Update libjpeg from 6b to 8b.
[reactos.git] / rosapps / lib / libpng / docs / example.c
1
2 #if 0 /* in case someone actually tries to compile this */
3
4 /* example.c - an example of using libpng
5 * Last changed in libpng 1.2.1 December 7, 2001.
6 * This file has been placed in the public domain by the authors.
7 * Maintained 1998-2007 Glenn Randers-Pehrson
8 * Maintained 1996, 1997 Andreas Dilger)
9 * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
10 */
11
12 /* This is an example of how to use libpng to read and write PNG files.
13 * The file libpng.txt is much more verbose then this. If you have not
14 * read it, do so first. This was designed to be a starting point of an
15 * implementation. This is not officially part of libpng, is hereby placed
16 * in the public domain, and therefore does not require a copyright notice.
17 *
18 * This file does not currently compile, because it is missing certain
19 * parts, like allocating memory to hold an image. You will have to
20 * supply these parts to get it to compile. For an example of a minimal
21 * working PNG reader/writer, see pngtest.c, included in this distribution;
22 * see also the programs in the contrib directory.
23 */
24
25 #include "png.h"
26
27 /* The png_jmpbuf() macro, used in error handling, became available in
28 * libpng version 1.0.6. If you want to be able to run your code with older
29 * versions of libpng, you must define the macro yourself (but only if it
30 * is not already defined by libpng!).
31 */
32
33 #ifndef png_jmpbuf
34 # define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
35 #endif
36
37 /* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp()
38 * returns zero if the image is a PNG and nonzero if it isn't a PNG.
39 *
40 * The function check_if_png() shown here, but not used, returns nonzero (true)
41 * if the file can be opened and is a PNG, 0 (false) otherwise.
42 *
43 * If this call is successful, and you are going to keep the file open,
44 * you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once
45 * you have created the png_ptr, so that libpng knows your application
46 * has read that many bytes from the start of the file. Make sure you
47 * don't call png_set_sig_bytes() with more than 8 bytes read or give it
48 * an incorrect number of bytes read, or you will either have read too
49 * many bytes (your fault), or you are telling libpng to read the wrong
50 * number of magic bytes (also your fault).
51 *
52 * Many applications already read the first 2 or 4 bytes from the start
53 * of the image to determine the file type, so it would be easiest just
54 * to pass the bytes to png_sig_cmp() or even skip that if you know
55 * you have a PNG file, and call png_set_sig_bytes().
56 */
57 #define PNG_BYTES_TO_CHECK 4
58 int check_if_png(char *file_name, FILE **fp)
59 {
60 char buf[PNG_BYTES_TO_CHECK];
61
62 /* Open the prospective PNG file. */
63 if ((*fp = fopen(file_name, "rb")) == NULL)
64 return 0;
65
66 /* Read in some of the signature bytes */
67 if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
68 return 0;
69
70 /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
71 Return nonzero (true) if they match */
72
73 return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
74 }
75
76 /* Read a PNG file. You may want to return an error code if the read
77 * fails (depending upon the failure). There are two "prototypes" given
78 * here - one where we are given the filename, and we need to open the
79 * file, and the other where we are given an open file (possibly with
80 * some or all of the magic bytes read - see comments above).
81 */
82 #ifdef open_file /* prototype 1 */
83 void read_png(char *file_name) /* We need to open the file */
84 {
85 png_structp png_ptr;
86 png_infop info_ptr;
87 unsigned int sig_read = 0;
88 png_uint_32 width, height;
89 int bit_depth, color_type, interlace_type;
90 FILE *fp;
91
92 if ((fp = fopen(file_name, "rb")) == NULL)
93 return (ERROR);
94 #else no_open_file /* prototype 2 */
95 void read_png(FILE *fp, unsigned int sig_read) /* file is already open */
96 {
97 png_structp png_ptr;
98 png_infop info_ptr;
99 png_uint_32 width, height;
100 int bit_depth, color_type, interlace_type;
101 #endif no_open_file /* only use one prototype! */
102
103 /* Create and initialize the png_struct with the desired error handler
104 * functions. If you want to use the default stderr and longjump method,
105 * you can supply NULL for the last three parameters. We also supply the
106 * the compiler header file version, so that we know if the application
107 * was compiled with a compatible version of the library. REQUIRED
108 */
109 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
110 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
111
112 if (png_ptr == NULL)
113 {
114 fclose(fp);
115 return (ERROR);
116 }
117
118 /* Allocate/initialize the memory for image information. REQUIRED. */
119 info_ptr = png_create_info_struct(png_ptr);
120 if (info_ptr == NULL)
121 {
122 fclose(fp);
123 png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
124 return (ERROR);
125 }
126
127 /* Set error handling if you are using the setjmp/longjmp method (this is
128 * the normal method of doing things with libpng). REQUIRED unless you
129 * set up your own error handlers in the png_create_read_struct() earlier.
130 */
131
132 if (setjmp(png_jmpbuf(png_ptr)))
133 {
134 /* Free all of the memory associated with the png_ptr and info_ptr */
135 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
136 fclose(fp);
137 /* If we get here, we had a problem reading the file */
138 return (ERROR);
139 }
140
141 /* One of the following I/O initialization methods is REQUIRED */
142 #ifdef streams /* PNG file I/O method 1 */
143 /* Set up the input control if you are using standard C streams */
144 png_init_io(png_ptr, fp);
145
146 #else no_streams /* PNG file I/O method 2 */
147 /* If you are using replacement read functions, instead of calling
148 * png_init_io() here you would call:
149 */
150 png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
151 /* where user_io_ptr is a structure you want available to the callbacks */
152 #endif no_streams /* Use only one I/O method! */
153
154 /* If we have already read some of the signature */
155 png_set_sig_bytes(png_ptr, sig_read);
156
157 #ifdef hilevel
158 /*
159 * If you have enough memory to read in the entire image at once,
160 * and you need to specify only transforms that can be controlled
161 * with one of the PNG_TRANSFORM_* bits (this presently excludes
162 * dithering, filling, setting background, and doing gamma
163 * adjustment), then you can read the entire image (including
164 * pixels) into the info structure with this call:
165 */
166 png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
167 #else
168 /* OK, you're doing it the hard way, with the lower-level functions */
169
170 /* The call to png_read_info() gives us all of the information from the
171 * PNG file before the first IDAT (image data chunk). REQUIRED
172 */
173 png_read_info(png_ptr, info_ptr);
174
175 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
176 &interlace_type, int_p_NULL, int_p_NULL);
177
178 /* Set up the data transformations you want. Note that these are all
179 * optional. Only call them if you want/need them. Many of the
180 * transformations only work on specific types of images, and many
181 * are mutually exclusive.
182 */
183
184 /* tell libpng to strip 16 bit/color files down to 8 bits/color */
185 png_set_strip_16(png_ptr);
186
187 /* Strip alpha bytes from the input data without combining with the
188 * background (not recommended).
189 */
190 png_set_strip_alpha(png_ptr);
191
192 /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
193 * byte into separate bytes (useful for paletted and grayscale images).
194 */
195 png_set_packing(png_ptr);
196
197 /* Change the order of packed pixels to least significant bit first
198 * (not useful if you are using png_set_packing). */
199 png_set_packswap(png_ptr);
200
201 /* Expand paletted colors into true RGB triplets */
202 if (color_type == PNG_COLOR_TYPE_PALETTE)
203 png_set_palette_to_rgb(png_ptr);
204
205 /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
206 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
207 png_set_gray_1_2_4_to_8(png_ptr);
208
209 /* Expand paletted or RGB images with transparency to full alpha channels
210 * so the data will be available as RGBA quartets.
211 */
212 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
213 png_set_tRNS_to_alpha(png_ptr);
214
215 /* Set the background color to draw transparent and alpha images over.
216 * It is possible to set the red, green, and blue components directly
217 * for paletted images instead of supplying a palette index. Note that
218 * even if the PNG file supplies a background, you are not required to
219 * use it - you should use the (solid) application background if it has one.
220 */
221
222 png_color_16 my_background, *image_background;
223
224 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
225 png_set_background(png_ptr, image_background,
226 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
227 else
228 png_set_background(png_ptr, &my_background,
229 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
230
231 /* Some suggestions as to how to get a screen gamma value */
232
233 /* Note that screen gamma is the display_exponent, which includes
234 * the CRT_exponent and any correction for viewing conditions */
235 if (/* We have a user-defined screen gamma value */)
236 {
237 screen_gamma = user-defined screen_gamma;
238 }
239 /* This is one way that applications share the same screen gamma value */
240 else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
241 {
242 screen_gamma = atof(gamma_str);
243 }
244 /* If we don't have another value */
245 else
246 {
247 screen_gamma = 2.2; /* A good guess for a PC monitors in a dimly
248 lit room */
249 screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */
250 }
251
252 /* Tell libpng to handle the gamma conversion for you. The final call
253 * is a good guess for PC generated images, but it should be configurable
254 * by the user at run time by the user. It is strongly suggested that
255 * your application support gamma correction.
256 */
257
258 int intent;
259
260 if (png_get_sRGB(png_ptr, info_ptr, &intent))
261 png_set_gamma(png_ptr, screen_gamma, 0.45455);
262 else
263 {
264 double image_gamma;
265 if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
266 png_set_gamma(png_ptr, screen_gamma, image_gamma);
267 else
268 png_set_gamma(png_ptr, screen_gamma, 0.45455);
269 }
270
271 /* Dither RGB files down to 8 bit palette or reduce palettes
272 * to the number of colors available on your screen.
273 */
274 if (color_type & PNG_COLOR_MASK_COLOR)
275 {
276 int num_palette;
277 png_colorp palette;
278
279 /* This reduces the image to the application supplied palette */
280 if (/* we have our own palette */)
281 {
282 /* An array of colors to which the image should be dithered */
283 png_color std_color_cube[MAX_SCREEN_COLORS];
284
285 png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
286 MAX_SCREEN_COLORS, png_uint_16p_NULL, 0);
287 }
288 /* This reduces the image to the palette supplied in the file */
289 else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette))
290 {
291 png_uint_16p histogram = NULL;
292
293 png_get_hIST(png_ptr, info_ptr, &histogram);
294
295 png_set_dither(png_ptr, palette, num_palette,
296 max_screen_colors, histogram, 0);
297 }
298 }
299
300 /* invert monochrome files to have 0 as white and 1 as black */
301 png_set_invert_mono(png_ptr);
302
303 /* If you want to shift the pixel values from the range [0,255] or
304 * [0,65535] to the original [0,7] or [0,31], or whatever range the
305 * colors were originally in:
306 */
307 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
308 {
309 png_color_8p sig_bit;
310
311 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
312 png_set_shift(png_ptr, sig_bit);
313 }
314
315 /* flip the RGB pixels to BGR (or RGBA to BGRA) */
316 if (color_type & PNG_COLOR_MASK_COLOR)
317 png_set_bgr(png_ptr);
318
319 /* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
320 png_set_swap_alpha(png_ptr);
321
322 /* swap bytes of 16 bit files to least significant byte first */
323 png_set_swap(png_ptr);
324
325 /* Add filler (or alpha) byte (before/after each RGB triplet) */
326 png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER);
327
328 /* Turn on interlace handling. REQUIRED if you are not using
329 * png_read_image(). To see how to handle interlacing passes,
330 * see the png_read_row() method below:
331 */
332 number_passes = png_set_interlace_handling(png_ptr);
333
334 /* Optional call to gamma correct and add the background to the palette
335 * and update info structure. REQUIRED if you are expecting libpng to
336 * update the palette for you (ie you selected such a transform above).
337 */
338 png_read_update_info(png_ptr, info_ptr);
339
340 /* Allocate the memory to hold the image using the fields of info_ptr. */
341
342 /* The easiest way to read the image: */
343 png_bytep row_pointers[height];
344
345 for (row = 0; row < height; row++)
346 {
347 row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
348 info_ptr));
349 }
350
351 /* Now it's time to read the image. One of these methods is REQUIRED */
352 #ifdef entire /* Read the entire image in one go */
353 png_read_image(png_ptr, row_pointers);
354
355 #else no_entire /* Read the image one or more scanlines at a time */
356 /* The other way to read images - deal with interlacing: */
357
358 for (pass = 0; pass < number_passes; pass++)
359 {
360 #ifdef single /* Read the image a single row at a time */
361 for (y = 0; y < height; y++)
362 {
363 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1);
364 }
365
366 #else no_single /* Read the image several rows at a time */
367 for (y = 0; y < height; y += number_of_rows)
368 {
369 #ifdef sparkle /* Read the image using the "sparkle" effect. */
370 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL,
371 number_of_rows);
372 #else no_sparkle /* Read the image using the "rectangle" effect */
373 png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y],
374 number_of_rows);
375 #endif no_sparkle /* use only one of these two methods */
376 }
377
378 /* if you want to display the image after every pass, do
379 so here */
380 #endif no_single /* use only one of these two methods */
381 }
382 #endif no_entire /* use only one of these two methods */
383
384 /* read rest of file, and get additional chunks in info_ptr - REQUIRED */
385 png_read_end(png_ptr, info_ptr);
386 #endif hilevel
387
388 /* At this point you have read the entire image */
389
390 /* clean up after the read, and free any memory allocated - REQUIRED */
391 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
392
393 /* close the file */
394 fclose(fp);
395
396 /* that's it */
397 return (OK);
398 }
399
400 /* progressively read a file */
401
402 int
403 initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
404 {
405 /* Create and initialize the png_struct with the desired error handler
406 * functions. If you want to use the default stderr and longjump method,
407 * you can supply NULL for the last three parameters. We also check that
408 * the library version is compatible in case we are using dynamically
409 * linked libraries.
410 */
411 *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
412 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
413
414 if (*png_ptr == NULL)
415 {
416 *info_ptr = NULL;
417 return (ERROR);
418 }
419
420 *info_ptr = png_create_info_struct(png_ptr);
421
422 if (*info_ptr == NULL)
423 {
424 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
425 return (ERROR);
426 }
427
428 if (setjmp(png_jmpbuf((*png_ptr))))
429 {
430 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
431 return (ERROR);
432 }
433
434 /* This one's new. You will need to provide all three
435 * function callbacks, even if you aren't using them all.
436 * If you aren't using all functions, you can specify NULL
437 * parameters. Even when all three functions are NULL,
438 * you need to call png_set_progressive_read_fn().
439 * These functions shouldn't be dependent on global or
440 * static variables if you are decoding several images
441 * simultaneously. You should store stream specific data
442 * in a separate struct, given as the second parameter,
443 * and retrieve the pointer from inside the callbacks using
444 * the function png_get_progressive_ptr(png_ptr).
445 */
446 png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
447 info_callback, row_callback, end_callback);
448
449 return (OK);
450 }
451
452 int
453 process_data(png_structp *png_ptr, png_infop *info_ptr,
454 png_bytep buffer, png_uint_32 length)
455 {
456 if (setjmp(png_jmpbuf((*png_ptr))))
457 {
458 /* Free the png_ptr and info_ptr memory on error */
459 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
460 return (ERROR);
461 }
462
463 /* This one's new also. Simply give it chunks of data as
464 * they arrive from the data stream (in order, of course).
465 * On Segmented machines, don't give it any more than 64K.
466 * The library seems to run fine with sizes of 4K, although
467 * you can give it much less if necessary (I assume you can
468 * give it chunks of 1 byte, but I haven't tried with less
469 * than 256 bytes yet). When this function returns, you may
470 * want to display any rows that were generated in the row
471 * callback, if you aren't already displaying them there.
472 */
473 png_process_data(*png_ptr, *info_ptr, buffer, length);
474 return (OK);
475 }
476
477 info_callback(png_structp png_ptr, png_infop info)
478 {
479 /* do any setup here, including setting any of the transformations
480 * mentioned in the Reading PNG files section. For now, you _must_
481 * call either png_start_read_image() or png_read_update_info()
482 * after all the transformations are set (even if you don't set
483 * any). You may start getting rows before png_process_data()
484 * returns, so this is your last chance to prepare for that.
485 */
486 }
487
488 row_callback(png_structp png_ptr, png_bytep new_row,
489 png_uint_32 row_num, int pass)
490 {
491 /*
492 * This function is called for every row in the image. If the
493 * image is interlaced, and you turned on the interlace handler,
494 * this function will be called for every row in every pass.
495 *
496 * In this function you will receive a pointer to new row data from
497 * libpng called new_row that is to replace a corresponding row (of
498 * the same data format) in a buffer allocated by your application.
499 *
500 * The new row data pointer new_row may be NULL, indicating there is
501 * no new data to be replaced (in cases of interlace loading).
502 *
503 * If new_row is not NULL then you need to call
504 * png_progressive_combine_row() to replace the corresponding row as
505 * shown below:
506 */
507 /* Check if row_num is in bounds. */
508 if((row_num >= 0) && (row_num < height))
509 {
510 /* Get pointer to corresponding row in our
511 * PNG read buffer.
512 */
513 png_bytep old_row = ((png_bytep *)our_data)[row_num];
514
515 /* If both rows are allocated then copy the new row
516 * data to the corresponding row data.
517 */
518 if((old_row != NULL) && (new_row != NULL))
519 png_progressive_combine_row(png_ptr, old_row, new_row);
520 }
521 /*
522 * The rows and passes are called in order, so you don't really
523 * need the row_num and pass, but I'm supplying them because it
524 * may make your life easier.
525 *
526 * For the non-NULL rows of interlaced images, you must call
527 * png_progressive_combine_row() passing in the new row and the
528 * old row, as demonstrated above. You can call this function for
529 * NULL rows (it will just return) and for non-interlaced images
530 * (it just does the png_memcpy for you) if it will make the code
531 * easier. Thus, you can just do this for all cases:
532 */
533
534 png_progressive_combine_row(png_ptr, old_row, new_row);
535
536 /* where old_row is what was displayed for previous rows. Note
537 * that the first pass (pass == 0 really) will completely cover
538 * the old row, so the rows do not have to be initialized. After
539 * the first pass (and only for interlaced images), you will have
540 * to pass the current row as new_row, and the function will combine
541 * the old row and the new row.
542 */
543 }
544
545 end_callback(png_structp png_ptr, png_infop info)
546 {
547 /* this function is called when the whole image has been read,
548 * including any chunks after the image (up to and including
549 * the IEND). You will usually have the same info chunk as you
550 * had in the header, although some data may have been added
551 * to the comments and time fields.
552 *
553 * Most people won't do much here, perhaps setting a flag that
554 * marks the image as finished.
555 */
556 }
557
558 /* write a png file */
559 void write_png(char *file_name /* , ... other image information ... */)
560 {
561 FILE *fp;
562 png_structp png_ptr;
563 png_infop info_ptr;
564 png_colorp palette;
565
566 /* open the file */
567 fp = fopen(file_name, "wb");
568 if (fp == NULL)
569 return (ERROR);
570
571 /* Create and initialize the png_struct with the desired error handler
572 * functions. If you want to use the default stderr and longjump method,
573 * you can supply NULL for the last three parameters. We also check that
574 * the library version is compatible with the one used at compile time,
575 * in case we are using dynamically linked libraries. REQUIRED.
576 */
577 png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
578 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
579
580 if (png_ptr == NULL)
581 {
582 fclose(fp);
583 return (ERROR);
584 }
585
586 /* Allocate/initialize the image information data. REQUIRED */
587 info_ptr = png_create_info_struct(png_ptr);
588 if (info_ptr == NULL)
589 {
590 fclose(fp);
591 png_destroy_write_struct(&png_ptr, png_infopp_NULL);
592 return (ERROR);
593 }
594
595 /* Set error handling. REQUIRED if you aren't supplying your own
596 * error handling functions in the png_create_write_struct() call.
597 */
598 if (setjmp(png_jmpbuf(png_ptr)))
599 {
600 /* If we get here, we had a problem reading the file */
601 fclose(fp);
602 png_destroy_write_struct(&png_ptr, &info_ptr);
603 return (ERROR);
604 }
605
606 /* One of the following I/O initialization functions is REQUIRED */
607 #ifdef streams /* I/O initialization method 1 */
608 /* set up the output control if you are using standard C streams */
609 png_init_io(png_ptr, fp);
610 #else no_streams /* I/O initialization method 2 */
611 /* If you are using replacement read functions, instead of calling
612 * png_init_io() here you would call */
613 png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
614 user_IO_flush_function);
615 /* where user_io_ptr is a structure you want available to the callbacks */
616 #endif no_streams /* only use one initialization method */
617
618 #ifdef hilevel
619 /* This is the easy way. Use it if you already have all the
620 * image info living info in the structure. You could "|" many
621 * PNG_TRANSFORM flags into the png_transforms integer here.
622 */
623 png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
624 #else
625 /* This is the hard way */
626
627 /* Set the image information here. Width and height are up to 2^31,
628 * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
629 * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
630 * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
631 * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or
632 * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
633 * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
634 */
635 png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
636 PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
637
638 /* set the palette if there is one. REQUIRED for indexed-color images */
639 palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
640 * png_sizeof (png_color));
641 /* ... set palette colors ... */
642 png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
643 /* You must not free palette here, because png_set_PLTE only makes a link to
644 the palette that you malloced. Wait until you are about to destroy
645 the png structure. */
646
647 /* optional significant bit chunk */
648 /* if we are dealing with a grayscale image then */
649 sig_bit.gray = true_bit_depth;
650 /* otherwise, if we are dealing with a color image then */
651 sig_bit.red = true_red_bit_depth;
652 sig_bit.green = true_green_bit_depth;
653 sig_bit.blue = true_blue_bit_depth;
654 /* if the image has an alpha channel then */
655 sig_bit.alpha = true_alpha_bit_depth;
656 png_set_sBIT(png_ptr, info_ptr, sig_bit);
657
658
659 /* Optional gamma chunk is strongly suggested if you have any guess
660 * as to the correct gamma of the image.
661 */
662 png_set_gAMA(png_ptr, info_ptr, gamma);
663
664 /* Optionally write comments into the image */
665 text_ptr[0].key = "Title";
666 text_ptr[0].text = "Mona Lisa";
667 text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
668 text_ptr[1].key = "Author";
669 text_ptr[1].text = "Leonardo DaVinci";
670 text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
671 text_ptr[2].key = "Description";
672 text_ptr[2].text = "<long text>";
673 text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
674 #ifdef PNG_iTXt_SUPPORTED
675 text_ptr[0].lang = NULL;
676 text_ptr[1].lang = NULL;
677 text_ptr[2].lang = NULL;
678 #endif
679 png_set_text(png_ptr, info_ptr, text_ptr, 3);
680
681 /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */
682 /* note that if sRGB is present the gAMA and cHRM chunks must be ignored
683 * on read and must be written in accordance with the sRGB profile */
684
685 /* Write the file header information. REQUIRED */
686 png_write_info(png_ptr, info_ptr);
687
688 /* If you want, you can write the info in two steps, in case you need to
689 * write your private chunk ahead of PLTE:
690 *
691 * png_write_info_before_PLTE(write_ptr, write_info_ptr);
692 * write_my_chunk();
693 * png_write_info(png_ptr, info_ptr);
694 *
695 * However, given the level of known- and unknown-chunk support in 1.1.0
696 * and up, this should no longer be necessary.
697 */
698
699 /* Once we write out the header, the compression type on the text
700 * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or
701 * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again
702 * at the end.
703 */
704
705 /* set up the transformations you want. Note that these are
706 * all optional. Only call them if you want them.
707 */
708
709 /* invert monochrome pixels */
710 png_set_invert_mono(png_ptr);
711
712 /* Shift the pixels up to a legal bit depth and fill in
713 * as appropriate to correctly scale the image.
714 */
715 png_set_shift(png_ptr, &sig_bit);
716
717 /* pack pixels into bytes */
718 png_set_packing(png_ptr);
719
720 /* swap location of alpha bytes from ARGB to RGBA */
721 png_set_swap_alpha(png_ptr);
722
723 /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into
724 * RGB (4 channels -> 3 channels). The second parameter is not used.
725 */
726 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
727
728 /* flip BGR pixels to RGB */
729 png_set_bgr(png_ptr);
730
731 /* swap bytes of 16-bit files to most significant byte first */
732 png_set_swap(png_ptr);
733
734 /* swap bits of 1, 2, 4 bit packed pixel formats */
735 png_set_packswap(png_ptr);
736
737 /* turn on interlace handling if you are not using png_write_image() */
738 if (interlacing)
739 number_passes = png_set_interlace_handling(png_ptr);
740 else
741 number_passes = 1;
742
743 /* The easiest way to write the image (you may have a different memory
744 * layout, however, so choose what fits your needs best). You need to
745 * use the first method if you aren't handling interlacing yourself.
746 */
747 png_uint_32 k, height, width;
748 png_byte image[height][width*bytes_per_pixel];
749 png_bytep row_pointers[height];
750
751 if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep))
752 png_error (png_ptr, "Image is too tall to process in memory");
753
754 for (k = 0; k < height; k++)
755 row_pointers[k] = image + k*width*bytes_per_pixel;
756
757 /* One of the following output methods is REQUIRED */
758 #ifdef entire /* write out the entire image data in one call */
759 png_write_image(png_ptr, row_pointers);
760
761 /* the other way to write the image - deal with interlacing */
762
763 #else no_entire /* write out the image data by one or more scanlines */
764 /* The number of passes is either 1 for non-interlaced images,
765 * or 7 for interlaced images.
766 */
767 for (pass = 0; pass < number_passes; pass++)
768 {
769 /* Write a few rows at a time. */
770 png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows);
771
772 /* If you are only writing one row at a time, this works */
773 for (y = 0; y < height; y++)
774 {
775 png_write_rows(png_ptr, &row_pointers[y], 1);
776 }
777 }
778 #endif no_entire /* use only one output method */
779
780 /* You can write optional chunks like tEXt, zTXt, and tIME at the end
781 * as well. Shouldn't be necessary in 1.1.0 and up as all the public
782 * chunks are supported and you can use png_set_unknown_chunks() to
783 * register unknown chunks into the info structure to be written out.
784 */
785
786 /* It is REQUIRED to call this to finish writing the rest of the file */
787 png_write_end(png_ptr, info_ptr);
788 #endif hilevel
789
790 /* If you png_malloced a palette, free it here (don't free info_ptr->palette,
791 as recommended in versions 1.0.5m and earlier of this example; if
792 libpng mallocs info_ptr->palette, libpng will free it). If you
793 allocated it with malloc() instead of png_malloc(), use free() instead
794 of png_free(). */
795 png_free(png_ptr, palette);
796 palette=NULL;
797
798 /* Similarly, if you png_malloced any data that you passed in with
799 png_set_something(), such as a hist or trans array, free it here,
800 when you can be sure that libpng is through with it. */
801 png_free(png_ptr, trans);
802 trans=NULL;
803
804 /* clean up after the write, and free any memory allocated */
805 png_destroy_write_struct(&png_ptr, &info_ptr);
806
807 /* close the file */
808 fclose(fp);
809
810 /* that's it */
811 return (OK);
812 }
813
814 #endif /* if 0 */