2 /* pngrtran.c - transforms the data in a row for PNG readers
4 * Last changed in libpng 1.5.14 [January 24, 2013]
5 * Copyright (c) 1998-2013 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains functions optionally called by an application
14 * in order to tell libpng how to handle data when reading a PNG.
15 * Transformations that are used in both reading and writing are
21 #ifdef PNG_READ_SUPPORTED
23 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
25 png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
27 png_debug(1, "in png_set_crc_action");
32 /* Tell libpng how we react to CRC errors in critical chunks */
35 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
38 case PNG_CRC_WARN_USE: /* Warn/use data */
39 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
40 png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
43 case PNG_CRC_QUIET_USE: /* Quiet/use data */
44 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
45 png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
46 PNG_FLAG_CRC_CRITICAL_IGNORE;
49 case PNG_CRC_WARN_DISCARD: /* Not a valid action for critical data */
51 "Can't discard critical data on CRC error");
52 case PNG_CRC_ERROR_QUIT: /* Error/quit */
56 png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
60 /* Tell libpng how we react to CRC errors in ancillary chunks */
63 case PNG_CRC_NO_CHANGE: /* Leave setting as is */
66 case PNG_CRC_WARN_USE: /* Warn/use data */
67 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
68 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
71 case PNG_CRC_QUIET_USE: /* Quiet/use data */
72 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
73 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
74 PNG_FLAG_CRC_ANCILLARY_NOWARN;
77 case PNG_CRC_ERROR_QUIT: /* Error/quit */
78 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
79 png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
82 case PNG_CRC_WARN_DISCARD: /* Warn/discard data */
86 png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
91 #ifdef PNG_READ_BACKGROUND_SUPPORTED
92 /* Handle alpha and tRNS via a background color */
94 png_set_background_fixed(png_structp png_ptr,
95 png_const_color_16p background_color, int background_gamma_code,
96 int need_expand, png_fixed_point background_gamma)
98 png_debug(1, "in png_set_background_fixed");
103 if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
105 png_warning(png_ptr, "Application must supply a known background gamma");
109 png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
110 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
111 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
113 png_memcpy(&(png_ptr->background), background_color,
114 png_sizeof(png_color_16));
115 png_ptr->background_gamma = background_gamma;
116 png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
118 png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
120 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
123 # ifdef PNG_FLOATING_POINT_SUPPORTED
125 png_set_background(png_structp png_ptr,
126 png_const_color_16p background_color, int background_gamma_code,
127 int need_expand, double background_gamma)
129 png_set_background_fixed(png_ptr, background_color, background_gamma_code,
130 need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
132 # endif /* FLOATING_POINT */
133 #endif /* READ_BACKGROUND */
135 /* Scale 16-bit depth files to 8-bit depth. If both of these are set then the
136 * one that pngrtran does first (scale) happens. This is necessary to allow the
137 * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
139 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
141 png_set_scale_16(png_structp png_ptr)
143 png_debug(1, "in png_set_scale_16");
148 png_ptr->transformations |= PNG_SCALE_16_TO_8;
152 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
153 /* Chop 16-bit depth files to 8-bit depth */
155 png_set_strip_16(png_structp png_ptr)
157 png_debug(1, "in png_set_strip_16");
162 png_ptr->transformations |= PNG_16_TO_8;
166 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
168 png_set_strip_alpha(png_structp png_ptr)
170 png_debug(1, "in png_set_strip_alpha");
175 png_ptr->transformations |= PNG_STRIP_ALPHA;
179 #if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
180 static png_fixed_point
181 translate_gamma_flags(png_structp png_ptr, png_fixed_point output_gamma,
184 /* Check for flag values. The main reason for having the old Mac value as a
185 * flag is that it is pretty near impossible to work out what the correct
186 * value is from Apple documentation - a working Mac system is needed to
187 * discover the value!
189 if (output_gamma == PNG_DEFAULT_sRGB ||
190 output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
192 /* If there is no sRGB support this just sets the gamma to the standard
193 * sRGB value. (This is a side effect of using this function!)
195 # ifdef PNG_READ_sRGB_SUPPORTED
196 png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
199 output_gamma = PNG_GAMMA_sRGB;
201 output_gamma = PNG_GAMMA_sRGB_INVERSE;
204 else if (output_gamma == PNG_GAMMA_MAC_18 ||
205 output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
208 output_gamma = PNG_GAMMA_MAC_OLD;
210 output_gamma = PNG_GAMMA_MAC_INVERSE;
216 # ifdef PNG_FLOATING_POINT_SUPPORTED
217 static png_fixed_point
218 convert_gamma_value(png_structp png_ptr, double output_gamma)
220 /* The following silently ignores cases where fixed point (times 100,000)
221 * gamma values are passed to the floating point API. This is safe and it
222 * means the fixed point constants work just fine with the floating point
223 * API. The alternative would just lead to undetected errors and spurious
224 * bug reports. Negative values fail inside the _fixed API unless they
225 * correspond to the flag values.
227 if (output_gamma > 0 && output_gamma < 128)
228 output_gamma *= PNG_FP_1;
230 /* This preserves -1 and -2 exactly: */
231 output_gamma = floor(output_gamma + .5);
233 if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
234 png_fixed_error(png_ptr, "gamma value");
236 return (png_fixed_point)output_gamma;
239 #endif /* READ_ALPHA_MODE || READ_GAMMA */
241 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
243 png_set_alpha_mode_fixed(png_structp png_ptr, int mode,
244 png_fixed_point output_gamma)
247 png_fixed_point file_gamma;
249 png_debug(1, "in png_set_alpha_mode");
254 output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
256 /* Validate the value to ensure it is in a reasonable range. The value
257 * is expected to be 1 or greater, but this range test allows for some
258 * viewing correction values. The intent is to weed out users of this API
259 * who use the inverse of the gamma value accidentally! Since some of these
260 * values are reasonable this may have to be changed.
262 if (output_gamma < 70000 || output_gamma > 300000)
263 png_error(png_ptr, "output gamma out of expected range");
265 /* The default file gamma is the inverse of the output gamma; the output
266 * gamma may be changed below so get the file value first:
268 file_gamma = png_reciprocal(output_gamma);
270 /* There are really 8 possibilities here, composed of any combination
273 * premultiply the color channels
274 * do not encode non-opaque pixels
275 * encode the alpha as well as the color channels
277 * The differences disappear if the input/output ('screen') gamma is 1.0,
278 * because then the encoding is a no-op and there is only the choice of
279 * premultiplying the color channels or not.
281 * png_set_alpha_mode and png_set_background interact because both use
282 * png_compose to do the work. Calling both is only useful when
283 * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
284 * with a default gamma value. Otherwise PNG_COMPOSE must not be set.
288 case PNG_ALPHA_PNG: /* default: png standard */
289 /* No compose, but it may be set by png_set_background! */
290 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
291 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
294 case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
296 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
297 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
298 /* The output is linear: */
299 output_gamma = PNG_FP_1;
302 case PNG_ALPHA_OPTIMIZED: /* associated, non-opaque pixels linear */
304 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
305 png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
306 /* output_gamma records the encoding of opaque pixels! */
309 case PNG_ALPHA_BROKEN: /* associated, non-linear, alpha encoded */
311 png_ptr->transformations |= PNG_ENCODE_ALPHA;
312 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
316 png_error(png_ptr, "invalid alpha mode");
319 /* Only set the default gamma if the file gamma has not been set (this has
320 * the side effect that the gamma in a second call to png_set_alpha_mode will
323 if (png_ptr->gamma == 0)
324 png_ptr->gamma = file_gamma;
326 /* But always set the output gamma: */
327 png_ptr->screen_gamma = output_gamma;
329 /* Finally, if pre-multiplying, set the background fields to achieve the
334 /* And obtain alpha pre-multiplication by composing on black: */
335 png_memset(&png_ptr->background, 0, sizeof png_ptr->background);
336 png_ptr->background_gamma = png_ptr->gamma; /* just in case */
337 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
338 png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
340 if (png_ptr->transformations & PNG_COMPOSE)
342 "conflicting calls to set alpha mode and background");
344 png_ptr->transformations |= PNG_COMPOSE;
347 /* New API, make sure apps call the correct initializers: */
348 png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
351 # ifdef PNG_FLOATING_POINT_SUPPORTED
353 png_set_alpha_mode(png_structp png_ptr, int mode, double output_gamma)
355 png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
361 #ifdef PNG_READ_QUANTIZE_SUPPORTED
362 /* Dither file to 8-bit. Supply a palette, the current number
363 * of elements in the palette, the maximum number of elements
364 * allowed, and a histogram if possible. If the current number
365 * of colors is greater then the maximum number, the palette will be
366 * modified to fit in the maximum number. "full_quantize" indicates
367 * whether we need a quantizing cube set up for RGB images, or if we
368 * simply are reducing the number of colors in a paletted image.
371 typedef struct png_dsort_struct
373 struct png_dsort_struct FAR * next;
377 typedef png_dsort FAR * png_dsortp;
378 typedef png_dsort FAR * FAR * png_dsortpp;
381 png_set_quantize(png_structp png_ptr, png_colorp palette,
382 int num_palette, int maximum_colors, png_const_uint_16p histogram,
385 png_debug(1, "in png_set_quantize");
390 png_ptr->transformations |= PNG_QUANTIZE;
396 png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
397 (png_uint_32)(num_palette * png_sizeof(png_byte)));
398 for (i = 0; i < num_palette; i++)
399 png_ptr->quantize_index[i] = (png_byte)i;
402 if (num_palette > maximum_colors)
404 if (histogram != NULL)
406 /* This is easy enough, just throw out the least used colors.
407 * Perhaps not the best solution, but good enough.
412 /* Initialize an array to sort colors */
413 png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
414 (png_uint_32)(num_palette * png_sizeof(png_byte)));
416 /* Initialize the quantize_sort array */
417 for (i = 0; i < num_palette; i++)
418 png_ptr->quantize_sort[i] = (png_byte)i;
420 /* Find the least used palette entries by starting a
421 * bubble sort, and running it until we have sorted
422 * out enough colors. Note that we don't care about
423 * sorting all the colors, just finding which are
427 for (i = num_palette - 1; i >= maximum_colors; i--)
429 int done; /* To stop early if the list is pre-sorted */
433 for (j = 0; j < i; j++)
435 if (histogram[png_ptr->quantize_sort[j]]
436 < histogram[png_ptr->quantize_sort[j + 1]])
440 t = png_ptr->quantize_sort[j];
441 png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
442 png_ptr->quantize_sort[j + 1] = t;
451 /* Swap the palette around, and set up a table, if necessary */
456 /* Put all the useful colors within the max, but don't
459 for (i = 0; i < maximum_colors; i++)
461 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
465 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
467 palette[i] = palette[j];
475 /* Move all the used colors inside the max limit, and
476 * develop a translation table.
478 for (i = 0; i < maximum_colors; i++)
480 /* Only move the colors we need to */
481 if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
487 while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
489 tmp_color = palette[j];
490 palette[j] = palette[i];
491 palette[i] = tmp_color;
492 /* Indicate where the color went */
493 png_ptr->quantize_index[j] = (png_byte)i;
494 png_ptr->quantize_index[i] = (png_byte)j;
498 /* Find closest color for those colors we are not using */
499 for (i = 0; i < num_palette; i++)
501 if ((int)png_ptr->quantize_index[i] >= maximum_colors)
503 int min_d, k, min_k, d_index;
505 /* Find the closest color to one we threw out */
506 d_index = png_ptr->quantize_index[i];
507 min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
508 for (k = 1, min_k = 0; k < maximum_colors; k++)
512 d = PNG_COLOR_DIST(palette[d_index], palette[k]);
520 /* Point to closest color */
521 png_ptr->quantize_index[i] = (png_byte)min_k;
525 png_free(png_ptr, png_ptr->quantize_sort);
526 png_ptr->quantize_sort = NULL;
530 /* This is much harder to do simply (and quickly). Perhaps
531 * we need to go through a median cut routine, but those
532 * don't always behave themselves with only a few colors
533 * as input. So we will just find the closest two colors,
534 * and throw out one of them (chosen somewhat randomly).
535 * [We don't understand this at all, so if someone wants to
536 * work on improving it, be our guest - AED, GRP]
546 /* Initialize palette index arrays */
547 png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
548 (png_uint_32)(num_palette * png_sizeof(png_byte)));
549 png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
550 (png_uint_32)(num_palette * png_sizeof(png_byte)));
552 /* Initialize the sort array */
553 for (i = 0; i < num_palette; i++)
555 png_ptr->index_to_palette[i] = (png_byte)i;
556 png_ptr->palette_to_index[i] = (png_byte)i;
559 hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
560 png_sizeof(png_dsortp)));
562 num_new_palette = num_palette;
564 /* Initial wild guess at how far apart the farthest pixel
565 * pair we will be eliminating will be. Larger
566 * numbers mean more areas will be allocated, Smaller
567 * numbers run the risk of not saving enough data, and
568 * having to do this all over again.
570 * I have not done extensive checking on this number.
574 while (num_new_palette > maximum_colors)
576 for (i = 0; i < num_new_palette - 1; i++)
580 for (j = i + 1; j < num_new_palette; j++)
584 d = PNG_COLOR_DIST(palette[i], palette[j]);
589 t = (png_dsortp)png_malloc_warn(png_ptr,
590 (png_uint_32)(png_sizeof(png_dsort)));
596 t->left = (png_byte)i;
597 t->right = (png_byte)j;
606 for (i = 0; i <= max_d; i++)
612 for (p = hash[i]; p; p = p->next)
614 if ((int)png_ptr->index_to_palette[p->left]
616 (int)png_ptr->index_to_palette[p->right]
621 if (num_new_palette & 0x01)
633 palette[png_ptr->index_to_palette[j]]
634 = palette[num_new_palette];
639 for (k = 0; k < num_palette; k++)
641 if (png_ptr->quantize_index[k] ==
642 png_ptr->index_to_palette[j])
643 png_ptr->quantize_index[k] =
644 png_ptr->index_to_palette[next_j];
646 if ((int)png_ptr->quantize_index[k] ==
648 png_ptr->quantize_index[k] =
649 png_ptr->index_to_palette[j];
653 png_ptr->index_to_palette[png_ptr->palette_to_index
654 [num_new_palette]] = png_ptr->index_to_palette[j];
656 png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
657 = png_ptr->palette_to_index[num_new_palette];
659 png_ptr->index_to_palette[j] =
660 (png_byte)num_new_palette;
662 png_ptr->palette_to_index[num_new_palette] =
665 if (num_new_palette <= maximum_colors)
668 if (num_new_palette <= maximum_colors)
673 for (i = 0; i < 769; i++)
677 png_dsortp p = hash[i];
681 png_free(png_ptr, p);
689 png_free(png_ptr, hash);
690 png_free(png_ptr, png_ptr->palette_to_index);
691 png_free(png_ptr, png_ptr->index_to_palette);
692 png_ptr->palette_to_index = NULL;
693 png_ptr->index_to_palette = NULL;
695 num_palette = maximum_colors;
697 if (png_ptr->palette == NULL)
699 png_ptr->palette = palette;
701 png_ptr->num_palette = (png_uint_16)num_palette;
707 int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
708 PNG_QUANTIZE_BLUE_BITS;
709 int num_red = (1 << PNG_QUANTIZE_RED_BITS);
710 int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
711 int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
712 png_size_t num_entries = ((png_size_t)1 << total_bits);
714 png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
715 (png_uint_32)(num_entries * png_sizeof(png_byte)));
717 distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
718 png_sizeof(png_byte)));
720 png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
722 for (i = 0; i < num_palette; i++)
725 int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
726 int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
727 int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
729 for (ir = 0; ir < num_red; ir++)
731 /* int dr = abs(ir - r); */
732 int dr = ((ir > r) ? ir - r : r - ir);
733 int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
734 PNG_QUANTIZE_GREEN_BITS));
736 for (ig = 0; ig < num_green; ig++)
738 /* int dg = abs(ig - g); */
739 int dg = ((ig > g) ? ig - g : g - ig);
741 int dm = ((dr > dg) ? dr : dg);
742 int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
744 for (ib = 0; ib < num_blue; ib++)
746 int d_index = index_g | ib;
747 /* int db = abs(ib - b); */
748 int db = ((ib > b) ? ib - b : b - ib);
749 int dmax = ((dm > db) ? dm : db);
750 int d = dmax + dt + db;
752 if (d < (int)distance[d_index])
754 distance[d_index] = (png_byte)d;
755 png_ptr->palette_lookup[d_index] = (png_byte)i;
762 png_free(png_ptr, distance);
765 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
767 #ifdef PNG_READ_GAMMA_SUPPORTED
769 png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,
770 png_fixed_point file_gamma)
772 png_debug(1, "in png_set_gamma_fixed");
777 /* New in libpng-1.5.4 - reserve particular negative values as flags. */
778 scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
779 file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
781 #if PNG_LIBPNG_VER >= 10600
782 /* Checking the gamma values for being >0 was added in 1.5.4 along with the
783 * premultiplied alpha support; this actually hides an undocumented feature
784 * of the previous implementation which allowed gamma processing to be
785 * disabled in background handling. There is no evidence (so far) that this
786 * was being used; however, png_set_background itself accepted and must still
787 * accept '0' for the gamma value it takes, because it isn't always used.
789 * Since this is an API change (albeit a very minor one that removes an
790 * undocumented API feature) it will not be made until libpng-1.6.0.
793 png_error(png_ptr, "invalid file gamma in png_set_gamma");
796 png_error(png_ptr, "invalid screen gamma in png_set_gamma");
799 /* Set the gamma values unconditionally - this overrides the value in the PNG
800 * file if a gAMA chunk was present. png_set_alpha_mode provides a
801 * different, easier, way to default the file gamma.
803 png_ptr->gamma = file_gamma;
804 png_ptr->screen_gamma = scrn_gamma;
807 # ifdef PNG_FLOATING_POINT_SUPPORTED
809 png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
811 png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
812 convert_gamma_value(png_ptr, file_gamma));
814 # endif /* FLOATING_POINT_SUPPORTED */
815 #endif /* READ_GAMMA */
817 #ifdef PNG_READ_EXPAND_SUPPORTED
818 /* Expand paletted images to RGB, expand grayscale images of
819 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
823 png_set_expand(png_structp png_ptr)
825 png_debug(1, "in png_set_expand");
830 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
831 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
834 /* GRR 19990627: the following three functions currently are identical
835 * to png_set_expand(). However, it is entirely reasonable that someone
836 * might wish to expand an indexed image to RGB but *not* expand a single,
837 * fully transparent palette entry to a full alpha channel--perhaps instead
838 * convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
839 * the transparent color with a particular RGB value, or drop tRNS entirely.
840 * IOW, a future version of the library may make the transformations flag
841 * a bit more fine-grained, with separate bits for each of these three
844 * More to the point, these functions make it obvious what libpng will be
845 * doing, whereas "expand" can (and does) mean any number of things.
847 * GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
848 * to expand only the sample depth but not to expand the tRNS to alpha
849 * and its name was changed to png_set_expand_gray_1_2_4_to_8().
852 /* Expand paletted images to RGB. */
854 png_set_palette_to_rgb(png_structp png_ptr)
856 png_debug(1, "in png_set_palette_to_rgb");
861 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
862 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
865 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
867 png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
869 png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
874 png_ptr->transformations |= PNG_EXPAND;
875 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
880 /* Expand tRNS chunks to alpha channels. */
882 png_set_tRNS_to_alpha(png_structp png_ptr)
884 png_debug(1, "in png_set_tRNS_to_alpha");
886 png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
887 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
889 #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
891 #ifdef PNG_READ_EXPAND_16_SUPPORTED
892 /* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
893 * it may not work correctly.)
896 png_set_expand_16(png_structp png_ptr)
898 png_debug(1, "in png_set_expand_16");
903 png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
904 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
906 /* New API, make sure apps call the correct initializers: */
907 png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
911 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
913 png_set_gray_to_rgb(png_structp png_ptr)
915 png_debug(1, "in png_set_gray_to_rgb");
919 /* Because rgb must be 8 bits or more: */
920 png_set_expand_gray_1_2_4_to_8(png_ptr);
921 png_ptr->transformations |= PNG_GRAY_TO_RGB;
922 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
927 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
929 png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
930 png_fixed_point red, png_fixed_point green)
932 png_debug(1, "in png_set_rgb_to_gray");
939 case PNG_ERROR_ACTION_NONE:
940 png_ptr->transformations |= PNG_RGB_TO_GRAY;
943 case PNG_ERROR_ACTION_WARN:
944 png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
947 case PNG_ERROR_ACTION_ERROR:
948 png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
952 png_error(png_ptr, "invalid error action to rgb_to_gray");
955 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
956 #ifdef PNG_READ_EXPAND_SUPPORTED
957 png_ptr->transformations |= PNG_EXPAND;
961 "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
963 png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
967 if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
969 png_uint_16 red_int, green_int;
971 /* NOTE: this calculation does not round, but this behavior is retained
972 * for consistency, the inaccuracy is very small. The code here always
973 * overwrites the coefficients, regardless of whether they have been
974 * defaulted or set already.
976 red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
977 green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
979 png_ptr->rgb_to_gray_red_coeff = red_int;
980 png_ptr->rgb_to_gray_green_coeff = green_int;
981 png_ptr->rgb_to_gray_coefficients_set = 1;
986 if (red >= 0 && green >= 0)
988 "ignoring out of range rgb_to_gray coefficients");
990 /* Use the defaults, from the cHRM chunk if set, else the historical
991 * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
992 * png_do_rgb_to_gray for more discussion of the values. In this case
993 * the coefficients are not marked as 'set' and are not overwritten if
994 * something has already provided a default.
996 if (png_ptr->rgb_to_gray_red_coeff == 0 &&
997 png_ptr->rgb_to_gray_green_coeff == 0)
999 png_ptr->rgb_to_gray_red_coeff = 6968;
1000 png_ptr->rgb_to_gray_green_coeff = 23434;
1001 /* png_ptr->rgb_to_gray_blue_coeff = 2366; */
1007 #ifdef PNG_FLOATING_POINT_SUPPORTED
1008 /* Convert a RGB image to a grayscale of the same width. This allows us,
1009 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
1013 png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
1016 if (png_ptr == NULL)
1019 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1020 png_fixed(png_ptr, red, "rgb to gray red coefficient"),
1021 png_fixed(png_ptr, green, "rgb to gray green coefficient"));
1023 #endif /* FLOATING POINT */
1027 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
1028 defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
1030 png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
1031 read_user_transform_fn)
1033 png_debug(1, "in png_set_read_user_transform_fn");
1035 if (png_ptr == NULL)
1038 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
1039 png_ptr->transformations |= PNG_USER_TRANSFORM;
1040 png_ptr->read_user_transform_fn = read_user_transform_fn;
1045 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
1046 #ifdef PNG_READ_GAMMA_SUPPORTED
1047 /* In the case of gamma transformations only do transformations on images where
1048 * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
1049 * slows things down slightly, and also needlessly introduces small errors.
1051 static int /* PRIVATE */
1052 png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
1054 /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
1055 * correction as a difference of the overall transform from 1.0
1057 * We want to compare the threshold with s*f - 1, if we get
1058 * overflow here it is because of wacky gamma values so we
1059 * turn on processing anyway.
1061 png_fixed_point gtest;
1062 return !png_muldiv(>est, screen_gamma, file_gamma, PNG_FP_1) ||
1063 png_gamma_significant(gtest);
1067 /* Initialize everything needed for the read. This includes modifying
1071 /*For the moment 'png_init_palette_transformations' and
1072 * 'png_init_rgb_transformations' only do some flag canceling optimizations.
1073 * The intent is that these two routines should have palette or rgb operations
1074 * extracted from 'png_init_read_transformations'.
1076 static void /* PRIVATE */
1077 png_init_palette_transformations(png_structp png_ptr)
1079 /* Called to handle the (input) palette case. In png_do_read_transformations
1080 * the first step is to expand the palette if requested, so this code must
1081 * take care to only make changes that are invariant with respect to the
1082 * palette expansion, or only do them if there is no expansion.
1084 * STRIP_ALPHA has already been handled in the caller (by setting num_trans
1087 int input_has_alpha = 0;
1088 int input_has_transparency = 0;
1090 if (png_ptr->num_trans > 0)
1094 /* Ignore if all the entries are opaque (unlikely!) */
1095 for (i=0; i<png_ptr->num_trans; ++i)
1096 if (png_ptr->trans_alpha[i] == 255)
1098 else if (png_ptr->trans_alpha[i] == 0)
1099 input_has_transparency = 1;
1101 input_has_alpha = 1;
1104 /* If no alpha we can optimize. */
1105 if (!input_has_alpha)
1107 /* Any alpha means background and associative alpha processing is
1108 * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
1109 * and ENCODE_ALPHA are irrelevant.
1111 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1112 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1114 if (!input_has_transparency)
1115 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1118 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1119 /* png_set_background handling - deals with the complexity of whether the
1120 * background color is in the file format or the screen format in the case
1121 * where an 'expand' will happen.
1124 /* The following code cannot be entered in the alpha pre-multiplication case
1125 * because PNG_BACKGROUND_EXPAND is cancelled below.
1127 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
1128 (png_ptr->transformations & PNG_EXPAND))
1131 png_ptr->background.red =
1132 png_ptr->palette[png_ptr->background.index].red;
1133 png_ptr->background.green =
1134 png_ptr->palette[png_ptr->background.index].green;
1135 png_ptr->background.blue =
1136 png_ptr->palette[png_ptr->background.index].blue;
1138 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1139 if (png_ptr->transformations & PNG_INVERT_ALPHA)
1141 if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
1143 /* Invert the alpha channel (in tRNS) unless the pixels are
1144 * going to be expanded, in which case leave it for later
1146 int i, istop = png_ptr->num_trans;
1148 for (i=0; i<istop; i++)
1149 png_ptr->trans_alpha[i] = (png_byte)(255 -
1150 png_ptr->trans_alpha[i]);
1153 #endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
1155 } /* background expand and (therefore) no alpha association. */
1156 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
1159 static void /* PRIVATE */
1160 png_init_rgb_transformations(png_structp png_ptr)
1162 /* Added to libpng-1.5.4: check the color type to determine whether there
1163 * is any alpha or transparency in the image and simply cancel the
1164 * background and alpha mode stuff if there isn't.
1166 int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
1167 int input_has_transparency = png_ptr->num_trans > 0;
1169 /* If no alpha we can optimize. */
1170 if (!input_has_alpha)
1172 /* Any alpha means background and associative alpha processing is
1173 * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
1174 * and ENCODE_ALPHA are irrelevant.
1176 # ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1177 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1178 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1181 if (!input_has_transparency)
1182 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
1185 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1186 /* png_set_background handling - deals with the complexity of whether the
1187 * background color is in the file format or the screen format in the case
1188 * where an 'expand' will happen.
1191 /* The following code cannot be entered in the alpha pre-multiplication case
1192 * because PNG_BACKGROUND_EXPAND is cancelled below.
1194 if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
1195 (png_ptr->transformations & PNG_EXPAND) &&
1196 !(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
1197 /* i.e., GRAY or GRAY_ALPHA */
1200 /* Expand background and tRNS chunks */
1201 int gray = png_ptr->background.gray;
1202 int trans_gray = png_ptr->trans_color.gray;
1204 switch (png_ptr->bit_depth)
1224 /* FALL THROUGH (already 8 bits) */
1227 /* Already a full 16 bits */
1231 png_ptr->background.red = png_ptr->background.green =
1232 png_ptr->background.blue = (png_uint_16)gray;
1234 if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
1236 png_ptr->trans_color.red = png_ptr->trans_color.green =
1237 png_ptr->trans_color.blue = (png_uint_16)trans_gray;
1240 } /* background expand and (therefore) no alpha association. */
1241 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
1245 png_init_read_transformations(png_structp png_ptr)
1247 png_debug(1, "in png_init_read_transformations");
1249 /* This internal function is called from png_read_start_row in pngrutil.c
1250 * and it is called before the 'rowbytes' calculation is done, so the code
1251 * in here can change or update the transformations flags.
1253 * First do updates that do not depend on the details of the PNG image data
1257 #ifdef PNG_READ_GAMMA_SUPPORTED
1258 /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
1259 * png_set_alpha_mode and this is another source for a default file gamma so
1260 * the test needs to be performed later - here. In addition prior to 1.5.4
1261 * the tests were repeated for the PALETTE color type here - this is no
1262 * longer necessary (and doesn't seem to have been necessary before.)
1265 /* The following temporary indicates if overall gamma correction is
1268 int gamma_correction = 0;
1270 if (png_ptr->gamma != 0) /* has been set */
1272 if (png_ptr->screen_gamma != 0) /* screen set too */
1273 gamma_correction = png_gamma_threshold(png_ptr->gamma,
1274 png_ptr->screen_gamma);
1277 /* Assume the output matches the input; a long time default behavior
1278 * of libpng, although the standard has nothing to say about this.
1280 png_ptr->screen_gamma = png_reciprocal(png_ptr->gamma);
1283 else if (png_ptr->screen_gamma != 0)
1284 /* The converse - assume the file matches the screen, note that this
1285 * perhaps undesireable default can (from 1.5.4) be changed by calling
1286 * png_set_alpha_mode (even if the alpha handling mode isn't required
1287 * or isn't changed from the default.)
1289 png_ptr->gamma = png_reciprocal(png_ptr->screen_gamma);
1291 else /* neither are set */
1292 /* Just in case the following prevents any processing - file and screen
1293 * are both assumed to be linear and there is no way to introduce a
1294 * third gamma value other than png_set_background with 'UNIQUE', and,
1297 png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;
1299 /* Now turn the gamma transformation on or off as appropriate. Notice
1300 * that PNG_GAMMA just refers to the file->screen correction. Alpha
1301 * composition may independently cause gamma correction because it needs
1302 * linear data (e.g. if the file has a gAMA chunk but the screen gamma
1303 * hasn't been specified.) In any case this flag may get turned off in
1304 * the code immediately below if the transform can be handled outside the
1307 if (gamma_correction)
1308 png_ptr->transformations |= PNG_GAMMA;
1311 png_ptr->transformations &= ~PNG_GAMMA;
1315 /* Certain transformations have the effect of preventing other
1316 * transformations that happen afterward in png_do_read_transformations,
1317 * resolve the interdependencies here. From the code of
1318 * png_do_read_transformations the order is:
1320 * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
1321 * 2) PNG_STRIP_ALPHA (if no compose)
1322 * 3) PNG_RGB_TO_GRAY
1323 * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
1326 * 7) PNG_STRIP_ALPHA (if compose)
1327 * 8) PNG_ENCODE_ALPHA
1328 * 9) PNG_SCALE_16_TO_8
1330 * 11) PNG_QUANTIZE (converts to palette)
1332 * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
1333 * 14) PNG_INVERT_MONO
1338 * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
1339 * 20) PNG_INVERT_ALPHA
1340 * 21) PNG_SWAP_ALPHA
1341 * 22) PNG_SWAP_BYTES
1342 * 23) PNG_USER_TRANSFORM [must be last]
1344 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1345 if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
1346 !(png_ptr->transformations & PNG_COMPOSE))
1348 /* Stripping the alpha channel happens immediately after the 'expand'
1349 * transformations, before all other transformation, so it cancels out
1350 * the alpha handling. It has the side effect negating the effect of
1351 * PNG_EXPAND_tRNS too:
1353 png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
1355 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1357 /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
1358 * so transparency information would remain just so long as it wasn't
1359 * expanded. This produces unexpected API changes if the set of things
1360 * that do PNG_EXPAND_tRNS changes (perfectly possible given the
1361 * documentation - which says ask for what you want, accept what you
1362 * get.) This makes the behavior consistent from 1.5.4:
1364 png_ptr->num_trans = 0;
1366 #endif /* STRIP_ALPHA supported, no COMPOSE */
1368 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1369 /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
1370 * settings will have no effect.
1372 if (!png_gamma_significant(png_ptr->screen_gamma))
1374 png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
1375 png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
1379 #if defined(PNG_READ_EXPAND_SUPPORTED) && \
1380 defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1381 defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
1382 /* Detect gray background and attempt to enable optimization for
1383 * gray --> RGB case.
1385 * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
1386 * RGB_ALPHA (in which case need_expand is superfluous anyway), the
1387 * background color might actually be gray yet not be flagged as such.
1388 * This is not a problem for the current code, which uses
1389 * PNG_BACKGROUND_IS_GRAY only to decide when to do the
1390 * png_do_gray_to_rgb() transformation.
1392 * TODO: this code needs to be revised to avoid the complexity and
1393 * interdependencies. The color type of the background should be recorded in
1394 * png_set_background, along with the bit depth, then the code has a record
1395 * of exactly what color space the background is currently in.
1397 if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
1399 /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
1400 * the file was grayscale the background value is gray.
1402 if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
1403 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1406 else if (png_ptr->transformations & PNG_COMPOSE)
1408 /* PNG_COMPOSE: png_set_background was called with need_expand false,
1409 * so the color is in the color space of the output or png_set_alpha_mode
1410 * was called and the color is black. Ignore RGB_TO_GRAY because that
1411 * happens before GRAY_TO_RGB.
1413 if (png_ptr->transformations & PNG_GRAY_TO_RGB)
1415 if (png_ptr->background.red == png_ptr->background.green &&
1416 png_ptr->background.red == png_ptr->background.blue)
1418 png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
1419 png_ptr->background.gray = png_ptr->background.red;
1423 #endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED (etc) */
1425 /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
1426 * can be performed directly on the palette, and some (such as rgb to gray)
1427 * can be optimized inside the palette. This is particularly true of the
1428 * composite (background and alpha) stuff, which can be pretty much all done
1429 * in the palette even if the result is expanded to RGB or gray afterward.
1431 * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
1432 * earlier and the palette stuff is actually handled on the first row. This
1433 * leads to the reported bug that the palette returned by png_get_PLTE is not
1436 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1437 png_init_palette_transformations(png_ptr);
1440 png_init_rgb_transformations(png_ptr);
1442 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1443 defined(PNG_READ_EXPAND_16_SUPPORTED)
1444 if ((png_ptr->transformations & PNG_EXPAND_16) &&
1445 (png_ptr->transformations & PNG_COMPOSE) &&
1446 !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
1447 png_ptr->bit_depth != 16)
1449 /* TODO: fix this. Because the expand_16 operation is after the compose
1450 * handling the background color must be 8, not 16, bits deep, but the
1451 * application will supply a 16-bit value so reduce it here.
1453 * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
1454 * present, so that case is ok (until do_expand_16 is moved.)
1456 * NOTE: this discards the low 16 bits of the user supplied background
1457 * color, but until expand_16 works properly there is no choice!
1459 # define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
1460 CHOP(png_ptr->background.red);
1461 CHOP(png_ptr->background.green);
1462 CHOP(png_ptr->background.blue);
1463 CHOP(png_ptr->background.gray);
1466 #endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
1468 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1469 (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
1470 defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
1471 if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
1472 (png_ptr->transformations & PNG_COMPOSE) &&
1473 !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
1474 png_ptr->bit_depth == 16)
1476 /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
1477 * component this will also happen after PNG_COMPOSE and so the background
1478 * color must be pre-expanded here.
1480 * TODO: fix this too.
1482 png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
1483 png_ptr->background.green =
1484 (png_uint_16)(png_ptr->background.green * 257);
1485 png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
1486 png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
1490 /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
1491 * background support (see the comments in scripts/pnglibconf.dfa), this
1492 * allows pre-multiplication of the alpha channel to be implemented as
1493 * compositing on black. This is probably sub-optimal and has been done in
1494 * 1.5.4 betas simply to enable external critique and testing (i.e. to
1495 * implement the new API quickly, without lots of internal changes.)
1498 #ifdef PNG_READ_GAMMA_SUPPORTED
1499 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1500 /* Includes ALPHA_MODE */
1501 png_ptr->background_1 = png_ptr->background;
1504 /* This needs to change - in the palette image case a whole set of tables are
1505 * built when it would be quicker to just calculate the correct value for
1506 * each palette entry directly. Also, the test is too tricky - why check
1507 * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
1508 * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
1509 * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
1510 * the gamma tables will not be built even if composition is required on a
1511 * gamma encoded value.
1513 * In 1.5.4 this is addressed below by an additional check on the individual
1514 * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
1517 if ((png_ptr->transformations & PNG_GAMMA)
1518 || ((png_ptr->transformations & PNG_RGB_TO_GRAY)
1519 && (png_gamma_significant(png_ptr->gamma) ||
1520 png_gamma_significant(png_ptr->screen_gamma)))
1521 || ((png_ptr->transformations & PNG_COMPOSE)
1522 && (png_gamma_significant(png_ptr->gamma)
1523 || png_gamma_significant(png_ptr->screen_gamma)
1524 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1525 || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
1526 && png_gamma_significant(png_ptr->background_gamma))
1528 )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
1529 && png_gamma_significant(png_ptr->screen_gamma))
1532 png_build_gamma_table(png_ptr, png_ptr->bit_depth);
1534 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1535 if (png_ptr->transformations & PNG_COMPOSE)
1537 /* Issue a warning about this combination: because RGB_TO_GRAY is
1538 * optimized to do the gamma transform if present yet do_background has
1539 * to do the same thing if both options are set a
1540 * double-gamma-correction happens. This is true in all versions of
1543 if (png_ptr->transformations & PNG_RGB_TO_GRAY)
1544 png_warning(png_ptr,
1545 "libpng does not support gamma+background+rgb_to_gray");
1547 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1549 /* We don't get to here unless there is a tRNS chunk with non-opaque
1550 * entries - see the checking code at the start of this function.
1552 png_color back, back_1;
1553 png_colorp palette = png_ptr->palette;
1554 int num_palette = png_ptr->num_palette;
1556 if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
1559 back.red = png_ptr->gamma_table[png_ptr->background.red];
1560 back.green = png_ptr->gamma_table[png_ptr->background.green];
1561 back.blue = png_ptr->gamma_table[png_ptr->background.blue];
1563 back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
1564 back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
1565 back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
1569 png_fixed_point g, gs;
1571 switch (png_ptr->background_gamma_type)
1573 case PNG_BACKGROUND_GAMMA_SCREEN:
1574 g = (png_ptr->screen_gamma);
1578 case PNG_BACKGROUND_GAMMA_FILE:
1579 g = png_reciprocal(png_ptr->gamma);
1580 gs = png_reciprocal2(png_ptr->gamma,
1581 png_ptr->screen_gamma);
1584 case PNG_BACKGROUND_GAMMA_UNIQUE:
1585 g = png_reciprocal(png_ptr->background_gamma);
1586 gs = png_reciprocal2(png_ptr->background_gamma,
1587 png_ptr->screen_gamma);
1590 g = PNG_FP_1; /* back_1 */
1591 gs = PNG_FP_1; /* back */
1595 if (png_gamma_significant(gs))
1597 back.red = png_gamma_8bit_correct(png_ptr->background.red,
1599 back.green = png_gamma_8bit_correct(png_ptr->background.green,
1601 back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1607 back.red = (png_byte)png_ptr->background.red;
1608 back.green = (png_byte)png_ptr->background.green;
1609 back.blue = (png_byte)png_ptr->background.blue;
1612 if (png_gamma_significant(g))
1614 back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
1616 back_1.green = png_gamma_8bit_correct(
1617 png_ptr->background.green, g);
1618 back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
1624 back_1.red = (png_byte)png_ptr->background.red;
1625 back_1.green = (png_byte)png_ptr->background.green;
1626 back_1.blue = (png_byte)png_ptr->background.blue;
1630 for (i = 0; i < num_palette; i++)
1632 if (i < (int)png_ptr->num_trans &&
1633 png_ptr->trans_alpha[i] != 0xff)
1635 if (png_ptr->trans_alpha[i] == 0)
1639 else /* if (png_ptr->trans_alpha[i] != 0xff) */
1643 v = png_ptr->gamma_to_1[palette[i].red];
1644 png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
1645 palette[i].red = png_ptr->gamma_from_1[w];
1647 v = png_ptr->gamma_to_1[palette[i].green];
1648 png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
1649 palette[i].green = png_ptr->gamma_from_1[w];
1651 v = png_ptr->gamma_to_1[palette[i].blue];
1652 png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
1653 palette[i].blue = png_ptr->gamma_from_1[w];
1658 palette[i].red = png_ptr->gamma_table[palette[i].red];
1659 palette[i].green = png_ptr->gamma_table[palette[i].green];
1660 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1664 /* Prevent the transformations being done again.
1666 * NOTE: this is highly dubious; it removes the transformations in
1667 * place. This seems inconsistent with the general treatment of the
1668 * transformations elsewhere.
1670 png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
1671 } /* color_type == PNG_COLOR_TYPE_PALETTE */
1673 /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
1674 else /* color_type != PNG_COLOR_TYPE_PALETTE */
1677 png_fixed_point g = PNG_FP_1; /* Correction to linear */
1678 png_fixed_point gs = PNG_FP_1; /* Correction to screen */
1680 switch (png_ptr->background_gamma_type)
1682 case PNG_BACKGROUND_GAMMA_SCREEN:
1683 g = png_ptr->screen_gamma;
1684 /* gs = PNG_FP_1; */
1687 case PNG_BACKGROUND_GAMMA_FILE:
1688 g = png_reciprocal(png_ptr->gamma);
1689 gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_gamma);
1692 case PNG_BACKGROUND_GAMMA_UNIQUE:
1693 g = png_reciprocal(png_ptr->background_gamma);
1694 gs = png_reciprocal2(png_ptr->background_gamma,
1695 png_ptr->screen_gamma);
1699 png_error(png_ptr, "invalid background gamma type");
1702 g_sig = png_gamma_significant(g);
1703 gs_sig = png_gamma_significant(gs);
1706 png_ptr->background_1.gray = png_gamma_correct(png_ptr,
1707 png_ptr->background.gray, g);
1710 png_ptr->background.gray = png_gamma_correct(png_ptr,
1711 png_ptr->background.gray, gs);
1713 if ((png_ptr->background.red != png_ptr->background.green) ||
1714 (png_ptr->background.red != png_ptr->background.blue) ||
1715 (png_ptr->background.red != png_ptr->background.gray))
1717 /* RGB or RGBA with color background */
1720 png_ptr->background_1.red = png_gamma_correct(png_ptr,
1721 png_ptr->background.red, g);
1723 png_ptr->background_1.green = png_gamma_correct(png_ptr,
1724 png_ptr->background.green, g);
1726 png_ptr->background_1.blue = png_gamma_correct(png_ptr,
1727 png_ptr->background.blue, g);
1732 png_ptr->background.red = png_gamma_correct(png_ptr,
1733 png_ptr->background.red, gs);
1735 png_ptr->background.green = png_gamma_correct(png_ptr,
1736 png_ptr->background.green, gs);
1738 png_ptr->background.blue = png_gamma_correct(png_ptr,
1739 png_ptr->background.blue, gs);
1745 /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
1746 png_ptr->background_1.red = png_ptr->background_1.green
1747 = png_ptr->background_1.blue = png_ptr->background_1.gray;
1749 png_ptr->background.red = png_ptr->background.green
1750 = png_ptr->background.blue = png_ptr->background.gray;
1753 /* The background is now in screen gamma: */
1754 png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
1755 } /* color_type != PNG_COLOR_TYPE_PALETTE */
1756 }/* png_ptr->transformations & PNG_BACKGROUND */
1759 /* Transformation does not include PNG_BACKGROUND */
1760 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
1761 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
1762 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1763 /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
1764 && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
1765 (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
1769 png_colorp palette = png_ptr->palette;
1770 int num_palette = png_ptr->num_palette;
1773 /* NOTE: there are other transformations that should probably be in
1776 for (i = 0; i < num_palette; i++)
1778 palette[i].red = png_ptr->gamma_table[palette[i].red];
1779 palette[i].green = png_ptr->gamma_table[palette[i].green];
1780 palette[i].blue = png_ptr->gamma_table[palette[i].blue];
1783 /* Done the gamma correction. */
1784 png_ptr->transformations &= ~PNG_GAMMA;
1785 } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
1787 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1790 #endif /* PNG_READ_GAMMA_SUPPORTED */
1792 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1793 /* No GAMMA transformation (see the hanging else 4 lines above) */
1794 if ((png_ptr->transformations & PNG_COMPOSE) &&
1795 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1798 int istop = (int)png_ptr->num_trans;
1800 png_colorp palette = png_ptr->palette;
1802 back.red = (png_byte)png_ptr->background.red;
1803 back.green = (png_byte)png_ptr->background.green;
1804 back.blue = (png_byte)png_ptr->background.blue;
1806 for (i = 0; i < istop; i++)
1808 if (png_ptr->trans_alpha[i] == 0)
1813 else if (png_ptr->trans_alpha[i] != 0xff)
1815 /* The png_composite() macro is defined in png.h */
1816 png_composite(palette[i].red, palette[i].red,
1817 png_ptr->trans_alpha[i], back.red);
1819 png_composite(palette[i].green, palette[i].green,
1820 png_ptr->trans_alpha[i], back.green);
1822 png_composite(palette[i].blue, palette[i].blue,
1823 png_ptr->trans_alpha[i], back.blue);
1827 png_ptr->transformations &= ~PNG_COMPOSE;
1829 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
1831 #ifdef PNG_READ_SHIFT_SUPPORTED
1832 if ((png_ptr->transformations & PNG_SHIFT) &&
1833 !(png_ptr->transformations & PNG_EXPAND) &&
1834 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
1837 int istop = png_ptr->num_palette;
1838 int shift = 8 - png_ptr->sig_bit.red;
1840 png_ptr->transformations &= ~PNG_SHIFT;
1842 /* significant bits can be in the range 1 to 7 for a meaninful result, if
1843 * the number of significant bits is 0 then no shift is done (this is an
1844 * error condition which is silently ignored.)
1846 if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
1848 int component = png_ptr->palette[i].red;
1850 component >>= shift;
1851 png_ptr->palette[i].red = (png_byte)component;
1854 shift = 8 - png_ptr->sig_bit.green;
1855 if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
1857 int component = png_ptr->palette[i].green;
1859 component >>= shift;
1860 png_ptr->palette[i].green = (png_byte)component;
1863 shift = 8 - png_ptr->sig_bit.blue;
1864 if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
1866 int component = png_ptr->palette[i].blue;
1868 component >>= shift;
1869 png_ptr->palette[i].blue = (png_byte)component;
1872 #endif /* PNG_READ_SHIFT_SUPPORTED */
1875 /* Modify the info structure to reflect the transformations. The
1876 * info should be updated so a PNG file could be written with it,
1877 * assuming the transformations result in valid PNG data.
1880 png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
1882 png_debug(1, "in png_read_transform_info");
1884 #ifdef PNG_READ_EXPAND_SUPPORTED
1885 if (png_ptr->transformations & PNG_EXPAND)
1887 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
1889 /* This check must match what actually happens in
1890 * png_do_expand_palette; if it ever checks the tRNS chunk to see if
1891 * it is all opaque we must do the same (at present it does not.)
1893 if (png_ptr->num_trans > 0)
1894 info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
1897 info_ptr->color_type = PNG_COLOR_TYPE_RGB;
1899 info_ptr->bit_depth = 8;
1900 info_ptr->num_trans = 0;
1904 if (png_ptr->num_trans)
1906 if (png_ptr->transformations & PNG_EXPAND_tRNS)
1907 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
1909 if (info_ptr->bit_depth < 8)
1910 info_ptr->bit_depth = 8;
1912 info_ptr->num_trans = 0;
1917 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
1918 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
1919 /* The following is almost certainly wrong unless the background value is in
1922 if (png_ptr->transformations & PNG_COMPOSE)
1923 info_ptr->background = png_ptr->background;
1926 #ifdef PNG_READ_GAMMA_SUPPORTED
1927 /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
1928 * however it seems that the code in png_init_read_transformations, which has
1929 * been called before this from png_read_update_info->png_read_start_row
1930 * sometimes does the gamma transform and cancels the flag.
1932 info_ptr->gamma = png_ptr->gamma;
1935 if (info_ptr->bit_depth == 16)
1937 # ifdef PNG_READ_16BIT_SUPPORTED
1938 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1939 if (png_ptr->transformations & PNG_SCALE_16_TO_8)
1940 info_ptr->bit_depth = 8;
1943 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1944 if (png_ptr->transformations & PNG_16_TO_8)
1945 info_ptr->bit_depth = 8;
1949 /* No 16 bit support: force chopping 16-bit input down to 8, in this case
1950 * the app program can chose if both APIs are available by setting the
1951 * correct scaling to use.
1953 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1954 /* For compatibility with previous versions use the strip method by
1955 * default. This code works because if PNG_SCALE_16_TO_8 is already
1956 * set the code below will do that in preference to the chop.
1958 png_ptr->transformations |= PNG_16_TO_8;
1959 info_ptr->bit_depth = 8;
1962 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1963 png_ptr->transformations |= PNG_SCALE_16_TO_8;
1964 info_ptr->bit_depth = 8;
1967 CONFIGURATION ERROR: you must enable at least one 16 to 8 method
1970 #endif /* !READ_16BIT_SUPPORTED */
1973 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1974 if (png_ptr->transformations & PNG_GRAY_TO_RGB)
1975 info_ptr->color_type = (png_byte)(info_ptr->color_type |
1976 PNG_COLOR_MASK_COLOR);
1979 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1980 if (png_ptr->transformations & PNG_RGB_TO_GRAY)
1981 info_ptr->color_type = (png_byte)(info_ptr->color_type &
1982 ~PNG_COLOR_MASK_COLOR);
1985 #ifdef PNG_READ_QUANTIZE_SUPPORTED
1986 if (png_ptr->transformations & PNG_QUANTIZE)
1988 if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
1989 (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
1990 png_ptr->palette_lookup && info_ptr->bit_depth == 8)
1992 info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
1997 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1998 if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
1999 info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
2001 info_ptr->bit_depth = 16;
2005 #ifdef PNG_READ_PACK_SUPPORTED
2006 if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
2007 info_ptr->bit_depth = 8;
2010 if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
2011 info_ptr->channels = 1;
2013 else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
2014 info_ptr->channels = 3;
2017 info_ptr->channels = 1;
2019 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2020 if (png_ptr->transformations & PNG_STRIP_ALPHA)
2022 info_ptr->color_type = (png_byte)(info_ptr->color_type &
2023 ~PNG_COLOR_MASK_ALPHA);
2024 info_ptr->num_trans = 0;
2028 if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
2029 info_ptr->channels++;
2031 #ifdef PNG_READ_FILLER_SUPPORTED
2032 /* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
2033 if ((png_ptr->transformations & PNG_FILLER) &&
2034 ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
2035 (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
2037 info_ptr->channels++;
2038 /* If adding a true alpha channel not just filler */
2039 if (png_ptr->transformations & PNG_ADD_ALPHA)
2040 info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
2044 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
2045 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
2046 if (png_ptr->transformations & PNG_USER_TRANSFORM)
2048 if (info_ptr->bit_depth < png_ptr->user_transform_depth)
2049 info_ptr->bit_depth = png_ptr->user_transform_depth;
2051 if (info_ptr->channels < png_ptr->user_transform_channels)
2052 info_ptr->channels = png_ptr->user_transform_channels;
2056 info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
2057 info_ptr->bit_depth);
2059 info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
2061 /* Adding in 1.5.4: cache the above value in png_struct so that we can later
2062 * check in png_rowbytes that the user buffer won't get overwritten. Note
2063 * that the field is not always set - if png_read_update_info isn't called
2064 * the application has to either not do any transforms or get the calculation
2067 png_ptr->info_rowbytes = info_ptr->rowbytes;
2069 #ifndef PNG_READ_EXPAND_SUPPORTED
2075 /* Transform the row. The order of transformations is significant,
2076 * and is very touchy. If you add a transformation, take care to
2077 * decide how it fits in with the other transformations here.
2080 png_do_read_transformations(png_structp png_ptr, png_row_infop row_info)
2082 png_debug(1, "in png_do_read_transformations");
2084 if (png_ptr->row_buf == NULL)
2086 /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
2087 * error is incredibly rare and incredibly easy to debug without this
2090 png_error(png_ptr, "NULL row buffer");
2093 /* The following is debugging; prior to 1.5.4 the code was never compiled in;
2094 * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
2095 * PNG_WARN_UNINITIALIZED_ROW removed. In 1.5 the new flag is set only for
2096 * selected new APIs to ensure that there is no API change.
2098 if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
2099 !(png_ptr->flags & PNG_FLAG_ROW_INIT))
2101 /* Application has failed to call either png_read_start_image() or
2102 * png_read_update_info() after setting transforms that expand pixels.
2103 * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
2105 png_error(png_ptr, "Uninitialized row");
2108 #ifdef PNG_READ_EXPAND_SUPPORTED
2109 if (png_ptr->transformations & PNG_EXPAND)
2111 if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
2113 png_do_expand_palette(row_info, png_ptr->row_buf + 1,
2114 png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
2119 if (png_ptr->num_trans &&
2120 (png_ptr->transformations & PNG_EXPAND_tRNS))
2121 png_do_expand(row_info, png_ptr->row_buf + 1,
2122 &(png_ptr->trans_color));
2125 png_do_expand(row_info, png_ptr->row_buf + 1,
2131 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2132 if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
2133 !(png_ptr->transformations & PNG_COMPOSE) &&
2134 (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2135 row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
2136 png_do_strip_channel(row_info, png_ptr->row_buf + 1,
2137 0 /* at_start == false, because SWAP_ALPHA happens later */);
2140 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2141 if (png_ptr->transformations & PNG_RGB_TO_GRAY)
2144 png_do_rgb_to_gray(png_ptr, row_info,
2145 png_ptr->row_buf + 1);
2149 png_ptr->rgb_to_gray_status=1;
2150 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
2151 PNG_RGB_TO_GRAY_WARN)
2152 png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
2154 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
2155 PNG_RGB_TO_GRAY_ERR)
2156 png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
2161 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
2163 * In most cases, the "simple transparency" should be done prior to doing
2164 * gray-to-RGB, or you will have to test 3x as many bytes to check if a
2165 * pixel is transparent. You would also need to make sure that the
2166 * transparency information is upgraded to RGB.
2168 * To summarize, the current flow is:
2169 * - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
2170 * with background "in place" if transparent,
2171 * convert to RGB if necessary
2172 * - Gray + alpha -> composite with gray background and remove alpha bytes,
2173 * convert to RGB if necessary
2175 * To support RGB backgrounds for gray images we need:
2176 * - Gray + simple transparency -> convert to RGB + simple transparency,
2177 * compare 3 or 6 bytes and composite with
2178 * background "in place" if transparent
2179 * (3x compare/pixel compared to doing
2180 * composite with gray bkgrnd)
2181 * - Gray + alpha -> convert to RGB + alpha, composite with background and
2182 * remove alpha bytes (3x float
2183 * operations/pixel compared with composite
2184 * on gray background)
2186 * Greg's change will do this. The reason it wasn't done before is for
2187 * performance, as this increases the per-pixel operations. If we would check
2188 * in advance if the background was gray or RGB, and position the gray-to-RGB
2189 * transform appropriately, then it would save a lot of work/time.
2192 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2193 /* If gray -> RGB, do so now only if background is non-gray; else do later
2194 * for performance reasons
2196 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
2197 !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
2198 png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
2201 #if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
2202 (defined PNG_READ_ALPHA_MODE_SUPPORTED)
2203 if (png_ptr->transformations & PNG_COMPOSE)
2204 png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
2207 #ifdef PNG_READ_GAMMA_SUPPORTED
2208 if ((png_ptr->transformations & PNG_GAMMA) &&
2209 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2210 /* Because RGB_TO_GRAY does the gamma transform. */
2211 !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
2213 #if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
2214 (defined PNG_READ_ALPHA_MODE_SUPPORTED)
2215 /* Because PNG_COMPOSE does the gamma transform if there is something to
2216 * do (if there is an alpha channel or transparency.)
2218 !((png_ptr->transformations & PNG_COMPOSE) &&
2219 ((png_ptr->num_trans != 0) ||
2220 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
2222 /* Because png_init_read_transformations transforms the palette, unless
2223 * RGB_TO_GRAY will do the transform.
2225 (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
2226 png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
2229 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2230 if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
2231 (png_ptr->transformations & PNG_COMPOSE) &&
2232 (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2233 row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
2234 png_do_strip_channel(row_info, png_ptr->row_buf + 1,
2235 0 /* at_start == false, because SWAP_ALPHA happens later */);
2238 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
2239 if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
2240 (row_info->color_type & PNG_COLOR_MASK_ALPHA))
2241 png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
2244 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2245 if (png_ptr->transformations & PNG_SCALE_16_TO_8)
2246 png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
2249 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2250 /* There is no harm in doing both of these because only one has any effect,
2251 * by putting the 'scale' option first if the app asks for scale (either by
2252 * calling the API or in a TRANSFORM flag) this is what happens.
2254 if (png_ptr->transformations & PNG_16_TO_8)
2255 png_do_chop(row_info, png_ptr->row_buf + 1);
2258 #ifdef PNG_READ_QUANTIZE_SUPPORTED
2259 if (png_ptr->transformations & PNG_QUANTIZE)
2261 png_do_quantize(row_info, png_ptr->row_buf + 1,
2262 png_ptr->palette_lookup, png_ptr->quantize_index);
2264 if (row_info->rowbytes == 0)
2265 png_error(png_ptr, "png_do_quantize returned rowbytes=0");
2267 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
2269 #ifdef PNG_READ_EXPAND_16_SUPPORTED
2270 /* Do the expansion now, after all the arithmetic has been done. Notice
2271 * that previous transformations can handle the PNG_EXPAND_16 flag if this
2272 * is efficient (particularly true in the case of gamma correction, where
2273 * better accuracy results faster!)
2275 if (png_ptr->transformations & PNG_EXPAND_16)
2276 png_do_expand_16(row_info, png_ptr->row_buf + 1);
2279 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2280 /* NOTE: moved here in 1.5.4 (from much later in this list.) */
2281 if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
2282 (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
2283 png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
2286 #ifdef PNG_READ_INVERT_SUPPORTED
2287 if (png_ptr->transformations & PNG_INVERT_MONO)
2288 png_do_invert(row_info, png_ptr->row_buf + 1);
2291 #ifdef PNG_READ_SHIFT_SUPPORTED
2292 if (png_ptr->transformations & PNG_SHIFT)
2293 png_do_unshift(row_info, png_ptr->row_buf + 1,
2297 #ifdef PNG_READ_PACK_SUPPORTED
2298 if (png_ptr->transformations & PNG_PACK)
2299 png_do_unpack(row_info, png_ptr->row_buf + 1);
2302 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
2303 /* Added at libpng-1.5.10 */
2304 if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
2305 png_ptr->num_palette_max >= 0)
2306 png_do_check_palette_indexes(png_ptr, row_info);
2309 #ifdef PNG_READ_BGR_SUPPORTED
2310 if (png_ptr->transformations & PNG_BGR)
2311 png_do_bgr(row_info, png_ptr->row_buf + 1);
2314 #ifdef PNG_READ_PACKSWAP_SUPPORTED
2315 if (png_ptr->transformations & PNG_PACKSWAP)
2316 png_do_packswap(row_info, png_ptr->row_buf + 1);
2319 #ifdef PNG_READ_FILLER_SUPPORTED
2320 if (png_ptr->transformations & PNG_FILLER)
2321 png_do_read_filler(row_info, png_ptr->row_buf + 1,
2322 (png_uint_32)png_ptr->filler, png_ptr->flags);
2325 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2326 if (png_ptr->transformations & PNG_INVERT_ALPHA)
2327 png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
2330 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2331 if (png_ptr->transformations & PNG_SWAP_ALPHA)
2332 png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
2335 #ifdef PNG_READ_16BIT_SUPPORTED
2336 #ifdef PNG_READ_SWAP_SUPPORTED
2337 if (png_ptr->transformations & PNG_SWAP_BYTES)
2338 png_do_swap(row_info, png_ptr->row_buf + 1);
2342 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
2343 if (png_ptr->transformations & PNG_USER_TRANSFORM)
2345 if (png_ptr->read_user_transform_fn != NULL)
2346 (*(png_ptr->read_user_transform_fn)) /* User read transform function */
2347 (png_ptr, /* png_ptr */
2348 row_info, /* row_info: */
2349 /* png_uint_32 width; width of row */
2350 /* png_size_t rowbytes; number of bytes in row */
2351 /* png_byte color_type; color type of pixels */
2352 /* png_byte bit_depth; bit depth of samples */
2353 /* png_byte channels; number of channels (1-4) */
2354 /* png_byte pixel_depth; bits per pixel (depth*channels) */
2355 png_ptr->row_buf + 1); /* start of pixel data for row */
2356 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
2357 if (png_ptr->user_transform_depth)
2358 row_info->bit_depth = png_ptr->user_transform_depth;
2360 if (png_ptr->user_transform_channels)
2361 row_info->channels = png_ptr->user_transform_channels;
2363 row_info->pixel_depth = (png_byte)(row_info->bit_depth *
2364 row_info->channels);
2366 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
2371 #ifdef PNG_READ_PACK_SUPPORTED
2372 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
2373 * without changing the actual values. Thus, if you had a row with
2374 * a bit depth of 1, you would end up with bytes that only contained
2375 * the numbers 0 or 1. If you would rather they contain 0 and 255, use
2376 * png_do_shift() after this.
2379 png_do_unpack(png_row_infop row_info, png_bytep row)
2381 png_debug(1, "in png_do_unpack");
2383 if (row_info->bit_depth < 8)
2386 png_uint_32 row_width=row_info->width;
2388 switch (row_info->bit_depth)
2392 png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
2393 png_bytep dp = row + (png_size_t)row_width - 1;
2394 png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
2395 for (i = 0; i < row_width; i++)
2397 *dp = (png_byte)((*sp >> shift) & 0x01);
2416 png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
2417 png_bytep dp = row + (png_size_t)row_width - 1;
2418 png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
2419 for (i = 0; i < row_width; i++)
2421 *dp = (png_byte)((*sp >> shift) & 0x03);
2439 png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
2440 png_bytep dp = row + (png_size_t)row_width - 1;
2441 png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
2442 for (i = 0; i < row_width; i++)
2444 *dp = (png_byte)((*sp >> shift) & 0x0f);
2463 row_info->bit_depth = 8;
2464 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2465 row_info->rowbytes = row_width * row_info->channels;
2470 #ifdef PNG_READ_SHIFT_SUPPORTED
2471 /* Reverse the effects of png_do_shift. This routine merely shifts the
2472 * pixels back to their significant bits values. Thus, if you have
2473 * a row of bit depth 8, but only 5 are significant, this will shift
2474 * the values back to 0 through 31.
2477 png_do_unshift(png_row_infop row_info, png_bytep row,
2478 png_const_color_8p sig_bits)
2482 png_debug(1, "in png_do_unshift");
2484 /* The palette case has already been handled in the _init routine. */
2485 color_type = row_info->color_type;
2487 if (color_type != PNG_COLOR_TYPE_PALETTE)
2491 int bit_depth = row_info->bit_depth;
2493 if (color_type & PNG_COLOR_MASK_COLOR)
2495 shift[channels++] = bit_depth - sig_bits->red;
2496 shift[channels++] = bit_depth - sig_bits->green;
2497 shift[channels++] = bit_depth - sig_bits->blue;
2502 shift[channels++] = bit_depth - sig_bits->gray;
2505 if (color_type & PNG_COLOR_MASK_ALPHA)
2507 shift[channels++] = bit_depth - sig_bits->alpha;
2513 for (c = have_shift = 0; c < channels; ++c)
2515 /* A shift of more than the bit depth is an error condition but it
2516 * gets ignored here.
2518 if (shift[c] <= 0 || shift[c] >= bit_depth)
2532 /* Must be 1bpp gray: should not be here! */
2537 /* Must be 2bpp gray */
2538 /* assert(channels == 1 && shift[0] == 1) */
2541 png_bytep bp_end = bp + row_info->rowbytes;
2545 int b = (*bp >> 1) & 0x55;
2546 *bp++ = (png_byte)b;
2552 /* Must be 4bpp gray */
2553 /* assert(channels == 1) */
2556 png_bytep bp_end = bp + row_info->rowbytes;
2557 int gray_shift = shift[0];
2558 int mask = 0xf >> gray_shift;
2564 int b = (*bp >> gray_shift) & mask;
2565 *bp++ = (png_byte)b;
2571 /* Single byte components, G, GA, RGB, RGBA */
2574 png_bytep bp_end = bp + row_info->rowbytes;
2579 int b = *bp >> shift[channel];
2580 if (++channel >= channels)
2582 *bp++ = (png_byte)b;
2587 #ifdef PNG_READ_16BIT_SUPPORTED
2589 /* Double byte components, G, GA, RGB, RGBA */
2592 png_bytep bp_end = bp + row_info->rowbytes;
2597 int value = (bp[0] << 8) + bp[1];
2599 value >>= shift[channel];
2600 if (++channel >= channels)
2602 *bp++ = (png_byte)(value >> 8);
2603 *bp++ = (png_byte)(value & 0xff);
2613 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2614 /* Scale rows of bit depth 16 down to 8 accurately */
2616 png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
2618 png_debug(1, "in png_do_scale_16_to_8");
2620 if (row_info->bit_depth == 16)
2622 png_bytep sp = row; /* source */
2623 png_bytep dp = row; /* destination */
2624 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2628 /* The input is an array of 16 bit components, these must be scaled to
2629 * 8 bits each. For a 16 bit value V the required value (from the PNG
2630 * specification) is:
2634 * This reduces to round(V / 257), or floor((V + 128.5)/257)
2636 * Represent V as the two byte value vhi.vlo. Make a guess that the
2637 * result is the top byte of V, vhi, then the correction to this value
2640 * error = floor(((V-vhi.vhi) + 128.5) / 257)
2641 * = floor(((vlo-vhi) + 128.5) / 257)
2643 * This can be approximated using integer arithmetic (and a signed
2646 * error = (vlo-vhi+128) >> 8;
2648 * The approximate differs from the exact answer only when (vlo-vhi) is
2649 * 128; it then gives a correction of +1 when the exact correction is
2650 * 0. This gives 128 errors. The exact answer (correct for all 16 bit
2653 * error = (vlo-vhi+128)*65535 >> 24;
2655 * An alternative arithmetic calculation which also gives no errors is:
2657 * (V * 255 + 32895) >> 16
2660 png_int_32 tmp = *sp++; /* must be signed! */
2661 tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
2662 *dp++ = (png_byte)tmp;
2665 row_info->bit_depth = 8;
2666 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2667 row_info->rowbytes = row_info->width * row_info->channels;
2672 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2674 /* Simply discard the low byte. This was the default behavior prior
2677 png_do_chop(png_row_infop row_info, png_bytep row)
2679 png_debug(1, "in png_do_chop");
2681 if (row_info->bit_depth == 16)
2683 png_bytep sp = row; /* source */
2684 png_bytep dp = row; /* destination */
2685 png_bytep ep = sp + row_info->rowbytes; /* end+1 */
2690 sp += 2; /* skip low byte */
2693 row_info->bit_depth = 8;
2694 row_info->pixel_depth = (png_byte)(8 * row_info->channels);
2695 row_info->rowbytes = row_info->width * row_info->channels;
2700 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2702 png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
2704 png_debug(1, "in png_do_read_swap_alpha");
2707 png_uint_32 row_width = row_info->width;
2708 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2710 /* This converts from RGBA to ARGB */
2711 if (row_info->bit_depth == 8)
2713 png_bytep sp = row + row_info->rowbytes;
2718 for (i = 0; i < row_width; i++)
2728 #ifdef PNG_READ_16BIT_SUPPORTED
2729 /* This converts from RRGGBBAA to AARRGGBB */
2732 png_bytep sp = row + row_info->rowbytes;
2737 for (i = 0; i < row_width; i++)
2754 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2756 /* This converts from GA to AG */
2757 if (row_info->bit_depth == 8)
2759 png_bytep sp = row + row_info->rowbytes;
2764 for (i = 0; i < row_width; i++)
2772 #ifdef PNG_READ_16BIT_SUPPORTED
2773 /* This converts from GGAA to AAGG */
2776 png_bytep sp = row + row_info->rowbytes;
2781 for (i = 0; i < row_width; i++)
2797 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2799 png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
2801 png_uint_32 row_width;
2802 png_debug(1, "in png_do_read_invert_alpha");
2804 row_width = row_info->width;
2805 if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
2807 if (row_info->bit_depth == 8)
2809 /* This inverts the alpha channel in RGBA */
2810 png_bytep sp = row + row_info->rowbytes;
2814 for (i = 0; i < row_width; i++)
2816 *(--dp) = (png_byte)(255 - *(--sp));
2818 /* This does nothing:
2822 We can replace it with:
2829 #ifdef PNG_READ_16BIT_SUPPORTED
2830 /* This inverts the alpha channel in RRGGBBAA */
2833 png_bytep sp = row + row_info->rowbytes;
2837 for (i = 0; i < row_width; i++)
2839 *(--dp) = (png_byte)(255 - *(--sp));
2840 *(--dp) = (png_byte)(255 - *(--sp));
2842 /* This does nothing:
2849 We can replace it with:
2857 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
2859 if (row_info->bit_depth == 8)
2861 /* This inverts the alpha channel in GA */
2862 png_bytep sp = row + row_info->rowbytes;
2866 for (i = 0; i < row_width; i++)
2868 *(--dp) = (png_byte)(255 - *(--sp));
2873 #ifdef PNG_READ_16BIT_SUPPORTED
2876 /* This inverts the alpha channel in GGAA */
2877 png_bytep sp = row + row_info->rowbytes;
2881 for (i = 0; i < row_width; i++)
2883 *(--dp) = (png_byte)(255 - *(--sp));
2884 *(--dp) = (png_byte)(255 - *(--sp));
2898 #ifdef PNG_READ_FILLER_SUPPORTED
2899 /* Add filler channel if we have RGB color */
2901 png_do_read_filler(png_row_infop row_info, png_bytep row,
2902 png_uint_32 filler, png_uint_32 flags)
2905 png_uint_32 row_width = row_info->width;
2907 #ifdef PNG_READ_16BIT_SUPPORTED
2908 png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
2910 png_byte lo_filler = (png_byte)(filler & 0xff);
2912 png_debug(1, "in png_do_read_filler");
2915 row_info->color_type == PNG_COLOR_TYPE_GRAY)
2917 if (row_info->bit_depth == 8)
2919 if (flags & PNG_FLAG_FILLER_AFTER)
2921 /* This changes the data from G to GX */
2922 png_bytep sp = row + (png_size_t)row_width;
2923 png_bytep dp = sp + (png_size_t)row_width;
2924 for (i = 1; i < row_width; i++)
2926 *(--dp) = lo_filler;
2929 *(--dp) = lo_filler;
2930 row_info->channels = 2;
2931 row_info->pixel_depth = 16;
2932 row_info->rowbytes = row_width * 2;
2937 /* This changes the data from G to XG */
2938 png_bytep sp = row + (png_size_t)row_width;
2939 png_bytep dp = sp + (png_size_t)row_width;
2940 for (i = 0; i < row_width; i++)
2943 *(--dp) = lo_filler;
2945 row_info->channels = 2;
2946 row_info->pixel_depth = 16;
2947 row_info->rowbytes = row_width * 2;
2951 #ifdef PNG_READ_16BIT_SUPPORTED
2952 else if (row_info->bit_depth == 16)
2954 if (flags & PNG_FLAG_FILLER_AFTER)
2956 /* This changes the data from GG to GGXX */
2957 png_bytep sp = row + (png_size_t)row_width * 2;
2958 png_bytep dp = sp + (png_size_t)row_width * 2;
2959 for (i = 1; i < row_width; i++)
2961 *(--dp) = hi_filler;
2962 *(--dp) = lo_filler;
2966 *(--dp) = hi_filler;
2967 *(--dp) = lo_filler;
2968 row_info->channels = 2;
2969 row_info->pixel_depth = 32;
2970 row_info->rowbytes = row_width * 4;
2975 /* This changes the data from GG to XXGG */
2976 png_bytep sp = row + (png_size_t)row_width * 2;
2977 png_bytep dp = sp + (png_size_t)row_width * 2;
2978 for (i = 0; i < row_width; i++)
2982 *(--dp) = hi_filler;
2983 *(--dp) = lo_filler;
2985 row_info->channels = 2;
2986 row_info->pixel_depth = 32;
2987 row_info->rowbytes = row_width * 4;
2991 } /* COLOR_TYPE == GRAY */
2992 else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
2994 if (row_info->bit_depth == 8)
2996 if (flags & PNG_FLAG_FILLER_AFTER)
2998 /* This changes the data from RGB to RGBX */
2999 png_bytep sp = row + (png_size_t)row_width * 3;
3000 png_bytep dp = sp + (png_size_t)row_width;
3001 for (i = 1; i < row_width; i++)
3003 *(--dp) = lo_filler;
3008 *(--dp) = lo_filler;
3009 row_info->channels = 4;
3010 row_info->pixel_depth = 32;
3011 row_info->rowbytes = row_width * 4;
3016 /* This changes the data from RGB to XRGB */
3017 png_bytep sp = row + (png_size_t)row_width * 3;
3018 png_bytep dp = sp + (png_size_t)row_width;
3019 for (i = 0; i < row_width; i++)
3024 *(--dp) = lo_filler;
3026 row_info->channels = 4;
3027 row_info->pixel_depth = 32;
3028 row_info->rowbytes = row_width * 4;
3032 #ifdef PNG_READ_16BIT_SUPPORTED
3033 else if (row_info->bit_depth == 16)
3035 if (flags & PNG_FLAG_FILLER_AFTER)
3037 /* This changes the data from RRGGBB to RRGGBBXX */
3038 png_bytep sp = row + (png_size_t)row_width * 6;
3039 png_bytep dp = sp + (png_size_t)row_width * 2;
3040 for (i = 1; i < row_width; i++)
3042 *(--dp) = hi_filler;
3043 *(--dp) = lo_filler;
3051 *(--dp) = hi_filler;
3052 *(--dp) = lo_filler;
3053 row_info->channels = 4;
3054 row_info->pixel_depth = 64;
3055 row_info->rowbytes = row_width * 8;
3060 /* This changes the data from RRGGBB to XXRRGGBB */
3061 png_bytep sp = row + (png_size_t)row_width * 6;
3062 png_bytep dp = sp + (png_size_t)row_width * 2;
3063 for (i = 0; i < row_width; i++)
3071 *(--dp) = hi_filler;
3072 *(--dp) = lo_filler;
3075 row_info->channels = 4;
3076 row_info->pixel_depth = 64;
3077 row_info->rowbytes = row_width * 8;
3081 } /* COLOR_TYPE == RGB */
3085 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
3086 /* Expand grayscale files to RGB, with or without alpha */
3088 png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
3091 png_uint_32 row_width = row_info->width;
3093 png_debug(1, "in png_do_gray_to_rgb");
3095 if (row_info->bit_depth >= 8 &&
3096 !(row_info->color_type & PNG_COLOR_MASK_COLOR))
3098 if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
3100 if (row_info->bit_depth == 8)
3102 /* This changes G to RGB */
3103 png_bytep sp = row + (png_size_t)row_width - 1;
3104 png_bytep dp = sp + (png_size_t)row_width * 2;
3105 for (i = 0; i < row_width; i++)
3115 /* This changes GG to RRGGBB */
3116 png_bytep sp = row + (png_size_t)row_width * 2 - 1;
3117 png_bytep dp = sp + (png_size_t)row_width * 4;
3118 for (i = 0; i < row_width; i++)
3121 *(dp--) = *(sp - 1);
3123 *(dp--) = *(sp - 1);
3130 else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
3132 if (row_info->bit_depth == 8)
3134 /* This changes GA to RGBA */
3135 png_bytep sp = row + (png_size_t)row_width * 2 - 1;
3136 png_bytep dp = sp + (png_size_t)row_width * 2;
3137 for (i = 0; i < row_width; i++)
3148 /* This changes GGAA to RRGGBBAA */
3149 png_bytep sp = row + (png_size_t)row_width * 4 - 1;
3150 png_bytep dp = sp + (png_size_t)row_width * 4;
3151 for (i = 0; i < row_width; i++)
3156 *(dp--) = *(sp - 1);
3158 *(dp--) = *(sp - 1);
3164 row_info->channels = (png_byte)(row_info->channels + 2);
3165 row_info->color_type |= PNG_COLOR_MASK_COLOR;
3166 row_info->pixel_depth = (png_byte)(row_info->channels *
3167 row_info->bit_depth);
3168 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
3173 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
3174 /* Reduce RGB files to grayscale, with or without alpha
3175 * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
3176 * <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
3177 * versions dated 1998 through November 2002 have been archived at
3178 * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
3179 * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
3180 * Charles Poynton poynton at poynton.com
3182 * Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
3184 * which can be expressed with integers as
3186 * Y = (6969 * R + 23434 * G + 2365 * B)/32768
3188 * Poynton's current link (as of January 2003 through July 2011):
3189 * <http://www.poynton.com/notes/colour_and_gamma/>
3190 * has changed the numbers slightly:
3192 * Y = 0.2126*R + 0.7152*G + 0.0722*B
3194 * which can be expressed with integers as
3196 * Y = (6966 * R + 23436 * G + 2366 * B)/32768
3198 * Historically, however, libpng uses numbers derived from the ITU-R Rec 709
3199 * end point chromaticities and the D65 white point. Depending on the
3200 * precision used for the D65 white point this produces a variety of different
3201 * numbers, however if the four decimal place value used in ITU-R Rec 709 is
3202 * used (0.3127,0.3290) the Y calculation would be:
3204 * Y = (6968 * R + 23435 * G + 2366 * B)/32768
3206 * While this is correct the rounding results in an overflow for white, because
3207 * the sum of the rounded coefficients is 32769, not 32768. Consequently
3208 * libpng uses, instead, the closest non-overflowing approximation:
3210 * Y = (6968 * R + 23434 * G + 2366 * B)/32768
3212 * Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
3213 * (including an sRGB chunk) then the chromaticities are used to calculate the
3214 * coefficients. See the chunk handling in pngrutil.c for more information.
3216 * In all cases the calculation is to be done in a linear colorspace. If no
3217 * gamma information is available to correct the encoding of the original RGB
3218 * values this results in an implicit assumption that the original PNG RGB
3219 * values were linear.
3221 * Other integer coefficents can be used via png_set_rgb_to_gray(). Because
3222 * the API takes just red and green coefficients the blue coefficient is
3223 * calculated to make the sum 32768. This will result in different rounding
3224 * to that used above.
3227 png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
3232 png_debug(1, "in png_do_rgb_to_gray");
3234 if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
3235 (row_info->color_type & PNG_COLOR_MASK_COLOR))
3237 PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
3238 PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
3239 PNG_CONST png_uint_32 bc = 32768 - rc - gc;
3240 PNG_CONST png_uint_32 row_width = row_info->width;
3241 PNG_CONST int have_alpha =
3242 (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
3244 if (row_info->bit_depth == 8)
3246 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
3247 /* Notice that gamma to/from 1 are not necessarily inverses (if
3248 * there is an overall gamma correction). Prior to 1.5.5 this code
3249 * checked the linearized values for equality; this doesn't match
3250 * the documentation, the original values must be checked.
3252 if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
3258 for (i = 0; i < row_width; i++)
3260 png_byte red = *(sp++);
3261 png_byte green = *(sp++);
3262 png_byte blue = *(sp++);
3264 if (red != green || red != blue)
3266 red = png_ptr->gamma_to_1[red];
3267 green = png_ptr->gamma_to_1[green];
3268 blue = png_ptr->gamma_to_1[blue];
3271 *(dp++) = png_ptr->gamma_from_1[
3272 (rc*red + gc*green + bc*blue + 16384)>>15];
3277 /* If there is no overall correction the table will not be
3280 if (png_ptr->gamma_table != NULL)
3281 red = png_ptr->gamma_table[red];
3297 for (i = 0; i < row_width; i++)
3299 png_byte red = *(sp++);
3300 png_byte green = *(sp++);
3301 png_byte blue = *(sp++);
3303 if (red != green || red != blue)
3306 /* NOTE: this is the historical approach which simply
3307 * truncates the results.
3309 *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
3321 else /* RGB bit_depth == 16 */
3323 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
3324 if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
3330 for (i = 0; i < row_width; i++)
3332 png_uint_16 red, green, blue, w;
3334 red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3335 green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3336 blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3338 if (red == green && red == blue)
3340 if (png_ptr->gamma_16_table != NULL)
3341 w = png_ptr->gamma_16_table[(red&0xff)
3342 >> png_ptr->gamma_shift][red>>8];
3350 png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red&0xff)
3351 >> png_ptr->gamma_shift][red>>8];
3352 png_uint_16 green_1 =
3353 png_ptr->gamma_16_to_1[(green&0xff) >>
3354 png_ptr->gamma_shift][green>>8];
3355 png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue&0xff)
3356 >> png_ptr->gamma_shift][blue>>8];
3357 png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
3358 + bc*blue_1 + 16384)>>15);
3359 w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
3360 png_ptr->gamma_shift][gray16 >> 8];
3364 *(dp++) = (png_byte)((w>>8) & 0xff);
3365 *(dp++) = (png_byte)(w & 0xff);
3381 for (i = 0; i < row_width; i++)
3383 png_uint_16 red, green, blue, gray16;
3385 red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3386 green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3387 blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
3389 if (red != green || red != blue)
3392 /* From 1.5.5 in the 16 bit case do the accurate conversion even
3393 * in the 'fast' case - this is because this is where the code
3394 * ends up when handling linear 16 bit data.
3396 gray16 = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
3398 *(dp++) = (png_byte)((gray16>>8) & 0xff);
3399 *(dp++) = (png_byte)(gray16 & 0xff);
3410 row_info->channels = (png_byte)(row_info->channels - 2);
3411 row_info->color_type = (png_byte)(row_info->color_type &
3412 ~PNG_COLOR_MASK_COLOR);
3413 row_info->pixel_depth = (png_byte)(row_info->channels *
3414 row_info->bit_depth);
3415 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
3420 #endif /* PNG_READ_TRANSFORMS_SUPPORTED */
3422 #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
3423 /* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
3424 * large of png_color. This lets grayscale images be treated as
3425 * paletted. Most useful for gamma correction and simplification
3426 * of code. This API is not used internally.
3429 png_build_grayscale_palette(int bit_depth, png_colorp palette)
3436 png_debug(1, "in png_do_build_grayscale_palette");
3438 if (palette == NULL)
3469 for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
3471 palette[i].red = (png_byte)v;
3472 palette[i].green = (png_byte)v;
3473 palette[i].blue = (png_byte)v;
3479 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
3480 #if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
3481 (defined PNG_READ_ALPHA_MODE_SUPPORTED)
3482 /* Replace any alpha or transparency with the supplied background color.
3483 * "background" is already in the screen gamma, while "background_1" is
3484 * at a gamma of 1.0. Paletted files have already been taken care of.
3487 png_do_compose(png_row_infop row_info, png_bytep row, png_structp png_ptr)
3489 #ifdef PNG_READ_GAMMA_SUPPORTED
3490 png_const_bytep gamma_table = png_ptr->gamma_table;
3491 png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
3492 png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
3493 png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
3494 png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
3495 png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
3496 int gamma_shift = png_ptr->gamma_shift;
3501 png_uint_32 row_width = row_info->width;
3502 int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
3505 png_debug(1, "in png_do_compose");
3508 switch (row_info->color_type)
3510 case PNG_COLOR_TYPE_GRAY:
3512 switch (row_info->bit_depth)
3518 for (i = 0; i < row_width; i++)
3520 if ((png_uint_16)((*sp >> shift) & 0x01)
3521 == png_ptr->trans_color.gray)
3523 *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
3524 *sp |= (png_byte)(png_ptr->background.gray << shift);
3541 #ifdef PNG_READ_GAMMA_SUPPORTED
3542 if (gamma_table != NULL)
3546 for (i = 0; i < row_width; i++)
3548 if ((png_uint_16)((*sp >> shift) & 0x03)
3549 == png_ptr->trans_color.gray)
3551 *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
3552 *sp |= (png_byte)(png_ptr->background.gray << shift);
3557 png_byte p = (png_byte)((*sp >> shift) & 0x03);
3558 png_byte g = (png_byte)((gamma_table [p | (p << 2) |
3559 (p << 4) | (p << 6)] >> 6) & 0x03);
3560 *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
3561 *sp |= (png_byte)(g << shift);
3580 for (i = 0; i < row_width; i++)
3582 if ((png_uint_16)((*sp >> shift) & 0x03)
3583 == png_ptr->trans_color.gray)
3585 *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
3586 *sp |= (png_byte)(png_ptr->background.gray << shift);
3604 #ifdef PNG_READ_GAMMA_SUPPORTED
3605 if (gamma_table != NULL)
3609 for (i = 0; i < row_width; i++)
3611 if ((png_uint_16)((*sp >> shift) & 0x0f)
3612 == png_ptr->trans_color.gray)
3614 *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
3615 *sp |= (png_byte)(png_ptr->background.gray << shift);
3620 png_byte p = (png_byte)((*sp >> shift) & 0x0f);
3621 png_byte g = (png_byte)((gamma_table[p |
3622 (p << 4)] >> 4) & 0x0f);
3623 *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
3624 *sp |= (png_byte)(g << shift);
3643 for (i = 0; i < row_width; i++)
3645 if ((png_uint_16)((*sp >> shift) & 0x0f)
3646 == png_ptr->trans_color.gray)
3648 *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
3649 *sp |= (png_byte)(png_ptr->background.gray << shift);
3667 #ifdef PNG_READ_GAMMA_SUPPORTED
3668 if (gamma_table != NULL)
3671 for (i = 0; i < row_width; i++, sp++)
3673 if (*sp == png_ptr->trans_color.gray)
3674 *sp = (png_byte)png_ptr->background.gray;
3677 *sp = gamma_table[*sp];
3684 for (i = 0; i < row_width; i++, sp++)
3686 if (*sp == png_ptr->trans_color.gray)
3687 *sp = (png_byte)png_ptr->background.gray;
3695 #ifdef PNG_READ_GAMMA_SUPPORTED
3696 if (gamma_16 != NULL)
3699 for (i = 0; i < row_width; i++, sp += 2)
3703 v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3705 if (v == png_ptr->trans_color.gray)
3707 /* Background is already in screen gamma */
3708 *sp = (png_byte)((png_ptr->background.gray >> 8)
3710 *(sp + 1) = (png_byte)(png_ptr->background.gray
3716 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3717 *sp = (png_byte)((v >> 8) & 0xff);
3718 *(sp + 1) = (png_byte)(v & 0xff);
3726 for (i = 0; i < row_width; i++, sp += 2)
3730 v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3732 if (v == png_ptr->trans_color.gray)
3734 *sp = (png_byte)((png_ptr->background.gray >> 8)
3736 *(sp + 1) = (png_byte)(png_ptr->background.gray
3750 case PNG_COLOR_TYPE_RGB:
3752 if (row_info->bit_depth == 8)
3754 #ifdef PNG_READ_GAMMA_SUPPORTED
3755 if (gamma_table != NULL)
3758 for (i = 0; i < row_width; i++, sp += 3)
3760 if (*sp == png_ptr->trans_color.red &&
3761 *(sp + 1) == png_ptr->trans_color.green &&
3762 *(sp + 2) == png_ptr->trans_color.blue)
3764 *sp = (png_byte)png_ptr->background.red;
3765 *(sp + 1) = (png_byte)png_ptr->background.green;
3766 *(sp + 2) = (png_byte)png_ptr->background.blue;
3771 *sp = gamma_table[*sp];
3772 *(sp + 1) = gamma_table[*(sp + 1)];
3773 *(sp + 2) = gamma_table[*(sp + 2)];
3781 for (i = 0; i < row_width; i++, sp += 3)
3783 if (*sp == png_ptr->trans_color.red &&
3784 *(sp + 1) == png_ptr->trans_color.green &&
3785 *(sp + 2) == png_ptr->trans_color.blue)
3787 *sp = (png_byte)png_ptr->background.red;
3788 *(sp + 1) = (png_byte)png_ptr->background.green;
3789 *(sp + 2) = (png_byte)png_ptr->background.blue;
3794 else /* if (row_info->bit_depth == 16) */
3796 #ifdef PNG_READ_GAMMA_SUPPORTED
3797 if (gamma_16 != NULL)
3800 for (i = 0; i < row_width; i++, sp += 6)
3802 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3804 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
3807 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
3810 if (r == png_ptr->trans_color.red &&
3811 g == png_ptr->trans_color.green &&
3812 b == png_ptr->trans_color.blue)
3814 /* Background is already in screen gamma */
3815 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3816 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3817 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3819 *(sp + 3) = (png_byte)(png_ptr->background.green
3821 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3823 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3828 png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3829 *sp = (png_byte)((v >> 8) & 0xff);
3830 *(sp + 1) = (png_byte)(v & 0xff);
3832 v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
3833 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
3834 *(sp + 3) = (png_byte)(v & 0xff);
3836 v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
3837 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
3838 *(sp + 5) = (png_byte)(v & 0xff);
3847 for (i = 0; i < row_width; i++, sp += 6)
3849 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3851 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
3854 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
3857 if (r == png_ptr->trans_color.red &&
3858 g == png_ptr->trans_color.green &&
3859 b == png_ptr->trans_color.blue)
3861 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
3862 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
3863 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
3865 *(sp + 3) = (png_byte)(png_ptr->background.green
3867 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
3869 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
3877 case PNG_COLOR_TYPE_GRAY_ALPHA:
3879 if (row_info->bit_depth == 8)
3881 #ifdef PNG_READ_GAMMA_SUPPORTED
3882 if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
3883 gamma_table != NULL)
3886 for (i = 0; i < row_width; i++, sp += 2)
3888 png_uint_16 a = *(sp + 1);
3891 *sp = gamma_table[*sp];
3895 /* Background is already in screen gamma */
3896 *sp = (png_byte)png_ptr->background.gray;
3903 v = gamma_to_1[*sp];
3904 png_composite(w, v, a, png_ptr->background_1.gray);
3906 w = gamma_from_1[w];
3915 for (i = 0; i < row_width; i++, sp += 2)
3917 png_byte a = *(sp + 1);
3920 *sp = (png_byte)png_ptr->background.gray;
3923 png_composite(*sp, *sp, a, png_ptr->background.gray);
3927 else /* if (png_ptr->bit_depth == 16) */
3929 #ifdef PNG_READ_GAMMA_SUPPORTED
3930 if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
3931 gamma_16_to_1 != NULL)
3934 for (i = 0; i < row_width; i++, sp += 4)
3936 png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
3939 if (a == (png_uint_16)0xffff)
3943 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
3944 *sp = (png_byte)((v >> 8) & 0xff);
3945 *(sp + 1) = (png_byte)(v & 0xff);
3950 /* Background is already in screen gamma */
3951 *sp = (png_byte)((png_ptr->background.gray >> 8)
3953 *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
3958 png_uint_16 g, v, w;
3960 g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
3961 png_composite_16(v, g, a, png_ptr->background_1.gray);
3965 w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
3966 *sp = (png_byte)((w >> 8) & 0xff);
3967 *(sp + 1) = (png_byte)(w & 0xff);
3975 for (i = 0; i < row_width; i++, sp += 4)
3977 png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
3982 *sp = (png_byte)((png_ptr->background.gray >> 8)
3984 *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
3987 else if (a < 0xffff)
3991 g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
3992 png_composite_16(v, g, a, png_ptr->background.gray);
3993 *sp = (png_byte)((v >> 8) & 0xff);
3994 *(sp + 1) = (png_byte)(v & 0xff);
4002 case PNG_COLOR_TYPE_RGB_ALPHA:
4004 if (row_info->bit_depth == 8)
4006 #ifdef PNG_READ_GAMMA_SUPPORTED
4007 if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
4008 gamma_table != NULL)
4011 for (i = 0; i < row_width; i++, sp += 4)
4013 png_byte a = *(sp + 3);
4017 *sp = gamma_table[*sp];
4018 *(sp + 1) = gamma_table[*(sp + 1)];
4019 *(sp + 2) = gamma_table[*(sp + 2)];
4024 /* Background is already in screen gamma */
4025 *sp = (png_byte)png_ptr->background.red;
4026 *(sp + 1) = (png_byte)png_ptr->background.green;
4027 *(sp + 2) = (png_byte)png_ptr->background.blue;
4034 v = gamma_to_1[*sp];
4035 png_composite(w, v, a, png_ptr->background_1.red);
4036 if (!optimize) w = gamma_from_1[w];
4039 v = gamma_to_1[*(sp + 1)];
4040 png_composite(w, v, a, png_ptr->background_1.green);
4041 if (!optimize) w = gamma_from_1[w];
4044 v = gamma_to_1[*(sp + 2)];
4045 png_composite(w, v, a, png_ptr->background_1.blue);
4046 if (!optimize) w = gamma_from_1[w];
4055 for (i = 0; i < row_width; i++, sp += 4)
4057 png_byte a = *(sp + 3);
4061 *sp = (png_byte)png_ptr->background.red;
4062 *(sp + 1) = (png_byte)png_ptr->background.green;
4063 *(sp + 2) = (png_byte)png_ptr->background.blue;
4068 png_composite(*sp, *sp, a, png_ptr->background.red);
4070 png_composite(*(sp + 1), *(sp + 1), a,
4071 png_ptr->background.green);
4073 png_composite(*(sp + 2), *(sp + 2), a,
4074 png_ptr->background.blue);
4079 else /* if (row_info->bit_depth == 16) */
4081 #ifdef PNG_READ_GAMMA_SUPPORTED
4082 if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
4083 gamma_16_to_1 != NULL)
4086 for (i = 0; i < row_width; i++, sp += 8)
4088 png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
4089 << 8) + (png_uint_16)(*(sp + 7)));
4091 if (a == (png_uint_16)0xffff)
4095 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
4096 *sp = (png_byte)((v >> 8) & 0xff);
4097 *(sp + 1) = (png_byte)(v & 0xff);
4099 v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
4100 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
4101 *(sp + 3) = (png_byte)(v & 0xff);
4103 v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
4104 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
4105 *(sp + 5) = (png_byte)(v & 0xff);
4110 /* Background is already in screen gamma */
4111 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
4112 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
4113 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
4115 *(sp + 3) = (png_byte)(png_ptr->background.green
4117 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
4119 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
4126 v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
4127 png_composite_16(w, v, a, png_ptr->background_1.red);
4129 w = gamma_16_from_1[((w&0xff) >> gamma_shift)]
4131 *sp = (png_byte)((w >> 8) & 0xff);
4132 *(sp + 1) = (png_byte)(w & 0xff);
4134 v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
4135 png_composite_16(w, v, a, png_ptr->background_1.green);
4137 w = gamma_16_from_1[((w&0xff) >> gamma_shift)]
4140 *(sp + 2) = (png_byte)((w >> 8) & 0xff);
4141 *(sp + 3) = (png_byte)(w & 0xff);
4143 v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
4144 png_composite_16(w, v, a, png_ptr->background_1.blue);
4146 w = gamma_16_from_1[((w&0xff) >> gamma_shift)]
4149 *(sp + 4) = (png_byte)((w >> 8) & 0xff);
4150 *(sp + 5) = (png_byte)(w & 0xff);
4159 for (i = 0; i < row_width; i++, sp += 8)
4161 png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
4162 << 8) + (png_uint_16)(*(sp + 7)));
4166 *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
4167 *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
4168 *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
4170 *(sp + 3) = (png_byte)(png_ptr->background.green
4172 *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
4174 *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
4177 else if (a < 0xffff)
4181 png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
4182 png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
4184 png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
4187 png_composite_16(v, r, a, png_ptr->background.red);
4188 *sp = (png_byte)((v >> 8) & 0xff);
4189 *(sp + 1) = (png_byte)(v & 0xff);
4191 png_composite_16(v, g, a, png_ptr->background.green);
4192 *(sp + 2) = (png_byte)((v >> 8) & 0xff);
4193 *(sp + 3) = (png_byte)(v & 0xff);
4195 png_composite_16(v, b, a, png_ptr->background.blue);
4196 *(sp + 4) = (png_byte)((v >> 8) & 0xff);
4197 *(sp + 5) = (png_byte)(v & 0xff);
4210 #endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
4212 #ifdef PNG_READ_GAMMA_SUPPORTED
4213 /* Gamma correct the image, avoiding the alpha channel. Make sure
4214 * you do this after you deal with the transparency issue on grayscale
4215 * or RGB images. If your bit depth is 8, use gamma_table, if it
4216 * is 16, use gamma_16_table and gamma_shift. Build these with
4217 * build_gamma_table().
4220 png_do_gamma(png_row_infop row_info, png_bytep row, png_structp png_ptr)
4222 png_const_bytep gamma_table = png_ptr->gamma_table;
4223 png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
4224 int gamma_shift = png_ptr->gamma_shift;
4228 png_uint_32 row_width=row_info->width;
4230 png_debug(1, "in png_do_gamma");
4232 if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
4233 (row_info->bit_depth == 16 && gamma_16_table != NULL)))
4235 switch (row_info->color_type)
4237 case PNG_COLOR_TYPE_RGB:
4239 if (row_info->bit_depth == 8)
4242 for (i = 0; i < row_width; i++)
4244 *sp = gamma_table[*sp];
4246 *sp = gamma_table[*sp];
4248 *sp = gamma_table[*sp];
4253 else /* if (row_info->bit_depth == 16) */
4256 for (i = 0; i < row_width; i++)
4260 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4261 *sp = (png_byte)((v >> 8) & 0xff);
4262 *(sp + 1) = (png_byte)(v & 0xff);
4265 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4266 *sp = (png_byte)((v >> 8) & 0xff);
4267 *(sp + 1) = (png_byte)(v & 0xff);
4270 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4271 *sp = (png_byte)((v >> 8) & 0xff);
4272 *(sp + 1) = (png_byte)(v & 0xff);
4279 case PNG_COLOR_TYPE_RGB_ALPHA:
4281 if (row_info->bit_depth == 8)
4284 for (i = 0; i < row_width; i++)
4286 *sp = gamma_table[*sp];
4289 *sp = gamma_table[*sp];
4292 *sp = gamma_table[*sp];
4299 else /* if (row_info->bit_depth == 16) */
4302 for (i = 0; i < row_width; i++)
4304 png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4305 *sp = (png_byte)((v >> 8) & 0xff);
4306 *(sp + 1) = (png_byte)(v & 0xff);
4309 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4310 *sp = (png_byte)((v >> 8) & 0xff);
4311 *(sp + 1) = (png_byte)(v & 0xff);
4314 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4315 *sp = (png_byte)((v >> 8) & 0xff);
4316 *(sp + 1) = (png_byte)(v & 0xff);
4323 case PNG_COLOR_TYPE_GRAY_ALPHA:
4325 if (row_info->bit_depth == 8)
4328 for (i = 0; i < row_width; i++)
4330 *sp = gamma_table[*sp];
4335 else /* if (row_info->bit_depth == 16) */
4338 for (i = 0; i < row_width; i++)
4340 png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4341 *sp = (png_byte)((v >> 8) & 0xff);
4342 *(sp + 1) = (png_byte)(v & 0xff);
4349 case PNG_COLOR_TYPE_GRAY:
4351 if (row_info->bit_depth == 2)
4354 for (i = 0; i < row_width; i += 4)
4362 ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)]) ) & 0xc0)|
4363 ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
4364 ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
4365 ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
4370 if (row_info->bit_depth == 4)
4373 for (i = 0; i < row_width; i += 2)
4375 int msb = *sp & 0xf0;
4376 int lsb = *sp & 0x0f;
4378 *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
4379 | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
4384 else if (row_info->bit_depth == 8)
4387 for (i = 0; i < row_width; i++)
4389 *sp = gamma_table[*sp];
4394 else if (row_info->bit_depth == 16)
4397 for (i = 0; i < row_width; i++)
4399 png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
4400 *sp = (png_byte)((v >> 8) & 0xff);
4401 *(sp + 1) = (png_byte)(v & 0xff);
4415 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
4416 /* Encode the alpha channel to the output gamma (the input channel is always
4417 * linear.) Called only with color types that have an alpha channel. Needs the
4421 png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structp png_ptr)
4423 png_uint_32 row_width = row_info->width;
4425 png_debug(1, "in png_do_encode_alpha");
4427 if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
4429 if (row_info->bit_depth == 8)
4431 PNG_CONST png_bytep table = png_ptr->gamma_from_1;
4435 PNG_CONST int step =
4436 (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
4438 /* The alpha channel is the last component: */
4441 for (; row_width > 0; --row_width, row += step)
4448 else if (row_info->bit_depth == 16)
4450 PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
4451 PNG_CONST int gamma_shift = png_ptr->gamma_shift;
4455 PNG_CONST int step =
4456 (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
4458 /* The alpha channel is the last component: */
4461 for (; row_width > 0; --row_width, row += step)
4465 v = table[*(row + 1) >> gamma_shift][*row];
4466 *row = (png_byte)((v >> 8) & 0xff);
4467 *(row + 1) = (png_byte)(v & 0xff);
4475 /* Only get to here if called with a weird row_info; no harm has been done,
4476 * so just issue a warning.
4478 png_warning(png_ptr, "png_do_encode_alpha: unexpected call");
4482 #ifdef PNG_READ_EXPAND_SUPPORTED
4483 /* Expands a palette row to an RGB or RGBA row depending
4484 * upon whether you supply trans and num_trans.
4487 png_do_expand_palette(png_row_infop row_info, png_bytep row,
4488 png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
4493 png_uint_32 row_width=row_info->width;
4495 png_debug(1, "in png_do_expand_palette");
4497 if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
4499 if (row_info->bit_depth < 8)
4501 switch (row_info->bit_depth)
4505 sp = row + (png_size_t)((row_width - 1) >> 3);
4506 dp = row + (png_size_t)row_width - 1;
4507 shift = 7 - (int)((row_width + 7) & 0x07);
4508 for (i = 0; i < row_width; i++)
4510 if ((*sp >> shift) & 0x01)
4532 sp = row + (png_size_t)((row_width - 1) >> 2);
4533 dp = row + (png_size_t)row_width - 1;
4534 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
4535 for (i = 0; i < row_width; i++)
4537 value = (*sp >> shift) & 0x03;
4538 *dp = (png_byte)value;
4555 sp = row + (png_size_t)((row_width - 1) >> 1);
4556 dp = row + (png_size_t)row_width - 1;
4557 shift = (int)((row_width & 0x01) << 2);
4558 for (i = 0; i < row_width; i++)
4560 value = (*sp >> shift) & 0x0f;
4561 *dp = (png_byte)value;
4579 row_info->bit_depth = 8;
4580 row_info->pixel_depth = 8;
4581 row_info->rowbytes = row_width;
4584 if (row_info->bit_depth == 8)
4589 sp = row + (png_size_t)row_width - 1;
4590 dp = row + (png_size_t)(row_width << 2) - 1;
4592 for (i = 0; i < row_width; i++)
4594 if ((int)(*sp) >= num_trans)
4598 *dp-- = trans_alpha[*sp];
4600 *dp-- = palette[*sp].blue;
4601 *dp-- = palette[*sp].green;
4602 *dp-- = palette[*sp].red;
4605 row_info->bit_depth = 8;
4606 row_info->pixel_depth = 32;
4607 row_info->rowbytes = row_width * 4;
4608 row_info->color_type = 6;
4609 row_info->channels = 4;
4614 sp = row + (png_size_t)row_width - 1;
4615 dp = row + (png_size_t)(row_width * 3) - 1;
4617 for (i = 0; i < row_width; i++)
4619 *dp-- = palette[*sp].blue;
4620 *dp-- = palette[*sp].green;
4621 *dp-- = palette[*sp].red;
4625 row_info->bit_depth = 8;
4626 row_info->pixel_depth = 24;
4627 row_info->rowbytes = row_width * 3;
4628 row_info->color_type = 2;
4629 row_info->channels = 3;
4636 /* If the bit depth < 8, it is expanded to 8. Also, if the already
4637 * expanded transparency value is supplied, an alpha channel is built.
4640 png_do_expand(png_row_infop row_info, png_bytep row,
4641 png_const_color_16p trans_color)
4646 png_uint_32 row_width=row_info->width;
4648 png_debug(1, "in png_do_expand");
4651 if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
4653 png_uint_16 gray = (png_uint_16)(trans_color ? trans_color->gray : 0);
4655 if (row_info->bit_depth < 8)
4657 switch (row_info->bit_depth)
4661 gray = (png_uint_16)((gray & 0x01) * 0xff);
4662 sp = row + (png_size_t)((row_width - 1) >> 3);
4663 dp = row + (png_size_t)row_width - 1;
4664 shift = 7 - (int)((row_width + 7) & 0x07);
4665 for (i = 0; i < row_width; i++)
4667 if ((*sp >> shift) & 0x01)
4689 gray = (png_uint_16)((gray & 0x03) * 0x55);
4690 sp = row + (png_size_t)((row_width - 1) >> 2);
4691 dp = row + (png_size_t)row_width - 1;
4692 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
4693 for (i = 0; i < row_width; i++)
4695 value = (*sp >> shift) & 0x03;
4696 *dp = (png_byte)(value | (value << 2) | (value << 4) |
4714 gray = (png_uint_16)((gray & 0x0f) * 0x11);
4715 sp = row + (png_size_t)((row_width - 1) >> 1);
4716 dp = row + (png_size_t)row_width - 1;
4717 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
4718 for (i = 0; i < row_width; i++)
4720 value = (*sp >> shift) & 0x0f;
4721 *dp = (png_byte)(value | (value << 4));
4740 row_info->bit_depth = 8;
4741 row_info->pixel_depth = 8;
4742 row_info->rowbytes = row_width;
4745 if (trans_color != NULL)
4747 if (row_info->bit_depth == 8)
4749 /* NOTE: prior to libpng 1.5.14 this cleared out the top bits of
4750 * 'gray', however if those are set it is an error.
4752 sp = row + (png_size_t)row_width - 1;
4753 dp = row + (png_size_t)(row_width << 1) - 1;
4755 for (i = 0; i < row_width; i++)
4767 else if (row_info->bit_depth == 16)
4769 png_byte gray_high = (png_byte)((gray >> 8) & 0xff);
4770 png_byte gray_low = (png_byte)(gray & 0xff);
4771 sp = row + row_info->rowbytes - 1;
4772 dp = row + (row_info->rowbytes << 1) - 1;
4773 for (i = 0; i < row_width; i++)
4775 if (*(sp - 1) == gray_high && *(sp) == gray_low)
4792 row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
4793 row_info->channels = 2;
4794 row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
4795 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
4799 else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
4801 if (row_info->bit_depth == 8)
4803 png_byte red = (png_byte)(trans_color->red & 0xff);
4804 png_byte green = (png_byte)(trans_color->green & 0xff);
4805 png_byte blue = (png_byte)(trans_color->blue & 0xff);
4806 sp = row + (png_size_t)row_info->rowbytes - 1;
4807 dp = row + (png_size_t)(row_width << 2) - 1;
4808 for (i = 0; i < row_width; i++)
4810 if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
4821 else if (row_info->bit_depth == 16)
4823 png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
4824 png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
4825 png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
4826 png_byte red_low = (png_byte)(trans_color->red & 0xff);
4827 png_byte green_low = (png_byte)(trans_color->green & 0xff);
4828 png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
4829 sp = row + row_info->rowbytes - 1;
4830 dp = row + (png_size_t)(row_width << 3) - 1;
4831 for (i = 0; i < row_width; i++)
4833 if (*(sp - 5) == red_high &&
4834 *(sp - 4) == red_low &&
4835 *(sp - 3) == green_high &&
4836 *(sp - 2) == green_low &&
4837 *(sp - 1) == blue_high &&
4858 row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
4859 row_info->channels = 4;
4860 row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
4861 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
4867 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4868 /* If the bit depth is 8 and the color type is not a palette type expand the
4869 * whole row to 16 bits. Has no effect otherwise.
4872 png_do_expand_16(png_row_infop row_info, png_bytep row)
4874 if (row_info->bit_depth == 8 &&
4875 row_info->color_type != PNG_COLOR_TYPE_PALETTE)
4877 /* The row have a sequence of bytes containing [0..255] and we need
4878 * to turn it into another row containing [0..65535], to do this we
4881 * (input / 255) * 65535
4883 * Which happens to be exactly input * 257 and this can be achieved
4884 * simply by byte replication in place (copying backwards).
4886 png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
4887 png_byte *dp = sp + row_info->rowbytes; /* destination, end + 1 */
4889 dp[-2] = dp[-1] = *--sp, dp -= 2;
4891 row_info->rowbytes *= 2;
4892 row_info->bit_depth = 16;
4893 row_info->pixel_depth = (png_byte)(row_info->channels * 16);
4898 #ifdef PNG_READ_QUANTIZE_SUPPORTED
4900 png_do_quantize(png_row_infop row_info, png_bytep row,
4901 png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
4905 png_uint_32 row_width=row_info->width;
4907 png_debug(1, "in png_do_quantize");
4909 if (row_info->bit_depth == 8)
4911 if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
4916 for (i = 0; i < row_width; i++)
4922 /* This looks real messy, but the compiler will reduce
4923 * it down to a reasonable formula. For example, with
4924 * 5 bits per color, we get:
4925 * p = (((r >> 3) & 0x1f) << 10) |
4926 * (((g >> 3) & 0x1f) << 5) |
4927 * ((b >> 3) & 0x1f);
4929 p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
4930 ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
4931 (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
4932 (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
4933 ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
4934 (PNG_QUANTIZE_BLUE_BITS)) |
4935 ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
4936 ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
4938 *dp++ = palette_lookup[p];
4941 row_info->color_type = PNG_COLOR_TYPE_PALETTE;
4942 row_info->channels = 1;
4943 row_info->pixel_depth = row_info->bit_depth;
4944 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
4947 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
4948 palette_lookup != NULL)
4953 for (i = 0; i < row_width; i++)
4960 p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
4961 ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
4962 (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
4963 (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
4964 ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
4965 (PNG_QUANTIZE_BLUE_BITS)) |
4966 ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
4967 ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
4969 *dp++ = palette_lookup[p];
4972 row_info->color_type = PNG_COLOR_TYPE_PALETTE;
4973 row_info->channels = 1;
4974 row_info->pixel_depth = row_info->bit_depth;
4975 row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
4978 else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
4983 for (i = 0; i < row_width; i++, sp++)
4985 *sp = quantize_lookup[*sp];
4990 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
4991 #endif /* PNG_READ_TRANSFORMS_SUPPORTED */
4993 #ifdef PNG_MNG_FEATURES_SUPPORTED
4994 /* Undoes intrapixel differencing */
4996 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
4998 png_debug(1, "in png_do_read_intrapixel");
5001 (row_info->color_type & PNG_COLOR_MASK_COLOR))
5003 int bytes_per_pixel;
5004 png_uint_32 row_width = row_info->width;
5006 if (row_info->bit_depth == 8)
5011 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
5012 bytes_per_pixel = 3;
5014 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
5015 bytes_per_pixel = 4;
5020 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
5022 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
5023 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
5026 else if (row_info->bit_depth == 16)
5031 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
5032 bytes_per_pixel = 6;
5034 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
5035 bytes_per_pixel = 8;
5040 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
5042 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
5043 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
5044 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
5045 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
5046 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
5047 *(rp ) = (png_byte)((red >> 8) & 0xff);
5048 *(rp + 1) = (png_byte)(red & 0xff);
5049 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
5050 *(rp + 5) = (png_byte)(blue & 0xff);
5055 #endif /* PNG_MNG_FEATURES_SUPPORTED */
5056 #endif /* PNG_READ_SUPPORTED */