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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 1.2.37 [June 4, 2009]
6 * This file has been placed in the public domain by the authors.
7 * Maintained 1998-2010 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
58int 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 */
83void 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
95#else no_open_file /* prototype 2 */
96void read_png(FILE *fp, unsigned int sig_read) /* File is already open */
97{
98 png_structp png_ptr;
99 png_infop info_ptr;
100 png_uint_32 width, height;
101 int bit_depth, color_type, interlace_type;
102#endif no_open_file /* Only use one prototype! */
103
104 /* Create and initialize the png_struct with the desired error handler
105 * functions. If you want to use the default stderr and longjump method,
106 * you can supply NULL for the last three parameters. We also supply the
107 * the compiler header file version, so that we know if the application
108 * was compiled with a compatible version of the library. REQUIRED
109 */
110 png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
111 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
112
113 if (png_ptr == NULL)
114 {
115 fclose(fp);
116 return (ERROR);
117 }
118
119 /* Allocate/initialize the memory for image information. REQUIRED. */
120 info_ptr = png_create_info_struct(png_ptr);
121 if (info_ptr == NULL)
122 {
123 fclose(fp);
124 png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
125 return (ERROR);
126 }
127
128 /* Set error handling if you are using the setjmp/longjmp method (this is
129 * the normal method of doing things with libpng). REQUIRED unless you
130 * set up your own error handlers in the png_create_read_struct() earlier.
131 */
132
133 if (setjmp(png_jmpbuf(png_ptr)))
134 {
135 /* Free all of the memory associated with the png_ptr and info_ptr */
136 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
137 fclose(fp);
138 /* If we get here, we had a problem reading the file */
139 return (ERROR);
140 }
141
142 /* One of the following I/O initialization methods is REQUIRED */
143#ifdef streams /* PNG file I/O method 1 */
144 /* Set up the input control if you are using standard C streams */
145 png_init_io(png_ptr, fp);
146
147#else no_streams /* PNG file I/O method 2 */
148 /* If you are using replacement read functions, instead of calling
149 * png_init_io() here you would call:
150 */
151 png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn);
152 /* where user_io_ptr is a structure you want available to the callbacks */
153#endif no_streams /* Use only one I/O method! */
154
155 /* If we have already read some of the signature */
156 png_set_sig_bytes(png_ptr, sig_read);
157
158#ifdef hilevel
159 /*
160 * If you have enough memory to read in the entire image at once,
161 * and you need to specify only transforms that can be controlled
162 * with one of the PNG_TRANSFORM_* bits (this presently excludes
163 * dithering, filling, setting background, and doing gamma
164 * adjustment), then you can read the entire image (including
165 * pixels) into the info structure with this call:
166 */
167 png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
168
169#else
170 /* OK, you're doing it the hard way, with the lower-level functions */
171
172 /* The call to png_read_info() gives us all of the information from the
173 * PNG file before the first IDAT (image data chunk). REQUIRED
174 */
175 png_read_info(png_ptr, info_ptr);
176
177 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
178 &interlace_type, int_p_NULL, int_p_NULL);
179
180 /* Set up the data transformations you want. Note that these are all
181 * optional. Only call them if you want/need them. Many of the
182 * transformations only work on specific types of images, and many
183 * are mutually exclusive.
184 */
185
186 /* Tell libpng to strip 16 bit/color files down to 8 bits/color */
187 png_set_strip_16(png_ptr);
188
189 /* Strip alpha bytes from the input data without combining with the
190 * background (not recommended).
191 */
192 png_set_strip_alpha(png_ptr);
193
194 /* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
195 * byte into separate bytes (useful for paletted and grayscale images).
196 */
197 png_set_packing(png_ptr);
198
199 /* Change the order of packed pixels to least significant bit first
200 * (not useful if you are using png_set_packing). */
201 png_set_packswap(png_ptr);
202
203 /* Expand paletted colors into true RGB triplets */
204 if (color_type == PNG_COLOR_TYPE_PALETTE)
205 png_set_palette_to_rgb(png_ptr);
206
207 /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
208 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
209 png_set_expand_gray_1_2_4_to_8(png_ptr);
210
211 /* Expand paletted or RGB images with transparency to full alpha channels
212 * so the data will be available as RGBA quartets.
213 */
214 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
215 png_set_tRNS_to_alpha(png_ptr);
216
217 /* Set the background color to draw transparent and alpha images over.
218 * It is possible to set the red, green, and blue components directly
219 * for paletted images instead of supplying a palette index. Note that
220 * even if the PNG file supplies a background, you are not required to
221 * use it - you should use the (solid) application background if it has one.
222 */
223
224 png_color_16 my_background, *image_background;
225
226 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
227 png_set_background(png_ptr, image_background,
228 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
229 else
230 png_set_background(png_ptr, &my_background,
231 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
232
233 /* Some suggestions as to how to get a screen gamma value
234 *
235 * Note that screen gamma is the display_exponent, which includes
236 * the CRT_exponent and any correction for viewing conditions
237 */
238 if (/* We have a user-defined screen gamma value */)
239 {
240 screen_gamma = user-defined screen_gamma;
241 }
242 /* This is one way that applications share the same screen gamma value */
243 else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL)
244 {
245 screen_gamma = atof(gamma_str);
246 }
247 /* If we don't have another value */
248 else
249 {
250 screen_gamma = 2.2; /* A good guess for a PC monitor in a dimly
251 lit room */
252 screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */
253 }
254
255 /* Tell libpng to handle the gamma conversion for you. The final call
256 * is a good guess for PC generated images, but it should be configurable
257 * by the user at run time by the user. It is strongly suggested that
258 * your application support gamma correction.
259 */
260
261 int intent;
262
263 if (png_get_sRGB(png_ptr, info_ptr, &intent))
264 png_set_gamma(png_ptr, screen_gamma, 0.45455);
265 else
266 {
267 double image_gamma;
268 if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
269 png_set_gamma(png_ptr, screen_gamma, image_gamma);
270 else
271 png_set_gamma(png_ptr, screen_gamma, 0.45455);
272 }
273
274 /* Dither RGB files down to 8 bit palette or reduce palettes
275 * to the number of colors available on your screen.
276 */
277 if (color_type & PNG_COLOR_MASK_COLOR)
278 {
279 int num_palette;
280 png_colorp palette;
281
282 /* This reduces the image to the application supplied palette */
283 if (/* We have our own palette */)
284 {
285 /* An array of colors to which the image should be dithered */
286 png_color std_color_cube[MAX_SCREEN_COLORS];
287
288 png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
289 MAX_SCREEN_COLORS, png_uint_16p_NULL, 0);
290 }
291 /* This reduces the image to the palette supplied in the file */
292 else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette))
293 {
294 png_uint_16p histogram = NULL;
295
296 png_get_hIST(png_ptr, info_ptr, &histogram);
297
298 png_set_dither(png_ptr, palette, num_palette,
299 max_screen_colors, histogram, 0);
300 }
301 }
302
303 /* Invert monochrome files to have 0 as white and 1 as black */
304 png_set_invert_mono(png_ptr);
305
306 /* If you want to shift the pixel values from the range [0,255] or
307 * [0,65535] to the original [0,7] or [0,31], or whatever range the
308 * colors were originally in:
309 */
310 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
311 {
312 png_color_8p sig_bit_p;
313
314 png_get_sBIT(png_ptr, info_ptr, &sig_bit_p);
315 png_set_shift(png_ptr, sig_bit_p);
316 }
317
318 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
319 if (color_type & PNG_COLOR_MASK_COLOR)
320 png_set_bgr(png_ptr);
321
322 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
323 png_set_swap_alpha(png_ptr);
324
325 /* Swap bytes of 16 bit files to least significant byte first */
326 png_set_swap(png_ptr);
327
328 /* Add filler (or alpha) byte (before/after each RGB triplet) */
329 png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER);
330
331 /* Turn on interlace handling. REQUIRED if you are not using
332 * png_read_image(). To see how to handle interlacing passes,
333 * see the png_read_row() method below:
334 */
335 number_passes = png_set_interlace_handling(png_ptr);
336
337 /* Optional call to gamma correct and add the background to the palette
338 * and update info structure. REQUIRED if you are expecting libpng to
339 * update the palette for you (ie you selected such a transform above).
340 */
341 png_read_update_info(png_ptr, info_ptr);
342
343 /* Allocate the memory to hold the image using the fields of info_ptr. */
344
345 /* The easiest way to read the image: */
346 png_bytep row_pointers[height];
347
348 /* Clear the pointer array */
349 for (row = 0; row < height; row++)
350 row_pointers[row] = NULL;
351
352 for (row = 0; row < height; row++)
353 row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
354 info_ptr));
355
356 /* Now it's time to read the image. One of these methods is REQUIRED */
357#ifdef entire /* Read the entire image in one go */
358 png_read_image(png_ptr, row_pointers);
359
360#else no_entire /* Read the image one or more scanlines at a time */
361 /* The other way to read images - deal with interlacing: */
362
363 for (pass = 0; pass < number_passes; pass++)
364 {
365#ifdef single /* Read the image a single row at a time */
366 for (y = 0; y < height; y++)
367 {
368 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1);
369 }
370
371#else no_single /* Read the image several rows at a time */
372 for (y = 0; y < height; y += number_of_rows)
373 {
374#ifdef sparkle /* Read the image using the "sparkle" effect. */
375 png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL,
376 number_of_rows);
377#else no_sparkle /* Read the image using the "rectangle" effect */
378 png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y],
379 number_of_rows);
380#endif no_sparkle /* Use only one of these two methods */
381 }
382
383 /* If you want to display the image after every pass, do so here */
384#endif no_single /* Use only one of these two methods */
385 }
386#endif no_entire /* Use only one of these two methods */
387
388 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
389 png_read_end(png_ptr, info_ptr);
390#endif hilevel
391
392 /* At this point you have read the entire image */
393
394 /* Clean up after the read, and free any memory allocated - REQUIRED */
395 png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
396
397 /* Close the file */
398 fclose(fp);
399
400 /* That's it */
401 return (OK);
402}
403
404/* Progressively read a file */
405
406int
407initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
408{
409 /* Create and initialize the png_struct with the desired error handler
410 * functions. If you want to use the default stderr and longjump method,
411 * you can supply NULL for the last three parameters. We also check that
412 * the library version is compatible in case we are using dynamically
413 * linked libraries.
414 */
415 *png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
416 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
417
418 if (*png_ptr == NULL)
419 {
420 *info_ptr = NULL;
421 return (ERROR);
422 }
423
424 *info_ptr = png_create_info_struct(png_ptr);
425
426 if (*info_ptr == NULL)
427 {
428 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
429 return (ERROR);
430 }
431
432 if (setjmp(png_jmpbuf((*png_ptr))))
433 {
434 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
435 return (ERROR);
436 }
437
438 /* This one's new. You will need to provide all three
439 * function callbacks, even if you aren't using them all.
440 * If you aren't using all functions, you can specify NULL
441 * parameters. Even when all three functions are NULL,
442 * you need to call png_set_progressive_read_fn().
443 * These functions shouldn't be dependent on global or
444 * static variables if you are decoding several images
445 * simultaneously. You should store stream specific data
446 * in a separate struct, given as the second parameter,
447 * and retrieve the pointer from inside the callbacks using
448 * the function png_get_progressive_ptr(png_ptr).
449 */
450 png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
451 info_callback, row_callback, end_callback);
452
453 return (OK);
454}
455
456int
457process_data(png_structp *png_ptr, png_infop *info_ptr,
458 png_bytep buffer, png_uint_32 length)
459{
460 if (setjmp(png_jmpbuf((*png_ptr))))
461 {
462 /* Free the png_ptr and info_ptr memory on error */
463 png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
464 return (ERROR);
465 }
466
467 /* This one's new also. Simply give it chunks of data as
468 * they arrive from the data stream (in order, of course).
469 * On segmented machines, don't give it any more than 64K.
470 * The library seems to run fine with sizes of 4K, although
471 * you can give it much less if necessary (I assume you can
472 * give it chunks of 1 byte, but I haven't tried with less
473 * than 256 bytes yet). When this function returns, you may
474 * want to display any rows that were generated in the row
475 * callback, if you aren't already displaying them there.
476 */
477 png_process_data(*png_ptr, *info_ptr, buffer, length);
478 return (OK);
479}
480
481info_callback(png_structp png_ptr, png_infop info)
482{
483 /* Do any setup here, including setting any of the transformations
484 * mentioned in the Reading PNG files section. For now, you _must_
485 * call either png_start_read_image() or png_read_update_info()
486 * after all the transformations are set (even if you don't set
487 * any). You may start getting rows before png_process_data()
488 * returns, so this is your last chance to prepare for that.
489 */
490}
491
492row_callback(png_structp png_ptr, png_bytep new_row,
493 png_uint_32 row_num, int pass)
494{
495 /*
496 * This function is called for every row in the image. If the
497 * image is interlaced, and you turned on the interlace handler,
498 * this function will be called for every row in every pass.
499 *
500 * In this function you will receive a pointer to new row data from
501 * libpng called new_row that is to replace a corresponding row (of
502 * the same data format) in a buffer allocated by your application.
503 *
504 * The new row data pointer "new_row" may be NULL, indicating there is
505 * no new data to be replaced (in cases of interlace loading).
506 *
507 * If new_row is not NULL then you need to call
508 * png_progressive_combine_row() to replace the corresponding row as
509 * shown below:
510 */
511
512 /* Get pointer to corresponding row in our
513 * PNG read buffer.
514 */
515 png_bytep old_row = ((png_bytep *)our_data)[row_num];
516
517 /* If both rows are allocated then copy the new row
518 * data to the corresponding row data.
519 */
520 if ((old_row != NULL) && (new_row != NULL))
521 png_progressive_combine_row(png_ptr, old_row, new_row);
522
523 /*
524 * The rows and passes are called in order, so you don't really
525 * need the row_num and pass, but I'm supplying them because it
526 * may make your life easier.
527 *
528 * For the non-NULL rows of interlaced images, you must call
529 * png_progressive_combine_row() passing in the new row and the
530 * old row, as demonstrated above. You can call this function for
531 * NULL rows (it will just return) and for non-interlaced images
532 * (it just does the png_memcpy for you) if it will make the code
533 * easier. Thus, you can just do this for all cases:
534 */
535
536 png_progressive_combine_row(png_ptr, old_row, new_row);
537
538 /* where old_row is what was displayed for previous rows. Note
539 * that the first pass (pass == 0 really) will completely cover
540 * the old row, so the rows do not have to be initialized. After
541 * the first pass (and only for interlaced images), you will have
542 * to pass the current row as new_row, and the function will combine
543 * the old row and the new row.
544 */
545}
546
547end_callback(png_structp png_ptr, png_infop info)
548{
549 /* This function is called when the whole image has been read,
550 * including any chunks after the image (up to and including
551 * the IEND). You will usually have the same info chunk as you
552 * had in the header, although some data may have been added
553 * to the comments and time fields.
554 *
555 * Most people won't do much here, perhaps setting a flag that
556 * marks the image as finished.
557 */
558}
559
560/* Write a png file */
561void write_png(char *file_name /* , ... other image information ... */)
562{
563 FILE *fp;
564 png_structp png_ptr;
565 png_infop info_ptr;
566 png_colorp palette;
567
568 /* Open the file */
569 fp = fopen(file_name, "wb");
570 if (fp == NULL)
571 return (ERROR);
572
573 /* Create and initialize the png_struct with the desired error handler
574 * functions. If you want to use the default stderr and longjump method,
575 * you can supply NULL for the last three parameters. We also check that
576 * the library version is compatible with the one used at compile time,
577 * in case we are using dynamically linked libraries. REQUIRED.
578 */
579 png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
580 png_voidp user_error_ptr, user_error_fn, user_warning_fn);
581
582 if (png_ptr == NULL)
583 {
584 fclose(fp);
585 return (ERROR);
586 }
587
588 /* Allocate/initialize the image information data. REQUIRED */
589 info_ptr = png_create_info_struct(png_ptr);
590 if (info_ptr == NULL)
591 {
592 fclose(fp);
593 png_destroy_write_struct(&png_ptr, png_infopp_NULL);
594 return (ERROR);
595 }
596
597 /* Set error handling. REQUIRED if you aren't supplying your own
598 * error handling functions in the png_create_write_struct() call.
599 */
600 if (setjmp(png_jmpbuf(png_ptr)))
601 {
602 /* If we get here, we had a problem writing the file */
603 fclose(fp);
604 png_destroy_write_struct(&png_ptr, &info_ptr);
605 return (ERROR);
606 }
607
608 /* One of the following I/O initialization functions is REQUIRED */
609
610#ifdef streams /* I/O initialization method 1 */
611 /* Set up the output control if you are using standard C streams */
612 png_init_io(png_ptr, fp);
613
614#else no_streams /* I/O initialization method 2 */
615 /* If you are using replacement write functions, instead of calling
616 * png_init_io() here you would call
617 */
618 png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
619 user_IO_flush_function);
620 /* where user_io_ptr is a structure you want available to the callbacks */
621#endif no_streams /* Only use one initialization method */
622
623#ifdef hilevel
624 /* This is the easy way. Use it if you already have all the
625 * image info living in the structure. You could "|" many
626 * PNG_TRANSFORM flags into the png_transforms integer here.
627 */
628 png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
629
630#else
631 /* This is the hard way */
632
633 /* Set the image information here. Width and height are up to 2^31,
634 * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
635 * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
636 * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
637 * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or
638 * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
639 * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
640 */
641 png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
642 PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
643
644 /* Set the palette if there is one. REQUIRED for indexed-color images */
645 palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
646 * png_sizeof(png_color));
647 /* ... Set palette colors ... */
648 png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
649 /* You must not free palette here, because png_set_PLTE only makes a link to
650 * the palette that you malloced. Wait until you are about to destroy
651 * the png structure.
652 */
653
654 /* Optional significant bit (sBIT) chunk */
655 png_color_8 sig_bit;
656 /* If we are dealing with a grayscale image then */
657 sig_bit.gray = true_bit_depth;
658 /* Otherwise, if we are dealing with a color image then */
659 sig_bit.red = true_red_bit_depth;
660 sig_bit.green = true_green_bit_depth;
661 sig_bit.blue = true_blue_bit_depth;
662 /* If the image has an alpha channel then */
663 sig_bit.alpha = true_alpha_bit_depth;
664 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
665
666
667 /* Optional gamma chunk is strongly suggested if you have any guess
668 * as to the correct gamma of the image.
669 */
670 png_set_gAMA(png_ptr, info_ptr, gamma);
671
672 /* Optionally write comments into the image */
673 text_ptr[0].key = "Title";
674 text_ptr[0].text = "Mona Lisa";
675 text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE;
676 text_ptr[1].key = "Author";
677 text_ptr[1].text = "Leonardo DaVinci";
678 text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
679 text_ptr[2].key = "Description";
680 text_ptr[2].text = "<long text>";
681 text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
682#ifdef PNG_iTXt_SUPPORTED
683 text_ptr[0].lang = NULL;
684 text_ptr[1].lang = NULL;
685 text_ptr[2].lang = NULL;
686#endif
687 png_set_text(png_ptr, info_ptr, text_ptr, 3);
688
689 /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs */
690
691 /* Note that if sRGB is present the gAMA and cHRM chunks must be ignored
692 * on read and, if your application chooses to write them, they must
693 * be written in accordance with the sRGB profile
694 */
695
696 /* Write the file header information. REQUIRED */
697 png_write_info(png_ptr, info_ptr);
698
699 /* If you want, you can write the info in two steps, in case you need to
700 * write your private chunk ahead of PLTE:
701 *
702 * png_write_info_before_PLTE(write_ptr, write_info_ptr);
703 * write_my_chunk();
704 * png_write_info(png_ptr, info_ptr);
705 *
706 * However, given the level of known- and unknown-chunk support in 1.2.0
707 * and up, this should no longer be necessary.
708 */
709
710 /* Once we write out the header, the compression type on the text
711 * chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or
712 * PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again
713 * at the end.
714 */
715
716 /* Set up the transformations you want. Note that these are
717 * all optional. Only call them if you want them.
718 */
719
720 /* Invert monochrome pixels */
721 png_set_invert_mono(png_ptr);
722
723 /* Shift the pixels up to a legal bit depth and fill in
724 * as appropriate to correctly scale the image.
725 */
726 png_set_shift(png_ptr, &sig_bit);
727
728 /* Pack pixels into bytes */
729 png_set_packing(png_ptr);
730
731 /* Swap location of alpha bytes from ARGB to RGBA */
732 png_set_swap_alpha(png_ptr);
733
734 /* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into
735 * RGB (4 channels -> 3 channels). The second parameter is not used.
736 */
737 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
738
739 /* Flip BGR pixels to RGB */
740 png_set_bgr(png_ptr);
741
742 /* Swap bytes of 16-bit files to most significant byte first */
743 png_set_swap(png_ptr);
744
745 /* Swap bits of 1, 2, 4 bit packed pixel formats */
746 png_set_packswap(png_ptr);
747
748 /* Turn on interlace handling if you are not using png_write_image() */
749 if (interlacing)
750 number_passes = png_set_interlace_handling(png_ptr);
751 else
752 number_passes = 1;
753
754 /* The easiest way to write the image (you may have a different memory
755 * layout, however, so choose what fits your needs best). You need to
756 * use the first method if you aren't handling interlacing yourself.
757 */
758 png_uint_32 k, height, width;
759 png_byte image[height][width*bytes_per_pixel];
760 png_bytep row_pointers[height];
761
762 if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep))
763 png_error (png_ptr, "Image is too tall to process in memory");
764
765 for (k = 0; k < height; k++)
766 row_pointers[k] = image + k*width*bytes_per_pixel;
767
768 /* One of the following output methods is REQUIRED */
769
770#ifdef entire /* Write out the entire image data in one call */
771 png_write_image(png_ptr, row_pointers);
772
773 /* The other way to write the image - deal with interlacing */
774
775#else no_entire /* Write out the image data by one or more scanlines */
776
777 /* The number of passes is either 1 for non-interlaced images,
778 * or 7 for interlaced images.
779 */
780 for (pass = 0; pass < number_passes; pass++)
781 {
782 /* Write a few rows at a time. */
783 png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows);
784
785 /* If you are only writing one row at a time, this works */
786 for (y = 0; y < height; y++)
787 png_write_rows(png_ptr, &row_pointers[y], 1);
788 }
789#endif no_entire /* Use only one output method */
790
791 /* You can write optional chunks like tEXt, zTXt, and tIME at the end
792 * as well. Shouldn't be necessary in 1.2.0 and up as all the public
793 * chunks are supported and you can use png_set_unknown_chunks() to
794 * register unknown chunks into the info structure to be written out.
795 */
796
797 /* It is REQUIRED to call this to finish writing the rest of the file */
798 png_write_end(png_ptr, info_ptr);
799#endif hilevel
800
801 /* If you png_malloced a palette, free it here (don't free info_ptr->palette,
802 * as recommended in versions 1.0.5m and earlier of this example; if
803 * libpng mallocs info_ptr->palette, libpng will free it). If you
804 * allocated it with malloc() instead of png_malloc(), use free() instead
805 * of png_free().
806 */
807 png_free(png_ptr, palette);
808 palette = NULL;
809
810 /* Similarly, if you png_malloced any data that you passed in with
811 * png_set_something(), such as a hist or trans array, free it here,
812 * when you can be sure that libpng is through with it.
813 */
814 png_free(png_ptr, trans);
815 trans = NULL;
816 /* Whenever you use png_free() it is a good idea to set the pointer to
817 * NULL in case your application inadvertently tries to png_free() it
818 * again. When png_free() sees a NULL it returns without action, thus
819 * avoiding the double-free security problem.
820 */
821
822 /* Clean up after the write, and free any memory allocated */
823 png_destroy_write_struct(&png_ptr, &info_ptr);
824
825 /* Close the file */
826 fclose(fp);
827
828 /* That's it */
829 return (OK);
830}
831
832#endif /* if 0 */
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