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1
2/* pngrtran.c - transforms the data in a row for PNG readers
3 *
4 * Copyright (c) 2018-2019 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * 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_ARM_NEON_IMPLEMENTATION
22# if PNG_ARM_NEON_IMPLEMENTATION == 1
23# define PNG_ARM_NEON_INTRINSICS_AVAILABLE
24# if defined(_MSC_VER) && defined(_M_ARM64)
25# include <arm64_neon.h>
26# else
27# include <arm_neon.h>
28# endif
29# endif
30#endif
31
32#ifdef PNG_READ_SUPPORTED
33
34/* Set the action on getting a CRC error for an ancillary or critical chunk. */
35void PNGAPI
36png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
37{
38 png_debug(1, "in png_set_crc_action");
39
40 if (png_ptr == NULL)
41 return;
42
43 /* Tell libpng how we react to CRC errors in critical chunks */
44 switch (crit_action)
45 {
46 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
47 break;
48
49 case PNG_CRC_WARN_USE: /* Warn/use data */
50 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
51 png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
52 break;
53
54 case PNG_CRC_QUIET_USE: /* Quiet/use data */
55 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
56 png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
57 PNG_FLAG_CRC_CRITICAL_IGNORE;
58 break;
59
60 case PNG_CRC_WARN_DISCARD: /* Not a valid action for critical data */
61 png_warning(png_ptr,
62 "Can't discard critical data on CRC error");
63 /* FALLTHROUGH */
64 case PNG_CRC_ERROR_QUIT: /* Error/quit */
65
66 case PNG_CRC_DEFAULT:
67 default:
68 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
69 break;
70 }
71
72 /* Tell libpng how we react to CRC errors in ancillary chunks */
73 switch (ancil_action)
74 {
75 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
76 break;
77
78 case PNG_CRC_WARN_USE: /* Warn/use data */
79 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
80 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
81 break;
82
83 case PNG_CRC_QUIET_USE: /* Quiet/use data */
84 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
85 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
86 PNG_FLAG_CRC_ANCILLARY_NOWARN;
87 break;
88
89 case PNG_CRC_ERROR_QUIT: /* Error/quit */
90 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
91 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
92 break;
93
94 case PNG_CRC_WARN_DISCARD: /* Warn/discard data */
95
96 case PNG_CRC_DEFAULT:
97 default:
98 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
99 break;
100 }
101}
102
103#ifdef PNG_READ_TRANSFORMS_SUPPORTED
104/* Is it OK to set a transformation now? Only if png_start_read_image or
105 * png_read_update_info have not been called. It is not necessary for the IHDR
106 * to have been read in all cases; the need_IHDR parameter allows for this
107 * check too.
108 */
109static int
110png_rtran_ok(png_structrp png_ptr, int need_IHDR)
111{
112 if (png_ptr != NULL)
113 {
114 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
115 png_app_error(png_ptr,
116 "invalid after png_start_read_image or png_read_update_info");
117
118 else if (need_IHDR && (png_ptr->mode & PNG_HAVE_IHDR) == 0)
119 png_app_error(png_ptr, "invalid before the PNG header has been read");
120
121 else
122 {
123 /* Turn on failure to initialize correctly for all transforms. */
124 png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
125
126 return 1; /* Ok */
127 }
128 }
129
130 return 0; /* no png_error possible! */
131}
132#endif
133
134#ifdef PNG_READ_BACKGROUND_SUPPORTED
135/* Handle alpha and tRNS via a background color */
136void PNGFAPI
137png_set_background_fixed(png_structrp png_ptr,
138 png_const_color_16p background_color, int background_gamma_code,
139 int need_expand, png_fixed_point background_gamma)
140{
141 png_debug(1, "in png_set_background_fixed");
142
143 if (png_rtran_ok(png_ptr, 0) == 0 || background_color == NULL)
144 return;
145
146 if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
147 {
148 png_warning(png_ptr, "Application must supply a known background gamma");
149 return;
150 }
151
152 png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
153 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
154 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
155
156 png_ptr->background = *background_color;
157 png_ptr->background_gamma = background_gamma;
158 png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
159 if (need_expand != 0)
160 png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
161 else
162 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
163}
164
165# ifdef PNG_FLOATING_POINT_SUPPORTED
166void PNGAPI
167png_set_background(png_structrp png_ptr,
168 png_const_color_16p background_color, int background_gamma_code,
169 int need_expand, double background_gamma)
170{
171 png_set_background_fixed(png_ptr, background_color, background_gamma_code,
172 need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
173}
174# endif /* FLOATING_POINT */
175#endif /* READ_BACKGROUND */
176
177/* Scale 16-bit depth files to 8-bit depth. If both of these are set then the
178 * one that pngrtran does first (scale) happens. This is necessary to allow the
179 * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
180 */
181#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
182void PNGAPI
183png_set_scale_16(png_structrp png_ptr)
184{
185 png_debug(1, "in png_set_scale_16");
186
187 if (png_rtran_ok(png_ptr, 0) == 0)
188 return;
189
190 png_ptr->transformations |= PNG_SCALE_16_TO_8;
191}
192#endif
193
194#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
195/* Chop 16-bit depth files to 8-bit depth */
196void PNGAPI
197png_set_strip_16(png_structrp png_ptr)
198{
199 png_debug(1, "in png_set_strip_16");
200
201 if (png_rtran_ok(png_ptr, 0) == 0)
202 return;
203
204 png_ptr->transformations |= PNG_16_TO_8;
205}
206#endif
207
208#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
209void PNGAPI
210png_set_strip_alpha(png_structrp png_ptr)
211{
212 png_debug(1, "in png_set_strip_alpha");
213
214 if (png_rtran_ok(png_ptr, 0) == 0)
215 return;
216
217 png_ptr->transformations |= PNG_STRIP_ALPHA;
218}
219#endif
220
221#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
222static png_fixed_point
223translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma,
224 int is_screen)
225{
226 /* Check for flag values. The main reason for having the old Mac value as a
227 * flag is that it is pretty near impossible to work out what the correct
228 * value is from Apple documentation - a working Mac system is needed to
229 * discover the value!
230 */
231 if (output_gamma == PNG_DEFAULT_sRGB ||
232 output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
233 {
234 /* If there is no sRGB support this just sets the gamma to the standard
235 * sRGB value. (This is a side effect of using this function!)
236 */
237# ifdef PNG_READ_sRGB_SUPPORTED
238 png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
239# else
240 PNG_UNUSED(png_ptr)
241# endif
242 if (is_screen != 0)
243 output_gamma = PNG_GAMMA_sRGB;
244 else
245 output_gamma = PNG_GAMMA_sRGB_INVERSE;
246 }
247
248 else if (output_gamma == PNG_GAMMA_MAC_18 ||
249 output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
250 {
251 if (is_screen != 0)
252 output_gamma = PNG_GAMMA_MAC_OLD;
253 else
254 output_gamma = PNG_GAMMA_MAC_INVERSE;
255 }
256
257 return output_gamma;
258}
259
260# ifdef PNG_FLOATING_POINT_SUPPORTED
261static png_fixed_point
262convert_gamma_value(png_structrp png_ptr, double output_gamma)
263{
264 /* The following silently ignores cases where fixed point (times 100,000)
265 * gamma values are passed to the floating point API. This is safe and it
266 * means the fixed point constants work just fine with the floating point
267 * API. The alternative would just lead to undetected errors and spurious
268 * bug reports. Negative values fail inside the _fixed API unless they
269 * correspond to the flag values.
270 */
271 if (output_gamma > 0 && output_gamma < 128)
272 output_gamma *= PNG_FP_1;
273
274 /* This preserves -1 and -2 exactly: */
275 output_gamma = floor(output_gamma + .5);
276
277 if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
278 png_fixed_error(png_ptr, "gamma value");
279
280 return (png_fixed_point)output_gamma;
281}
282# endif
283#endif /* READ_ALPHA_MODE || READ_GAMMA */
284
285#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
286void PNGFAPI
287png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
288 png_fixed_point output_gamma)
289{
290 int compose = 0;
291 png_fixed_point file_gamma;
292
293 png_debug(1, "in png_set_alpha_mode");
294
295 if (png_rtran_ok(png_ptr, 0) == 0)
296 return;
297
298 output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
299
300 /* Validate the value to ensure it is in a reasonable range. The value
301 * is expected to be 1 or greater, but this range test allows for some
302 * viewing correction values. The intent is to weed out users of this API
303 * who use the inverse of the gamma value accidentally! Since some of these
304 * values are reasonable this may have to be changed:
305 *
306 * 1.6.x: changed from 0.07..3 to 0.01..100 (to accommodate the optimal 16-bit
307 * gamma of 36, and its reciprocal.)
308 */
309 if (output_gamma < 1000 || output_gamma > 10000000)
310 png_error(png_ptr, "output gamma out of expected range");
311
312 /* The default file gamma is the inverse of the output gamma; the output
313 * gamma may be changed below so get the file value first:
314 */
315 file_gamma = png_reciprocal(output_gamma);
316
317 /* There are really 8 possibilities here, composed of any combination
318 * of:
319 *
320 * premultiply the color channels
321 * do not encode non-opaque pixels
322 * encode the alpha as well as the color channels
323 *
324 * The differences disappear if the input/output ('screen') gamma is 1.0,
325 * because then the encoding is a no-op and there is only the choice of
326 * premultiplying the color channels or not.
327 *
328 * png_set_alpha_mode and png_set_background interact because both use
329 * png_compose to do the work. Calling both is only useful when
330 * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
331 * with a default gamma value. Otherwise PNG_COMPOSE must not be set.
332 */
333 switch (mode)
334 {
335 case PNG_ALPHA_PNG: /* default: png standard */
336 /* No compose, but it may be set by png_set_background! */
337 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
338 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
339 break;
340
341 case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
342 compose = 1;
343 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
344 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
345 /* The output is linear: */
346 output_gamma = PNG_FP_1;
347 break;
348
349 case PNG_ALPHA_OPTIMIZED: /* associated, non-opaque pixels linear */
350 compose = 1;
351 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
352 png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
353 /* output_gamma records the encoding of opaque pixels! */
354 break;
355
356 case PNG_ALPHA_BROKEN: /* associated, non-linear, alpha encoded */
357 compose = 1;
358 png_ptr->transformations |= PNG_ENCODE_ALPHA;
359 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
360 break;
361
362 default:
363 png_error(png_ptr, "invalid alpha mode");
364 }
365
366 /* Only set the default gamma if the file gamma has not been set (this has
367 * the side effect that the gamma in a second call to png_set_alpha_mode will
368 * be ignored.)
369 */
370 if (png_ptr->colorspace.gamma == 0)
371 {
372 png_ptr->colorspace.gamma = file_gamma;
373 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
374 }
375
376 /* But always set the output gamma: */
377 png_ptr->screen_gamma = output_gamma;
378
379 /* Finally, if pre-multiplying, set the background fields to achieve the
380 * desired result.
381 */
382 if (compose != 0)
383 {
384 /* And obtain alpha pre-multiplication by composing on black: */
385 memset(&png_ptr->background, 0, (sizeof png_ptr->background));
386 png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */
387 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
388 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
389
390 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
391 png_error(png_ptr,
392 "conflicting calls to set alpha mode and background");
393
394 png_ptr->transformations |= PNG_COMPOSE;
395 }
396}
397
398# ifdef PNG_FLOATING_POINT_SUPPORTED
399void PNGAPI
400png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
401{
402 png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
403 output_gamma));
404}
405# endif
406#endif
407
408#ifdef PNG_READ_QUANTIZE_SUPPORTED
409/* Dither file to 8-bit. Supply a palette, the current number
410 * of elements in the palette, the maximum number of elements
411 * allowed, and a histogram if possible. If the current number
412 * of colors is greater than the maximum number, the palette will be
413 * modified to fit in the maximum number. "full_quantize" indicates
414 * whether we need a quantizing cube set up for RGB images, or if we
415 * simply are reducing the number of colors in a paletted image.
416 */
417
418typedef struct png_dsort_struct
419{
420 struct png_dsort_struct * next;
421 png_byte left;
422 png_byte right;
423} png_dsort;
424typedef png_dsort * png_dsortp;
425typedef png_dsort * * png_dsortpp;
426
427void PNGAPI
428png_set_quantize(png_structrp png_ptr, png_colorp palette,
429 int num_palette, int maximum_colors, png_const_uint_16p histogram,
430 int full_quantize)
431{
432 png_debug(1, "in png_set_quantize");
433
434 if (png_rtran_ok(png_ptr, 0) == 0)
435 return;
436
437 png_ptr->transformations |= PNG_QUANTIZE;
438
439 if (full_quantize == 0)
440 {
441 int i;
442
443 png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
444 (png_alloc_size_t)((png_uint_32)num_palette * (sizeof (png_byte))));
445 for (i = 0; i < num_palette; i++)
446 png_ptr->quantize_index[i] = (png_byte)i;
447 }
448
449 if (num_palette > maximum_colors)
450 {
451 if (histogram != NULL)
452 {
453 /* This is easy enough, just throw out the least used colors.
454 * Perhaps not the best solution, but good enough.
455 */
456
457 int i;
458
459 /* Initialize an array to sort colors */
460 png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
461 (png_alloc_size_t)((png_uint_32)num_palette * (sizeof (png_byte))));
462
463 /* Initialize the quantize_sort array */
464 for (i = 0; i < num_palette; i++)
465 png_ptr->quantize_sort[i] = (png_byte)i;
466
467 /* Find the least used palette entries by starting a
468 * bubble sort, and running it until we have sorted
469 * out enough colors. Note that we don't care about
470 * sorting all the colors, just finding which are
471 * least used.
472 */
473
474 for (i = num_palette - 1; i >= maximum_colors; i--)
475 {
476 int done; /* To stop early if the list is pre-sorted */
477 int j;
478
479 done = 1;
480 for (j = 0; j < i; j++)
481 {
482 if (histogram[png_ptr->quantize_sort[j]]
483 < histogram[png_ptr->quantize_sort[j + 1]])
484 {
485 png_byte t;
486
487 t = png_ptr->quantize_sort[j];
488 png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
489 png_ptr->quantize_sort[j + 1] = t;
490 done = 0;
491 }
492 }
493
494 if (done != 0)
495 break;
496 }
497
498 /* Swap the palette around, and set up a table, if necessary */
499 if (full_quantize != 0)
500 {
501 int j = num_palette;
502
503 /* Put all the useful colors within the max, but don't
504 * move the others.
505 */
506 for (i = 0; i < maximum_colors; i++)
507 {
508 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
509 {
510 do
511 j--;
512 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
513
514 palette[i] = palette[j];
515 }
516 }
517 }
518 else
519 {
520 int j = num_palette;
521
522 /* Move all the used colors inside the max limit, and
523 * develop a translation table.
524 */
525 for (i = 0; i < maximum_colors; i++)
526 {
527 /* Only move the colors we need to */
528 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
529 {
530 png_color tmp_color;
531
532 do
533 j--;
534 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
535
536 tmp_color = palette[j];
537 palette[j] = palette[i];
538 palette[i] = tmp_color;
539 /* Indicate where the color went */
540 png_ptr->quantize_index[j] = (png_byte)i;
541 png_ptr->quantize_index[i] = (png_byte)j;
542 }
543 }
544
545 /* Find closest color for those colors we are not using */
546 for (i = 0; i < num_palette; i++)
547 {
548 if ((int)png_ptr->quantize_index[i] >= maximum_colors)
549 {
550 int min_d, k, min_k, d_index;
551
552 /* Find the closest color to one we threw out */
553 d_index = png_ptr->quantize_index[i];
554 min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
555 for (k = 1, min_k = 0; k < maximum_colors; k++)
556 {
557 int d;
558
559 d = PNG_COLOR_DIST(palette[d_index], palette[k]);
560
561 if (d < min_d)
562 {
563 min_d = d;
564 min_k = k;
565 }
566 }
567 /* Point to closest color */
568 png_ptr->quantize_index[i] = (png_byte)min_k;
569 }
570 }
571 }
572 png_free(png_ptr, png_ptr->quantize_sort);
573 png_ptr->quantize_sort = NULL;
574 }
575 else
576 {
577 /* This is much harder to do simply (and quickly). Perhaps
578 * we need to go through a median cut routine, but those
579 * don't always behave themselves with only a few colors
580 * as input. So we will just find the closest two colors,
581 * and throw out one of them (chosen somewhat randomly).
582 * [We don't understand this at all, so if someone wants to
583 * work on improving it, be our guest - AED, GRP]
584 */
585 int i;
586 int max_d;
587 int num_new_palette;
588 png_dsortp t;
589 png_dsortpp hash;
590
591 t = NULL;
592
593 /* Initialize palette index arrays */
594 png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
595 (png_alloc_size_t)((png_uint_32)num_palette *
596 (sizeof (png_byte))));
597 png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
598 (png_alloc_size_t)((png_uint_32)num_palette *
599 (sizeof (png_byte))));
600
601 /* Initialize the sort array */
602 for (i = 0; i < num_palette; i++)
603 {
604 png_ptr->index_to_palette[i] = (png_byte)i;
605 png_ptr->palette_to_index[i] = (png_byte)i;
606 }
607
608 hash = (png_dsortpp)png_calloc(png_ptr, (png_alloc_size_t)(769 *
609 (sizeof (png_dsortp))));
610
611 num_new_palette = num_palette;
612
613 /* Initial wild guess at how far apart the farthest pixel
614 * pair we will be eliminating will be. Larger
615 * numbers mean more areas will be allocated, Smaller
616 * numbers run the risk of not saving enough data, and
617 * having to do this all over again.
618 *
619 * I have not done extensive checking on this number.
620 */
621 max_d = 96;
622
623 while (num_new_palette > maximum_colors)
624 {
625 for (i = 0; i < num_new_palette - 1; i++)
626 {
627 int j;
628
629 for (j = i + 1; j < num_new_palette; j++)
630 {
631 int d;
632
633 d = PNG_COLOR_DIST(palette[i], palette[j]);
634
635 if (d <= max_d)
636 {
637
638 t = (png_dsortp)png_malloc_warn(png_ptr,
639 (png_alloc_size_t)(sizeof (png_dsort)));
640
641 if (t == NULL)
642 break;
643
644 t->next = hash[d];
645 t->left = (png_byte)i;
646 t->right = (png_byte)j;
647 hash[d] = t;
648 }
649 }
650 if (t == NULL)
651 break;
652 }
653
654 if (t != NULL)
655 for (i = 0; i <= max_d; i++)
656 {
657 if (hash[i] != NULL)
658 {
659 png_dsortp p;
660
661 for (p = hash[i]; p; p = p->next)
662 {
663 if ((int)png_ptr->index_to_palette[p->left]
664 < num_new_palette &&
665 (int)png_ptr->index_to_palette[p->right]
666 < num_new_palette)
667 {
668 int j, next_j;
669
670 if (num_new_palette & 0x01)
671 {
672 j = p->left;
673 next_j = p->right;
674 }
675 else
676 {
677 j = p->right;
678 next_j = p->left;
679 }
680
681 num_new_palette--;
682 palette[png_ptr->index_to_palette[j]]
683 = palette[num_new_palette];
684 if (full_quantize == 0)
685 {
686 int k;
687
688 for (k = 0; k < num_palette; k++)
689 {
690 if (png_ptr->quantize_index[k] ==
691 png_ptr->index_to_palette[j])
692 png_ptr->quantize_index[k] =
693 png_ptr->index_to_palette[next_j];
694
695 if ((int)png_ptr->quantize_index[k] ==
696 num_new_palette)
697 png_ptr->quantize_index[k] =
698 png_ptr->index_to_palette[j];
699 }
700 }
701
702 png_ptr->index_to_palette[png_ptr->palette_to_index
703 [num_new_palette]] = png_ptr->index_to_palette[j];
704
705 png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
706 = png_ptr->palette_to_index[num_new_palette];
707
708 png_ptr->index_to_palette[j] =
709 (png_byte)num_new_palette;
710
711 png_ptr->palette_to_index[num_new_palette] =
712 (png_byte)j;
713 }
714 if (num_new_palette <= maximum_colors)
715 break;
716 }
717 if (num_new_palette <= maximum_colors)
718 break;
719 }
720 }
721
722 for (i = 0; i < 769; i++)
723 {
724 if (hash[i] != NULL)
725 {
726 png_dsortp p = hash[i];
727 while (p)
728 {
729 t = p->next;
730 png_free(png_ptr, p);
731 p = t;
732 }
733 }
734 hash[i] = 0;
735 }
736 max_d += 96;
737 }
738 png_free(png_ptr, hash);
739 png_free(png_ptr, png_ptr->palette_to_index);
740 png_free(png_ptr, png_ptr->index_to_palette);
741 png_ptr->palette_to_index = NULL;
742 png_ptr->index_to_palette = NULL;
743 }
744 num_palette = maximum_colors;
745 }
746 if (png_ptr->palette == NULL)
747 {
748 png_ptr->palette = palette;
749 }
750 png_ptr->num_palette = (png_uint_16)num_palette;
751
752 if (full_quantize != 0)
753 {
754 int i;
755 png_bytep distance;
756 int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
757 PNG_QUANTIZE_BLUE_BITS;
758 int num_red = (1 << PNG_QUANTIZE_RED_BITS);
759 int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
760 int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
761 size_t num_entries = ((size_t)1 << total_bits);
762
763 png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
764 (png_alloc_size_t)(num_entries * (sizeof (png_byte))));
765
766 distance = (png_bytep)png_malloc(png_ptr, (png_alloc_size_t)(num_entries *
767 (sizeof (png_byte))));
768
769 memset(distance, 0xff, num_entries * (sizeof (png_byte)));
770
771 for (i = 0; i < num_palette; i++)
772 {
773 int ir, ig, ib;
774 int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
775 int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
776 int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
777
778 for (ir = 0; ir < num_red; ir++)
779 {
780 /* int dr = abs(ir - r); */
781 int dr = ((ir > r) ? ir - r : r - ir);
782 int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
783 PNG_QUANTIZE_GREEN_BITS));
784
785 for (ig = 0; ig < num_green; ig++)
786 {
787 /* int dg = abs(ig - g); */
788 int dg = ((ig > g) ? ig - g : g - ig);
789 int dt = dr + dg;
790 int dm = ((dr > dg) ? dr : dg);
791 int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
792
793 for (ib = 0; ib < num_blue; ib++)
794 {
795 int d_index = index_g | ib;
796 /* int db = abs(ib - b); */
797 int db = ((ib > b) ? ib - b : b - ib);
798 int dmax = ((dm > db) ? dm : db);
799 int d = dmax + dt + db;
800
801 if (d < (int)distance[d_index])
802 {
803 distance[d_index] = (png_byte)d;
804 png_ptr->palette_lookup[d_index] = (png_byte)i;
805 }
806 }
807 }
808 }
809 }
810
811 png_free(png_ptr, distance);
812 }
813}
814#endif /* READ_QUANTIZE */
815
816#ifdef PNG_READ_GAMMA_SUPPORTED
817void PNGFAPI
818png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
819 png_fixed_point file_gamma)
820{
821 png_debug(1, "in png_set_gamma_fixed");
822
823 if (png_rtran_ok(png_ptr, 0) == 0)
824 return;
825
826 /* New in libpng-1.5.4 - reserve particular negative values as flags. */
827 scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
828 file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
829
830 /* Checking the gamma values for being >0 was added in 1.5.4 along with the
831 * premultiplied alpha support; this actually hides an undocumented feature
832 * of the previous implementation which allowed gamma processing to be
833 * disabled in background handling. There is no evidence (so far) that this
834 * was being used; however, png_set_background itself accepted and must still
835 * accept '0' for the gamma value it takes, because it isn't always used.
836 *
837 * Since this is an API change (albeit a very minor one that removes an
838 * undocumented API feature) the following checks were only enabled in
839 * libpng-1.6.0.
840 */
841 if (file_gamma <= 0)
842 png_error(png_ptr, "invalid file gamma in png_set_gamma");
843
844 if (scrn_gamma <= 0)
845 png_error(png_ptr, "invalid screen gamma in png_set_gamma");
846
847 /* Set the gamma values unconditionally - this overrides the value in the PNG
848 * file if a gAMA chunk was present. png_set_alpha_mode provides a
849 * different, easier, way to default the file gamma.
850 */
851 png_ptr->colorspace.gamma = file_gamma;
852 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
853 png_ptr->screen_gamma = scrn_gamma;
854}
855
856# ifdef PNG_FLOATING_POINT_SUPPORTED
857void PNGAPI
858png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
859{
860 png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
861 convert_gamma_value(png_ptr, file_gamma));
862}
863# endif /* FLOATING_POINT */
864#endif /* READ_GAMMA */
865
866#ifdef PNG_READ_EXPAND_SUPPORTED
867/* Expand paletted images to RGB, expand grayscale images of
868 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
869 * to alpha channels.
870 */
871void PNGAPI
872png_set_expand(png_structrp png_ptr)
873{
874 png_debug(1, "in png_set_expand");
875
876 if (png_rtran_ok(png_ptr, 0) == 0)
877 return;
878
879 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
880}
881
882/* GRR 19990627: the following three functions currently are identical
883 * to png_set_expand(). However, it is entirely reasonable that someone
884 * might wish to expand an indexed image to RGB but *not* expand a single,
885 * fully transparent palette entry to a full alpha channel--perhaps instead
886 * convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
887 * the transparent color with a particular RGB value, or drop tRNS entirely.
888 * IOW, a future version of the library may make the transformations flag
889 * a bit more fine-grained, with separate bits for each of these three
890 * functions.
891 *
892 * More to the point, these functions make it obvious what libpng will be
893 * doing, whereas "expand" can (and does) mean any number of things.
894 *
895 * GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
896 * to expand only the sample depth but not to expand the tRNS to alpha
897 * and its name was changed to png_set_expand_gray_1_2_4_to_8().
898 */
899
900/* Expand paletted images to RGB. */
901void PNGAPI
902png_set_palette_to_rgb(png_structrp png_ptr)
903{
904 png_debug(1, "in png_set_palette_to_rgb");
905
906 if (png_rtran_ok(png_ptr, 0) == 0)
907 return;
908
909 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
910}
911
912/* Expand grayscale images of less than 8-bit depth to 8 bits. */
913void PNGAPI
914png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
915{
916 png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
917
918 if (png_rtran_ok(png_ptr, 0) == 0)
919 return;
920
921 png_ptr->transformations |= PNG_EXPAND;
922}
923
924/* Expand tRNS chunks to alpha channels. */
925void PNGAPI
926png_set_tRNS_to_alpha(png_structrp png_ptr)
927{
928 png_debug(1, "in png_set_tRNS_to_alpha");
929
930 if (png_rtran_ok(png_ptr, 0) == 0)
931 return;
932
933 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
934}
935#endif /* READ_EXPAND */
936
937#ifdef PNG_READ_EXPAND_16_SUPPORTED
938/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
939 * it may not work correctly.)
940 */
941void PNGAPI
942png_set_expand_16(png_structrp png_ptr)
943{
944 png_debug(1, "in png_set_expand_16");
945
946 if (png_rtran_ok(png_ptr, 0) == 0)
947 return;
948
949 png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
950}
951#endif
952
953#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
954void PNGAPI
955png_set_gray_to_rgb(png_structrp png_ptr)
956{
957 png_debug(1, "in png_set_gray_to_rgb");
958
959 if (png_rtran_ok(png_ptr, 0) == 0)
960 return;
961
962 /* Because rgb must be 8 bits or more: */
963 png_set_expand_gray_1_2_4_to_8(png_ptr);
964 png_ptr->transformations |= PNG_GRAY_TO_RGB;
965}
966#endif
967
968#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
969void PNGFAPI
970png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
971 png_fixed_point red, png_fixed_point green)
972{
973 png_debug(1, "in png_set_rgb_to_gray");
974
975 /* Need the IHDR here because of the check on color_type below. */
976 /* TODO: fix this */
977 if (png_rtran_ok(png_ptr, 1) == 0)
978 return;
979
980 switch (error_action)
981 {
982 case PNG_ERROR_ACTION_NONE:
983 png_ptr->transformations |= PNG_RGB_TO_GRAY;
984 break;
985
986 case PNG_ERROR_ACTION_WARN:
987 png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
988 break;
989
990 case PNG_ERROR_ACTION_ERROR:
991 png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
992 break;
993
994 default:
995 png_error(png_ptr, "invalid error action to rgb_to_gray");
996 }
997
998 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
999#ifdef PNG_READ_EXPAND_SUPPORTED
1000 png_ptr->transformations |= PNG_EXPAND;
1001#else
1002 {
1003 /* Make this an error in 1.6 because otherwise the application may assume
1004 * that it just worked and get a memory overwrite.
1005 */
1006 png_error(png_ptr,
1007 "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
1008
1009 /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
1010 }
1011#endif
1012 {
1013 if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
1014 {
1015 png_uint_16 red_int, green_int;
1016
1017 /* NOTE: this calculation does not round, but this behavior is retained
1018 * for consistency; the inaccuracy is very small. The code here always
1019 * overwrites the coefficients, regardless of whether they have been
1020 * defaulted or set already.
1021 */
1022 red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
1023 green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
1024
1025 png_ptr->rgb_to_gray_red_coeff = red_int;
1026 png_ptr->rgb_to_gray_green_coeff = green_int;
1027 png_ptr->rgb_to_gray_coefficients_set = 1;
1028 }
1029
1030 else
1031 {
1032 if (red >= 0 && green >= 0)
1033 png_app_warning(png_ptr,
1034 "ignoring out of range rgb_to_gray coefficients");
1035
1036 /* Use the defaults, from the cHRM chunk if set, else the historical
1037 * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
1038 * png_do_rgb_to_gray for more discussion of the values. In this case
1039 * the coefficients are not marked as 'set' and are not overwritten if
1040 * something has already provided a default.
1041 */
1042 if (png_ptr->rgb_to_gray_red_coeff == 0 &&
1043 png_ptr->rgb_to_gray_green_coeff == 0)
1044 {
1045 png_ptr->rgb_to_gray_red_coeff = 6968;
1046 png_ptr->rgb_to_gray_green_coeff = 23434;
1047 /* png_ptr->rgb_to_gray_blue_coeff = 2366; */
1048 }
1049 }
1050 }
1051}
1052
1053#ifdef PNG_FLOATING_POINT_SUPPORTED
1054/* Convert a RGB image to a grayscale of the same width. This allows us,
1055 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
1056 */
1057
1058void PNGAPI
1059png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
1060 double green)
1061{
1062 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1063 png_fixed(png_ptr, red, "rgb to gray red coefficient"),
1064 png_fixed(png_ptr, green, "rgb to gray green coefficient"));
1065}
1066#endif /* FLOATING POINT */
1067
1068#endif /* RGB_TO_GRAY */
1069
1070#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
1071 defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
1072void PNGAPI
1073png_set_read_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
1074 read_user_transform_fn)
1075{
1076 png_debug(1, "in png_set_read_user_transform_fn");
1077
1078#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
1079 png_ptr->transformations |= PNG_USER_TRANSFORM;
1080 png_ptr->read_user_transform_fn = read_user_transform_fn;
1081#endif
1082}
1083#endif
1084
1085#ifdef PNG_READ_TRANSFORMS_SUPPORTED
1086#ifdef PNG_READ_GAMMA_SUPPORTED
1087/* In the case of gamma transformations only do transformations on images where
1088 * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
1089 * slows things down slightly, and also needlessly introduces small errors.
1090 */
1091static int /* PRIVATE */
1092png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
1093{
1094 /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
1095 * correction as a difference of the overall transform from 1.0
1096 *
1097 * We want to compare the threshold with s*f - 1, if we get
1098 * overflow here it is because of wacky gamma values so we
1099 * turn on processing anyway.
1100 */
1101 png_fixed_point gtest;
1102 return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
1103 png_gamma_significant(gtest);
1104}
1105#endif
1106
1107/* Initialize everything needed for the read. This includes modifying
1108 * the palette.
1109 */
1110
1111/* For the moment 'png_init_palette_transformations' and
1112 * 'png_init_rgb_transformations' only do some flag canceling optimizations.
1113 * The intent is that these two routines should have palette or rgb operations
1114 * extracted from 'png_init_read_transformations'.
1115 */
1116static void /* PRIVATE */
1117png_init_palette_transformations(png_structrp png_ptr)
1118{
1119 /* Called to handle the (input) palette case. In png_do_read_transformations
1120 * the first step is to expand the palette if requested, so this code must
1121 * take care to only make changes that are invariant with respect to the
1122 * palette expansion, or only do them if there is no expansion.
1123 *
1124 * STRIP_ALPHA has already been handled in the caller (by setting num_trans
1125 * to 0.)
1126 */
1127 int input_has_alpha = 0;
1128 int input_has_transparency = 0;
1129
1130 if (png_ptr->num_trans > 0)
1131 {
1132 int i;
1133
1134 /* Ignore if all the entries are opaque (unlikely!) */
1135 for (i=0; i<png_ptr->num_trans; ++i)
1136 {
1137 if (png_ptr->trans_alpha[i] == 255)
1138 continue;
1139 else if (png_ptr->trans_alpha[i] == 0)
1140 input_has_transparency = 1;
1141 else
1142 {
1143 input_has_transparency = 1;
1144 input_has_alpha = 1;
1145 break;
1146 }
1147 }
1148 }
1149
1150 /* If no alpha we can optimize. */
1151 if (input_has_alpha == 0)
1152 {
1153 /* Any alpha means background and associative alpha processing is
1154 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1155 * and ENCODE_ALPHA are irrelevant.
1156 */
1157 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1158 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1159
1160 if (input_has_transparency == 0)
1161 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1162 }
1163
1164#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1165 /* png_set_background handling - deals with the complexity of whether the
1166 * background color is in the file format or the screen format in the case
1167 * where an 'expand' will happen.
1168 */
1169
1170 /* The following code cannot be entered in the alpha pre-multiplication case
1171 * because PNG_BACKGROUND_EXPAND is cancelled below.
1172 */
1173 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0 &&
1174 (png_ptr->transformations & PNG_EXPAND) != 0)
1175 {
1176 {
1177 png_ptr->background.red =
1178 png_ptr->palette[png_ptr->background.index].red;
1179 png_ptr->background.green =
1180 png_ptr->palette[png_ptr->background.index].green;
1181 png_ptr->background.blue =
1182 png_ptr->palette[png_ptr->background.index].blue;
1183
1184#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1185 if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0)
1186 {
1187 if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
1188 {
1189 /* Invert the alpha channel (in tRNS) unless the pixels are
1190 * going to be expanded, in which case leave it for later
1191 */
1192 int i, istop = png_ptr->num_trans;
1193
1194 for (i = 0; i < istop; i++)
1195 png_ptr->trans_alpha[i] =
1196 (png_byte)(255 - png_ptr->trans_alpha[i]);
1197 }
1198 }
1199#endif /* READ_INVERT_ALPHA */
1200 }
1201 } /* background expand and (therefore) no alpha association. */
1202#endif /* READ_EXPAND && READ_BACKGROUND */
1203}
1204
1205static void /* PRIVATE */
1206png_init_rgb_transformations(png_structrp png_ptr)
1207{
1208 /* Added to libpng-1.5.4: check the color type to determine whether there
1209 * is any alpha or transparency in the image and simply cancel the
1210 * background and alpha mode stuff if there isn't.
1211 */
1212 int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
1213 int input_has_transparency = png_ptr->num_trans > 0;
1214
1215 /* If no alpha we can optimize. */
1216 if (input_has_alpha == 0)
1217 {
1218 /* Any alpha means background and associative alpha processing is
1219 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1220 * and ENCODE_ALPHA are irrelevant.
1221 */
1222# ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1223 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1224 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1225# endif
1226
1227 if (input_has_transparency == 0)
1228 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1229 }
1230
1231#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1232 /* png_set_background handling - deals with the complexity of whether the
1233 * background color is in the file format or the screen format in the case
1234 * where an 'expand' will happen.
1235 */
1236
1237 /* The following code cannot be entered in the alpha pre-multiplication case
1238 * because PNG_BACKGROUND_EXPAND is cancelled below.
1239 */
1240 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0 &&
1241 (png_ptr->transformations & PNG_EXPAND) != 0 &&
1242 (png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
1243 /* i.e., GRAY or GRAY_ALPHA */
1244 {
1245 {
1246 /* Expand background and tRNS chunks */
1247 int gray = png_ptr->background.gray;
1248 int trans_gray = png_ptr->trans_color.gray;
1249
1250 switch (png_ptr->bit_depth)
1251 {
1252 case 1:
1253 gray *= 0xff;
1254 trans_gray *= 0xff;
1255 break;
1256
1257 case 2:
1258 gray *= 0x55;
1259 trans_gray *= 0x55;
1260 break;
1261
1262 case 4:
1263 gray *= 0x11;
1264 trans_gray *= 0x11;
1265 break;
1266
1267 default:
1268
1269 case 8:
1270 /* FALLTHROUGH */ /* (Already 8 bits) */
1271
1272 case 16:
1273 /* Already a full 16 bits */
1274 break;
1275 }
1276
1277 png_ptr->background.red = png_ptr->background.green =
1278 png_ptr->background.blue = (png_uint_16)gray;
1279
1280 if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
1281 {
1282 png_ptr->trans_color.red = png_ptr->trans_color.green =
1283 png_ptr->trans_color.blue = (png_uint_16)trans_gray;
1284 }
1285 }
1286 } /* background expand and (therefore) no alpha association. */
1287#endif /* READ_EXPAND && READ_BACKGROUND */
1288}
1289
1290void /* PRIVATE */
1291png_init_read_transformations(png_structrp png_ptr)
1292{
1293 png_debug(1, "in png_init_read_transformations");
1294
1295 /* This internal function is called from png_read_start_row in pngrutil.c
1296 * and it is called before the 'rowbytes' calculation is done, so the code
1297 * in here can change or update the transformations flags.
1298 *
1299 * First do updates that do not depend on the details of the PNG image data
1300 * being processed.
1301 */
1302
1303#ifdef PNG_READ_GAMMA_SUPPORTED
1304 /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
1305 * png_set_alpha_mode and this is another source for a default file gamma so
1306 * the test needs to be performed later - here. In addition prior to 1.5.4
1307 * the tests were repeated for the PALETTE color type here - this is no
1308 * longer necessary (and doesn't seem to have been necessary before.)
1309 */
1310 {
1311 /* The following temporary indicates if overall gamma correction is
1312 * required.
1313 */
1314 int gamma_correction = 0;
1315
1316 if (png_ptr->colorspace.gamma != 0) /* has been set */
1317 {
1318 if (png_ptr->screen_gamma != 0) /* screen set too */
1319 gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
1320 png_ptr->screen_gamma);
1321
1322 else
1323 /* Assume the output matches the input; a long time default behavior
1324 * of libpng, although the standard has nothing to say about this.
1325 */
1326 png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma);
1327 }
1328
1329 else if (png_ptr->screen_gamma != 0)
1330 /* The converse - assume the file matches the screen, note that this
1331 * perhaps undesirable default can (from 1.5.4) be changed by calling
1332 * png_set_alpha_mode (even if the alpha handling mode isn't required
1333 * or isn't changed from the default.)
1334 */
1335 png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma);
1336
1337 else /* neither are set */
1338 /* Just in case the following prevents any processing - file and screen
1339 * are both assumed to be linear and there is no way to introduce a
1340 * third gamma value other than png_set_background with 'UNIQUE', and,
1341 * prior to 1.5.4
1342 */
1343 png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1;
1344
1345 /* We have a gamma value now. */
1346 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
1347
1348 /* Now turn the gamma transformation on or off as appropriate. Notice
1349 * that PNG_GAMMA just refers to the file->screen correction. Alpha
1350 * composition may independently cause gamma correction because it needs
1351 * linear data (e.g. if the file has a gAMA chunk but the screen gamma
1352 * hasn't been specified.) In any case this flag may get turned off in
1353 * the code immediately below if the transform can be handled outside the
1354 * row loop.
1355 */
1356 if (gamma_correction != 0)
1357 png_ptr->transformations |= PNG_GAMMA;
1358
1359 else
1360 png_ptr->transformations &= ~PNG_GAMMA;
1361 }
1362#endif
1363
1364 /* Certain transformations have the effect of preventing other
1365 * transformations that happen afterward in png_do_read_transformations;
1366 * resolve the interdependencies here. From the code of
1367 * png_do_read_transformations the order is:
1368 *
1369 * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
1370 * 2) PNG_STRIP_ALPHA (if no compose)
1371 * 3) PNG_RGB_TO_GRAY
1372 * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
1373 * 5) PNG_COMPOSE
1374 * 6) PNG_GAMMA
1375 * 7) PNG_STRIP_ALPHA (if compose)
1376 * 8) PNG_ENCODE_ALPHA
1377 * 9) PNG_SCALE_16_TO_8
1378 * 10) PNG_16_TO_8
1379 * 11) PNG_QUANTIZE (converts to palette)
1380 * 12) PNG_EXPAND_16
1381 * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
1382 * 14) PNG_INVERT_MONO
1383 * 15) PNG_INVERT_ALPHA
1384 * 16) PNG_SHIFT
1385 * 17) PNG_PACK
1386 * 18) PNG_BGR
1387 * 19) PNG_PACKSWAP
1388 * 20) PNG_FILLER (includes PNG_ADD_ALPHA)
1389 * 21) PNG_SWAP_ALPHA
1390 * 22) PNG_SWAP_BYTES
1391 * 23) PNG_USER_TRANSFORM [must be last]
1392 */
1393#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1394 if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0 &&
1395 (png_ptr->transformations & PNG_COMPOSE) == 0)
1396 {
1397 /* Stripping the alpha channel happens immediately after the 'expand'
1398 * transformations, before all other transformation, so it cancels out
1399 * the alpha handling. It has the side effect negating the effect of
1400 * PNG_EXPAND_tRNS too:
1401 */
1402 png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
1403 PNG_EXPAND_tRNS);
1404 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1405
1406 /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
1407 * so transparency information would remain just so long as it wasn't
1408 * expanded. This produces unexpected API changes if the set of things
1409 * that do PNG_EXPAND_tRNS changes (perfectly possible given the
1410 * documentation - which says ask for what you want, accept what you
1411 * get.) This makes the behavior consistent from 1.5.4:
1412 */
1413 png_ptr->num_trans = 0;
1414 }
1415#endif /* STRIP_ALPHA supported, no COMPOSE */
1416
1417#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1418 /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
1419 * settings will have no effect.
1420 */
1421 if (png_gamma_significant(png_ptr->screen_gamma) == 0)
1422 {
1423 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1424 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1425 }
1426#endif
1427
1428#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1429 /* Make sure the coefficients for the rgb to gray conversion are set
1430 * appropriately.
1431 */
1432 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
1433 png_colorspace_set_rgb_coefficients(png_ptr);
1434#endif
1435
1436#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1437#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1438 /* Detect gray background and attempt to enable optimization for
1439 * gray --> RGB case.
1440 *
1441 * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
1442 * RGB_ALPHA (in which case need_expand is superfluous anyway), the
1443 * background color might actually be gray yet not be flagged as such.
1444 * This is not a problem for the current code, which uses
1445 * PNG_BACKGROUND_IS_GRAY only to decide when to do the
1446 * png_do_gray_to_rgb() transformation.
1447 *
1448 * TODO: this code needs to be revised to avoid the complexity and
1449 * interdependencies. The color type of the background should be recorded in
1450 * png_set_background, along with the bit depth, then the code has a record
1451 * of exactly what color space the background is currently in.
1452 */
1453 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) != 0)
1454 {
1455 /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
1456 * the file was grayscale the background value is gray.
1457 */
1458 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
1459 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1460 }
1461
1462 else if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1463 {
1464 /* PNG_COMPOSE: png_set_background was called with need_expand false,
1465 * so the color is in the color space of the output or png_set_alpha_mode
1466 * was called and the color is black. Ignore RGB_TO_GRAY because that
1467 * happens before GRAY_TO_RGB.
1468 */
1469 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
1470 {
1471 if (png_ptr->background.red == png_ptr->background.green &&
1472 png_ptr->background.red == png_ptr->background.blue)
1473 {
1474 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1475 png_ptr->background.gray = png_ptr->background.red;
1476 }
1477 }
1478 }
1479#endif /* READ_EXPAND && READ_BACKGROUND */
1480#endif /* READ_GRAY_TO_RGB */
1481
1482 /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
1483 * can be performed directly on the palette, and some (such as rgb to gray)
1484 * can be optimized inside the palette. This is particularly true of the
1485 * composite (background and alpha) stuff, which can be pretty much all done
1486 * in the palette even if the result is expanded to RGB or gray afterward.
1487 *
1488 * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
1489 * earlier and the palette stuff is actually handled on the first row. This
1490 * leads to the reported bug that the palette returned by png_get_PLTE is not
1491 * updated.
1492 */
1493 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1494 png_init_palette_transformations(png_ptr);
1495
1496 else
1497 png_init_rgb_transformations(png_ptr);
1498
1499#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1500 defined(PNG_READ_EXPAND_16_SUPPORTED)
1501 if ((png_ptr->transformations & PNG_EXPAND_16) != 0 &&
1502 (png_ptr->transformations & PNG_COMPOSE) != 0 &&
1503 (png_ptr->transformations & PNG_BACKGROUND_EXPAND) == 0 &&
1504 png_ptr->bit_depth != 16)
1505 {
1506 /* TODO: fix this. Because the expand_16 operation is after the compose
1507 * handling the background color must be 8, not 16, bits deep, but the
1508 * application will supply a 16-bit value so reduce it here.
1509 *
1510 * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
1511 * present, so that case is ok (until do_expand_16 is moved.)
1512 *
1513 * NOTE: this discards the low 16 bits of the user supplied background
1514 * color, but until expand_16 works properly there is no choice!
1515 */
1516# define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
1517 CHOP(png_ptr->background.red);
1518 CHOP(png_ptr->background.green);
1519 CHOP(png_ptr->background.blue);
1520 CHOP(png_ptr->background.gray);
1521# undef CHOP
1522 }
1523#endif /* READ_BACKGROUND && READ_EXPAND_16 */
1524
1525#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1526 (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
1527 defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
1528 if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) != 0 &&
1529 (png_ptr->transformations & PNG_COMPOSE) != 0 &&
1530 (png_ptr->transformations & PNG_BACKGROUND_EXPAND) == 0 &&
1531 png_ptr->bit_depth == 16)
1532 {
1533 /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
1534 * component this will also happen after PNG_COMPOSE and so the background
1535 * color must be pre-expanded here.
1536 *
1537 * TODO: fix this too.
1538 */
1539 png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
1540 png_ptr->background.green =
1541 (png_uint_16)(png_ptr->background.green * 257);
1542 png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
1543 png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
1544 }
1545#endif
1546
1547 /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
1548 * background support (see the comments in scripts/pnglibconf.dfa), this
1549 * allows pre-multiplication of the alpha channel to be implemented as
1550 * compositing on black. This is probably sub-optimal and has been done in
1551 * 1.5.4 betas simply to enable external critique and testing (i.e. to
1552 * implement the new API quickly, without lots of internal changes.)
1553 */
1554
1555#ifdef PNG_READ_GAMMA_SUPPORTED
1556# ifdef PNG_READ_BACKGROUND_SUPPORTED
1557 /* Includes ALPHA_MODE */
1558 png_ptr->background_1 = png_ptr->background;
1559# endif
1560
1561 /* This needs to change - in the palette image case a whole set of tables are
1562 * built when it would be quicker to just calculate the correct value for
1563 * each palette entry directly. Also, the test is too tricky - why check
1564 * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
1565 * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
1566 * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
1567 * the gamma tables will not be built even if composition is required on a
1568 * gamma encoded value.
1569 *
1570 * In 1.5.4 this is addressed below by an additional check on the individual
1571 * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
1572 * tables.
1573 */
1574 if ((png_ptr->transformations & PNG_GAMMA) != 0 ||
1575 ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0 &&
1576 (png_gamma_significant(png_ptr->colorspace.gamma) != 0 ||
1577 png_gamma_significant(png_ptr->screen_gamma) != 0)) ||
1578 ((png_ptr->transformations & PNG_COMPOSE) != 0 &&
1579 (png_gamma_significant(png_ptr->colorspace.gamma) != 0 ||
1580 png_gamma_significant(png_ptr->screen_gamma) != 0
1581# ifdef PNG_READ_BACKGROUND_SUPPORTED
1582 || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE &&
1583 png_gamma_significant(png_ptr->background_gamma) != 0)
1584# endif
1585 )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA) != 0 &&
1586 png_gamma_significant(png_ptr->screen_gamma) != 0))
1587 {
1588 png_build_gamma_table(png_ptr, png_ptr->bit_depth);
1589
1590#ifdef PNG_READ_BACKGROUND_SUPPORTED
1591 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1592 {
1593 /* Issue a warning about this combination: because RGB_TO_GRAY is
1594 * optimized to do the gamma transform if present yet do_background has
1595 * to do the same thing if both options are set a
1596 * double-gamma-correction happens. This is true in all versions of
1597 * libpng to date.
1598 */
1599 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
1600 png_warning(png_ptr,
1601 "libpng does not support gamma+background+rgb_to_gray");
1602
1603 if ((png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) != 0)
1604 {
1605 /* We don't get to here unless there is a tRNS chunk with non-opaque
1606 * entries - see the checking code at the start of this function.
1607 */
1608 png_color back, back_1;
1609 png_colorp palette = png_ptr->palette;
1610 int num_palette = png_ptr->num_palette;
1611 int i;
1612 if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
1613 {
1614
1615 back.red = png_ptr->gamma_table[png_ptr->background.red];
1616 back.green = png_ptr->gamma_table[png_ptr->background.green];
1617 back.blue = png_ptr->gamma_table[png_ptr->background.blue];
1618
1619 back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
1620 back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
1621 back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
1622 }
1623 else
1624 {
1625 png_fixed_point g, gs;
1626
1627 switch (png_ptr->background_gamma_type)
1628 {
1629 case PNG_BACKGROUND_GAMMA_SCREEN:
1630 g = (png_ptr->screen_gamma);
1631 gs = PNG_FP_1;
1632 break;
1633
1634 case PNG_BACKGROUND_GAMMA_FILE:
1635 g = png_reciprocal(png_ptr->colorspace.gamma);
1636 gs = png_reciprocal2(png_ptr->colorspace.gamma,
1637 png_ptr->screen_gamma);
1638 break;
1639
1640 case PNG_BACKGROUND_GAMMA_UNIQUE:
1641 g = png_reciprocal(png_ptr->background_gamma);
1642 gs = png_reciprocal2(png_ptr->background_gamma,
1643 png_ptr->screen_gamma);
1644 break;
1645 default:
1646 g = PNG_FP_1; /* back_1 */
1647 gs = PNG_FP_1; /* back */
1648 break;
1649 }
1650
1651 if (png_gamma_significant(gs) != 0)
1652 {
1653 back.red = png_gamma_8bit_correct(png_ptr->background.red,
1654 gs);
1655 back.green = png_gamma_8bit_correct(png_ptr->background.green,
1656 gs);
1657 back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1658 gs);
1659 }
1660
1661 else
1662 {
1663 back.red = (png_byte)png_ptr->background.red;
1664 back.green = (png_byte)png_ptr->background.green;
1665 back.blue = (png_byte)png_ptr->background.blue;
1666 }
1667
1668 if (png_gamma_significant(g) != 0)
1669 {
1670 back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
1671 g);
1672 back_1.green = png_gamma_8bit_correct(
1673 png_ptr->background.green, g);
1674 back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1675 g);
1676 }
1677
1678 else
1679 {
1680 back_1.red = (png_byte)png_ptr->background.red;
1681 back_1.green = (png_byte)png_ptr->background.green;
1682 back_1.blue = (png_byte)png_ptr->background.blue;
1683 }
1684 }
1685
1686 for (i = 0; i < num_palette; i++)
1687 {
1688 if (i < (int)png_ptr->num_trans &&
1689 png_ptr->trans_alpha[i] != 0xff)
1690 {
1691 if (png_ptr->trans_alpha[i] == 0)
1692 {
1693 palette[i] = back;
1694 }
1695 else /* if (png_ptr->trans_alpha[i] != 0xff) */
1696 {
1697 png_byte v, w;
1698
1699 v = png_ptr->gamma_to_1[palette[i].red];
1700 png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
1701 palette[i].red = png_ptr->gamma_from_1[w];
1702
1703 v = png_ptr->gamma_to_1[palette[i].green];
1704 png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
1705 palette[i].green = png_ptr->gamma_from_1[w];
1706
1707 v = png_ptr->gamma_to_1[palette[i].blue];
1708 png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
1709 palette[i].blue = png_ptr->gamma_from_1[w];
1710 }
1711 }
1712 else
1713 {
1714 palette[i].red = png_ptr->gamma_table[palette[i].red];
1715 palette[i].green = png_ptr->gamma_table[palette[i].green];
1716 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1717 }
1718 }
1719
1720 /* Prevent the transformations being done again.
1721 *
1722 * NOTE: this is highly dubious; it removes the transformations in
1723 * place. This seems inconsistent with the general treatment of the
1724 * transformations elsewhere.
1725 */
1726 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
1727 } /* color_type == PNG_COLOR_TYPE_PALETTE */
1728
1729 /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
1730 else /* color_type != PNG_COLOR_TYPE_PALETTE */
1731 {
1732 int gs_sig, g_sig;
1733 png_fixed_point g = PNG_FP_1; /* Correction to linear */
1734 png_fixed_point gs = PNG_FP_1; /* Correction to screen */
1735
1736 switch (png_ptr->background_gamma_type)
1737 {
1738 case PNG_BACKGROUND_GAMMA_SCREEN:
1739 g = png_ptr->screen_gamma;
1740 /* gs = PNG_FP_1; */
1741 break;
1742
1743 case PNG_BACKGROUND_GAMMA_FILE:
1744 g = png_reciprocal(png_ptr->colorspace.gamma);
1745 gs = png_reciprocal2(png_ptr->colorspace.gamma,
1746 png_ptr->screen_gamma);
1747 break;
1748
1749 case PNG_BACKGROUND_GAMMA_UNIQUE:
1750 g = png_reciprocal(png_ptr->background_gamma);
1751 gs = png_reciprocal2(png_ptr->background_gamma,
1752 png_ptr->screen_gamma);
1753 break;
1754
1755 default:
1756 png_error(png_ptr, "invalid background gamma type");
1757 }
1758
1759 g_sig = png_gamma_significant(g);
1760 gs_sig = png_gamma_significant(gs);
1761
1762 if (g_sig != 0)
1763 png_ptr->background_1.gray = png_gamma_correct(png_ptr,
1764 png_ptr->background.gray, g);
1765
1766 if (gs_sig != 0)
1767 png_ptr->background.gray = png_gamma_correct(png_ptr,
1768 png_ptr->background.gray, gs);
1769
1770 if ((png_ptr->background.red != png_ptr->background.green) ||
1771 (png_ptr->background.red != png_ptr->background.blue) ||
1772 (png_ptr->background.red != png_ptr->background.gray))
1773 {
1774 /* RGB or RGBA with color background */
1775 if (g_sig != 0)
1776 {
1777 png_ptr->background_1.red = png_gamma_correct(png_ptr,
1778 png_ptr->background.red, g);
1779
1780 png_ptr->background_1.green = png_gamma_correct(png_ptr,
1781 png_ptr->background.green, g);
1782
1783 png_ptr->background_1.blue = png_gamma_correct(png_ptr,
1784 png_ptr->background.blue, g);
1785 }
1786
1787 if (gs_sig != 0)
1788 {
1789 png_ptr->background.red = png_gamma_correct(png_ptr,
1790 png_ptr->background.red, gs);
1791
1792 png_ptr->background.green = png_gamma_correct(png_ptr,
1793 png_ptr->background.green, gs);
1794
1795 png_ptr->background.blue = png_gamma_correct(png_ptr,
1796 png_ptr->background.blue, gs);
1797 }
1798 }
1799
1800 else
1801 {
1802 /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
1803 png_ptr->background_1.red = png_ptr->background_1.green
1804 = png_ptr->background_1.blue = png_ptr->background_1.gray;
1805
1806 png_ptr->background.red = png_ptr->background.green
1807 = png_ptr->background.blue = png_ptr->background.gray;
1808 }
1809
1810 /* The background is now in screen gamma: */
1811 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
1812 } /* color_type != PNG_COLOR_TYPE_PALETTE */
1813 }/* png_ptr->transformations & PNG_BACKGROUND */
1814
1815 else
1816 /* Transformation does not include PNG_BACKGROUND */
1817#endif /* READ_BACKGROUND */
1818 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
1819#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1820 /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
1821 && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
1822 (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
1823#endif
1824 )
1825 {
1826 png_colorp palette = png_ptr->palette;
1827 int num_palette = png_ptr->num_palette;
1828 int i;
1829
1830 /* NOTE: there are other transformations that should probably be in
1831 * here too.
1832 */
1833 for (i = 0; i < num_palette; i++)
1834 {
1835 palette[i].red = png_ptr->gamma_table[palette[i].red];
1836 palette[i].green = png_ptr->gamma_table[palette[i].green];
1837 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1838 }
1839
1840 /* Done the gamma correction. */
1841 png_ptr->transformations &= ~PNG_GAMMA;
1842 } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
1843 }
1844#ifdef PNG_READ_BACKGROUND_SUPPORTED
1845 else
1846#endif
1847#endif /* READ_GAMMA */
1848
1849#ifdef PNG_READ_BACKGROUND_SUPPORTED
1850 /* No GAMMA transformation (see the hanging else 4 lines above) */
1851 if ((png_ptr->transformations & PNG_COMPOSE) != 0 &&
1852 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1853 {
1854 int i;
1855 int istop = (int)png_ptr->num_trans;
1856 png_color back;
1857 png_colorp palette = png_ptr->palette;
1858
1859 back.red = (png_byte)png_ptr->background.red;
1860 back.green = (png_byte)png_ptr->background.green;
1861 back.blue = (png_byte)png_ptr->background.blue;
1862
1863 for (i = 0; i < istop; i++)
1864 {
1865 if (png_ptr->trans_alpha[i] == 0)
1866 {
1867 palette[i] = back;
1868 }
1869
1870 else if (png_ptr->trans_alpha[i] != 0xff)
1871 {
1872 /* The png_composite() macro is defined in png.h */
1873 png_composite(palette[i].red, palette[i].red,
1874 png_ptr->trans_alpha[i], back.red);
1875
1876 png_composite(palette[i].green, palette[i].green,
1877 png_ptr->trans_alpha[i], back.green);
1878
1879 png_composite(palette[i].blue, palette[i].blue,
1880 png_ptr->trans_alpha[i], back.blue);
1881 }
1882 }
1883
1884 png_ptr->transformations &= ~PNG_COMPOSE;
1885 }
1886#endif /* READ_BACKGROUND */
1887
1888#ifdef PNG_READ_SHIFT_SUPPORTED
1889 if ((png_ptr->transformations & PNG_SHIFT) != 0 &&
1890 (png_ptr->transformations & PNG_EXPAND) == 0 &&
1891 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1892 {
1893 int i;
1894 int istop = png_ptr->num_palette;
1895 int shift = 8 - png_ptr->sig_bit.red;
1896
1897 png_ptr->transformations &= ~PNG_SHIFT;
1898
1899 /* significant bits can be in the range 1 to 7 for a meaningful result, if
1900 * the number of significant bits is 0 then no shift is done (this is an
1901 * error condition which is silently ignored.)
1902 */
1903 if (shift > 0 && shift < 8)
1904 for (i=0; i<istop; ++i)
1905 {
1906 int component = png_ptr->palette[i].red;
1907
1908 component >>= shift;
1909 png_ptr->palette[i].red = (png_byte)component;
1910 }
1911
1912 shift = 8 - png_ptr->sig_bit.green;
1913 if (shift > 0 && shift < 8)
1914 for (i=0; i<istop; ++i)
1915 {
1916 int component = png_ptr->palette[i].green;
1917
1918 component >>= shift;
1919 png_ptr->palette[i].green = (png_byte)component;
1920 }
1921
1922 shift = 8 - png_ptr->sig_bit.blue;
1923 if (shift > 0 && shift < 8)
1924 for (i=0; i<istop; ++i)
1925 {
1926 int component = png_ptr->palette[i].blue;
1927
1928 component >>= shift;
1929 png_ptr->palette[i].blue = (png_byte)component;
1930 }
1931 }
1932#endif /* READ_SHIFT */
1933}
1934
1935/* Modify the info structure to reflect the transformations. The
1936 * info should be updated so a PNG file could be written with it,
1937 * assuming the transformations result in valid PNG data.
1938 */
1939void /* PRIVATE */
1940png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
1941{
1942 png_debug(1, "in png_read_transform_info");
1943
1944#ifdef PNG_READ_EXPAND_SUPPORTED
1945 if ((png_ptr->transformations & PNG_EXPAND) != 0)
1946 {
1947 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1948 {
1949 /* This check must match what actually happens in
1950 * png_do_expand_palette; if it ever checks the tRNS chunk to see if
1951 * it is all opaque we must do the same (at present it does not.)
1952 */
1953 if (png_ptr->num_trans > 0)
1954 info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
1955
1956 else
1957 info_ptr->color_type = PNG_COLOR_TYPE_RGB;
1958
1959 info_ptr->bit_depth = 8;
1960 info_ptr->num_trans = 0;
1961
1962 if (png_ptr->palette == NULL)
1963 png_error (png_ptr, "Palette is NULL in indexed image");
1964 }
1965 else
1966 {
1967 if (png_ptr->num_trans != 0)
1968 {
1969 if ((png_ptr->transformations & PNG_EXPAND_tRNS) != 0)
1970 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
1971 }
1972 if (info_ptr->bit_depth < 8)
1973 info_ptr->bit_depth = 8;
1974
1975 info_ptr->num_trans = 0;
1976 }
1977 }
1978#endif
1979
1980#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
1981 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
1982 /* The following is almost certainly wrong unless the background value is in
1983 * the screen space!
1984 */
1985 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
1986 info_ptr->background = png_ptr->background;
1987#endif
1988
1989#ifdef PNG_READ_GAMMA_SUPPORTED
1990 /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
1991 * however it seems that the code in png_init_read_transformations, which has
1992 * been called before this from png_read_update_info->png_read_start_row
1993 * sometimes does the gamma transform and cancels the flag.
1994 *
1995 * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
1996 * the screen_gamma value. The following probably results in weirdness if
1997 * the info_ptr is used by the app after the rows have been read.
1998 */
1999 info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
2000#endif
2001
2002 if (info_ptr->bit_depth == 16)
2003 {
2004# ifdef PNG_READ_16BIT_SUPPORTED
2005# ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2006 if ((png_ptr->transformations & PNG_SCALE_16_TO_8) != 0)
2007 info_ptr->bit_depth = 8;
2008# endif
2009
2010# ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2011 if ((png_ptr->transformations & PNG_16_TO_8) != 0)
2012 info_ptr->bit_depth = 8;
2013# endif
2014
2015# else
2016 /* No 16-bit support: force chopping 16-bit input down to 8, in this case
2017 * the app program can chose if both APIs are available by setting the
2018 * correct scaling to use.
2019 */
2020# ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2021 /* For compatibility with previous versions use the strip method by
2022 * default. This code works because if PNG_SCALE_16_TO_8 is already
2023 * set the code below will do that in preference to the chop.
2024 */
2025 png_ptr->transformations |= PNG_16_TO_8;
2026 info_ptr->bit_depth = 8;
2027# else
2028
2029# ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2030 png_ptr->transformations |= PNG_SCALE_16_TO_8;
2031 info_ptr->bit_depth = 8;
2032# else
2033
2034 CONFIGURATION ERROR: you must enable at least one 16 to 8 method
2035# endif
2036# endif
2037#endif /* !READ_16BIT */
2038 }
2039
2040#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2041 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
2042 info_ptr->color_type = (png_byte)(info_ptr->color_type |
2043 PNG_COLOR_MASK_COLOR);
2044#endif
2045
2046#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2047 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
2048 info_ptr->color_type = (png_byte)(info_ptr->color_type &
2049 ~PNG_COLOR_MASK_COLOR);
2050#endif
2051
2052#ifdef PNG_READ_QUANTIZE_SUPPORTED
2053 if ((png_ptr->transformations & PNG_QUANTIZE) != 0)
2054 {
2055 if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
2056 (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
2057 png_ptr->palette_lookup != 0 && info_ptr->bit_depth == 8)
2058 {
2059 info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
2060 }
2061 }
2062#endif
2063
2064#ifdef PNG_READ_EXPAND_16_SUPPORTED
2065 if ((png_ptr->transformations & PNG_EXPAND_16) != 0 &&
2066 info_ptr->bit_depth == 8 &&
2067 info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
2068 {
2069 info_ptr->bit_depth = 16;
2070 }
2071#endif
2072
2073#ifdef PNG_READ_PACK_SUPPORTED
2074 if ((png_ptr->transformations & PNG_PACK) != 0 &&
2075 (info_ptr->bit_depth < 8))
2076 info_ptr->bit_depth = 8;
2077#endif
2078
2079 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
2080 info_ptr->channels = 1;
2081
2082 else if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
2083 info_ptr->channels = 3;
2084
2085 else
2086 info_ptr->channels = 1;
2087
2088#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2089 if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0)
2090 {
2091 info_ptr->color_type = (png_byte)(info_ptr->color_type &
2092 ~PNG_COLOR_MASK_ALPHA);
2093 info_ptr->num_trans = 0;
2094 }
2095#endif
2096
2097 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
2098 info_ptr->channels++;
2099
2100#ifdef PNG_READ_FILLER_SUPPORTED
2101 /* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
2102 if ((png_ptr->transformations & PNG_FILLER) != 0 &&
2103 (info_ptr->color_type == PNG_COLOR_TYPE_RGB ||
2104 info_ptr->color_type == PNG_COLOR_TYPE_GRAY))
2105 {
2106 info_ptr->channels++;
2107 /* If adding a true alpha channel not just filler */
2108 if ((png_ptr->transformations & PNG_ADD_ALPHA) != 0)
2109 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
2110 }
2111#endif
2112
2113#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
2114defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
2115 if ((png_ptr->transformations & PNG_USER_TRANSFORM) != 0)
2116 {
2117 if (png_ptr->user_transform_depth != 0)
2118 info_ptr->bit_depth = png_ptr->user_transform_depth;
2119
2120 if (png_ptr->user_transform_channels != 0)
2121 info_ptr->channels = png_ptr->user_transform_channels;
2122 }
2123#endif
2124
2125 info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
2126 info_ptr->bit_depth);
2127
2128 info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
2129
2130 /* Adding in 1.5.4: cache the above value in png_struct so that we can later
2131 * check in png_rowbytes that the user buffer won't get overwritten. Note
2132 * that the field is not always set - if png_read_update_info isn't called
2133 * the application has to either not do any transforms or get the calculation
2134 * right itself.
2135 */
2136 png_ptr->info_rowbytes = info_ptr->rowbytes;
2137
2138#ifndef PNG_READ_EXPAND_SUPPORTED
2139 if (png_ptr != NULL)
2140 return;
2141#endif
2142}
2143
2144#ifdef PNG_READ_PACK_SUPPORTED
2145/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
2146 * without changing the actual values. Thus, if you had a row with
2147 * a bit depth of 1, you would end up with bytes that only contained
2148 * the numbers 0 or 1. If you would rather they contain 0 and 255, use
2149 * png_do_shift() after this.
2150 */
2151static void
2152png_do_unpack(png_row_infop row_info, png_bytep row)
2153{
2154 png_debug(1, "in png_do_unpack");
2155
2156 if (row_info->bit_depth < 8)
2157 {
2158 png_uint_32 i;
2159 png_uint_32 row_width=row_info->width;
2160
2161 switch (row_info->bit_depth)
2162 {
2163 case 1:
2164 {
2165 png_bytep sp = row + (size_t)((row_width - 1) >> 3);
2166 png_bytep dp = row + (size_t)row_width - 1;
2167 png_uint_32 shift = 7U - ((row_width + 7U) & 0x07);
2168 for (i = 0; i < row_width; i++)
2169 {
2170 *dp = (png_byte)((*sp >> shift) & 0x01);
2171
2172 if (shift == 7)
2173 {
2174 shift = 0;
2175 sp--;
2176 }
2177
2178 else
2179 shift++;
2180
2181 dp--;
2182 }
2183 break;
2184 }
2185
2186 case 2:
2187 {
2188
2189 png_bytep sp = row + (size_t)((row_width - 1) >> 2);
2190 png_bytep dp = row + (size_t)row_width - 1;
2191 png_uint_32 shift = ((3U - ((row_width + 3U) & 0x03)) << 1);
2192 for (i = 0; i < row_width; i++)
2193 {
2194 *dp = (png_byte)((*sp >> shift) & 0x03);
2195
2196 if (shift == 6)
2197 {
2198 shift = 0;
2199 sp--;
2200 }
2201
2202 else
2203 shift += 2;
2204
2205 dp--;
2206 }
2207 break;
2208 }
2209
2210 case 4:
2211 {
2212 png_bytep sp = row + (size_t)((row_width - 1) >> 1);
2213 png_bytep dp = row + (size_t)row_width - 1;
2214 png_uint_32 shift = ((1U - ((row_width + 1U) & 0x01)) << 2);
2215 for (i = 0; i < row_width; i++)
2216 {
2217 *dp = (png_byte)((*sp >> shift) & 0x0f);
2218
2219 if (shift == 4)
2220 {
2221 shift = 0;
2222 sp--;
2223 }
2224
2225 else
2226 shift = 4;
2227
2228 dp--;
2229 }
2230 break;
2231 }
2232
2233 default:
2234 break;
2235 }
2236 row_info->bit_depth = 8;
2237 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2238 row_info->rowbytes = row_width * row_info->channels;
2239 }
2240}
2241#endif
2242
2243#ifdef PNG_READ_SHIFT_SUPPORTED
2244/* Reverse the effects of png_do_shift. This routine merely shifts the
2245 * pixels back to their significant bits values. Thus, if you have
2246 * a row of bit depth 8, but only 5 are significant, this will shift
2247 * the values back to 0 through 31.
2248 */
2249static void
2250png_do_unshift(png_row_infop row_info, png_bytep row,
2251 png_const_color_8p sig_bits)
2252{
2253 int color_type;
2254
2255 png_debug(1, "in png_do_unshift");
2256
2257 /* The palette case has already been handled in the _init routine. */
2258 color_type = row_info->color_type;
2259
2260 if (color_type != PNG_COLOR_TYPE_PALETTE)
2261 {
2262 int shift[4];
2263 int channels = 0;
2264 int bit_depth = row_info->bit_depth;
2265
2266 if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
2267 {
2268 shift[channels++] = bit_depth - sig_bits->red;
2269 shift[channels++] = bit_depth - sig_bits->green;
2270 shift[channels++] = bit_depth - sig_bits->blue;
2271 }
2272
2273 else
2274 {
2275 shift[channels++] = bit_depth - sig_bits->gray;
2276 }
2277
2278 if ((color_type & PNG_COLOR_MASK_ALPHA) != 0)
2279 {
2280 shift[channels++] = bit_depth - sig_bits->alpha;
2281 }
2282
2283 {
2284 int c, have_shift;
2285
2286 for (c = have_shift = 0; c < channels; ++c)
2287 {
2288 /* A shift of more than the bit depth is an error condition but it
2289 * gets ignored here.
2290 */
2291 if (shift[c] <= 0 || shift[c] >= bit_depth)
2292 shift[c] = 0;
2293
2294 else
2295 have_shift = 1;
2296 }
2297
2298 if (have_shift == 0)
2299 return;
2300 }
2301
2302 switch (bit_depth)
2303 {
2304 default:
2305 /* Must be 1bpp gray: should not be here! */
2306 /* NOTREACHED */
2307 break;
2308
2309 case 2:
2310 /* Must be 2bpp gray */
2311 /* assert(channels == 1 && shift[0] == 1) */
2312 {
2313 png_bytep bp = row;
2314 png_bytep bp_end = bp + row_info->rowbytes;
2315
2316 while (bp < bp_end)
2317 {
2318 int b = (*bp >> 1) & 0x55;
2319 *bp++ = (png_byte)b;
2320 }
2321 break;
2322 }
2323
2324 case 4:
2325 /* Must be 4bpp gray */
2326 /* assert(channels == 1) */
2327 {
2328 png_bytep bp = row;
2329 png_bytep bp_end = bp + row_info->rowbytes;
2330 int gray_shift = shift[0];
2331 int mask = 0xf >> gray_shift;
2332
2333 mask |= mask << 4;
2334
2335 while (bp < bp_end)
2336 {
2337 int b = (*bp >> gray_shift) & mask;
2338 *bp++ = (png_byte)b;
2339 }
2340 break;
2341 }
2342
2343 case 8:
2344 /* Single byte components, G, GA, RGB, RGBA */
2345 {
2346 png_bytep bp = row;
2347 png_bytep bp_end = bp + row_info->rowbytes;
2348 int channel = 0;
2349
2350 while (bp < bp_end)
2351 {
2352 int b = *bp >> shift[channel];
2353 if (++channel >= channels)
2354 channel = 0;
2355 *bp++ = (png_byte)b;
2356 }
2357 break;
2358 }
2359
2360#ifdef PNG_READ_16BIT_SUPPORTED
2361 case 16:
2362 /* Double byte components, G, GA, RGB, RGBA */
2363 {
2364 png_bytep bp = row;
2365 png_bytep bp_end = bp + row_info->rowbytes;
2366 int channel = 0;
2367
2368 while (bp < bp_end)
2369 {
2370 int value = (bp[0] << 8) + bp[1];
2371
2372 value >>= shift[channel];
2373 if (++channel >= channels)
2374 channel = 0;
2375 *bp++ = (png_byte)(value >> 8);
2376 *bp++ = (png_byte)value;
2377 }
2378 break;
2379 }
2380#endif
2381 }
2382 }
2383}
2384#endif
2385
2386#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2387/* Scale rows of bit depth 16 down to 8 accurately */
2388static void
2389png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
2390{
2391 png_debug(1, "in png_do_scale_16_to_8");
2392
2393 if (row_info->bit_depth == 16)
2394 {
2395 png_bytep sp = row; /* source */
2396 png_bytep dp = row; /* destination */
2397 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2398
2399 while (sp < ep)
2400 {
2401 /* The input is an array of 16-bit components, these must be scaled to
2402 * 8 bits each. For a 16-bit value V the required value (from the PNG
2403 * specification) is:
2404 *
2405 * (V * 255) / 65535
2406 *
2407 * This reduces to round(V / 257), or floor((V + 128.5)/257)
2408 *
2409 * Represent V as the two byte value vhi.vlo. Make a guess that the
2410 * result is the top byte of V, vhi, then the correction to this value
2411 * is:
2412 *
2413 * error = floor(((V-vhi.vhi) + 128.5) / 257)
2414 * = floor(((vlo-vhi) + 128.5) / 257)
2415 *
2416 * This can be approximated using integer arithmetic (and a signed
2417 * shift):
2418 *
2419 * error = (vlo-vhi+128) >> 8;
2420 *
2421 * The approximate differs from the exact answer only when (vlo-vhi) is
2422 * 128; it then gives a correction of +1 when the exact correction is
2423 * 0. This gives 128 errors. The exact answer (correct for all 16-bit
2424 * input values) is:
2425 *
2426 * error = (vlo-vhi+128)*65535 >> 24;
2427 *
2428 * An alternative arithmetic calculation which also gives no errors is:
2429 *
2430 * (V * 255 + 32895) >> 16
2431 */
2432
2433 png_int_32 tmp = *sp++; /* must be signed! */
2434 tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
2435 *dp++ = (png_byte)tmp;
2436 }
2437
2438 row_info->bit_depth = 8;
2439 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2440 row_info->rowbytes = row_info->width * row_info->channels;
2441 }
2442}
2443#endif
2444
2445#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2446static void
2447/* Simply discard the low byte. This was the default behavior prior
2448 * to libpng-1.5.4.
2449 */
2450png_do_chop(png_row_infop row_info, png_bytep row)
2451{
2452 png_debug(1, "in png_do_chop");
2453
2454 if (row_info->bit_depth == 16)
2455 {
2456 png_bytep sp = row; /* source */
2457 png_bytep dp = row; /* destination */
2458 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2459
2460 while (sp < ep)
2461 {
2462 *dp++ = *sp;
2463 sp += 2; /* skip low byte */
2464 }
2465
2466 row_info->bit_depth = 8;
2467 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2468 row_info->rowbytes = row_info->width * row_info->channels;
2469 }
2470}
2471#endif
2472
2473#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2474static void
2475png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
2476{
2477 png_uint_32 row_width = row_info->width;
2478
2479 png_debug(1, "in png_do_read_swap_alpha");
2480
2481 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2482 {
2483 /* This converts from RGBA to ARGB */
2484 if (row_info->bit_depth == 8)
2485 {
2486 png_bytep sp = row + row_info->rowbytes;
2487 png_bytep dp = sp;
2488 png_byte save;
2489 png_uint_32 i;
2490
2491 for (i = 0; i < row_width; i++)
2492 {
2493 save = *(--sp);
2494 *(--dp) = *(--sp);
2495 *(--dp) = *(--sp);
2496 *(--dp) = *(--sp);
2497 *(--dp) = save;
2498 }
2499 }
2500
2501#ifdef PNG_READ_16BIT_SUPPORTED
2502 /* This converts from RRGGBBAA to AARRGGBB */
2503 else
2504 {
2505 png_bytep sp = row + row_info->rowbytes;
2506 png_bytep dp = sp;
2507 png_byte save[2];
2508 png_uint_32 i;
2509
2510 for (i = 0; i < row_width; i++)
2511 {
2512 save[0] = *(--sp);
2513 save[1] = *(--sp);
2514 *(--dp) = *(--sp);
2515 *(--dp) = *(--sp);
2516 *(--dp) = *(--sp);
2517 *(--dp) = *(--sp);
2518 *(--dp) = *(--sp);
2519 *(--dp) = *(--sp);
2520 *(--dp) = save[0];
2521 *(--dp) = save[1];
2522 }
2523 }
2524#endif
2525 }
2526
2527 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2528 {
2529 /* This converts from GA to AG */
2530 if (row_info->bit_depth == 8)
2531 {
2532 png_bytep sp = row + row_info->rowbytes;
2533 png_bytep dp = sp;
2534 png_byte save;
2535 png_uint_32 i;
2536
2537 for (i = 0; i < row_width; i++)
2538 {
2539 save = *(--sp);
2540 *(--dp) = *(--sp);
2541 *(--dp) = save;
2542 }
2543 }
2544
2545#ifdef PNG_READ_16BIT_SUPPORTED
2546 /* This converts from GGAA to AAGG */
2547 else
2548 {
2549 png_bytep sp = row + row_info->rowbytes;
2550 png_bytep dp = sp;
2551 png_byte save[2];
2552 png_uint_32 i;
2553
2554 for (i = 0; i < row_width; i++)
2555 {
2556 save[0] = *(--sp);
2557 save[1] = *(--sp);
2558 *(--dp) = *(--sp);
2559 *(--dp) = *(--sp);
2560 *(--dp) = save[0];
2561 *(--dp) = save[1];
2562 }
2563 }
2564#endif
2565 }
2566}
2567#endif
2568
2569#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2570static void
2571png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
2572{
2573 png_uint_32 row_width;
2574 png_debug(1, "in png_do_read_invert_alpha");
2575
2576 row_width = row_info->width;
2577 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2578 {
2579 if (row_info->bit_depth == 8)
2580 {
2581 /* This inverts the alpha channel in RGBA */
2582 png_bytep sp = row + row_info->rowbytes;
2583 png_bytep dp = sp;
2584 png_uint_32 i;
2585
2586 for (i = 0; i < row_width; i++)
2587 {
2588 *(--dp) = (png_byte)(255 - *(--sp));
2589
2590/* This does nothing:
2591 *(--dp) = *(--sp);
2592 *(--dp) = *(--sp);
2593 *(--dp) = *(--sp);
2594 We can replace it with:
2595*/
2596 sp-=3;
2597 dp=sp;
2598 }
2599 }
2600
2601#ifdef PNG_READ_16BIT_SUPPORTED
2602 /* This inverts the alpha channel in RRGGBBAA */
2603 else
2604 {
2605 png_bytep sp = row + row_info->rowbytes;
2606 png_bytep dp = sp;
2607 png_uint_32 i;
2608
2609 for (i = 0; i < row_width; i++)
2610 {
2611 *(--dp) = (png_byte)(255 - *(--sp));
2612 *(--dp) = (png_byte)(255 - *(--sp));
2613
2614/* This does nothing:
2615 *(--dp) = *(--sp);
2616 *(--dp) = *(--sp);
2617 *(--dp) = *(--sp);
2618 *(--dp) = *(--sp);
2619 *(--dp) = *(--sp);
2620 *(--dp) = *(--sp);
2621 We can replace it with:
2622*/
2623 sp-=6;
2624 dp=sp;
2625 }
2626 }
2627#endif
2628 }
2629 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2630 {
2631 if (row_info->bit_depth == 8)
2632 {
2633 /* This inverts the alpha channel in GA */
2634 png_bytep sp = row + row_info->rowbytes;
2635 png_bytep dp = sp;
2636 png_uint_32 i;
2637
2638 for (i = 0; i < row_width; i++)
2639 {
2640 *(--dp) = (png_byte)(255 - *(--sp));
2641 *(--dp) = *(--sp);
2642 }
2643 }
2644
2645#ifdef PNG_READ_16BIT_SUPPORTED
2646 else
2647 {
2648 /* This inverts the alpha channel in GGAA */
2649 png_bytep sp = row + row_info->rowbytes;
2650 png_bytep dp = sp;
2651 png_uint_32 i;
2652
2653 for (i = 0; i < row_width; i++)
2654 {
2655 *(--dp) = (png_byte)(255 - *(--sp));
2656 *(--dp) = (png_byte)(255 - *(--sp));
2657/*
2658 *(--dp) = *(--sp);
2659 *(--dp) = *(--sp);
2660*/
2661 sp-=2;
2662 dp=sp;
2663 }
2664 }
2665#endif
2666 }
2667}
2668#endif
2669
2670#ifdef PNG_READ_FILLER_SUPPORTED
2671/* Add filler channel if we have RGB color */
2672static void
2673png_do_read_filler(png_row_infop row_info, png_bytep row,
2674 png_uint_32 filler, png_uint_32 flags)
2675{
2676 png_uint_32 i;
2677 png_uint_32 row_width = row_info->width;
2678
2679#ifdef PNG_READ_16BIT_SUPPORTED
2680 png_byte hi_filler = (png_byte)(filler>>8);
2681#endif
2682 png_byte lo_filler = (png_byte)filler;
2683
2684 png_debug(1, "in png_do_read_filler");
2685
2686 if (
2687 row_info->color_type == PNG_COLOR_TYPE_GRAY)
2688 {
2689 if (row_info->bit_depth == 8)
2690 {
2691 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2692 {
2693 /* This changes the data from G to GX */
2694 png_bytep sp = row + (size_t)row_width;
2695 png_bytep dp = sp + (size_t)row_width;
2696 for (i = 1; i < row_width; i++)
2697 {
2698 *(--dp) = lo_filler;
2699 *(--dp) = *(--sp);
2700 }
2701 *(--dp) = lo_filler;
2702 row_info->channels = 2;
2703 row_info->pixel_depth = 16;
2704 row_info->rowbytes = row_width * 2;
2705 }
2706
2707 else
2708 {
2709 /* This changes the data from G to XG */
2710 png_bytep sp = row + (size_t)row_width;
2711 png_bytep dp = sp + (size_t)row_width;
2712 for (i = 0; i < row_width; i++)
2713 {
2714 *(--dp) = *(--sp);
2715 *(--dp) = lo_filler;
2716 }
2717 row_info->channels = 2;
2718 row_info->pixel_depth = 16;
2719 row_info->rowbytes = row_width * 2;
2720 }
2721 }
2722
2723#ifdef PNG_READ_16BIT_SUPPORTED
2724 else if (row_info->bit_depth == 16)
2725 {
2726 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2727 {
2728 /* This changes the data from GG to GGXX */
2729 png_bytep sp = row + (size_t)row_width * 2;
2730 png_bytep dp = sp + (size_t)row_width * 2;
2731 for (i = 1; i < row_width; i++)
2732 {
2733 *(--dp) = lo_filler;
2734 *(--dp) = hi_filler;
2735 *(--dp) = *(--sp);
2736 *(--dp) = *(--sp);
2737 }
2738 *(--dp) = lo_filler;
2739 *(--dp) = hi_filler;
2740 row_info->channels = 2;
2741 row_info->pixel_depth = 32;
2742 row_info->rowbytes = row_width * 4;
2743 }
2744
2745 else
2746 {
2747 /* This changes the data from GG to XXGG */
2748 png_bytep sp = row + (size_t)row_width * 2;
2749 png_bytep dp = sp + (size_t)row_width * 2;
2750 for (i = 0; i < row_width; i++)
2751 {
2752 *(--dp) = *(--sp);
2753 *(--dp) = *(--sp);
2754 *(--dp) = lo_filler;
2755 *(--dp) = hi_filler;
2756 }
2757 row_info->channels = 2;
2758 row_info->pixel_depth = 32;
2759 row_info->rowbytes = row_width * 4;
2760 }
2761 }
2762#endif
2763 } /* COLOR_TYPE == GRAY */
2764 else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
2765 {
2766 if (row_info->bit_depth == 8)
2767 {
2768 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2769 {
2770 /* This changes the data from RGB to RGBX */
2771 png_bytep sp = row + (size_t)row_width * 3;
2772 png_bytep dp = sp + (size_t)row_width;
2773 for (i = 1; i < row_width; i++)
2774 {
2775 *(--dp) = lo_filler;
2776 *(--dp) = *(--sp);
2777 *(--dp) = *(--sp);
2778 *(--dp) = *(--sp);
2779 }
2780 *(--dp) = lo_filler;
2781 row_info->channels = 4;
2782 row_info->pixel_depth = 32;
2783 row_info->rowbytes = row_width * 4;
2784 }
2785
2786 else
2787 {
2788 /* This changes the data from RGB to XRGB */
2789 png_bytep sp = row + (size_t)row_width * 3;
2790 png_bytep dp = sp + (size_t)row_width;
2791 for (i = 0; i < row_width; i++)
2792 {
2793 *(--dp) = *(--sp);
2794 *(--dp) = *(--sp);
2795 *(--dp) = *(--sp);
2796 *(--dp) = lo_filler;
2797 }
2798 row_info->channels = 4;
2799 row_info->pixel_depth = 32;
2800 row_info->rowbytes = row_width * 4;
2801 }
2802 }
2803
2804#ifdef PNG_READ_16BIT_SUPPORTED
2805 else if (row_info->bit_depth == 16)
2806 {
2807 if ((flags & PNG_FLAG_FILLER_AFTER) != 0)
2808 {
2809 /* This changes the data from RRGGBB to RRGGBBXX */
2810 png_bytep sp = row + (size_t)row_width * 6;
2811 png_bytep dp = sp + (size_t)row_width * 2;
2812 for (i = 1; i < row_width; i++)
2813 {
2814 *(--dp) = lo_filler;
2815 *(--dp) = hi_filler;
2816 *(--dp) = *(--sp);
2817 *(--dp) = *(--sp);
2818 *(--dp) = *(--sp);
2819 *(--dp) = *(--sp);
2820 *(--dp) = *(--sp);
2821 *(--dp) = *(--sp);
2822 }
2823 *(--dp) = lo_filler;
2824 *(--dp) = hi_filler;
2825 row_info->channels = 4;
2826 row_info->pixel_depth = 64;
2827 row_info->rowbytes = row_width * 8;
2828 }
2829
2830 else
2831 {
2832 /* This changes the data from RRGGBB to XXRRGGBB */
2833 png_bytep sp = row + (size_t)row_width * 6;
2834 png_bytep dp = sp + (size_t)row_width * 2;
2835 for (i = 0; i < row_width; i++)
2836 {
2837 *(--dp) = *(--sp);
2838 *(--dp) = *(--sp);
2839 *(--dp) = *(--sp);
2840 *(--dp) = *(--sp);
2841 *(--dp) = *(--sp);
2842 *(--dp) = *(--sp);
2843 *(--dp) = lo_filler;
2844 *(--dp) = hi_filler;
2845 }
2846
2847 row_info->channels = 4;
2848 row_info->pixel_depth = 64;
2849 row_info->rowbytes = row_width * 8;
2850 }
2851 }
2852#endif
2853 } /* COLOR_TYPE == RGB */
2854}
2855#endif
2856
2857#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2858/* Expand grayscale files to RGB, with or without alpha */
2859static void
2860png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
2861{
2862 png_uint_32 i;
2863 png_uint_32 row_width = row_info->width;
2864
2865 png_debug(1, "in png_do_gray_to_rgb");
2866
2867 if (row_info->bit_depth >= 8 &&
2868 (row_info->color_type & PNG_COLOR_MASK_COLOR) == 0)
2869 {
2870 if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
2871 {
2872 if (row_info->bit_depth == 8)
2873 {
2874 /* This changes G to RGB */
2875 png_bytep sp = row + (size_t)row_width - 1;
2876 png_bytep dp = sp + (size_t)row_width * 2;
2877 for (i = 0; i < row_width; i++)
2878 {
2879 *(dp--) = *sp;
2880 *(dp--) = *sp;
2881 *(dp--) = *(sp--);
2882 }
2883 }
2884
2885 else
2886 {
2887 /* This changes GG to RRGGBB */
2888 png_bytep sp = row + (size_t)row_width * 2 - 1;
2889 png_bytep dp = sp + (size_t)row_width * 4;
2890 for (i = 0; i < row_width; i++)
2891 {
2892 *(dp--) = *sp;
2893 *(dp--) = *(sp - 1);
2894 *(dp--) = *sp;
2895 *(dp--) = *(sp - 1);
2896 *(dp--) = *(sp--);
2897 *(dp--) = *(sp--);
2898 }
2899 }
2900 }
2901
2902 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2903 {
2904 if (row_info->bit_depth == 8)
2905 {
2906 /* This changes GA to RGBA */
2907 png_bytep sp = row + (size_t)row_width * 2 - 1;
2908 png_bytep dp = sp + (size_t)row_width * 2;
2909 for (i = 0; i < row_width; i++)
2910 {
2911 *(dp--) = *(sp--);
2912 *(dp--) = *sp;
2913 *(dp--) = *sp;
2914 *(dp--) = *(sp--);
2915 }
2916 }
2917
2918 else
2919 {
2920 /* This changes GGAA to RRGGBBAA */
2921 png_bytep sp = row + (size_t)row_width * 4 - 1;
2922 png_bytep dp = sp + (size_t)row_width * 4;
2923 for (i = 0; i < row_width; i++)
2924 {
2925 *(dp--) = *(sp--);
2926 *(dp--) = *(sp--);
2927 *(dp--) = *sp;
2928 *(dp--) = *(sp - 1);
2929 *(dp--) = *sp;
2930 *(dp--) = *(sp - 1);
2931 *(dp--) = *(sp--);
2932 *(dp--) = *(sp--);
2933 }
2934 }
2935 }
2936 row_info->channels = (png_byte)(row_info->channels + 2);
2937 row_info->color_type |= PNG_COLOR_MASK_COLOR;
2938 row_info->pixel_depth = (png_byte)(row_info->channels *
2939 row_info->bit_depth);
2940 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
2941 }
2942}
2943#endif
2944
2945#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2946/* Reduce RGB files to grayscale, with or without alpha
2947 * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
2948 * <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
2949 * versions dated 1998 through November 2002 have been archived at
2950 * https://web.archive.org/web/20000816232553/www.inforamp.net/
2951 * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
2952 * Charles Poynton poynton at poynton.com
2953 *
2954 * Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2955 *
2956 * which can be expressed with integers as
2957 *
2958 * Y = (6969 * R + 23434 * G + 2365 * B)/32768
2959 *
2960 * Poynton's current link (as of January 2003 through July 2011):
2961 * <http://www.poynton.com/notes/colour_and_gamma/>
2962 * has changed the numbers slightly:
2963 *
2964 * Y = 0.2126*R + 0.7152*G + 0.0722*B
2965 *
2966 * which can be expressed with integers as
2967 *
2968 * Y = (6966 * R + 23436 * G + 2366 * B)/32768
2969 *
2970 * Historically, however, libpng uses numbers derived from the ITU-R Rec 709
2971 * end point chromaticities and the D65 white point. Depending on the
2972 * precision used for the D65 white point this produces a variety of different
2973 * numbers, however if the four decimal place value used in ITU-R Rec 709 is
2974 * used (0.3127,0.3290) the Y calculation would be:
2975 *
2976 * Y = (6968 * R + 23435 * G + 2366 * B)/32768
2977 *
2978 * While this is correct the rounding results in an overflow for white, because
2979 * the sum of the rounded coefficients is 32769, not 32768. Consequently
2980 * libpng uses, instead, the closest non-overflowing approximation:
2981 *
2982 * Y = (6968 * R + 23434 * G + 2366 * B)/32768
2983 *
2984 * Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
2985 * (including an sRGB chunk) then the chromaticities are used to calculate the
2986 * coefficients. See the chunk handling in pngrutil.c for more information.
2987 *
2988 * In all cases the calculation is to be done in a linear colorspace. If no
2989 * gamma information is available to correct the encoding of the original RGB
2990 * values this results in an implicit assumption that the original PNG RGB
2991 * values were linear.
2992 *
2993 * Other integer coefficients can be used via png_set_rgb_to_gray(). Because
2994 * the API takes just red and green coefficients the blue coefficient is
2995 * calculated to make the sum 32768. This will result in different rounding
2996 * to that used above.
2997 */
2998static int
2999png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
3000{
3001 int rgb_error = 0;
3002
3003 png_debug(1, "in png_do_rgb_to_gray");
3004
3005 if ((row_info->color_type & PNG_COLOR_MASK_PALETTE) == 0 &&
3006 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
3007 {
3008 png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
3009 png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
3010 png_uint_32 bc = 32768 - rc - gc;
3011 png_uint_32 row_width = row_info->width;
3012 int have_alpha = (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
3013
3014 if (row_info->bit_depth == 8)
3015 {
3016#ifdef PNG_READ_GAMMA_SUPPORTED
3017 /* Notice that gamma to/from 1 are not necessarily inverses (if
3018 * there is an overall gamma correction). Prior to 1.5.5 this code
3019 * checked the linearized values for equality; this doesn't match
3020 * the documentation, the original values must be checked.
3021 */
3022 if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
3023 {
3024 png_bytep sp = row;
3025 png_bytep dp = row;
3026 png_uint_32 i;
3027
3028 for (i = 0; i < row_width; i++)
3029 {
3030 png_byte red = *(sp++);
3031 png_byte green = *(sp++);
3032 png_byte blue = *(sp++);
3033
3034 if (red != green || red != blue)
3035 {
3036 red = png_ptr->gamma_to_1[red];
3037 green = png_ptr->gamma_to_1[green];
3038 blue = png_ptr->gamma_to_1[blue];
3039
3040 rgb_error |= 1;
3041 *(dp++) = png_ptr->gamma_from_1[
3042 (rc*red + gc*green + bc*blue + 16384)>>15];
3043 }
3044
3045 else
3046 {
3047 /* If there is no overall correction the table will not be
3048 * set.
3049 */
3050 if (png_ptr->gamma_table != NULL)
3051 red = png_ptr->gamma_table[red];
3052
3053 *(dp++) = red;
3054 }
3055
3056 if (have_alpha != 0)
3057 *(dp++) = *(sp++);
3058 }
3059 }
3060 else
3061#endif
3062 {
3063 png_bytep sp = row;
3064 png_bytep dp = row;
3065 png_uint_32 i;
3066
3067 for (i = 0; i < row_width; i++)
3068 {
3069 png_byte red = *(sp++);
3070 png_byte green = *(sp++);
3071 png_byte blue = *(sp++);
3072
3073 if (red != green || red != blue)
3074 {
3075 rgb_error |= 1;
3076 /* NOTE: this is the historical approach which simply
3077 * truncates the results.
3078 */
3079 *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
3080 }
3081
3082 else
3083 *(dp++) = red;
3084
3085 if (have_alpha != 0)
3086 *(dp++) = *(sp++);
3087 }
3088 }
3089 }
3090
3091 else /* RGB bit_depth == 16 */
3092 {
3093#ifdef PNG_READ_GAMMA_SUPPORTED
3094 if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
3095 {
3096 png_bytep sp = row;
3097 png_bytep dp = row;
3098 png_uint_32 i;
3099
3100 for (i = 0; i < row_width; i++)
3101 {
3102 png_uint_16 red, green, blue, w;
3103 png_byte hi,lo;
3104
3105 hi=*(sp)++; lo=*(sp)++; red = (png_uint_16)((hi << 8) | (lo));
3106 hi=*(sp)++; lo=*(sp)++; green = (png_uint_16)((hi << 8) | (lo));
3107 hi=*(sp)++; lo=*(sp)++; blue = (png_uint_16)((hi << 8) | (lo));
3108
3109 if (red == green && red == blue)
3110 {
3111 if (png_ptr->gamma_16_table != NULL)
3112 w = png_ptr->gamma_16_table[(red & 0xff)
3113 >> png_ptr->gamma_shift][red >> 8];
3114
3115 else
3116 w = red;
3117 }
3118
3119 else
3120 {
3121 png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red & 0xff)
3122 >> png_ptr->gamma_shift][red>>8];
3123 png_uint_16 green_1 =
3124 png_ptr->gamma_16_to_1[(green & 0xff) >>
3125 png_ptr->gamma_shift][green>>8];
3126 png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue & 0xff)
3127 >> png_ptr->gamma_shift][blue>>8];
3128 png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
3129 + bc*blue_1 + 16384)>>15);
3130 w = png_ptr->gamma_16_from_1[(gray16 & 0xff) >>
3131 png_ptr->gamma_shift][gray16 >> 8];
3132 rgb_error |= 1;
3133 }
3134
3135 *(dp++) = (png_byte)((w>>8) & 0xff);
3136 *(dp++) = (png_byte)(w & 0xff);
3137
3138 if (have_alpha != 0)
3139 {
3140 *(dp++) = *(sp++);
3141 *(dp++) = *(sp++);
3142 }
3143 }
3144 }
3145 else
3146#endif
3147 {
3148 png_bytep sp = row;
3149 png_bytep dp = row;
3150 png_uint_32 i;
3151
3152 for (i = 0; i < row_width; i++)
3153 {
3154 png_uint_16 red, green, blue, gray16;
3155 png_byte hi,lo;
3156
3157 hi=*(sp)++; lo=*(sp)++; red = (png_uint_16)((hi << 8) | (lo));
3158 hi=*(sp)++; lo=*(sp)++; green = (png_uint_16)((hi << 8) | (lo));
3159 hi=*(sp)++; lo=*(sp)++; blue = (png_uint_16)((hi << 8) | (lo));
3160
3161 if (red != green || red != blue)
3162 rgb_error |= 1;
3163
3164 /* From 1.5.5 in the 16-bit case do the accurate conversion even
3165 * in the 'fast' case - this is because this is where the code
3166 * ends up when handling linear 16-bit data.
3167 */
3168 gray16 = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
3169 15);
3170 *(dp++) = (png_byte)((gray16 >> 8) & 0xff);
3171 *(dp++) = (png_byte)(gray16 & 0xff);
3172
3173 if (have_alpha != 0)
3174 {
3175 *(dp++) = *(sp++);
3176 *(dp++) = *(sp++);
3177 }
3178 }
3179 }
3180 }
3181
3182 row_info->channels = (png_byte)(row_info->channels - 2);
3183 row_info->color_type = (png_byte)(row_info->color_type &
3184 ~PNG_COLOR_MASK_COLOR);
3185 row_info->pixel_depth = (png_byte)(row_info->channels *
3186 row_info->bit_depth);
3187 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
3188 }
3189 return rgb_error;
3190}
3191#endif
3192
3193#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
3194 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
3195/* Replace any alpha or transparency with the supplied background color.
3196 * "background" is already in the screen gamma, while "background_1" is
3197 * at a gamma of 1.0. Paletted files have already been taken care of.
3198 */
3199static void
3200png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
3201{
3202#ifdef PNG_READ_GAMMA_SUPPORTED
3203 png_const_bytep gamma_table = png_ptr->gamma_table;
3204 png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
3205 png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
3206 png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
3207 png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
3208 png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
3209 int gamma_shift = png_ptr->gamma_shift;
3210 int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
3211#endif
3212
3213 png_bytep sp;
3214 png_uint_32 i;
3215 png_uint_32 row_width = row_info->width;
3216 int shift;
3217
3218 png_debug(1, "in png_do_compose");
3219
3220 switch (row_info->color_type)
3221 {
3222 case PNG_COLOR_TYPE_GRAY:
3223 {
3224 switch (row_info->bit_depth)
3225 {
3226 case 1:
3227 {
3228 sp = row;
3229 shift = 7;
3230 for (i = 0; i < row_width; i++)
3231 {
3232 if ((png_uint_16)((*sp >> shift) & 0x01)
3233 == png_ptr->trans_color.gray)
3234 {
3235 unsigned int tmp = *sp & (0x7f7f >> (7 - shift));
3236 tmp |=
3237 (unsigned int)(png_ptr->background.gray << shift);
3238 *sp = (png_byte)(tmp & 0xff);
3239 }
3240
3241 if (shift == 0)
3242 {
3243 shift = 7;
3244 sp++;
3245 }
3246
3247 else
3248 shift--;
3249 }
3250 break;
3251 }
3252
3253 case 2:
3254 {
3255#ifdef PNG_READ_GAMMA_SUPPORTED
3256 if (gamma_table != NULL)
3257 {
3258 sp = row;
3259 shift = 6;
3260 for (i = 0; i < row_width; i++)
3261 {
3262 if ((png_uint_16)((*sp >> shift) & 0x03)
3263 == png_ptr->trans_color.gray)
3264 {
3265 unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
3266 tmp |=
3267 (unsigned int)png_ptr->background.gray << shift;
3268 *sp = (png_byte)(tmp & 0xff);
3269 }
3270
3271 else
3272 {
3273 unsigned int p = (*sp >> shift) & 0x03;
3274 unsigned int g = (gamma_table [p | (p << 2) |
3275 (p << 4) | (p << 6)] >> 6) & 0x03;
3276 unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
3277 tmp |= (unsigned int)(g << shift);
3278 *sp = (png_byte)(tmp & 0xff);
3279 }
3280
3281 if (shift == 0)
3282 {
3283 shift = 6;
3284 sp++;
3285 }
3286
3287 else
3288 shift -= 2;
3289 }
3290 }
3291
3292 else
3293#endif
3294 {
3295 sp = row;
3296 shift = 6;
3297 for (i = 0; i < row_width; i++)
3298 {
3299 if ((png_uint_16)((*sp >> shift) & 0x03)
3300 == png_ptr->trans_color.gray)
3301 {
3302 unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
3303 tmp |=
3304 (unsigned int)png_ptr->background.gray << shift;
3305 *sp = (png_byte)(tmp & 0xff);
3306 }
3307
3308 if (shift == 0)
3309 {
3310 shift = 6;
3311 sp++;
3312 }
3313
3314 else
3315 shift -= 2;
3316 }
3317 }
3318 break;
3319 }
3320
3321 case 4:
3322 {
3323#ifdef PNG_READ_GAMMA_SUPPORTED
3324 if (gamma_table != NULL)
3325 {
3326 sp = row;
3327 shift = 4;
3328 for (i = 0; i < row_width; i++)
3329 {
3330 if ((png_uint_16)((*sp >> shift) & 0x0f)
3331 == png_ptr->trans_color.gray)
3332 {
3333 unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
3334 tmp |=
3335 (unsigned int)(png_ptr->background.gray << shift);
3336 *sp = (png_byte)(tmp & 0xff);
3337 }
3338
3339 else
3340 {
3341 unsigned int p = (*sp >> shift) & 0x0f;
3342 unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
3343 0x0f;
3344 unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
3345 tmp |= (unsigned int)(g << shift);
3346 *sp = (png_byte)(tmp & 0xff);
3347 }
3348
3349 if (shift == 0)
3350 {
3351 shift = 4;
3352 sp++;
3353 }
3354
3355 else
3356 shift -= 4;
3357 }
3358 }
3359
3360 else
3361#endif
3362 {
3363 sp = row;
3364 shift = 4;
3365 for (i = 0; i < row_width; i++)
3366 {
3367 if ((png_uint_16)((*sp >> shift) & 0x0f)
3368 == png_ptr->trans_color.gray)
3369 {
3370 unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
3371 tmp |=
3372 (unsigned int)(png_ptr->background.gray << shift);
3373 *sp = (png_byte)(tmp & 0xff);
3374 }
3375
3376 if (shift == 0)
3377 {
3378 shift = 4;
3379 sp++;
3380 }
3381
3382 else
3383 shift -= 4;
3384 }
3385 }
3386 break;
3387 }
3388
3389 case 8:
3390 {
3391#ifdef PNG_READ_GAMMA_SUPPORTED
3392 if (gamma_table != NULL)
3393 {
3394 sp = row;
3395 for (i = 0; i < row_width; i++, sp++)
3396 {
3397 if (*sp == png_ptr->trans_color.gray)
3398 *sp = (png_byte)png_ptr->background.gray;
3399
3400 else
3401 *sp = gamma_table[*sp];
3402 }
3403 }
3404 else
3405#endif
3406 {
3407 sp = row;
3408 for (i = 0; i < row_width; i++, sp++)
3409 {
3410 if (*sp == png_ptr->trans_color.gray)
3411 *sp = (png_byte)png_ptr->background.gray;
3412 }
3413 }
3414 break;
3415 }
3416
3417 case 16:
3418 {
3419#ifdef PNG_READ_GAMMA_SUPPORTED
3420 if (gamma_16 != NULL)
3421 {
3422 sp = row;
3423 for (i = 0; i < row_width; i++, sp += 2)
3424 {
3425 png_uint_16 v;
3426
3427 v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3428
3429 if (v == png_ptr->trans_color.gray)
3430 {
3431 /* Background is already in screen gamma */
3432 *sp = (png_byte)((png_ptr->background.gray >> 8)
3433 & 0xff);
3434 *(sp + 1) = (png_byte)(png_ptr->background.gray
3435 & 0xff);
3436 }
3437
3438 else
3439 {
3440 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3441 *sp = (png_byte)((v >> 8) & 0xff);
3442 *(sp + 1) = (png_byte)(v & 0xff);
3443 }
3444 }
3445 }
3446 else
3447#endif
3448 {
3449 sp = row;
3450 for (i = 0; i < row_width; i++, sp += 2)
3451 {
3452 png_uint_16 v;
3453
3454 v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3455
3456 if (v == png_ptr->trans_color.gray)
3457 {
3458 *sp = (png_byte)((png_ptr->background.gray >> 8)
3459 & 0xff);
3460 *(sp + 1) = (png_byte)(png_ptr->background.gray
3461 & 0xff);
3462 }
3463 }
3464 }
3465 break;
3466 }
3467
3468 default:
3469 break;
3470 }
3471 break;
3472 }
3473
3474 case PNG_COLOR_TYPE_RGB:
3475 {
3476 if (row_info->bit_depth == 8)
3477 {
3478#ifdef PNG_READ_GAMMA_SUPPORTED
3479 if (gamma_table != NULL)
3480 {
3481 sp = row;
3482 for (i = 0; i < row_width; i++, sp += 3)
3483 {
3484 if (*sp == png_ptr->trans_color.red &&
3485 *(sp + 1) == png_ptr->trans_color.green &&
3486 *(sp + 2) == png_ptr->trans_color.blue)
3487 {
3488 *sp = (png_byte)png_ptr->background.red;
3489 *(sp + 1) = (png_byte)png_ptr->background.green;
3490 *(sp + 2) = (png_byte)png_ptr->background.blue;
3491 }
3492
3493 else
3494 {
3495 *sp = gamma_table[*sp];
3496 *(sp + 1) = gamma_table[*(sp + 1)];
3497 *(sp + 2) = gamma_table[*(sp + 2)];
3498 }
3499 }
3500 }
3501 else
3502#endif
3503 {
3504 sp = row;
3505 for (i = 0; i < row_width; i++, sp += 3)
3506 {
3507 if (*sp == png_ptr->trans_color.red &&
3508 *(sp + 1) == png_ptr->trans_color.green &&
3509 *(sp + 2) == png_ptr->trans_color.blue)
3510 {
3511 *sp = (png_byte)png_ptr->background.red;
3512 *(sp + 1) = (png_byte)png_ptr->background.green;
3513 *(sp + 2) = (png_byte)png_ptr->background.blue;
3514 }
3515 }
3516 }
3517 }
3518 else /* if (row_info->bit_depth == 16) */
3519 {
3520#ifdef PNG_READ_GAMMA_SUPPORTED
3521 if (gamma_16 != NULL)
3522 {
3523 sp = row;
3524 for (i = 0; i < row_width; i++, sp += 6)
3525 {
3526 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3527
3528 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
3529 + *(sp + 3));
3530
3531 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
3532 + *(sp + 5));
3533
3534 if (r == png_ptr->trans_color.red &&
3535 g == png_ptr->trans_color.green &&
3536 b == png_ptr->trans_color.blue)
3537 {
3538 /* Background is already in screen gamma */
3539 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3540 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3541 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3542 & 0xff);
3543 *(sp + 3) = (png_byte)(png_ptr->background.green
3544 & 0xff);
3545 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3546 & 0xff);
3547 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3548 }
3549
3550 else
3551 {
3552 png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3553 *sp = (png_byte)((v >> 8) & 0xff);
3554 *(sp + 1) = (png_byte)(v & 0xff);
3555
3556 v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
3557 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
3558 *(sp + 3) = (png_byte)(v & 0xff);
3559
3560 v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
3561 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
3562 *(sp + 5) = (png_byte)(v & 0xff);
3563 }
3564 }
3565 }
3566
3567 else
3568#endif
3569 {
3570 sp = row;
3571 for (i = 0; i < row_width; i++, sp += 6)
3572 {
3573 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3574
3575 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
3576 + *(sp + 3));
3577
3578 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
3579 + *(sp + 5));
3580
3581 if (r == png_ptr->trans_color.red &&
3582 g == png_ptr->trans_color.green &&
3583 b == png_ptr->trans_color.blue)
3584 {
3585 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3586 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3587 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3588 & 0xff);
3589 *(sp + 3) = (png_byte)(png_ptr->background.green
3590 & 0xff);
3591 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3592 & 0xff);
3593 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3594 }
3595 }
3596 }
3597 }
3598 break;
3599 }
3600
3601 case PNG_COLOR_TYPE_GRAY_ALPHA:
3602 {
3603 if (row_info->bit_depth == 8)
3604 {
3605#ifdef PNG_READ_GAMMA_SUPPORTED
3606 if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
3607 gamma_table != NULL)
3608 {
3609 sp = row;
3610 for (i = 0; i < row_width; i++, sp += 2)
3611 {
3612 png_uint_16 a = *(sp + 1);
3613
3614 if (a == 0xff)
3615 *sp = gamma_table[*sp];
3616
3617 else if (a == 0)
3618 {
3619 /* Background is already in screen gamma */
3620 *sp = (png_byte)png_ptr->background.gray;
3621 }
3622
3623 else
3624 {
3625 png_byte v, w;
3626
3627 v = gamma_to_1[*sp];
3628 png_composite(w, v, a, png_ptr->background_1.gray);
3629 if (optimize == 0)
3630 w = gamma_from_1[w];
3631 *sp = w;
3632 }
3633 }
3634 }
3635 else
3636#endif
3637 {
3638 sp = row;
3639 for (i = 0; i < row_width; i++, sp += 2)
3640 {
3641 png_byte a = *(sp + 1);
3642
3643 if (a == 0)
3644 *sp = (png_byte)png_ptr->background.gray;
3645
3646 else if (a < 0xff)
3647 png_composite(*sp, *sp, a, png_ptr->background.gray);
3648 }
3649 }
3650 }
3651 else /* if (png_ptr->bit_depth == 16) */
3652 {
3653#ifdef PNG_READ_GAMMA_SUPPORTED
3654 if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
3655 gamma_16_to_1 != NULL)
3656 {
3657 sp = row;
3658 for (i = 0; i < row_width; i++, sp += 4)
3659 {
3660 png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
3661 + *(sp + 3));
3662
3663 if (a == (png_uint_16)0xffff)
3664 {
3665 png_uint_16 v;
3666
3667 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3668 *sp = (png_byte)((v >> 8) & 0xff);
3669 *(sp + 1) = (png_byte)(v & 0xff);
3670 }
3671
3672 else if (a == 0)
3673 {
3674 /* Background is already in screen gamma */
3675 *sp = (png_byte)((png_ptr->background.gray >> 8)
3676 & 0xff);
3677 *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
3678 }
3679
3680 else
3681 {
3682 png_uint_16 g, v, w;
3683
3684 g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
3685 png_composite_16(v, g, a, png_ptr->background_1.gray);
3686 if (optimize != 0)
3687 w = v;
3688 else
3689 w = gamma_16_from_1[(v & 0xff) >>
3690 gamma_shift][v >> 8];
3691 *sp = (png_byte)((w >> 8) & 0xff);
3692 *(sp + 1) = (png_byte)(w & 0xff);
3693 }
3694 }
3695 }
3696 else
3697#endif
3698 {
3699 sp = row;
3700 for (i = 0; i < row_width; i++, sp += 4)
3701 {
3702 png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
3703 + *(sp + 3));
3704
3705 if (a == 0)
3706 {
3707 *sp = (png_byte)((png_ptr->background.gray >> 8)
3708 & 0xff);
3709 *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
3710 }
3711
3712 else if (a < 0xffff)
3713 {
3714 png_uint_16 g, v;
3715
3716 g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3717 png_composite_16(v, g, a, png_ptr->background.gray);
3718 *sp = (png_byte)((v >> 8) & 0xff);
3719 *(sp + 1) = (png_byte)(v & 0xff);
3720 }
3721 }
3722 }
3723 }
3724 break;
3725 }
3726
3727 case PNG_COLOR_TYPE_RGB_ALPHA:
3728 {
3729 if (row_info->bit_depth == 8)
3730 {
3731#ifdef PNG_READ_GAMMA_SUPPORTED
3732 if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
3733 gamma_table != NULL)
3734 {
3735 sp = row;
3736 for (i = 0; i < row_width; i++, sp += 4)
3737 {
3738 png_byte a = *(sp + 3);
3739
3740 if (a == 0xff)
3741 {
3742 *sp = gamma_table[*sp];
3743 *(sp + 1) = gamma_table[*(sp + 1)];
3744 *(sp + 2) = gamma_table[*(sp + 2)];
3745 }
3746
3747 else if (a == 0)
3748 {
3749 /* Background is already in screen gamma */
3750 *sp = (png_byte)png_ptr->background.red;
3751 *(sp + 1) = (png_byte)png_ptr->background.green;
3752 *(sp + 2) = (png_byte)png_ptr->background.blue;
3753 }
3754
3755 else
3756 {
3757 png_byte v, w;
3758
3759 v = gamma_to_1[*sp];
3760 png_composite(w, v, a, png_ptr->background_1.red);
3761 if (optimize == 0) w = gamma_from_1[w];
3762 *sp = w;
3763
3764 v = gamma_to_1[*(sp + 1)];
3765 png_composite(w, v, a, png_ptr->background_1.green);
3766 if (optimize == 0) w = gamma_from_1[w];
3767 *(sp + 1) = w;
3768
3769 v = gamma_to_1[*(sp + 2)];
3770 png_composite(w, v, a, png_ptr->background_1.blue);
3771 if (optimize == 0) w = gamma_from_1[w];
3772 *(sp + 2) = w;
3773 }
3774 }
3775 }
3776 else
3777#endif
3778 {
3779 sp = row;
3780 for (i = 0; i < row_width; i++, sp += 4)
3781 {
3782 png_byte a = *(sp + 3);
3783
3784 if (a == 0)
3785 {
3786 *sp = (png_byte)png_ptr->background.red;
3787 *(sp + 1) = (png_byte)png_ptr->background.green;
3788 *(sp + 2) = (png_byte)png_ptr->background.blue;
3789 }
3790
3791 else if (a < 0xff)
3792 {
3793 png_composite(*sp, *sp, a, png_ptr->background.red);
3794
3795 png_composite(*(sp + 1), *(sp + 1), a,
3796 png_ptr->background.green);
3797
3798 png_composite(*(sp + 2), *(sp + 2), a,
3799 png_ptr->background.blue);
3800 }
3801 }
3802 }
3803 }
3804 else /* if (row_info->bit_depth == 16) */
3805 {
3806#ifdef PNG_READ_GAMMA_SUPPORTED
3807 if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
3808 gamma_16_to_1 != NULL)
3809 {
3810 sp = row;
3811 for (i = 0; i < row_width; i++, sp += 8)
3812 {
3813 png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
3814 << 8) + (png_uint_16)(*(sp + 7)));
3815
3816 if (a == (png_uint_16)0xffff)
3817 {
3818 png_uint_16 v;
3819
3820 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3821 *sp = (png_byte)((v >> 8) & 0xff);
3822 *(sp + 1) = (png_byte)(v & 0xff);
3823
3824 v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
3825 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
3826 *(sp + 3) = (png_byte)(v & 0xff);
3827
3828 v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
3829 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
3830 *(sp + 5) = (png_byte)(v & 0xff);
3831 }
3832
3833 else if (a == 0)
3834 {
3835 /* Background is already in screen gamma */
3836 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3837 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3838 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3839 & 0xff);
3840 *(sp + 3) = (png_byte)(png_ptr->background.green
3841 & 0xff);
3842 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3843 & 0xff);
3844 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3845 }
3846
3847 else
3848 {
3849 png_uint_16 v, w;
3850
3851 v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
3852 png_composite_16(w, v, a, png_ptr->background_1.red);
3853 if (optimize == 0)
3854 w = gamma_16_from_1[((w & 0xff) >> gamma_shift)][w >>
3855 8];
3856 *sp = (png_byte)((w >> 8) & 0xff);
3857 *(sp + 1) = (png_byte)(w & 0xff);
3858
3859 v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
3860 png_composite_16(w, v, a, png_ptr->background_1.green);
3861 if (optimize == 0)
3862 w = gamma_16_from_1[((w & 0xff) >> gamma_shift)][w >>
3863 8];
3864
3865 *(sp + 2) = (png_byte)((w >> 8) & 0xff);
3866 *(sp + 3) = (png_byte)(w & 0xff);
3867
3868 v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
3869 png_composite_16(w, v, a, png_ptr->background_1.blue);
3870 if (optimize == 0)
3871 w = gamma_16_from_1[((w & 0xff) >> gamma_shift)][w >>
3872 8];
3873
3874 *(sp + 4) = (png_byte)((w >> 8) & 0xff);
3875 *(sp + 5) = (png_byte)(w & 0xff);
3876 }
3877 }
3878 }
3879
3880 else
3881#endif
3882 {
3883 sp = row;
3884 for (i = 0; i < row_width; i++, sp += 8)
3885 {
3886 png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
3887 << 8) + (png_uint_16)(*(sp + 7)));
3888
3889 if (a == 0)
3890 {
3891 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3892 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3893 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3894 & 0xff);
3895 *(sp + 3) = (png_byte)(png_ptr->background.green
3896 & 0xff);
3897 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3898 & 0xff);
3899 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3900 }
3901
3902 else if (a < 0xffff)
3903 {
3904 png_uint_16 v;
3905
3906 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3907 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
3908 + *(sp + 3));
3909 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
3910 + *(sp + 5));
3911
3912 png_composite_16(v, r, a, png_ptr->background.red);
3913 *sp = (png_byte)((v >> 8) & 0xff);
3914 *(sp + 1) = (png_byte)(v & 0xff);
3915
3916 png_composite_16(v, g, a, png_ptr->background.green);
3917 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
3918 *(sp + 3) = (png_byte)(v & 0xff);
3919
3920 png_composite_16(v, b, a, png_ptr->background.blue);
3921 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
3922 *(sp + 5) = (png_byte)(v & 0xff);
3923 }
3924 }
3925 }
3926 }
3927 break;
3928 }
3929
3930 default:
3931 break;
3932 }
3933}
3934#endif /* READ_BACKGROUND || READ_ALPHA_MODE */
3935
3936#ifdef PNG_READ_GAMMA_SUPPORTED
3937/* Gamma correct the image, avoiding the alpha channel. Make sure
3938 * you do this after you deal with the transparency issue on grayscale
3939 * or RGB images. If your bit depth is 8, use gamma_table, if it
3940 * is 16, use gamma_16_table and gamma_shift. Build these with
3941 * build_gamma_table().
3942 */
3943static void
3944png_do_gamma(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
3945{
3946 png_const_bytep gamma_table = png_ptr->gamma_table;
3947 png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
3948 int gamma_shift = png_ptr->gamma_shift;
3949
3950 png_bytep sp;
3951 png_uint_32 i;
3952 png_uint_32 row_width=row_info->width;
3953
3954 png_debug(1, "in png_do_gamma");
3955
3956 if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
3957 (row_info->bit_depth == 16 && gamma_16_table != NULL)))
3958 {
3959 switch (row_info->color_type)
3960 {
3961 case PNG_COLOR_TYPE_RGB:
3962 {
3963 if (row_info->bit_depth == 8)
3964 {
3965 sp = row;
3966 for (i = 0; i < row_width; i++)
3967 {
3968 *sp = gamma_table[*sp];
3969 sp++;
3970 *sp = gamma_table[*sp];
3971 sp++;
3972 *sp = gamma_table[*sp];
3973 sp++;
3974 }
3975 }
3976
3977 else /* if (row_info->bit_depth == 16) */
3978 {
3979 sp = row;
3980 for (i = 0; i < row_width; i++)
3981 {
3982 png_uint_16 v;
3983
3984 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
3985 *sp = (png_byte)((v >> 8) & 0xff);
3986 *(sp + 1) = (png_byte)(v & 0xff);
3987 sp += 2;
3988
3989 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
3990 *sp = (png_byte)((v >> 8) & 0xff);
3991 *(sp + 1) = (png_byte)(v & 0xff);
3992 sp += 2;
3993
3994 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
3995 *sp = (png_byte)((v >> 8) & 0xff);
3996 *(sp + 1) = (png_byte)(v & 0xff);
3997 sp += 2;
3998 }
3999 }
4000 break;
4001 }
4002
4003 case PNG_COLOR_TYPE_RGB_ALPHA:
4004 {
4005 if (row_info->bit_depth == 8)
4006 {
4007 sp = row;
4008 for (i = 0; i < row_width; i++)
4009 {
4010 *sp = gamma_table[*sp];
4011 sp++;
4012
4013 *sp = gamma_table[*sp];
4014 sp++;
4015
4016 *sp = gamma_table[*sp];
4017 sp++;
4018
4019 sp++;
4020 }
4021 }
4022
4023 else /* if (row_info->bit_depth == 16) */
4024 {
4025 sp = row;
4026 for (i = 0; i < row_width; i++)
4027 {
4028 png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4029 *sp = (png_byte)((v >> 8) & 0xff);
4030 *(sp + 1) = (png_byte)(v & 0xff);
4031 sp += 2;
4032
4033 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4034 *sp = (png_byte)((v >> 8) & 0xff);
4035 *(sp + 1) = (png_byte)(v & 0xff);
4036 sp += 2;
4037
4038 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4039 *sp = (png_byte)((v >> 8) & 0xff);
4040 *(sp + 1) = (png_byte)(v & 0xff);
4041 sp += 4;
4042 }
4043 }
4044 break;
4045 }
4046
4047 case PNG_COLOR_TYPE_GRAY_ALPHA:
4048 {
4049 if (row_info->bit_depth == 8)
4050 {
4051 sp = row;
4052 for (i = 0; i < row_width; i++)
4053 {
4054 *sp = gamma_table[*sp];
4055 sp += 2;
4056 }
4057 }
4058
4059 else /* if (row_info->bit_depth == 16) */
4060 {
4061 sp = row;
4062 for (i = 0; i < row_width; i++)
4063 {
4064 png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4065 *sp = (png_byte)((v >> 8) & 0xff);
4066 *(sp + 1) = (png_byte)(v & 0xff);
4067 sp += 4;
4068 }
4069 }
4070 break;
4071 }
4072
4073 case PNG_COLOR_TYPE_GRAY:
4074 {
4075 if (row_info->bit_depth == 2)
4076 {
4077 sp = row;
4078 for (i = 0; i < row_width; i += 4)
4079 {
4080 int a = *sp & 0xc0;
4081 int b = *sp & 0x30;
4082 int c = *sp & 0x0c;
4083 int d = *sp & 0x03;
4084
4085 *sp = (png_byte)(
4086 ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)]) ) & 0xc0)|
4087 ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
4088 ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
4089 ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
4090 sp++;
4091 }
4092 }
4093
4094 if (row_info->bit_depth == 4)
4095 {
4096 sp = row;
4097 for (i = 0; i < row_width; i += 2)
4098 {
4099 int msb = *sp & 0xf0;
4100 int lsb = *sp & 0x0f;
4101
4102 *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
4103 | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
4104 sp++;
4105 }
4106 }
4107
4108 else if (row_info->bit_depth == 8)
4109 {
4110 sp = row;
4111 for (i = 0; i < row_width; i++)
4112 {
4113 *sp = gamma_table[*sp];
4114 sp++;
4115 }
4116 }
4117
4118 else if (row_info->bit_depth == 16)
4119 {
4120 sp = row;
4121 for (i = 0; i