptr->bit_depth = 8;
2013 # else
2014
2015 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2016 png_ptr->transformations |= PNG_SCALE_16_TO_8;
2017 info_ptr->bit_depth = 8;
2018 # else
2019
2020 CONFIGURATION ERROR: you must enable at least one 16 to 8 method
2021 # endif
2022 # endif
2023 #endif /* !READ_16BIT */
2024 }
2025
2026 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2027 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
2028 info_ptr->color_type = (png_byte)(info_ptr->color_type |
2029 PNG_COLOR_MASK_COLOR);
2030 #endif
2031
2032 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2033 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
2034 info_ptr->color_type = (png_byte)(info_ptr->color_type &
2035 ~PNG_COLOR_MASK_COLOR);
2036 #endif
2037
2038 #ifdef PNG_READ_QUANTIZE_SUPPORTED
2039 if ((png_ptr->transformations & PNG_QUANTIZE) != 0)
2040 {
2041 if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
2042 (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
2043 png_ptr->palette_lookup != 0 && info_ptr->bit_depth == 8)
2044 {
2045 info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
2046 }
2047 }
2048 #endif
2049
2050 #ifdef PNG_READ_EXPAND_16_SUPPORTED
2051 if ((png_ptr->transformations & PNG_EXPAND_16) != 0 &&
2052 info_ptr->bit_depth == 8 &&
2053 info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
2054 {
2055 info_ptr->bit_depth = 16;
2056 }
2057 #endif
2058
2059 #ifdef PNG_READ_PACK_SUPPORTED
2060 if ((png_ptr->transformations & PNG_PACK) != 0 &&
2061 (info_ptr->bit_depth < 8))
2062 info_ptr->bit_depth = 8;
2063 #endif
2064
2065 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
2066 info_ptr->channels = 1;
2067
2068 else if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
2069 info_ptr->channels = 3;
2070
2071 else
2072 info_ptr->channels = 1;
2073
2074 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2075 if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0)
2076 {
2077 info_ptr->color_type = (png_byte)(info_ptr->color_type &
2078 ~PNG_COLOR_MASK_ALPHA);
2079 info_ptr->num_trans = 0;
2080 }
2081 #endif
2082
2083 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
2084 info_ptr->channels++;
2085
2086 #ifdef PNG_READ_FILLER_SUPPORTED
2087 /* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
2088 if ((png_ptr->transformations & PNG_FILLER) != 0 &&
2089 (info_ptr->color_type == PNG_COLOR_TYPE_RGB ||
2090 info_ptr->color_type == PNG_COLOR_TYPE_GRAY))
2091 {
2092 info_ptr->channels++;
2093 /* If adding a true alpha channel not just filler */
2094 if ((png_ptr->transformations & PNG_ADD_ALPHA) != 0)
2095 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
2096 }
2097 #endif
2098
2099 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
2100 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
2101 if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
2102 {
2103 if (png_ptr->user_transform_depth != 0)
2104 info_ptr->bit_depth = png_ptr->user_transform_depth;
2105
2106 if (png_ptr->user_transform_channels != 0)
2107 info_ptr->channels = png_ptr->user_transform_channels;
2108 }
2109 #endif
2110
2111 info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
2112 info_ptr->bit_depth);
2113
2114 info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
2115
2116 /* Adding in 1.5.4: cache the above value in png_struct so that we can later
2117 * check in png_rowbytes that the user buffer won't get overwritten. Note
2118 * that the field is not always set - if png_read_update_info isn't called
2119 * the application has to either not do any transforms or get the calculation
2120 * right itself.
2121 */
2122 png_ptr->info_rowbytes = info_ptr->rowbytes;
2123
2124 #ifndef PNG_READ_EXPAND_SUPPORTED
2125 if (png_ptr != NULL)
2126 return;
2127 #endif
2128 }
2129
2130 #ifdef PNG_READ_PACK_SUPPORTED
2131 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
2132 * without changing the actual values. Thus, if you had a row with
2133 * a bit depth of 1, you would end up with bytes that only contained
2134 * the numbers 0 or 1. If you would rather they contain 0 and 255, use
2135 * png_do_shift() after this.
2136 */
2137 static void
2138 png_do_unpack(png_row_infop row_info, png_bytep row)
2139 {
2140 png_debug(1, "in png_do_unpack");
2141
2142 if (row_info->bit_depth < 8)
2143 {
2144 png_uint_32 i;
2145 png_uint_32 row_width=row_info->width;
2146
2147 switch (row_info->bit_depth)
2148 {
2149 case 1:
2150 {
2151 png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
2152 png_bytep dp = row + (png_size_t)row_width - 1;
2153 png_uint_32 shift = 7U - ((row_width + 7U) & 0x07);
2154 for (i = 0; i < row_width; i++)
2155 {
2156 *dp = (png_byte)((*sp >> shift) & 0x01);
2157
2158 if (shift == 7)
2159 {
2160 shift = 0;
2161 sp--;
2162 }
2163
2164 else
2165 shift++;
2166
2167 dp--;
2168 }
2169 break;
2170 }
2171
2172 case 2:
2173 {
2174
2175 png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
2176 png_bytep dp = row + (png_size_t)row_width - 1;
2177 png_uint_32 shift = ((3U - ((row_width + 3U) & 0x03)) << 1);
2178 for (i = 0; i < row_width; i++)
2179 {
2180 *dp = (png_byte)((*sp >> shift) & 0x03);
2181
2182 if (shift == 6)
2183 {
2184 shift = 0;
2185 sp--;
2186 }
2187
2188 else
2189 shift += 2;
2190
2191 dp--;
2192 }
2193 break;
2194 }
2195
2196 case 4:
2197 {
2198 png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
2199 png_bytep dp = row + (png_size_t)row_width - 1;
2200 png_uint_32 shift = ((1U - ((row_width + 1U) & 0x01)) << 2);
2201 for (i = 0; i < row_width; i++)
2202 {
2203 *dp = (png_byte)((*sp >> shift) & 0x0f);
2204
2205 if (shift == 4)
2206 {
2207 shift = 0;
2208 sp--;
2209 }
2210
2211 else
2212 shift = 4;
2213
2214 dp--;
2215 }
2216 break;
2217 }
2218
2219 default:
2220 break;
2221 }
2222 row_info->bit_depth = 8;
2223 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2224 row_info->rowbytes = row_width * row_info->channels;
2225 }
2226 }
2227 #endif
2228
2229 #ifdef PNG_READ_SHIFT_SUPPORTED
2230 /* Reverse the effects of png_do_shift. This routine merely shifts the
2231 * pixels back to their significant bits values. Thus, if you have
2232 * a row of bit depth 8, but only 5 are significant, this will shift
2233 * the values back to 0 through 31.
2234 */
2235 static void
2236 png_do_unshift(png_row_infop row_info, png_bytep row,
2237 png_const_color_8p sig_bits)
2238 {
2239 int color_type;
2240
2241 png_debug(1, "in png_do_unshift");
2242
2243 /* The palette case has already been handled in the _init routine. */
2244 color_type = row_info->color_type;
2245
2246 if (color_type != PNG_COLOR_TYPE_PALETTE)
2247 {
2248 int shift[4];
2249 int channels = 0;
2250 int bit_depth = row_info->bit_depth;
2251
2252 if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
2253 {
2254 shift[channels++] = bit_depth - sig_bits->red;
2255 shift[channels++] = bit_depth - sig_bits->green;
2256 shift[channels++] = bit_depth - sig_bits->blue;
2257 }
2258
2259 else
2260 {
2261 shift[channels++] = bit_depth - sig_bits->gray;
2262 }
2263
2264 if ((color_type & PNG_COLOR_MASK_ALPHA) != 0)
2265 {
2266 shift[channels++] = bit_depth - sig_bits->alpha;
2267 }
2268
2269 {
2270 int c, have_shift;
2271
2272 for (c = have_shift = 0; c < channels; ++c)
2273 {
2274 /* A shift of more than the bit depth is an error condition but it
2275 * gets ignored here.
2276 */
2277 if (shift[c] <= 0 || shift[c] >= bit_depth)
2278 shift[c] = 0;
2279
2280 else
2281 have_shift = 1;
2282 }
2283
2284 if (have_shift == 0)
2285 return;
2286 }
2287
2288 switch (bit_depth)
2289 {
2290 default:
2291 /* Must be 1bpp gray: should not be here! */
2292 /* NOTREACHED */
2293 break;
2294
2295 case 2:
2296 /* Must be 2bpp gray */
2297 /* assert(channels == 1 && shift[0] == 1) */
2298 {
2299 png_bytep bp = row;
2300 png_bytep bp_end = bp + row_info->rowbytes;
2301
2302 while (bp < bp_end)
2303 {
2304 int b = (*bp >> 1) & 0x55;
2305 *bp++ = (png_byte)b;
2306 }
2307 break;
2308 }
2309
2310 case 4:
2311 /* Must be 4bpp gray */
2312 /* assert(channels == 1) */
2313 {
2314 png_bytep bp = row;
2315 png_bytep bp_end = bp + row_info->rowbytes;
2316 int gray_shift = shift[0];
2317 int mask = 0xf >> gray_shift;
2318
2319 mask |= mask << 4;
2320
2321 while (bp < bp_end)
2322 {
2323 int b = (*bp >> gray_shift) & mask;
2324 *bp++ = (png_byte)b;
2325 }
2326 break;
2327 }
2328
2329 case 8:
2330 /* Single byte components, G, GA, RGB, RGBA */
2331 {
2332 png_bytep bp = row;
2333 png_bytep bp_end = bp + row_info->rowbytes;
2334 int channel = 0;
2335
2336 while (bp < bp_end)
2337 {
2338 int b = *bp >> shift[channel];
2339 if (++channel >= channels)
2340 channel = 0;
2341 *bp++ = (png_byte)b;
2342 }
2343 break;
2344 }
2345
2346 #ifdef PNG_READ_16BIT_SUPPORTED
2347 case 16:
2348 /* Double byte components, G, GA, RGB, RGBA */
2349 {
2350 png_bytep bp = row;
2351 png_bytep bp_end = bp + row_info->rowbytes;
2352 int channel = 0;
2353
2354 while (bp < bp_end)
2355 {
2356 int value = (bp[0] << 8) + bp[1];
2357
2358 value >>= shift[channel];
2359 if (++channel >= channels)
2360 channel = 0;
2361 *bp++ = (png_byte)(value >> 8);
2362 *bp++ = (png_byte)value;
2363 }
2364 break;
2365 }
2366 #endif
2367 }
2368 }
2369 }
2370 #endif
2371
2372 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2373 /* Scale rows of bit depth 16 down to 8 accurately */
2374 static void
2375 png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
2376 {
2377 png_debug(1, "in png_do_scale_16_to_8");
2378
2379 if (row_info->bit_depth == 16)
2380 {
2381 png_bytep sp = row; /* source */
2382 png_bytep dp = row; /* destination */
2383 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2384
2385 while (sp < ep)
2386 {
2387 /* The input is an array of 16-bit components, these must be scaled to
2388 * 8 bits each. For a 16-bit value V the required value (from the PNG
2389 * specification) is:
2390 *
2391 * (V * 255) / 65535
2392 *
2393 * This reduces to round(V / 257), or floor((V + 128.5)/257)
2394 *
2395 * Represent V as the two byte value vhi.vlo. Make a guess that the
2396 * result is the top byte of V, vhi, then the correction to this value
2397 * is:
2398 *
2399 * error = floor(((V-vhi.vhi) + 128.5) / 257)
2400 * = floor(((vlo-vhi) + 128.5) / 257)
2401 *
2402 * This can be approximated using integer arithmetic (and a signed
2403 * shift):
2404 *
2405 * error = (vlo-vhi+128) >> 8;
2406 *
2407 * The approximate differs from the exact answer only when (vlo-vhi) is
2408 * 128; it then gives a correction of +1 when the exact correction is
2409 * 0. This gives 128 errors. The exact answer (correct for all 16-bit
2410 * input values) is:
2411 *
2412 * error = (vlo-vhi+128)*65535 >> 24;
2413 *
2414 * An alternative arithmetic calculation which also gives no errors is:
2415 *
2416 * (V * 255 + 32895) >> 16
2417 */
2418
2419 png_int_32 tmp = *sp++; /* must be signed! */
2420 tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
2421 *dp++ = (png_byte)tmp;
2422 }
2423
2424 row_info->bit_depth = 8;
2425 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2426 row_info->rowbytes = row_info->width * row_info->channels;
2427 }
2428 }
2429 #endif
2430
2431 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2432 static void
2433 /* Simply discard the low byte. This was the default behavior prior
2434 * to libpng-1.5.4.
2435 */
2436 png_do_chop(png_row_infop row_info, png_bytep row)
2437 {
2438 png_debug(1, "in png_do_chop");
2439
2440 if (row_info->bit_depth == 16)
2441 {
2442 png_bytep sp = row; /* source */
2443 png_bytep dp = row; /* destination */
2444 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2445
2446 while (sp < ep)
2447 {
2448 *dp++ = *sp;
2449 sp += 2; /* skip low byte */
2450 }
2451
2452 row_info->bit_depth = 8;
2453 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2454 row_info->rowbytes = row_info->width * row_info->channels;
2455 }
2456 }
2457 #endif
2458
2459 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2460 static void
2461 png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
2462 {
2463 png_debug(1, "in png_do_read_swap_alpha");
2464
2465 {
2466 png_uint_32 row_width = row_info->width;
2467 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2468 {
2469 /* This converts from RGBA to ARGB */
2470 if (row_info->bit_depth == 8)
2471 {
2472 png_bytep sp = row + row_info->rowbytes;
2473 png_bytep dp = sp;
2474 png_byte save;
2475 png_uint_32 i;
2476
2477 for (i = 0; i < row_width; i++)
2478 {
2479 save = *(--sp);
2480 *(--dp) = *(--sp);
2481 *(--dp) = *(--sp);
2482 *(--dp) = *(--sp);
2483 *(--dp) = save;
2484 }
2485 }
2486
2487 #ifdef PNG_READ_16BIT_SUPPORTED
2488 /* This converts from RRGGBBAA to AARRGGBB */
2489 else
2490 {
2491 png_bytep sp = row + row_info->rowbytes;
2492 png_bytep dp = sp;
2493 png_byte save[2];
2494 png_uint_32 i;
2495
2496 for (i = 0; i < row_width; i++)
2497 {
2498 save[0] = *(--sp);
2499 save[1] = *(--sp);
2500 *(--dp) = *(--sp);
2501 *(--dp) = *(--sp);
2502 *(--dp) = *(--sp);
2503 *(--dp) = *(--sp);
2504 *(--dp) = *(--sp);
2505 *(--dp) = *(--sp);
2506 *(--dp) = save[0];
2507 *(--dp) = save[1];
2508 }
2509 }
2510 #endif
2511 }
2512
2513 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2514 {
2515 /* This converts from GA to AG */
2516 if (row_info->bit_depth == 8)
2517 {
2518 png_bytep sp = row + row_info->rowbytes;
2519 png_bytep dp = sp;
2520 png_byte save;
2521 png_uint_32 i;
2522
2523 for (i = 0; i < row_width; i++)
2524 {
2525 save = *(--sp);
2526 *(--dp) = *(--sp);
2527 *(--dp) = save;
2528 }
2529 }
2530
2531 #ifdef PNG_READ_16BIT_SUPPORTED
2532 /* This converts from GGAA to AAGG */
2533 else
2534 {
2535 png_bytep sp = row + row_info->rowbytes;
2536 png_bytep dp = sp;
2537 png_byte save[2];
2538 png_uint_32 i;
2539
2540 for (i = 0; i < row_width; i++)
2541 {
2542 save[0] = *(--sp);
2543 save[1] = *(--sp);
2544 *(--dp) = *(--sp);
2545 *(--dp) = *(--sp);
2546 *(--dp) = save[0];
2547 *(--dp) = save[1];
2548 }
2549 }
2550 #endif
2551 }
2552 }
2553 }
2554 #endif
2555
2556 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2557 static void
2558 png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
2559 {
2560 png_uint_32 row_width;
2561 png_debug(1, "in png_do_read_invert_alpha");
2562
2563 row_width = row_info->width;
2564 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2565 {
2566 if (row_info->bit_depth == 8)
2567 {
2568 /* This inverts the alpha channel in RGBA */
2569 png_bytep sp = row + row_info->rowbytes;
2570 png_bytep dp = sp;
2571 png_uint_32 i;
2572
2573 for (i = 0; i < row_width; i++)
2574 {
2575 *(--dp) = (png_byte)(255 - *(--sp));
2576
2577 /* This does nothing:
2578 *(--dp) = *(--sp);
2579 *(--dp) = *(--sp);
2580 *(--dp) = *(--sp);
2581 We can replace it with:
2582 */
2583 sp-=3;
2584 dp=sp;
2585 }
2586 }
2587
2588 #ifdef PNG_READ_16BIT_SUPPORTED
2589 /* This inverts the alpha channel in RRGGBBAA */
2590 else
2591 {
2592 png_bytep sp = row + row_info->rowbytes;
2593 png_bytep dp = sp;
2594 png_uint_32 i;
2595
2596 for (i = 0; i < row_width; i++)
2597 {
2598 *(--dp) = (png_byte)(255 - *(--sp));
2599 *(--dp) = (png_byte)(255 - *(--sp));
2600
2601 /* This does nothing:
2602 *(--dp) = *(--sp);
2603 *(--dp) = *(--sp);
2604 *(--dp) = *(--sp);
2605 *(--dp) = *(--sp);
2606 *(--dp) = *(--sp);
2607 *(--dp) = *(--sp);
2608 We can replace it with:
2609 */
2610 sp-=6;
2611 dp=sp;
2612 }
2613 }
2614 #endif
2615 }
2616 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2617 {
2618 if (row_info->bit_depth == 8)
2619 {
2620 /* This inverts the alpha channel in GA */
2621 png_bytep sp = row + row_info->rowbytes;
2622 png_bytep dp = sp;
2623 png_uint_32 i;
2624
2625 for (i = 0; i < row_width; i++)
2626 {
2627 *(--dp) = (png_byte)(255 - *(--sp));
2628 *(--dp) = *(--sp);
2629 }
2630 }
2631
2632 #ifdef PNG_READ_16BIT_SUPPORTED
2633 else
2634 {
2635 /* This inverts the alpha channel in GGAA */
2636 png_bytep sp = row + row_info->rowbytes;
2637 png_bytep dp = sp;
2638 png_uint_32 i;
2639
2640 for (i = 0; i < row_width; i++)
2641 {
2642 *(--dp) = (png_byte)(255 - *(--sp));
2643 *(--dp) = (png_byte)(255 - *(--sp));
2644 /*
2645 *(--dp) = *(--sp);
2646 *(--dp) = *(--sp);
2647 */
2648 sp-=2;
2649 dp=sp;
2650 }
2651 }
2652 #endif
2653 }
2654 }
2655 #endif
2656
2657 #ifdef PNG_READ_FILLER_SUPPORTED
2658 /* Add filler channel if we have RGB color */
2659 static void
2660 png_do_read_filler(png_row_infop row_info, png_bytep row,
2661 png_uint_32 filler, png_uint_32 flags)
2662 {
2663 png_uint_32 i;
2664 png_uint_32 row_width = row_info->width;
2665
2666 #ifdef PNG_READ_16BIT_SUPPORTED
2667 png_byte hi_filler = (png_byte)(filler>>8);
2668 #endif
2669 png_byte lo_filler = (png_byte)filler;
2670
2671 png_debug(1, "in png_do_read_filler");
2672
2673 if (
2674 row_info->color_type == PNG_COLOR_TYPE_GRAY)
2675 {
2676 if (row_info->bit_depth == 8)
2677 {
2678 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2679 {
2680 /* This changes the data from G to GX */
2681 png_bytep sp = row + (png_size_t)row_width;
2682 png_bytep dp = sp + (png_size_t)row_width;
2683 for (i = 1; i < row_width; i++)
2684 {
2685 *(--dp) = lo_filler;
2686 *(--dp) = *(--sp);
2687 }
2688 *(--dp) = lo_filler;
2689 row_info->channels = 2;
2690 row_info->pixel_depth = 16;
2691 row_info->rowbytes = row_width * 2;
2692 }
2693
2694 else
2695 {
2696 /* This changes the data from G to XG */
2697 png_bytep sp = row + (png_size_t)row_width;
2698 png_bytep dp = sp + (png_size_t)row_width;
2699 for (i = 0; i < row_width; i++)
2700 {
2701 *(--dp) = *(--sp);
2702 *(--dp) = lo_filler;
2703 }
2704 row_info->channels = 2;
2705 row_info->pixel_depth = 16;
2706 row_info->rowbytes = row_width * 2;
2707 }
2708 }
2709
2710 #ifdef PNG_READ_16BIT_SUPPORTED
2711 else if (row_info->bit_depth == 16)
2712 {
2713 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2714 {
2715 /* This changes the data from GG to GGXX */
2716 png_bytep sp = row + (png_size_t)row_width * 2;
2717 png_bytep dp = sp + (png_size_t)row_width * 2;
2718 for (i = 1; i < row_width; i++)
2719 {
2720 *(--dp) = lo_filler;
2721 *(--dp) = hi_filler;
2722 *(--dp) = *(--sp);
2723 *(--dp) = *(--sp);
2724 }
2725 *(--dp) = lo_filler;
2726 *(--dp) = hi_filler;
2727 row_info->channels = 2;
2728 row_info->pixel_depth = 32;
2729 row_info->rowbytes = row_width * 4;
2730 }
2731
2732 else
2733 {
2734 /* This changes the data from GG to XXGG */
2735 png_bytep sp = row + (png_size_t)row_width * 2;
2736 png_bytep dp = sp + (png_size_t)row_width * 2;
2737 for (i = 0; i < row_width; i++)
2738 {
2739 *(--dp) = *(--sp);
2740 *(--dp) = *(--sp);
2741 *(--dp) = lo_filler;
2742 *(--dp) = hi_filler;
2743 }
2744 row_info->channels = 2;
2745 row_info->pixel_depth = 32;
2746 row_info->rowbytes = row_width * 4;
2747 }
2748 }
2749 #endif
2750 } /* COLOR_TYPE == GRAY */
2751 else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
2752 {
2753 if (row_info->bit_depth == 8)
2754 {
2755 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2756 {
2757 /* This changes the data from RGB to RGBX */
2758 png_bytep sp = row + (png_size_t)row_width * 3;
2759 png_bytep dp = sp + (png_size_t)row_width;
2760 for (i = 1; i < row_width; i++)
2761 {
2762 *(--dp) = lo_filler;
2763 *(--dp) = *(--sp);
2764 *(--dp) = *(--sp);
2765 *(--dp) = *(--sp);
2766 }
2767 *(--dp) = lo_filler;
2768 row_info->channels = 4;
2769 row_info->pixel_depth = 32;
2770 row_info->rowbytes = row_width * 4;
2771 }
2772
2773 else
2774 {
2775 /* This changes the data from RGB to XRGB */
2776 png_bytep sp = row + (png_size_t)row_width * 3;
2777 png_bytep dp = sp + (png_size_t)row_width;
2778 for (i = 0; i < row_width; i++)
2779 {
2780 *(--dp) = *(--sp);
2781 *(--dp) = *(--sp);
2782 *(--dp) = *(--sp);
2783 *(--dp) = lo_filler;
2784 }
2785 row_info->channels = 4;
2786 row_info->pixel_depth = 32;
2787 row_info->rowbytes = row_width * 4;
2788 }
2789 }
2790
2791 #ifdef PNG_READ_16BIT_SUPPORTED
2792 else if (row_info->bit_depth == 16)
2793 {
2794 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2795 {
2796 /* This changes the data from RRGGBB to RRGGBBXX */
2797 png_bytep sp = row + (png_size_t)row_width * 6;
2798 png_bytep dp = sp + (png_size_t)row_width * 2;
2799 for (i = 1; i < row_width; i++)
2800 {
2801 *(--dp) = lo_filler;
2802 *(--dp) = hi_filler;
2803 *(--dp) = *(--sp);
2804 *(--dp) = *(--sp);
2805 *(--dp) = *(--sp);
2806 *(--dp) = *(--sp);
2807 *(--dp) = *(--sp);
2808 *(--dp) = *(--sp);
2809 }
2810 *(--dp) = lo_filler;
2811 *(--dp) = hi_filler;
2812 row_info->channels = 4;
2813 row_info->pixel_depth = 64;
2814 row_info->rowbytes = row_width * 8;
2815 }
2816
2817 else
2818 {
2819 /* This changes the data from RRGGBB to XXRRGGBB */
2820 png_bytep sp = row + (png_size_t)row_width * 6;
2821 png_bytep dp = sp + (png_size_t)row_width * 2;
2822 for (i = 0; i < row_width; i++)
2823 {
2824 *(--dp) = *(--sp);
2825 *(--dp) = *(--sp);
2826 *(--dp) = *(--sp);
2827 *(--dp) = *(--sp);
2828 *(--dp) = *(--sp);
2829 *(--dp) = *(--sp);
2830 *(--dp) = lo_filler;
2831 *(--dp) = hi_filler;
2832 }
2833
2834 row_info->channels = 4;
2835 row_info->pixel_depth = 64;
2836 row_info->rowbytes = row_width * 8;
2837 }
2838 }
2839 #endif
2840 } /* COLOR_TYPE == RGB */
2841 }
2842 #endif
2843
2844 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2845 /* Expand grayscale files to RGB, with or without alpha */
2846 static void
2847 png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
2848 {
2849 png_uint_32 i;
2850 png_uint_32 row_width = row_info->width;
2851
2852 png_debug(1, "in png_do_gray_to_rgb");
2853
2854 if (row_info->bit_depth >= 8 &&
2855 (row_info->color_type & PNG_COLOR_MASK_COLOR) == 0)
2856 {
2857 if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
2858 {
2859 if (row_info->bit_depth == 8)
2860 {
2861 /* This changes G to RGB */
2862 png_bytep sp = row + (png_size_t)row_width - 1;
2863 png_bytep dp = sp + (png_size_t)row_width * 2;
2864 for (i = 0; i < row_width; i++)
2865 {
2866 *(dp--) = *sp;
2867 *(dp--) = *sp;
2868 *(dp--) = *(sp--);
2869 }
2870 }
2871
2872 else
2873 {
2874 /* This changes GG to RRGGBB */
2875 png_bytep sp = row + (png_size_t)row_width * 2 - 1;
2876 png_bytep dp = sp + (png_size_t)row_width * 4;
2877 for (i = 0; i < row_width; i++)
2878 {
2879 *(dp--) = *sp;
2880 *(dp--) = *(sp - 1);
2881 *(dp--) = *sp;
2882 *(dp--) = *(sp - 1);
2883 *(dp--) = *(sp--);
2884 *(dp--) = *(sp--);
2885 }
2886 }
2887 }
2888
2889 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2890 {
2891 if (row_info->bit_depth == 8)
2892 {
2893 /* This changes GA to RGBA */
2894 png_bytep sp = row + (png_size_t)row_width * 2 - 1;
2895 png_bytep dp = sp + (png_size_t)row_width * 2;
2896 for (i = 0; i < row_width; i++)
2897 {
2898 *(dp--) = *(sp--);
2899 *(dp--) = *sp;
2900 *(dp--) = *sp;
2901 *(dp--) = *(sp--);
2902 }
2903 }
2904
2905 else
2906 {
2907 /* This changes GGAA to RRGGBBAA */
2908 png_bytep sp = row + (png_size_t)row_width * 4 - 1;
2909 png_bytep dp = sp + (png_size_t)row_width * 4;
2910 for (i = 0; i < row_width; i++)
2911 {
2912 *(dp--) = *(sp--);
2913 *(dp--) = *(sp--);
2914 *(dp--) = *sp;
2915 *(dp--) = *(sp - 1);
2916 *(dp--) = *sp;
2917 *(dp--) = *(sp - 1);
2918 *(dp--) = *(sp--);
2919 *(dp--) = *(sp--);
2920 }
2921 }
2922 }
2923 row_info->channels = (png_byte)(row_info->channels + 2);
2924 row_info->color_type |= PNG_COLOR_MASK_COLOR;
2925 row_info->pixel_depth = (png_byte)(row_info->channels *
2926 row_info->bit_depth);
2927 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
2928 }
2929 }
2930 #endif
2931
2932 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2933 /* Reduce RGB files to grayscale, with or without alpha
2934 * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
2935 * <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
2936 * versions dated 1998 through November 2002 have been archived at
2937 * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
2938 * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
2939 * Charles Poynton poynton at poynton.com
2940 *
2941 * Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2942 *
2943 * which can be expressed with integers as
2944 *
2945 * Y = (6969 * R + 23434 * G + 2365 * B)/32768
2946 *
2947 * Poynton's current link (as of January 2003 through July 2011):
2948 * <http://www.poynton.com/notes/colour_and_gamma/>
2949 * has changed the numbers slightly:
2950 *
2951 * Y = 0.2126*R + 0.7152*G + 0.0722*B
2952 *
2953 * which can be expressed with integers as
2954 *
2955 * Y = (6966 * R + 23436 * G + 2366 * B)/32768
2956 *
2957 * Historically, however, libpng uses numbers derived from the ITU-R Rec 709
2958 * end point chromaticities and the D65 white point. Depending on the
2959 * precision used for the D65 white point this produces a variety of different
2960 * numbers, however if the four decimal place value used in ITU-R Rec 709 is
2961 * used (0.3127,0.3290) the Y calculation would be:
2962 *
2963 * Y = (6968 * R + 23435 * G + 2366 * B)/32768
2964 *
2965 * While this is correct the rounding results in an overflow for white, because
2966 * the sum of the rounded coefficients is 32769, not 32768. Consequently
2967 * libpng uses, instead, the closest non-overflowing approximation:
2968 *
2969 * Y = (6968 * R + 23434 * G + 2366 * B)/32768
2970 *
2971 * Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
2972 * (including an sRGB chunk) then the chromaticities are used to calculate the
2973 * coefficients. See the chunk handling in pngrutil.c for more information.
2974 *
2975 * In all cases the calculation is to be done in a linear colorspace. If no
2976 * gamma information is available to correct the encoding of the original RGB
2977 * values this results in an implicit assumption that the original PNG RGB
2978 * values were linear.
2979 *
2980 * Other integer coefficents can be used via png_set_rgb_to_gray(). Because
2981 * the API takes just red and green coefficients the blue coefficient is
2982 * calculated to make the sum 32768. This will result in different rounding
2983 * to that used above.
2984 */
2985 static int
2986 png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
2987
2988 {
2989 int rgb_error = 0;
2990
2991 png_debug(1, "in png_do_rgb_to_gray");
2992
2993 if ((row_info->color_type & PNG_COLOR_MASK_PALETTE) == 0 &&
2994 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
2995 {
2996 PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
2997 PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
2998 PNG_CONST png_uint_32 bc = 32768 - rc - gc;
2999 PNG_CONST png_uint_32 row_width = row_info->width;
3000 PNG_CONST int have_alpha =
3001 (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
3002
3003 if (row_info->bit_depth == 8)
3004 {
3005 #ifdef PNG_READ_GAMMA_SUPPORTED
3006 /* Notice that gamma to/from 1 are not necessarily inverses (if
3007 * there is an overall gamma correction). Prior to 1.5.5 this code
3008 * checked the linearized values for equality; this doesn't match
3009 * the documentation, the original values must be checked.
3010 */
3011 if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
3012 {
3013 png_bytep sp = row;
3014 png_bytep dp = row;
3015 png_uint_32 i;
3016
3017 for (i = 0; i < row_width; i++)
3018 {
3019 png_byte red = *(sp++);
3020 png_byte green = *(sp++);
3021 png_byte blue = *(sp++);
3022
3023 if (red != green || red != blue)
3024 {
3025 red = png_ptr->gamma_to_1[red];
3026 green = png_ptr->gamma_to_1[green];
3027 blue = png_ptr->gamma_to_1[blue];
3028
3029 rgb_error |= 1;
3030 *(dp++) = png_ptr->gamma_from_1[
3031 (rc*red + gc*green + bc*blue + 16384)>>15];
3032 }
3033
3034 else
3035 {
3036 /* If there is no overall correction the table will not be
3037 * set.
3038 */
3039 if (png_ptr->gamma_table != NULL)
3040 red = png_ptr->gamma_table[red];
3041
3042 *(dp++) = red;
3043 }
3044
3045 if (have_alpha != 0)
3046 *(dp++) = *(sp++);
3047 }
3048 }
3049 else
3050 #endif
3051 {
3052 png_bytep sp = row;
3053 png_bytep dp = row;
3054 png_uint_32 i;
3055
3056 for (i = 0; i < row_width; i++)
3057 {
3058 png_byte red = *(sp++);
3059 png_byte green = *(sp++);
3060 png_byte blue = *(sp++);
3061
3062 if (red != green || red != blue)
3063 {
3064 rgb_error |= 1;
3065 /* NOTE: this is the historical approach which simply
3066 * truncates the results.
3067 */
3068 *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
3069 }
3070
3071 else
3072 *(dp++) = red;
3073
3074 if (have_alpha != 0)
3075 *(dp++) = *(sp++);
3076 }
3077 }
3078 }
3079
3080 else /* RGB bit_depth == 16 */
3081 {
3082 #ifdef PNG_READ_GAMMA_SUPPORTED
3083 if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
3084 {
3085 png_bytep sp = row;
3086 png_bytep dp = row;
3087 png_uint_32 i;
3088
3089 for (i = 0; i < row_width; i++)
3090 {
3091 png_uint_16 red, green, blue, w;
3092 png_byte hi,lo;
3093
3094 hi=*(sp)++; lo=*(sp)++; red = (png_uint_16)((hi << 8) | (lo));
3095 hi=*(sp)++; lo=*(sp)++; green = (png_uint_16)((hi << 8) | (lo));
3096 hi=*(sp)++; lo=*(sp)++; blue = (png_uint_16)((hi << 8) | (lo));
3097
3098 if (red == green && red == blue)
3099 {
3100 if (png_ptr->gamma_16_table != NULL)
3101 w = png_ptr->gamma_16_table[(red & 0xff)
3102 >> png_ptr->gamma_shift][red >> 8];
3103
3104 else
3105 w = red;
3106 }
3107
3108 else
3109 {
3110 png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red & 0xff)
3111 >> png_ptr->gamma_shift][red>>8];
3112 png_uint_16 green_1 =
3113 png_ptr->gamma_16_to_1[(green & 0xff) >>
3114 png_ptr->gamma_shift][green>>8];
3115 png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue & 0xff)
3116 >> png_ptr->gamma_shift][blue>>8];
3117 png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
3118 + bc*blue_1 + 16384)>>15);
3119 w = png_ptr->gamma_16_from_1[(gray16 & 0xff) >>
3120 png_ptr->gamma_shift][gray16 >> 8];
3121 rgb_error |= 1;
3122 }
3123
3124 *(dp++) = (png_byte)((w>>8) & 0xff);
3125 *(dp++) = (png_byte)(w & 0xff);
3126
3127 if (have_alpha != 0)
3128 {
3129 *(dp++) = *(sp++);
3130 *(dp++) = *(sp++);
3131 }
3132 }
3133 }
3134 else
3135 #endif
3136 {
3137 png_bytep sp = row;
3138 png_bytep dp = row;
3139 png_uint_32 i;
3140
3141 for (i = 0; i < row_width; i++)
3142 {
3143 png_uint_16 red, green, blue, gray16;
3144 png_byte hi,lo;
3145
3146 hi=*(sp)++; lo=*(sp)++; red = (png_uint_16)((hi << 8) | (lo));
3147 hi=*(sp)++; lo=*(sp)++; green = (png_uint_16)((hi << 8) | (lo));
3148 hi=*(sp)++; lo=*(sp)++; blue = (png_uint_16)((hi << 8) | (lo));
3149
3150 if (red != green || red != blue)
3151 rgb_error |= 1;
3152
3153 /* From 1.5.5 in the 16-bit case do the accurate conversion even
3154 * in the 'fast' case - this is because this is where the code
3155 * ends up when handling linear 16-bit data.
3156 */
3157 gray16 = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
3158 15);
3159 *(dp++) = (png_byte)((gray16 >> 8) & 0xff);
3160 *(dp++) = (png_byte)(gray16 & 0xff);
3161
3162 if (have_alpha != 0)
3163 {
3164 *(dp++) = *(sp++);
3165 *(dp++) = *(sp++);
3166 }
3167 }
3168 }
3169 }
3170
3171 row_info->channels = (png_byte)(row_info->channels - 2);
3172 row_info->color_type = (png_byte)(row_info->color_type &
3173 ~PNG_COLOR_MASK_COLOR);
3174 row_info->pixel_depth = (png_byte)(row_info->channels *
3175 row_info->bit_depth);
3176 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
3177 }
3178 return rgb_error;
3179 }
3180 #endif
3181
3182 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
3183 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
3184 /* Replace any alpha or transparency with the supplied background color.
3185 * "background" is already in the screen gamma, while "background_1" is
3186 * at a gamma of 1.0. Paletted files have already been taken care of.
3187 */
3188 static void
3189 png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
3190 {
3191 #ifdef PNG_READ_GAMMA_SUPPORTED
3192 png_const_bytep gamma_table = png_ptr->gamma_table;
3193 png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
3194 png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
3195 png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
3196 png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
3197 png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
3198 int gamma_shift = png_ptr->gamma_shift;
3199 int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
3200 #endif
3201
3202 png_bytep sp;
3203 png_uint_32 i;
3204 png_uint_32 row_width = row_info->width;
3205 int shift;
3206
3207 png_debug(1, "in png_do_compose");
3208
3209 {
3210 switch (row_info->color_type)
3211 {
3212 case PNG_COLOR_TYPE_GRAY:
3213 {
3214 switch (row_info->bit_depth)
3215 {