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/* pngrtran.c - transforms the data in a row for PNG readers
*
* Last changed in libpng 1.5.11 [June 14, 2012]
* Copyright (c) 1998-2012 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* This file contains functions optionally called by an application
* in order to tell libpng how to handle data when reading a PNG.
* Transformations that are used in both reading and writing are
* in pngtrans.c.
*/
#include "pngpriv.h"
#ifdef PNG_READ_SUPPORTED
/* Set the action on getting a CRC error for an ancillary or critical chunk. */
void PNGAPI
png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
{
png_debug(1, "in png_set_crc_action");
if (png_ptr == NULL)
return;
/* Tell libpng how we react to CRC errors in critical chunks */
switch (crit_action)
{
case PNG_CRC_NO_CHANGE: /* Leave setting as is */
break;
case PNG_CRC_WARN_USE: /* Warn/use data */
png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
break;
case PNG_CRC_QUIET_USE: /* Quiet/use data */
png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
PNG_FLAG_CRC_CRITICAL_IGNORE;
break;
case PNG_CRC_WARN_DISCARD: /* Not a valid action for critical data */
png_warning(png_ptr,
"Can't discard critical data on CRC error");
case PNG_CRC_ERROR_QUIT: /* Error/quit */
case PNG_CRC_DEFAULT:
default:
png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
break;
}
/* Tell libpng how we react to CRC errors in ancillary chunks */
switch (ancil_action)
{
case PNG_CRC_NO_CHANGE: /* Leave setting as is */
break;
case PNG_CRC_WARN_USE: /* Warn/use data */
png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
break;
case PNG_CRC_QUIET_USE: /* Quiet/use data */
png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
PNG_FLAG_CRC_ANCILLARY_NOWARN;
break;
case PNG_CRC_ERROR_QUIT: /* Error/quit */
png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
break;
case PNG_CRC_WARN_DISCARD: /* Warn/discard data */
case PNG_CRC_DEFAULT:
default:
png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
break;
}
}
#ifdef PNG_READ_BACKGROUND_SUPPORTED
/* Handle alpha and tRNS via a background color */
void PNGFAPI
png_set_background_fixed(png_structp png_ptr,
png_const_color_16p background_color, int background_gamma_code,
int need_expand, png_fixed_point background_gamma)
{
png_debug(1, "in png_set_background_fixed");
if (png_ptr == NULL)
return;
if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
{
png_warning(png_ptr, "Application must supply a known background gamma");
return;
}
png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
png_memcpy(&(png_ptr->background), background_color,
png_sizeof(png_color_16));
png_ptr->background_gamma = background_gamma;
png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
if (need_expand)
png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
else
png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
}
# ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_background(png_structp png_ptr,
png_const_color_16p background_color, int background_gamma_code,
int need_expand, double background_gamma)
{
png_set_background_fixed(png_ptr, background_color, background_gamma_code,
need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
}
# endif /* FLOATING_POINT */
#endif /* READ_BACKGROUND */
/* Scale 16-bit depth files to 8-bit depth. If both of these are set then the
* one that pngrtran does first (scale) happens. This is necessary to allow the
* TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
*/
#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
void PNGAPI
png_set_scale_16(png_structp png_ptr)
{
png_debug(1, "in png_set_scale_16");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_SCALE_16_TO_8;
}
#endif
#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
/* Chop 16-bit depth files to 8-bit depth */
void PNGAPI
png_set_strip_16(png_structp png_ptr)
{
png_debug(1, "in png_set_strip_16");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_16_TO_8;
}
#endif
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
void PNGAPI
png_set_strip_alpha(png_structp png_ptr)
{
png_debug(1, "in png_set_strip_alpha");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_STRIP_ALPHA;
}
#endif
#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
static png_fixed_point
translate_gamma_flags(png_structp png_ptr, png_fixed_point output_gamma,
int is_screen)
{
/* Check for flag values. The main reason for having the old Mac value as a
* flag is that it is pretty near impossible to work out what the correct
* value is from Apple documentation - a working Mac system is needed to
* discover the value!
*/
if (output_gamma == PNG_DEFAULT_sRGB ||
output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
{
/* If there is no sRGB support this just sets the gamma to the standard
* sRGB value. (This is a side effect of using this function!)
*/
# ifdef PNG_READ_sRGB_SUPPORTED
png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
# endif
if (is_screen)
output_gamma = PNG_GAMMA_sRGB;
else
output_gamma = PNG_GAMMA_sRGB_INVERSE;
}
else if (output_gamma == PNG_GAMMA_MAC_18 ||
output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
{
if (is_screen)
output_gamma = PNG_GAMMA_MAC_OLD;
else
output_gamma = PNG_GAMMA_MAC_INVERSE;
}
return output_gamma;
}
# ifdef PNG_FLOATING_POINT_SUPPORTED
static png_fixed_point
convert_gamma_value(png_structp png_ptr, double output_gamma)
{
/* The following silently ignores cases where fixed point (times 100,000)
* gamma values are passed to the floating point API. This is safe and it
* means the fixed point constants work just fine with the floating point
* API. The alternative would just lead to undetected errors and spurious
* bug reports. Negative values fail inside the _fixed API unless they
* correspond to the flag values.
*/
if (output_gamma > 0 && output_gamma < 128)
output_gamma *= PNG_FP_1;
/* This preserves -1 and -2 exactly: */
output_gamma = floor(output_gamma + .5);
if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
png_fixed_error(png_ptr, "gamma value");
return (png_fixed_point)output_gamma;
}
# endif
#endif /* READ_ALPHA_MODE || READ_GAMMA */
#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
void PNGFAPI
png_set_alpha_mode_fixed(png_structp png_ptr, int mode,
png_fixed_point output_gamma)
{
int compose = 0;
png_fixed_point file_gamma;
png_debug(1, "in png_set_alpha_mode");
if (png_ptr == NULL)
return;
output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
/* Validate the value to ensure it is in a reasonable range. The value
* is expected to be 1 or greater, but this range test allows for some
* viewing correction values. The intent is to weed out users of this API
* who use the inverse of the gamma value accidentally! Since some of these
* values are reasonable this may have to be changed.
*/
if (output_gamma < 70000 || output_gamma > 300000)
png_error(png_ptr, "output gamma out of expected range");
/* The default file gamma is the inverse of the output gamma; the output
* gamma may be changed below so get the file value first:
*/
file_gamma = png_reciprocal(output_gamma);
/* There are really 8 possibilities here, composed of any combination
* of:
*
* premultiply the color channels
* do not encode non-opaque pixels
* encode the alpha as well as the color channels
*
* The differences disappear if the input/output ('screen') gamma is 1.0,
* because then the encoding is a no-op and there is only the choice of
* premultiplying the color channels or not.
*
* png_set_alpha_mode and png_set_background interact because both use
* png_compose to do the work. Calling both is only useful when
* png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
* with a default gamma value. Otherwise PNG_COMPOSE must not be set.
*/
switch (mode)
{
case PNG_ALPHA_PNG: /* default: png standard */
/* No compose, but it may be set by png_set_background! */
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
break;
case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
compose = 1;
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
/* The output is linear: */
output_gamma = PNG_FP_1;
break;
case PNG_ALPHA_OPTIMIZED: /* associated, non-opaque pixels linear */
compose = 1;
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
/* output_gamma records the encoding of opaque pixels! */
break;
case PNG_ALPHA_BROKEN: /* associated, non-linear, alpha encoded */
compose = 1;
png_ptr->transformations |= PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
break;
default:
png_error(png_ptr, "invalid alpha mode");
}
/* Only set the default gamma if the file gamma has not been set (this has
* the side effect that the gamma in a second call to png_set_alpha_mode will
* be ignored.)
*/
if (png_ptr->gamma == 0)
png_ptr->gamma = file_gamma;
/* But always set the output gamma: */
png_ptr->screen_gamma = output_gamma;
/* Finally, if pre-multiplying, set the background fields to achieve the
* desired result.
*/
if (compose)
{
/* And obtain alpha pre-multiplication by composing on black: */
png_memset(&png_ptr->background, 0, sizeof png_ptr->background);
png_ptr->background_gamma = png_ptr->gamma; /* just in case */
png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
if (png_ptr->transformations & PNG_COMPOSE)
png_error(png_ptr,
"conflicting calls to set alpha mode and background");
png_ptr->transformations |= PNG_COMPOSE;
}
/* New API, make sure apps call the correct initializers: */
png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
}
# ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_alpha_mode(png_structp png_ptr, int mode, double output_gamma)
{
png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
output_gamma));
}
# endif
#endif
#ifdef PNG_READ_QUANTIZE_SUPPORTED
/* Dither file to 8-bit. Supply a palette, the current number
* of elements in the palette, the maximum number of elements
* allowed, and a histogram if possible. If the current number
* of colors is greater then the maximum number, the palette will be
* modified to fit in the maximum number. "full_quantize" indicates
* whether we need a quantizing cube set up for RGB images, or if we
* simply are reducing the number of colors in a paletted image.
*/
typedef struct png_dsort_struct
{
struct png_dsort_struct FAR * next;
png_byte left;
png_byte right;
} png_dsort;
typedef png_dsort FAR * png_dsortp;
typedef png_dsort FAR * FAR * png_dsortpp;
void PNGAPI
png_set_quantize(png_structp png_ptr, png_colorp palette,
int num_palette, int maximum_colors, png_const_uint_16p histogram,
int full_quantize)
{
png_debug(1, "in png_set_quantize");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_QUANTIZE;
if (!full_quantize)
{
int i;
png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
(png_uint_32)(num_palette * png_sizeof(png_byte)));
for (i = 0; i < num_palette; i++)
png_ptr->quantize_index[i] = (png_byte)i;
}
if (num_palette > maximum_colors)
{
if (histogram != NULL)
{
/* This is easy enough, just throw out the least used colors.
* Perhaps not the best solution, but good enough.
*/
int i;
/* Initialize an array to sort colors */
png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
(png_uint_32)(num_palette * png_sizeof(png_byte)));
/* Initialize the quantize_sort array */
for (i = 0; i < num_palette; i++)
png_ptr->quantize_sort[i] = (png_byte)i;
/* Find the least used palette entries by starting a
* bubble sort, and running it until we have sorted
* out enough colors. Note that we don't care about
* sorting all the colors, just finding which are
* least used.
*/
for (i = num_palette - 1; i >= maximum_colors; i--)
{
int done; /* To stop early if the list is pre-sorted */
int j;
done = 1;
for (j = 0; j < i; j++)
{
if (histogram[png_ptr->quantize_sort[j]]
< histogram[png_ptr->quantize_sort[j + 1]])
{
png_byte t;
t = png_ptr->quantize_sort[j];
png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
png_ptr->quantize_sort[j + 1] = t;
done = 0;
}
}
if (done)
break;
}
/* Swap the palette around, and set up a table, if necessary */
if (full_quantize)
{
int j = num_palette;
/* Put all the useful colors within the max, but don't
* move the others.
*/
for (i = 0; i < maximum_colors; i++)
{
if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
{
do
j--;
while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
palette[i] = palette[j];
}
}
}
else
{
int j = num_palette;
/* Move all the used colors inside the max limit, and
* develop a translation table.
*/
for (i = 0; i < maximum_colors; i++)
{
/* Only move the colors we need to */
if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
{
png_color tmp_color;
do
j--;
while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
tmp_color = palette[j];
palette[j] = palette[i];
palette[i] = tmp_color;
/* Indicate where the color went */
png_ptr->quantize_index[j] = (png_byte)i;
png_ptr->quantize_index[i] = (png_byte)j;
}
}
/* Find closest color for those colors we are not using */
for (i = 0; i < num_palette; i++)
{
if ((int)png_ptr->quantize_index[i] >= maximum_colors)
{
int min_d, k, min_k, d_index;
/* Find the closest color to one we threw out */
d_index = png_ptr->quantize_index[i];
min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
for (k = 1, min_k = 0; k < maximum_colors; k++)
{
int d;
d = PNG_COLOR_DIST(palette[d_index], palette[k]);
if (d < min_d)
{
min_d = d;
min_k = k;
}
}
/* Point to closest color */
png_ptr->quantize_index[i] = (png_byte)min_k;
}
}
}
png_free(png_ptr, png_ptr->quantize_sort);
png_ptr->quantize_sort = NULL;
}
else
{
/* This is much harder to do simply (and quickly). Perhaps
* we need to go through a median cut routine, but those
* don't always behave themselves with only a few colors
* as input. So we will just find the closest two colors,
* and throw out one of them (chosen somewhat randomly).
* [We don't understand this at all, so if someone wants to
* work on improving it, be our guest - AED, GRP]
*/
int i;
int max_d;
int num_new_palette;
png_dsortp t;
png_dsortpp hash;
t = NULL;
/* Initialize palette index arrays */
png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
(png_uint_32)(num_palette * png_sizeof(png_byte)));
png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
(png_uint_32)(num_palette * png_sizeof(png_byte)));
/* Initialize the sort array */
for (i = 0; i < num_palette; i++)
{
png_ptr->index_to_palette[i] = (png_byte)i;
png_ptr->palette_to_index[i] = (png_byte)i;
}
hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
png_sizeof(png_dsortp)));
num_new_palette = num_palette;
/* Initial wild guess at how far apart the farthest pixel
* pair we will be eliminating will be. Larger
* numbers mean more areas will be allocated, Smaller
* numbers run the risk of not saving enough data, and
* having to do this all over again.
*
* I have not done extensive checking on this number.
*/
max_d = 96;
while (num_new_palette > maximum_colors)
{
for (i = 0; i < num_new_palette - 1; i++)
{
int j;
for (j = i + 1; j < num_new_palette; j++)
{
int d;
d = PNG_COLOR_DIST(palette[i], palette[j]);
if (d <= max_d)
{
t = (png_dsortp)png_malloc_warn(png_ptr,
(png_uint_32)(png_sizeof(png_dsort)));
if (t == NULL)
break;
t->next = hash[d];
t->left = (png_byte)i;
t->right = (png_byte)j;
hash[d] = t;
}
}
if (t == NULL)
break;
}
if (t != NULL)
for (i = 0; i <= max_d; i++)
{
if (hash[i] != NULL)
{
png_dsortp p;
for (p = hash[i]; p; p = p->next)
{
if ((int)png_ptr->index_to_palette[p->left]
< num_new_palette &&
(int)png_ptr->index_to_palette[p->right]
< num_new_palette)
{
int j, next_j;
if (num_new_palette & 0x01)
{
j = p->left;
next_j = p->right;
}
else
{
j = p->right;
next_j = p->left;
}
num_new_palette--;
palette[png_ptr->index_to_palette[j]]
= palette[num_new_palette];
if (!full_quantize)
{
int k;
for (k = 0; k < num_palette; k++)
{
if (png_ptr->quantize_index[k] ==
png_ptr->index_to_palette[j])
png_ptr->quantize_index[k] =
png_ptr->index_to_palette[next_j];
if ((int)png_ptr->quantize_index[k] ==
num_new_palette)
png_ptr->quantize_index[k] =
png_ptr->index_to_palette[j];
}
}
png_ptr->index_to_palette[png_ptr->palette_to_index
[num_new_palette]] = png_ptr->index_to_palette[j];
png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
= png_ptr->palette_to_index[num_new_palette];
png_ptr->index_to_palette[j] =
(png_byte)num_new_palette;
png_ptr->palette_to_index[num_new_palette] =
(png_byte)j;
}
if (num_new_palette <= maximum_colors)
break;
}
if (num_new_palette <= maximum_colors)
break;
}
}
for (i = 0; i < 769; i++)
{
if (hash[i] != NULL)
{
png_dsortp p = hash[i];
while (p)
{
t = p->next;
png_free(png_ptr, p);
p = t;
}
}
hash[i] = 0;
}
max_d += 96;
}
png_free(png_ptr, hash);
png_free(png_ptr, png_ptr->palette_to_index);
png_free(png_ptr, png_ptr->index_to_palette);
png_ptr->palette_to_index = NULL;
png_ptr->index_to_palette = NULL;
}
num_palette = maximum_colors;
}
if (png_ptr->palette == NULL)
{
png_ptr->palette = palette;
}
png_ptr->num_palette = (png_uint_16)num_palette;
if (full_quantize)
{
int i;
png_bytep distance;
int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
PNG_QUANTIZE_BLUE_BITS;
int num_red = (1 << PNG_QUANTIZE_RED_BITS);
int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
png_size_t num_entries = ((png_size_t)1 << total_bits);
png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
(png_uint_32)(num_entries * png_sizeof(png_byte)));
distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
png_sizeof(png_byte)));
png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
for (i = 0; i < num_palette; i++)
{
int ir, ig, ib;
int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
for (ir = 0; ir < num_red; ir++)
{
/* int dr = abs(ir - r); */
int dr = ((ir > r) ? ir - r : r - ir);
int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
PNG_QUANTIZE_GREEN_BITS));
for (ig = 0; ig < num_green; ig++)
{
/* int dg = abs(ig - g); */
int dg = ((ig > g) ? ig - g : g - ig);
int dt = dr + dg;
int dm = ((dr > dg) ? dr : dg);
int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
for (ib = 0; ib < num_blue; ib++)
{
int d_index = index_g | ib;
/* int db = abs(ib - b); */
int db = ((ib > b) ? ib - b : b - ib);
int dmax = ((dm > db) ? dm : db);
int d = dmax + dt + db;
if (d < (int)distance[d_index])
{
distance[d_index] = (png_byte)d;
png_ptr->palette_lookup[d_index] = (png_byte)i;
}
}
}
}
}
png_free(png_ptr, distance);
}
}
#endif /* PNG_READ_QUANTIZE_SUPPORTED */
#ifdef PNG_READ_GAMMA_SUPPORTED
void PNGFAPI
png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,
png_fixed_point file_gamma)
{
png_debug(1, "in png_set_gamma_fixed");
if (png_ptr == NULL)
return;
/* New in libpng-1.5.4 - reserve particular negative values as flags. */
scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
#if PNG_LIBPNG_VER >= 10600
/* Checking the gamma values for being >0 was added in 1.5.4 along with the
* premultiplied alpha support; this actually hides an undocumented feature
* of the previous implementation which allowed gamma processing to be
* disabled in background handling. There is no evidence (so far) that this
* was being used; however, png_set_background itself accepted and must still
* accept '0' for the gamma value it takes, because it isn't always used.
*
* Since this is an API change (albeit a very minor one that removes an
* undocumented API feature) it will not be made until libpng-1.6.0.
*/
if (file_gamma <= 0)
png_error(png_ptr, "invalid file gamma in png_set_gamma");
if (scrn_gamma <= 0)
png_error(png_ptr, "invalid screen gamma in png_set_gamma");
#endif
/* Set the gamma values unconditionally - this overrides the value in the PNG
* file if a gAMA chunk was present. png_set_alpha_mode provides a
* different, easier, way to default the file gamma.
*/
png_ptr->gamma = file_gamma;
png_ptr->screen_gamma = scrn_gamma;
}
# ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
{
png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
convert_gamma_value(png_ptr, file_gamma));
}
# endif /* FLOATING_POINT_SUPPORTED */
#endif /* READ_GAMMA */
#ifdef PNG_READ_EXPAND_SUPPORTED
/* Expand paletted images to RGB, expand grayscale images of
* less than 8-bit depth to 8-bit depth, and expand tRNS chunks
* to alpha channels.
*/
void PNGAPI
png_set_expand(png_structp png_ptr)
{
png_debug(1, "in png_set_expand");
if (png_ptr == NULL)
return;
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
/* GRR 19990627: the following three functions currently are identical
* to png_set_expand(). However, it is entirely reasonable that someone
* might wish to expand an indexed image to RGB but *not* expand a single,
* fully transparent palette entry to a full alpha channel--perhaps instead
* convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
* the transparent color with a particular RGB value, or drop tRNS entirely.
* IOW, a future version of the library may make the transformations flag
* a bit more fine-grained, with separate bits for each of these three
* functions.
*
* More to the point, these functions make it obvious what libpng will be
* doing, whereas "expand" can (and does) mean any number of things.
*
* GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
* to expand only the sample depth but not to expand the tRNS to alpha
* and its name was changed to png_set_expand_gray_1_2_4_to_8().
*/
/* Expand paletted images to RGB. */
void PNGAPI
png_set_palette_to_rgb(png_structp png_ptr)
{
png_debug(1, "in png_set_palette_to_rgb");
if (png_ptr == NULL)
return;
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
/* Expand grayscale images of less than 8-bit depth to 8 bits. */
void PNGAPI
png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
{
png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_EXPAND;
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
/* Expand tRNS chunks to alpha channels. */
void PNGAPI
png_set_tRNS_to_alpha(png_structp png_ptr)
{
png_debug(1, "in png_set_tRNS_to_alpha");
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
#ifdef PNG_READ_EXPAND_16_SUPPORTED
/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
* it may not work correctly.)
*/
void PNGAPI
png_set_expand_16(png_structp png_ptr)
{
png_debug(1, "in png_set_expand_16");
if (png_ptr == NULL)
return;
png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
/* New API, make sure apps call the correct initializers: */
png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
}
#endif
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
void PNGAPI
png_set_gray_to_rgb(png_structp png_ptr)
{
png_debug(1, "in png_set_gray_to_rgb");
if (png_ptr != NULL)
{
/* Because rgb must be 8 bits or more: */
png_set_expand_gray_1_2_4_to_8(png_ptr);
png_ptr->transformations |= PNG_GRAY_TO_RGB;
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
}
#endif
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
void PNGFAPI
png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
png_fixed_point red, png_fixed_point green)
{
png_debug(1, "in png_set_rgb_to_gray");
if (png_ptr == NULL)
return;
switch(error_action)
{
case PNG_ERROR_ACTION_NONE:
png_ptr->transformations |= PNG_RGB_TO_GRAY;
break;
case PNG_ERROR_ACTION_WARN:
png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
break;
case PNG_ERROR_ACTION_ERROR:
png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
break;
default:
png_error(png_ptr, "invalid error action to rgb_to_gray");
break;
}
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
#ifdef PNG_READ_EXPAND_SUPPORTED
png_ptr->transformations |= PNG_EXPAND;
#else
{
png_warning(png_ptr,
"Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
}
#endif
{
if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
{
png_uint_16 red_int, green_int;
/* NOTE: this calculation does not round, but this behavior is retained
* for consistency, the inaccuracy is very small. The code here always
* overwrites the coefficients, regardless of whether they have been
* defaulted or set already.
*/
red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
png_ptr->rgb_to_gray_red_coeff = red_int;
png_ptr->rgb_to_gray_green_coeff = green_int;
png_ptr->rgb_to_gray_coefficients_set = 1;
}
else
{
if (red >= 0 && green >= 0)
png_warning(png_ptr,
"ignoring out of range rgb_to_gray coefficients");
/* Use the defaults, from the cHRM chunk if set, else the historical
* values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
* png_do_rgb_to_gray for more discussion of the values. In this case
* the coefficients are not marked as 'set' and are not overwritten if
* something has already provided a default.
*/
if (png_ptr->rgb_to_gray_red_coeff == 0 &&
png_ptr->rgb_to_gray_green_coeff == 0)
{
png_ptr->rgb_to_gray_red_coeff = 6968;
png_ptr->rgb_to_gray_green_coeff = 23434;
/* png_ptr->rgb_to_gray_blue_coeff = 2366; */
}
}
}
}
#ifdef PNG_FLOATING_POINT_SUPPORTED
/* Convert a RGB image to a grayscale of the same width. This allows us,
* for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
*/
void PNGAPI
png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
double green)
{
if (png_ptr == NULL)
return;
png_set_rgb_to_gray_fixed(png_ptr, error_action,
png_fixed(png_ptr, red, "rgb to gray red coefficient"),
png_fixed(png_ptr, green, "rgb to gray green coefficient"));
}
#endif /* FLOATING POINT */
#endif
#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
void PNGAPI
png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
read_user_transform_fn)
{
png_debug(1, "in png_set_read_user_transform_fn");
if (png_ptr == NULL)
return;
#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
png_ptr->transformations |= PNG_USER_TRANSFORM;
png_ptr->read_user_transform_fn = read_user_transform_fn;
#endif
}
#endif
#ifdef PNG_READ_TRANSFORMS_SUPPORTED
#ifdef PNG_READ_GAMMA_SUPPORTED
/* In the case of gamma transformations only do transformations on images where
* the [file] gamma and screen_gamma are not close reciprocals, otherwise it
* slows things down slightly, and also needlessly introduces small errors.
*/
static int /* PRIVATE */
png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
{
/* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
* correction as a difference of the overall transform from 1.0
*
* We want to compare the threshold with s*f - 1, if we get
* overflow here it is because of wacky gamma values so we
* turn on processing anyway.
*/
png_fixed_point gtest;
return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
png_gamma_significant(gtest);
}
#endif
/* Initialize everything needed for the read. This includes modifying
* the palette.
*/
/*For the moment 'png_init_palette_transformations' and
* 'png_init_rgb_transformations' only do some flag canceling optimizations.
* The intent is that these two routines should have palette or rgb operations
* extracted from 'png_init_read_transformations'.
*/
static void /* PRIVATE */
png_init_palette_transformations(png_structp png_ptr)
{
/* Called to handle the (input) palette case. In png_do_read_transformations
* the first step is to expand the palette if requested, so this code must
* take care to only make changes that are invariant with respect to the
* palette expansion, or only do them if there is no expansion.
*
* STRIP_ALPHA has already been handled in the caller (by setting num_trans
* to 0.)
*/
int input_has_alpha = 0;
int input_has_transparency = 0;
if (png_ptr->num_trans > 0)
{
int i;
/* Ignore if all the entries are opaque (unlikely!) */
for (i=0; i<png_ptr->num_trans; ++i)
if (png_ptr->trans_alpha[i] == 255)
continue;
else if (png_ptr->trans_alpha[i] == 0)
input_has_transparency = 1;
else
input_has_alpha = 1;
}
/* If no alpha we can optimize. */
if (!input_has_alpha)
{
/* Any alpha means background and associative alpha processing is
* required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
* and ENCODE_ALPHA are irrelevant.
*/
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
if (!input_has_transparency)
png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
}
#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
/* png_set_background handling - deals with the complexity of whether the
* background color is in the file format or the screen format in the case
* where an 'expand' will happen.
*/
/* The following code cannot be entered in the alpha pre-multiplication case
* because PNG_BACKGROUND_EXPAND is cancelled below.
*/
if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
(png_ptr->transformations & PNG_EXPAND))
{
{
png_ptr->background.red =
png_ptr->palette[png_ptr->background.index].red;
png_ptr->background.green =
png_ptr->palette[png_ptr->background.index].green;
png_ptr->background.blue =
png_ptr->palette[png_ptr->background.index].blue;
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
if (png_ptr->transformations & PNG_INVERT_ALPHA)
{
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
{
/* Invert the alpha channel (in tRNS) unless the pixels are
* going to be expanded, in which case leave it for later
*/
int i, istop = png_ptr->num_trans;
for (i=0; i<istop; i++)
png_ptr->trans_alpha[i] = (png_byte)(255 -
png_ptr->trans_alpha[i]);
}
}
#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
}
} /* background expand and (therefore) no alpha association. */
#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
}
static void /* PRIVATE */
png_init_rgb_transformations(png_structp png_ptr)
{
/* Added to libpng-1.5.4: check the color type to determine whether there
* is any alpha or transparency in the image and simply cancel the
* background and alpha mode stuff if there isn't.
*/
int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
int input_has_transparency = png_ptr->num_trans > 0;
/* If no alpha we can optimize. */
if (!input_has_alpha)
{
/* Any alpha means background and associative alpha processing is
* required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
* and ENCODE_ALPHA are irrelevant.
*/
# ifdef PNG_READ_ALPHA_MODE_SUPPORTED
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
# endif
if (!input_has_transparency)
png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
}
#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
/* png_set_background handling - deals with the complexity of whether the
* background color is in the file format or the screen format in the case
* where an 'expand' will happen.
*/
/* The following code cannot be entered in the alpha pre-multiplication case
* because PNG_BACKGROUND_EXPAND is cancelled below.
*/
if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
(png_ptr->transformations & PNG_EXPAND) &&
!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
/* i.e., GRAY or GRAY_ALPHA */
{
{
/* Expand background and tRNS chunks */
int gray = png_ptr->background.gray;
int trans_gray = png_ptr->trans_color.gray;
switch (png_ptr->bit_depth)
{
case 1:
gray *= 0xff;
trans_gray *= 0xff;
break;
case 2:
gray *= 0x55;
trans_gray *= 0x55;
break;
case 4:
gray *= 0x11;
trans_gray *= 0x11;
break;
default:
case 8:
/* Already 8 bits, fall through */
case 16:
/* Already a full 16 bits */
break;
}
png_ptr->background.red = png_ptr->background.green =
png_ptr->background.blue = (png_uint_16)gray;
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
{
png_ptr->trans_color.red = png_ptr->trans_color.green =
png_ptr->trans_color.blue = (png_uint_16)trans_gray;
}
}
} /* background expand and (therefore) no alpha association. */
#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
}
void /* PRIVATE */
png_init_read_transformations(png_structp png_ptr)
{
png_debug(1, "in png_init_read_transformations");
/* This internal function is called from png_read_start_row in pngrutil.c
* and it is called before the 'rowbytes' calculation is done, so the code
* in here can change or update the transformations flags.
*
* First do updates that do not depend on the details of the PNG image data
* being processed.
*/
#ifdef PNG_READ_GAMMA_SUPPORTED
/* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
* png_set_alpha_mode and this is another source for a default file gamma so
* the test needs to be performed later - here. In addition prior to 1.5.4
* the tests were repeated for the PALETTE color type here - this is no
* longer necessary (and doesn't seem to have been necessary before.)
*/
{
/* The following temporary indicates if overall gamma correction is
* required.
*/
int gamma_correction = 0;
if (png_ptr->gamma != 0) /* has been set */
{
if (png_ptr->screen_gamma != 0) /* screen set too */
gamma_correction = png_gamma_threshold(png_ptr->gamma,
png_ptr->screen_gamma);
else
/* Assume the output matches the input; a long time default behavior
* of libpng, although the standard has nothing to say about this.
*/
png_ptr->screen_gamma = png_reciprocal(png_ptr->gamma);
}
else if (png_ptr->screen_gamma != 0)
/* The converse - assume the file matches the screen, note that this
* perhaps undesireable default can (from 1.5.4) be changed by calling
* png_set_alpha_mode (even if the alpha handling mode isn't required
* or isn't changed from the default.)
*/
png_ptr->gamma = png_reciprocal(png_ptr->screen_gamma);
else /* neither are set */
/* Just in case the following prevents any processing - file and screen
* are both assumed to be linear and there is no way to introduce a
* third gamma value other than png_set_background with 'UNIQUE', and,
* prior to 1.5.4
*/
png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;
/* Now turn the gamma transformation on or off as appropriate. Notice
* that PNG_GAMMA just refers to the file->screen correction. Alpha
* composition may independently cause gamma correction because it needs
* linear data (e.g. if the file has a gAMA chunk but the screen gamma
* hasn't been specified.) In any case this flag may get turned off in
* the code immediately below if the transform can be handled outside the
* row loop.
*/
if (gamma_correction)
png_ptr->transformations |= PNG_GAMMA;
else
png_ptr->transformations &= ~PNG_GAMMA;
}
#endif
/* Certain transformations have the effect of preventing other
* transformations that happen afterward in png_do_read_transformations,
* resolve the interdependencies here. From the code of
* png_do_read_transformations the order is:
*
* 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
* 2) PNG_STRIP_ALPHA (if no compose)
* 3) PNG_RGB_TO_GRAY
* 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
* 5) PNG_COMPOSE
* 6) PNG_GAMMA
* 7) PNG_STRIP_ALPHA (if compose)
* 8) PNG_ENCODE_ALPHA
* 9) PNG_SCALE_16_TO_8
* 10) PNG_16_TO_8
* 11) PNG_QUANTIZE (converts to palette)
* 12) PNG_EXPAND_16
* 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
* 14) PNG_INVERT_MONO
* 15) PNG_SHIFT
* 16) PNG_PACK
* 17) PNG_BGR
* 18) PNG_PACKSWAP
* 19) PNG_FILLER (includes PNG_ADD_ALPHA)
* 20) PNG_INVERT_ALPHA
* 21) PNG_SWAP_ALPHA
* 22) PNG_SWAP_BYTES
* 23) PNG_USER_TRANSFORM [must be last]
*/
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
!(png_ptr->transformations & PNG_COMPOSE))
{
/* Stripping the alpha channel happens immediately after the 'expand'
* transformations, before all other transformation, so it cancels out
* the alpha handling. It has the side effect negating the effect of
* PNG_EXPAND_tRNS too:
*/
png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
PNG_EXPAND_tRNS);
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
/* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
* so transparency information would remain just so long as it wasn't
* expanded. This produces unexpected API changes if the set of things
* that do PNG_EXPAND_tRNS changes (perfectly possible given the
* documentation - which says ask for what you want, accept what you
* get.) This makes the behavior consistent from 1.5.4:
*/
png_ptr->num_trans = 0;
}
#endif /* STRIP_ALPHA supported, no COMPOSE */
#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
/* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
* settings will have no effect.
*/
if (!png_gamma_significant(png_ptr->screen_gamma))
{
png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
}
#endif
#if defined(PNG_READ_EXPAND_SUPPORTED) && \
defined(PNG_READ_BACKGROUND_SUPPORTED) && \
defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
/* Detect gray background and attempt to enable optimization for
* gray --> RGB case.
*
* Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
* RGB_ALPHA (in which case need_expand is superfluous anyway), the
* background color might actually be gray yet not be flagged as such.
* This is not a problem for the current code, which uses
* PNG_BACKGROUND_IS_GRAY only to decide when to do the
* png_do_gray_to_rgb() transformation.
*
* TODO: this code needs to be revised to avoid the complexity and
* interdependencies. The color type of the background should be recorded in
* png_set_background, along with the bit depth, then the code has a record
* of exactly what color space the background is currently in.
*/
if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
{
/* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
* the file was grayscale the background value is gray.
*/
if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
}
else if (png_ptr->transformations & PNG_COMPOSE)
{
/* PNG_COMPOSE: png_set_background was called with need_expand false,
* so the color is in the color space of the output or png_set_alpha_mode
* was called and the color is black. Ignore RGB_TO_GRAY because that
* happens before GRAY_TO_RGB.
*/
if (png_ptr->transformations & PNG_GRAY_TO_RGB)
{
if (png_ptr->background.red == png_ptr->background.green &&
png_ptr->background.red == png_ptr->background.blue)
{
png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
png_ptr->background.gray = png_ptr->background.red;
}
}
}
#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED (etc) */
/* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
* can be performed directly on the palette, and some (such as rgb to gray)
* can be optimized inside the palette. This is particularly true of the
* composite (background and alpha) stuff, which can be pretty much all done
* in the palette even if the result is expanded to RGB or gray afterward.
*
* NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
* earlier and the palette stuff is actually handled on the first row. This
* leads to the reported bug that the palette returned by png_get_PLTE is not
* updated.
*/
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
png_init_palette_transformations(png_ptr);
else
png_init_rgb_transformations(png_ptr);
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
defined(PNG_READ_EXPAND_16_SUPPORTED)
if ((png_ptr->transformations & PNG_EXPAND_16) &&
(png_ptr->transformations & PNG_COMPOSE) &&
!(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
png_ptr->bit_depth != 16)
{
/* TODO: fix this. Because the expand_16 operation is after the compose
* handling the background color must be 8, not 16, bits deep, but the
* application will supply a 16-bit value so reduce it here.
*
* The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
* present, so that case is ok (until do_expand_16 is moved.)
*
* NOTE: this discards the low 16 bits of the user supplied background
* color, but until expand_16 works properly there is no choice!
*/
# define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
CHOP(png_ptr->background.red);
CHOP(png_ptr->background.green);
CHOP(png_ptr->background.blue);
CHOP(png_ptr->background.gray);
# undef CHOP
}
#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
(defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
(png_ptr->transformations & PNG_COMPOSE) &&
!(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
png_ptr->bit_depth == 16)
{
/* On the other hand, if a 16-bit file is to be reduced to 8-bits per
* component this will also happen after PNG_COMPOSE and so the background
* color must be pre-expanded here.
*
* TODO: fix this too.
*/
png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
png_ptr->background.green =
(png_uint_16)(png_ptr->background.green * 257);
png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
}
#endif
/* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
* background support (see the comments in scripts/pnglibconf.dfa), this
* allows pre-multiplication of the alpha channel to be implemented as
* compositing on black. This is probably sub-optimal and has been done in
* 1.5.4 betas simply to enable external critique and testing (i.e. to
* implement the new API quickly, without lots of internal changes.)
*/
#ifdef PNG_READ_GAMMA_SUPPORTED
# ifdef PNG_READ_BACKGROUND_SUPPORTED
/* Includes ALPHA_MODE */
png_ptr->background_1 = png_ptr->background;
# endif
/* This needs to change - in the palette image case a whole set of tables are
* built when it would be quicker to just calculate the correct value for
* each palette entry directly. Also, the test is too tricky - why check
* PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
* PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
* PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
* the gamma tables will not be built even if composition is required on a
* gamma encoded value.
*
* In 1.5.4 this is addressed below by an additional check on the individual
* file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
* tables.
*/
if ((png_ptr->transformations & PNG_GAMMA)
|| ((png_ptr->transformations & PNG_RGB_TO_GRAY)
&& (png_gamma_significant(png_ptr->gamma) ||
png_gamma_significant(png_ptr->screen_gamma)))
|| ((png_ptr->transformations & PNG_COMPOSE)
&& (png_gamma_significant(png_ptr->gamma)
|| png_gamma_significant(png_ptr->screen_gamma)
# ifdef PNG_READ_BACKGROUND_SUPPORTED
|| (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
&& png_gamma_significant(png_ptr->background_gamma))
# endif
)) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
&& png_gamma_significant(png_ptr->screen_gamma))
)
{
png_build_gamma_table(png_ptr, png_ptr->bit_depth);
#ifdef PNG_READ_BACKGROUND_SUPPORTED
if (png_ptr->transformations & PNG_COMPOSE)
{
/* Issue a warning about this combination: because RGB_TO_GRAY is
* optimized to do the gamma transform if present yet do_background has
* to do the same thing if both options are set a
* double-gamma-correction happens. This is true in all versions of
* libpng to date.
*/
if (png_ptr->transformations & PNG_RGB_TO_GRAY)
png_warning(png_ptr,
"libpng does not support gamma+background+rgb_to_gray");
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
{
/* We don't get to here unless there is a tRNS chunk with non-opaque
* entries - see the checking code at the start of this function.
*/
png_color back, back_1;
png_colorp palette = png_ptr->palette;
int num_palette = png_ptr->num_palette;
int i;
if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
{
back.red = png_ptr->gamma_table[png_ptr->background.red];
back.green = png_ptr->gamma_table[png_ptr->background.green];
back.blue = png_ptr->gamma_table[png_ptr->background.blue];
back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
}
else
{
png_fixed_point g, gs;
switch (png_ptr->background_gamma_type)
{
case PNG_BACKGROUND_GAMMA_SCREEN:
g = (png_ptr->screen_gamma);
gs = PNG_FP_1;
break;
case PNG_BACKGROUND_GAMMA_FILE:
g = png_reciprocal(png_ptr->gamma);
gs = png_reciprocal2(png_ptr->gamma,
png_ptr->screen_gamma);
break;
case PNG_BACKGROUND_GAMMA_UNIQUE:
g = png_reciprocal(png_ptr->background_gamma);
gs = png_reciprocal2(png_ptr->background_gamma,
png_ptr->screen_gamma);
break;
default:
g = PNG_FP_1; /* back_1 */
gs = PNG_FP_1; /* back */
break;
}
if (png_gamma_significant(gs))
{
back.red = png_gamma_8bit_correct(png_ptr->background.red,
gs);
back.green = png_gamma_8bit_correct(png_ptr->background.green,
gs);
back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
gs);
}
else
{
back.red = (png_byte)png_ptr->background.red;
back.green = (png_byte)png_ptr->background.green;
back.blue = (png_byte)png_ptr->background.blue;
}
if (png_gamma_significant(g))
{
back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
g);
back_1.green = png_gamma_8bit_correct(
png_ptr->background.green, g);
back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
g);
}
else
{
back_1.red = (png_byte)png_ptr->background.red;
back_1.green = (png_byte)png_ptr->background.green;
back_1.blue = (png_byte)png_ptr->background.blue;
}
}
for (i = 0; i < num_palette; i++)
{
if (i < (int)png_ptr->num_trans &&
png_ptr->trans_alpha[i] != 0xff)
{
if (png_ptr->trans_alpha[i] == 0)
{
palette[i] = back;
}
else /* if (png_ptr->trans_alpha[i] != 0xff) */
{
png_byte v, w;
v = png_ptr->gamma_to_1[palette[i].red];
png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
palette[i].red = png_ptr->gamma_from_1[w];
v = png_ptr->gamma_to_1[palette[i].green];
png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
palette[i].green = png_ptr->gamma_from_1[w];
v = png_ptr->gamma_to_1[palette[i].blue];
png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
palette[i].blue = png_ptr->gamma_from_1[w];
}
}
else
{
palette[i].red = png_ptr->gamma_table[palette[i].red];
palette[i].green = png_ptr->gamma_table[palette[i].green];
palette[i].blue = png_ptr->gamma_table[palette[i].blue];
}
}
/* Prevent the transformations being done again.
*
* NOTE: this is highly dubious; it removes the transformations in
* place. This seems inconsistent with the general treatment of the
* transformations elsewhere.
*/
png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
} /* color_type == PNG_COLOR_TYPE_PALETTE */
/* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
else /* color_type != PNG_COLOR_TYPE_PALETTE */
{
int gs_sig, g_sig;
png_fixed_point g = PNG_FP_1; /* Correction to linear */
png_fixed_point gs = PNG_FP_1; /* Correction to screen */
switch (png_ptr->background_gamma_type)
{
case PNG_BACKGROUND_GAMMA_SCREEN:
g = png_ptr->screen_gamma;
/* gs = PNG_FP_1; */
break;
case PNG_BACKGROUND_GAMMA_FILE:
g = png_reciprocal(png_ptr->gamma);
gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_gamma);
break;
case PNG_BACKGROUND_GAMMA_UNIQUE:
g = png_reciprocal(png_ptr->background_gamma);
gs = png_reciprocal2(png_ptr->background_gamma,
png_ptr->screen_gamma);
break;
default:
png_error(png_ptr, "invalid background gamma type");
}
g_sig = png_gamma_significant(g);
gs_sig = png_gamma_significant(gs);
if (g_sig)
png_ptr->background_1.gray = png_gamma_correct(png_ptr,
png_ptr->background.gray, g);
if (gs_sig)
png_ptr->background.gray = png_gamma_correct(png_ptr,
png_ptr->background.gray, gs);
if ((png_ptr->background.red != png_ptr->background.green) ||
(png_ptr->background.red != png_ptr->background.blue) ||
(png_ptr->background.red != png_ptr->background.gray))
{
/* RGB or RGBA with color background */
if (g_sig)
{
png_ptr->background_1.red = png_gamma_correct(png_ptr,
png_ptr->background.red, g);
png_ptr->background_1.green = png_gamma_correct(png_ptr,
png_ptr->background.green, g);
png_ptr->background_1.blue = png_gamma_correct(png_ptr,
png_ptr->background.blue, g);
}
if (gs_sig)
{
png_ptr->background.red = png_gamma_correct(png_ptr,
png_ptr->background.red, gs);
png_ptr->background.green = png_gamma_correct(png_ptr,
png_ptr->background.green, gs);
png_ptr->background.blue = png_gamma_correct(png_ptr,
png_ptr->background.blue, gs);
}
}
else
{
/* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
png_ptr->background_1.red = png_ptr->background_1.green
= png_ptr->background_1.blue = png_ptr->background_1.gray;
png_ptr->background.red = png_ptr->background.green
= png_ptr->background.blue = png_ptr->background.gray;
}
/* The background is now in screen gamma: */
png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
} /* color_type != PNG_COLOR_TYPE_PALETTE */
}/* png_ptr->transformations & PNG_BACKGROUND */
else
/* Transformation does not include PNG_BACKGROUND */
#endif /* PNG_READ_BACKGROUND_SUPPORTED */
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
/* RGB_TO_GRAY needs to have non-gamma-corrected values! */
&& ((png_ptr->transformations & PNG_EXPAND) == 0 ||
(png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
#endif
)
{
png_colorp palette = png_ptr->palette;
int num_palette = png_ptr->num_palette;
int i;
/* NOTE: there are other transformations that should probably be in
* here too.
*/
for (i = 0; i < num_palette; i++)
{
palette[i].red = png_ptr->gamma_table[palette[i].red];
palette[i].green = png_ptr->gamma_table[palette[i].green];
palette[i].blue = png_ptr->gamma_table[palette[i].blue];
}
/* Done the gamma correction. */
png_ptr->transformations &= ~PNG_GAMMA;
} /* color_type == PALETTE && !PNG_BACKGROUND transformation */
}
#ifdef PNG_READ_BACKGROUND_SUPPORTED
else
#endif
#endif /* PNG_READ_GAMMA_SUPPORTED */
#ifdef PNG_READ_BACKGROUND_SUPPORTED
/* No GAMMA transformation (see the hanging else 4 lines above) */
if ((png_ptr->transformations & PNG_COMPOSE) &&
(png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
{
int i;
int istop = (int)png_ptr->num_trans;
png_color back;
png_colorp palette = png_ptr->palette;
back.red = (png_byte)png_ptr->background.red;
back.green = (png_byte)png_ptr->background.green;
back.blue = (png_byte)png_ptr->background.blue;
for (i = 0; i < istop; i++)
{
if (png_ptr->trans_alpha[i] == 0)
{
palette[i] = back;
}
else if (png_ptr->trans_alpha[i] != 0xff)
{
/* The png_composite() macro is defined in png.h */
png_composite(palette[i].red, palette[i].red,
png_ptr->trans_alpha[i], back.red);
png_composite(palette[i].green, palette[i].green,
png_ptr->trans_alpha[i], back.green);
png_composite(palette[i].blue, palette[i].blue,
png_ptr->trans_alpha[i], back.blue);
}
}
png_ptr->transformations &= ~PNG_COMPOSE;
}
#endif /* PNG_READ_BACKGROUND_SUPPORTED */
#ifdef PNG_READ_SHIFT_SUPPORTED
if ((png_ptr->transformations & PNG_SHIFT) &&
!(png_ptr->transformations & PNG_EXPAND) &&
(png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
{
int i;
int istop = png_ptr->num_palette;
int shift = 8 - png_ptr->sig_bit.red;
png_ptr->transformations &= ~PNG_SHIFT;
/* significant bits can be in the range 1 to 7 for a meaninful result, if
* the number of significant bits is 0 then no shift is done (this is an
* error condition which is silently ignored.)
*/
if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
{
int component = png_ptr->palette[i].red;
component >>= shift;
png_ptr->palette[i].red = (png_byte)component;
}
shift = 8 - png_ptr->sig_bit.green;
if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
{
int component = png_ptr->palette[i].green;
component >>= shift;
png_ptr->palette[i].green = (png_byte)component;
}
shift = 8 - png_ptr->sig_bit.blue;
if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
{
int component = png_ptr->palette[i].blue;
component >>= shift;
png_ptr->palette[i].blue = (png_byte)component;
}
}
#endif /* PNG_READ_SHIFT_SUPPORTED */
}
/* Modify the info structure to reflect the transformations. The
* info should be updated so a PNG file could be written with it,
* assuming the transformations result in valid PNG data.
*/
void /* PRIVATE */
png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
{
png_debug(1, "in png_read_transform_info");
#ifdef PNG_READ_EXPAND_SUPPORTED
if (png_ptr->transformations & PNG_EXPAND)
{
if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
{
/* This check must match what actually happens in
* png_do_expand_palette; if it ever checks the tRNS chunk to see if
* it is all opaque we must do the same (at present it does not.)
*/
if (png_ptr->num_trans > 0)
info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
else
info_ptr->color_type = PNG_COLOR_TYPE_RGB;
info_ptr->bit_depth = 8;
info_ptr->num_trans = 0;
}
else
{
if (png_ptr->num_trans)
{
if (png_ptr->transformations & PNG_EXPAND_tRNS)
info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
}
if (info_ptr->bit_depth < 8)
info_ptr->bit_depth = 8;
info_ptr->num_trans = 0;
}
}
#endif
#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
defined(PNG_READ_ALPHA_MODE_SUPPORTED)
/* The following is almost certainly wrong unless the background value is in
* the screen space!
*/
if (png_ptr->transformations & PNG_COMPOSE)
info_ptr->background = png_ptr->background;
#endif
#ifdef PNG_READ_GAMMA_SUPPORTED
/* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
* however it seems that the code in png_init_read_transformations, which has
* been called before this from png_read_update_info->png_read_start_row
* sometimes does the gamma transform and cancels the flag.
*/
info_ptr->gamma = png_ptr->gamma;
#endif
if (info_ptr->bit_depth == 16)
{
# ifdef PNG_READ_16BIT_SUPPORTED
# ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
if (png_ptr->transformations & PNG_SCALE_16_TO_8)
info_ptr->bit_depth = 8;
# endif
# ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
if (png_ptr->transformations & PNG_16_TO_8)
info_ptr->bit_depth = 8;
# endif
# else
/* No 16 bit support: force chopping 16-bit input down to 8, in this case
* the app program can chose if both APIs are available by setting the
* correct scaling to use.
*/
# ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
/* For compatibility with previous versions use the strip method by
* default. This code works because if PNG_SCALE_16_TO_8 is already
* set the code below will do that in preference to the chop.
*/
png_ptr->transformations |= PNG_16_TO_8;
info_ptr->bit_depth = 8;
# else
# ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
png_ptr->transformations |= PNG_SCALE_16_TO_8;
info_ptr->bit_depth = 8;
# else
CONFIGURATION ERROR: you must enable at least one 16 to 8 method
# endif
# endif
#endif /* !READ_16BIT_SUPPORTED */
}
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
if (png_ptr->transformations & PNG_GRAY_TO_RGB)
info_ptr->color_type = (png_byte)(info_ptr->color_type |
PNG_COLOR_MASK_COLOR);
#endif
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
if (png_ptr->transformations & PNG_RGB_TO_GRAY)
info_ptr->color_type = (png_byte)(info_ptr->color_type &
~PNG_COLOR_MASK_COLOR);
#endif
#ifdef PNG_READ_QUANTIZE_SUPPORTED
if (png_ptr->transformations & PNG_QUANTIZE)
{
if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
(info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
png_ptr->palette_lookup && info_ptr->bit_depth == 8)
{
info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
}
}
#endif
#ifdef PNG_READ_EXPAND_16_SUPPORTED
if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
{
info_ptr->bit_depth = 16;
}
#endif
#ifdef PNG_READ_PACK_SUPPORTED
if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
info_ptr->bit_depth = 8;
#endif
if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
info_ptr->channels = 1;
else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
info_ptr->channels = 3;
else
info_ptr->channels = 1;
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
if (png_ptr->transformations & PNG_STRIP_ALPHA)
{
info_ptr->color_type = (png_byte)(info_ptr->color_type &
~PNG_COLOR_MASK_ALPHA);
info_ptr->num_trans = 0;
}
#endif
if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
info_ptr->channels++;
#ifdef PNG_READ_FILLER_SUPPORTED
/* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
if ((png_ptr->transformations & PNG_FILLER) &&
((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
(info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
{
info_ptr->channels++;
/* If adding a true alpha channel not just filler */
if (png_ptr->transformations & PNG_ADD_ALPHA)
info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
}
#endif
#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
if (png_ptr->transformations & PNG_USER_TRANSFORM)
{
if (info_ptr->bit_depth < png_ptr->user_transform_depth)
info_ptr->bit_depth = png_ptr->user_transform_depth;
if (info_ptr->channels < png_ptr->user_transform_channels)
info_ptr->channels = png_ptr->user_transform_channels;
}
#endif
info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
info_ptr->bit_depth);
info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
/* Adding in 1.5.4: cache the above value in png_struct so that we can later
* check in png_rowbytes that the user buffer won't get overwritten. Note
* that the field is not always set - if png_read_update_info isn't called
* the application has to either not do any transforms or get the calculation
* right itself.
*/
png_ptr->info_rowbytes = info_ptr->rowbytes;
#ifndef PNG_READ_EXPAND_SUPPORTED
if (png_ptr)
return;
#endif
}
/* Transform the row. The order of transformations is significant,
* and is very touchy. If you add a transformation, take care to
* decide how it fits in with the other transformations here.
*/
void /* PRIVATE */
png_do_read_transformations(png_structp png_ptr, png_row_infop row_info)
{
png_debug(1, "in png_do_read_transformations");
if (png_ptr->row_buf == NULL)
{
/* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
* error is incredibly rare and incredibly easy to debug without this
* information.
*/
png_error(png_ptr, "NULL row buffer");
}
/* The following is debugging; prior to 1.5.4 the code was never compiled in;
* in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
* PNG_WARN_UNINITIALIZED_ROW removed. In 1.5 the new flag is set only for
* selected new APIs to ensure that there is no API change.
*/
if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
!(png_ptr->flags & PNG_FLAG_ROW_INIT))
{
/* Application has failed to call either png_read_start_image() or
* png_read_update_info() after setting transforms that expand pixels.
* This check added to libpng-1.2.19 (but not enabled until 1.5.4).
*/
png_error(png_ptr, "Uninitialized row");
}
#ifdef PNG_READ_EXPAND_SUPPORTED
if (png_ptr->transformations & PNG_EXPAND)
{
if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
{
png_do_expand_palette(row_info, png_ptr->row_buf + 1,
png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
}
else
{
if (png_ptr->num_trans &&
(png_ptr->transformations & PNG_EXPAND_tRNS))
png_do_expand(row_info, png_ptr->row_buf + 1,
&(png_ptr->trans_color));
else
png_do_expand(row_info, png_ptr->row_buf + 1,
NULL);
}
}
#endif
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
!(png_ptr->transformations & PNG_COMPOSE) &&
(row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
png_do_strip_channel(row_info, png_ptr->row_buf + 1,
0 /* at_start == false, because SWAP_ALPHA happens later */);
#endif
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
if (png_ptr->transformations & PNG_RGB_TO_GRAY)
{
int rgb_error =
png_do_rgb_to_gray(png_ptr, row_info,
png_ptr->row_buf + 1);
if (rgb_error)
{
png_ptr->rgb_to_gray_status=1;
if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
PNG_RGB_TO_GRAY_WARN)
png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
PNG_RGB_TO_GRAY_ERR)
png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
}
}
#endif
/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
*
* In most cases, the "simple transparency" should be done prior to doing
* gray-to-RGB, or you will have to test 3x as many bytes to check if a
* pixel is transparent. You would also need to make sure that the
* transparency information is upgraded to RGB.
*
* To summarize, the current flow is:
* - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
* with background "in place" if transparent,
* convert to RGB if necessary
* - Gray + alpha -> composite with gray background and remove alpha bytes,
* convert to RGB if necessary
*
* To support RGB backgrounds for gray images we need:
* - Gray + simple transparency -> convert to RGB + simple transparency,
* compare 3 or 6 bytes and composite with
* background "in place" if transparent
* (3x compare/pixel compared to doing
* composite with gray bkgrnd)
* - Gray + alpha -> convert to RGB + alpha, composite with background and
* remove alpha bytes (3x float
* operations/pixel compared with composite
* on gray background)
*
* Greg's change will do this. The reason it wasn't done before is for
* performance, as this increases the per-pixel operations. If we would check
* in advance if the background was gray or RGB, and position the gray-to-RGB
* transform appropriately, then it would save a lot of work/time.
*/
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
/* If gray -> RGB, do so now only if background is non-gray; else do later
* for performance reasons
*/
if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
!(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
#endif
#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
(defined PNG_READ_ALPHA_MODE_SUPPORTED)
if (png_ptr->transformations & PNG_COMPOSE)
png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
#endif
#ifdef PNG_READ_GAMMA_SUPPORTED
if ((png_ptr->transformations & PNG_GAMMA) &&
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
/* Because RGB_TO_GRAY does the gamma transform. */
!(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
#endif
#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
(defined PNG_READ_ALPHA_MODE_SUPPORTED)
/* Because PNG_COMPOSE does the gamma transform if there is something to
* do (if there is an alpha channel or transparency.)
*/
!((png_ptr->transformations & PNG_COMPOSE) &&
((png_ptr->num_trans != 0) ||
(png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
#endif
/* Because png_init_read_transformations transforms the palette, unless
* RGB_TO_GRAY will do the transform.
*/
(png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
#endif
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
(png_ptr->transformations & PNG_COMPOSE) &&
(row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
png_do_strip_channel(row_info, png_ptr->row_buf + 1,
0 /* at_start == false, because SWAP_ALPHA happens later */);
#endif
#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
(row_info->color_type & PNG_COLOR_MASK_ALPHA))
png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
#endif
#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
if (png_ptr->transformations & PNG_SCALE_16_TO_8)
png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
/* There is no harm in doing both of these because only one has any effect,
* by putting the 'scale' option first if the app asks for scale (either by
* calling the API or in a TRANSFORM flag) this is what happens.
*/
if (png_ptr->transformations & PNG_16_TO_8)
png_do_chop(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_QUANTIZE_SUPPORTED
if (png_ptr->transformations & PNG_QUANTIZE)
{
png_do_quantize(row_info, png_ptr->row_buf + 1,
png_ptr->palette_lookup, png_ptr->quantize_index);
if (row_info->rowbytes == 0)
png_error(png_ptr, "png_do_quantize returned rowbytes=0");
}
#endif /* PNG_READ_QUANTIZE_SUPPORTED */
#ifdef PNG_READ_EXPAND_16_SUPPORTED
/* Do the expansion now, after all the arithmetic has been done. Notice
* that previous transformations can handle the PNG_EXPAND_16 flag if this
* is efficient (particularly true in the case of gamma correction, where
* better accuracy results faster!)
*/
if (png_ptr->transformations & PNG_EXPAND_16)
png_do_expand_16(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
/* NOTE: moved here in 1.5.4 (from much later in this list.) */
if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_INVERT_SUPPORTED
if (png_ptr->transformations & PNG_INVERT_MONO)
png_do_invert(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_SHIFT_SUPPORTED
if (png_ptr->transformations & PNG_SHIFT)
png_do_unshift(row_info, png_ptr->row_buf + 1,
&(png_ptr->shift));
#endif
#ifdef PNG_READ_PACK_SUPPORTED
if (png_ptr->transformations & PNG_PACK)
png_do_unpack(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
/* Added at libpng-1.5.10 */
if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
png_ptr->num_palette_max >= 0)
png_do_check_palette_indexes(png_ptr, row_info);
#endif
#ifdef PNG_READ_BGR_SUPPORTED
if (png_ptr->transformations & PNG_BGR)
png_do_bgr(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_PACKSWAP_SUPPORTED
if (png_ptr->transformations & PNG_PACKSWAP)
png_do_packswap(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_FILLER_SUPPORTED
if (png_ptr->transformations & PNG_FILLER)
png_do_read_filler(row_info, png_ptr->row_buf + 1,
(png_uint_32)png_ptr->filler, png_ptr->flags);
#endif
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
if (png_ptr->transformations & PNG_INVERT_ALPHA)
png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
if (png_ptr->transformations & PNG_SWAP_ALPHA)
png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
#endif
#ifdef PNG_READ_16BIT_SUPPORTED
#ifdef PNG_READ_SWAP_SUPPORTED
if (png_ptr->transformations & PNG_SWAP_BYTES)
png_do_swap(row_info, png_ptr->row_buf + 1);
#endif
#endif
#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
if (png_ptr->transformations & PNG_USER_TRANSFORM)
{
if (png_ptr->read_user_transform_fn != NULL)
(*(png_ptr->read_user_transform_fn)) /* User read transform function */
(png_ptr, /* png_ptr */
row_info, /* row_info: */
/* png_uint_32 width; width of row */
/* png_size_t rowbytes; number of bytes in row */
/* png_byte color_type; color type of pixels */
/* png_byte bit_depth; bit depth of samples */
/* png_byte channels; number of channels (1-4) */
/* png_byte pixel_depth; bits per pixel (depth*channels) */
png_ptr->row_buf + 1); /* start of pixel data for row */
#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
if (png_ptr->user_transform_depth)
row_info->bit_depth = png_ptr->user_transform_depth;
if (png_ptr->user_transform_channels)
row_info->channels = png_ptr->user_transform_channels;
#endif
row_info->pixel_depth = (png_byte)(row_info->bit_depth *
row_info->channels);
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
}
#endif
}
#ifdef PNG_READ_PACK_SUPPORTED
/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
* without changing the actual values. Thus, if you had a row with
* a bit depth of 1, you would end up with bytes that only contained
* the numbers 0 or 1. If you would rather they contain 0 and 255, use
* png_do_shift() after this.
*/
void /* PRIVATE */
png_do_unpack(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_unpack");
if (row_info->bit_depth < 8)
{
png_uint_32 i;
png_uint_32 row_width=row_info->width;
switch (row_info->bit_depth)
{
case 1:
{
png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
png_bytep dp = row + (png_size_t)row_width - 1;
png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
for (i = 0; i < row_width; i++)
{
*dp = (png_byte)((*sp >> shift) & 0x01);
if (shift == 7)
{
shift = 0;
sp--;
}
else
shift++;
dp--;
}
break;
}
case 2:
{
png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
png_bytep dp = row + (png_size_t)row_width - 1;
png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
for (i = 0; i < row_width; i++)
{
*dp = (png_byte)((*sp >> shift) & 0x03);
if (shift == 6)
{
shift = 0;
sp--;
}
else
shift += 2;
dp--;
}
break;
}
case 4:
{
png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
png_bytep dp = row + (png_size_t)row_width - 1;
png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
for (i = 0; i < row_width; i++)
{
*dp = (png_byte)((*sp >> shift) & 0x0f);
if (shift == 4)
{
shift = 0;
sp--;
}
else
shift = 4;
dp--;
}
break;
}
default:
break;
}
row_info->bit_depth = 8;
row_info->pixel_depth = (png_byte)(8 * row_info->channels);
row_info->rowbytes = row_width * row_info->channels;
}
}
#endif
#ifdef PNG_READ_SHIFT_SUPPORTED
/* Reverse the effects of png_do_shift. This routine merely shifts the
* pixels back to their significant bits values. Thus, if you have
* a row of bit depth 8, but only 5 are significant, this will shift
* the values back to 0 through 31.
*/
void /* PRIVATE */
png_do_unshift(png_row_infop row_info, png_bytep row,
png_const_color_8p sig_bits)
{
int color_type;
png_debug(1, "in png_do_unshift");
/* The palette case has already been handled in the _init routine. */
color_type = row_info->color_type;
if (color_type != PNG_COLOR_TYPE_PALETTE)
{
int shift[4];
int channels = 0;
int bit_depth = row_info->bit_depth;
if (color_type & PNG_COLOR_MASK_COLOR)
{
shift[channels++] = bit_depth - sig_bits->red;
shift[channels++] = bit_depth - sig_bits->green;
shift[channels++] = bit_depth - sig_bits->blue;
}
else
{
shift[channels++] = bit_depth - sig_bits->gray;
}
if (color_type & PNG_COLOR_MASK_ALPHA)
{
shift[channels++] = bit_depth - sig_bits->alpha;
}
{
int c, have_shift;
for (c = have_shift = 0; c < channels; ++c)
{
/* A shift of more than the bit depth is an error condition but it
* gets ignored here.
*/
if (shift[c] <= 0 || shift[c] >= bit_depth)
shift[c] = 0;
else
have_shift = 1;
}
if (!have_shift)
return;
}
switch (bit_depth)
{
default:
/* Must be 1bpp gray: should not be here! */
/* NOTREACHED */
break;
case 2:
/* Must be 2bpp gray */
/* assert(channels == 1 && shift[0] == 1) */
{
png_bytep bp = row;
png_bytep bp_end = bp + row_info->rowbytes;
while (bp < bp_end)
{
int b = (*bp >> 1) & 0x55;
*bp++ = (png_byte)b;
}
break;
}
case 4:
/* Must be 4bpp gray */
/* assert(channels == 1) */
{
png_bytep bp = row;
png_bytep bp_end = bp + row_info->rowbytes;
int gray_shift = shift[0];
int mask = 0xf >> gray_shift;
mask |= mask << 4;
while (bp < bp_end)
{
int b = (*bp >> gray_shift) & mask;
*bp++ = (png_byte)b;
}
break;
}
case 8:
/* Single byte components, G, GA, RGB, RGBA */
{
png_bytep bp = row;
png_bytep bp_end = bp + row_info->rowbytes;
int channel = 0;
while (bp < bp_end)
{
int b = *bp >> shift[channel];
if (++channel >= channels)
channel = 0;
*bp++ = (png_byte)b;
}
break;
}
#ifdef PNG_READ_16BIT_SUPPORTED
case 16:
/* Double byte components, G, GA, RGB, RGBA */
{
png_bytep bp = row;
png_bytep bp_end = bp + row_info->rowbytes;
int channel = 0;
while (bp < bp_end)
{
int value = (bp[0] << 8) + bp[1];
value >>= shift[channel];
if (++channel >= channels)
channel = 0;
*bp++ = (png_byte)(value >> 8);
*bp++ = (png_byte)(value & 0xff);
}
break;
}
#endif
}
}
}
#endif
#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
/* Scale rows of bit depth 16 down to 8 accurately */
void /* PRIVATE */
png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_scale_16_to_8");
if (row_info->bit_depth == 16)
{
png_bytep sp = row; /* source */
png_bytep dp = row; /* destination */
png_bytep ep = sp + row_info->rowbytes; /* end+1 */
while (sp < ep)
{
/* The input is an array of 16 bit components, these must be scaled to
* 8 bits each. For a 16 bit value V the required value (from the PNG
* specification) is:
*
* (V * 255) / 65535
*
* This reduces to round(V / 257), or floor((V + 128.5)/257)
*
* Represent V as the two byte value vhi.vlo. Make a guess that the
* result is the top byte of V, vhi, then the correction to this value
* is:
*
* error = floor(((V-vhi.vhi) + 128.5) / 257)
* = floor(((vlo-vhi) + 128.5) / 257)
*
* This can be approximated using integer arithmetic (and a signed
* shift):
*
* error = (vlo-vhi+128) >> 8;
*
* The approximate differs from the exact answer only when (vlo-vhi) is
* 128; it then gives a correction of +1 when the exact correction is
* 0. This gives 128 errors. The exact answer (correct for all 16 bit
* input values) is:
*
* error = (vlo-vhi+128)*65535 >> 24;
*
* An alternative arithmetic calculation which also gives no errors is:
*
* (V * 255 + 32895) >> 16
*/
png_int_32 tmp = *sp++; /* must be signed! */
tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
*dp++ = (png_byte)tmp;
}
row_info->bit_depth = 8;
row_info->pixel_depth = (png_byte)(8 * row_info->channels);
row_info->rowbytes = row_info->width * row_info->channels;
}
}
#endif
#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
void /* PRIVATE */
/* Simply discard the low byte. This was the default behavior prior
* to libpng-1.5.4.
*/
png_do_chop(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_chop");
if (row_info->bit_depth == 16)
{
png_bytep sp = row; /* source */
png_bytep dp = row; /* destination */
png_bytep ep = sp + row_info->rowbytes; /* end+1 */
while (sp < ep)
{
*dp++ = *sp;
sp += 2; /* skip low byte */
}
row_info->bit_depth = 8;
row_info->pixel_depth = (png_byte)(8 * row_info->channels);
row_info->rowbytes = row_info->width * row_info->channels;
}
}
#endif
#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_read_swap_alpha");
{
png_uint_32 row_width = row_info->width;
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
/* This converts from RGBA to ARGB */
if (row_info->bit_depth == 8)
{
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_byte save;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
save = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = save;
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
/* This converts from RRGGBBAA to AARRGGBB */
else
{
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_byte save[2];
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
save[0] = *(--sp);
save[1] = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = save[0];
*(--dp) = save[1];
}
}
#endif
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
/* This converts from GA to AG */
if (row_info->bit_depth == 8)
{
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_byte save;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
save = *(--sp);
*(--dp) = *(--sp);
*(--dp) = save;
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
/* This converts from GGAA to AAGG */
else
{
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_byte save[2];
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
save[0] = *(--sp);
save[1] = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = save[0];
*(--dp) = save[1];
}
}
#endif
}
}
}
#endif
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
{
png_uint_32 row_width;
png_debug(1, "in png_do_read_invert_alpha");
row_width = row_info->width;
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This inverts the alpha channel in RGBA */
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
*(--dp) = (png_byte)(255 - *(--sp));
/* This does nothing:
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
We can replace it with:
*/
sp-=3;
dp=sp;
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
/* This inverts the alpha channel in RRGGBBAA */
else
{
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
*(--dp) = (png_byte)(255 - *(--sp));
*(--dp) = (png_byte)(255 - *(--sp));
/* This does nothing:
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
We can replace it with:
*/
sp-=6;
dp=sp;
}
}
#endif
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This inverts the alpha channel in GA */
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
*(--dp) = (png_byte)(255 - *(--sp));
*(--dp) = *(--sp);
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
else
{
/* This inverts the alpha channel in GGAA */
png_bytep sp = row + row_info->rowbytes;
png_bytep dp = sp;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
*(--dp) = (png_byte)(255 - *(--sp));
*(--dp) = (png_byte)(255 - *(--sp));
/*
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*/
sp-=2;
dp=sp;
}
}
#endif
}
}
#endif
#ifdef PNG_READ_FILLER_SUPPORTED
/* Add filler channel if we have RGB color */
void /* PRIVATE */
png_do_read_filler(png_row_infop row_info, png_bytep row,
png_uint_32 filler, png_uint_32 flags)
{
png_uint_32 i;
png_uint_32 row_width = row_info->width;
#ifdef PNG_READ_16BIT_SUPPORTED
png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
#endif
png_byte lo_filler = (png_byte)(filler & 0xff);
png_debug(1, "in png_do_read_filler");
if (
row_info->color_type == PNG_COLOR_TYPE_GRAY)
{
if (row_info->bit_depth == 8)
{
if (flags & PNG_FLAG_FILLER_AFTER)
{
/* This changes the data from G to GX */
png_bytep sp = row + (png_size_t)row_width;
png_bytep dp = sp + (png_size_t)row_width;
for (i = 1; i < row_width; i++)
{
*(--dp) = lo_filler;
*(--dp) = *(--sp);
}
*(--dp) = lo_filler;
row_info->channels = 2;
row_info->pixel_depth = 16;
row_info->rowbytes = row_width * 2;
}
else
{
/* This changes the data from G to XG */
png_bytep sp = row + (png_size_t)row_width;
png_bytep dp = sp + (png_size_t)row_width;
for (i = 0; i < row_width; i++)
{
*(--dp) = *(--sp);
*(--dp) = lo_filler;
}
row_info->channels = 2;
row_info->pixel_depth = 16;
row_info->rowbytes = row_width * 2;
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
else if (row_info->bit_depth == 16)
{
if (flags & PNG_FLAG_FILLER_AFTER)
{
/* This changes the data from GG to GGXX */
png_bytep sp = row + (png_size_t)row_width * 2;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 1; i < row_width; i++)
{
*(--dp) = hi_filler;
*(--dp) = lo_filler;
*(--dp) = *(--sp);
*(--dp) = *(--sp);
}
*(--dp) = hi_filler;
*(--dp) = lo_filler;
row_info->channels = 2;
row_info->pixel_depth = 32;
row_info->rowbytes = row_width * 4;
}
else
{
/* This changes the data from GG to XXGG */
png_bytep sp = row + (png_size_t)row_width * 2;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 0; i < row_width; i++)
{
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = hi_filler;
*(--dp) = lo_filler;
}
row_info->channels = 2;
row_info->pixel_depth = 32;
row_info->rowbytes = row_width * 4;
}
}
#endif
} /* COLOR_TYPE == GRAY */
else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
{
if (row_info->bit_depth == 8)
{
if (flags & PNG_FLAG_FILLER_AFTER)
{
/* This changes the data from RGB to RGBX */
png_bytep sp = row + (png_size_t)row_width * 3;
png_bytep dp = sp + (png_size_t)row_width;
for (i = 1; i < row_width; i++)
{
*(--dp) = lo_filler;
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
}
*(--dp) = lo_filler;
row_info->channels = 4;
row_info->pixel_depth = 32;
row_info->rowbytes = row_width * 4;
}
else
{
/* This changes the data from RGB to XRGB */
png_bytep sp = row + (png_size_t)row_width * 3;
png_bytep dp = sp + (png_size_t)row_width;
for (i = 0; i < row_width; i++)
{
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = lo_filler;
}
row_info->channels = 4;
row_info->pixel_depth = 32;
row_info->rowbytes = row_width * 4;
}
}
#ifdef PNG_READ_16BIT_SUPPORTED
else if (row_info->bit_depth == 16)
{
if (flags & PNG_FLAG_FILLER_AFTER)
{
/* This changes the data from RRGGBB to RRGGBBXX */
png_bytep sp = row + (png_size_t)row_width * 6;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 1; i < row_width; i++)
{
*(--dp) = hi_filler;
*(--dp) = lo_filler;
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
}
*(--dp) = hi_filler;
*(--dp) = lo_filler;
row_info->channels = 4;
row_info->pixel_depth = 64;
row_info->rowbytes = row_width * 8;
}
else
{
/* This changes the data from RRGGBB to XXRRGGBB */
png_bytep sp = row + (png_size_t)row_width * 6;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 0; i < row_width; i++)
{
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = *(--sp);
*(--dp) = hi_filler;
*(--dp) = lo_filler;
}
row_info->channels = 4;
row_info->pixel_depth = 64;
row_info->rowbytes = row_width * 8;
}
}
#endif
} /* COLOR_TYPE == RGB */
}
#endif
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
/* Expand grayscale files to RGB, with or without alpha */
void /* PRIVATE */
png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
{
png_uint_32 i;
png_uint_32 row_width = row_info->width;
png_debug(1, "in png_do_gray_to_rgb");
if (row_info->bit_depth >= 8 &&
!(row_info->color_type & PNG_COLOR_MASK_COLOR))
{
if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
{
if (row_info->bit_depth == 8)
{
/* This changes G to RGB */
png_bytep sp = row + (png_size_t)row_width - 1;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 0; i < row_width; i++)
{
*(dp--) = *sp;
*(dp--) = *sp;
*(dp--) = *(sp--);
}
}
else
{
/* This changes GG to RRGGBB */
png_bytep sp = row + (png_size_t)row_width * 2 - 1;
png_bytep dp = sp + (png_size_t)row_width * 4;
for (i = 0; i < row_width; i++)
{
*(dp--) = *sp;
*(dp--) = *(sp - 1);
*(dp--) = *sp;
*(dp--) = *(sp - 1);
*(dp--) = *(sp--);
*(dp--) = *(sp--);
}
}
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This changes GA to RGBA */
png_bytep sp = row + (png_size_t)row_width * 2 - 1;
png_bytep dp = sp + (png_size_t)row_width * 2;
for (i = 0; i < row_width; i++)
{
*(dp--) = *(sp--);
*(dp--) = *sp;
*(dp--) = *sp;
*(dp--) = *(sp--);
}
}
else
{
/* This changes GGAA to RRGGBBAA */
png_bytep sp = row + (png_size_t)row_width * 4 - 1;
png_bytep dp = sp + (png_size_t)row_width * 4;
for (i = 0; i < row_width; i++)
{
*(dp--) = *(sp--);
*(dp--) = *(sp--);
*(dp--) = *sp;
*(dp--) = *(sp - 1);
*(dp--) = *sp;
*(dp--) = *(sp - 1);
*(dp--) = *(sp--);
*(dp--) = *(sp--);
}
}
}
row_info->channels = (png_byte)(row_info->channels + 2);
row_info->color_type |= PNG_COLOR_MASK_COLOR;
row_info->pixel_depth = (png_byte)(row_info->channels *
row_info->bit_depth);
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
}
}
#endif
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
/* Reduce RGB files to grayscale, with or without alpha
* using the equation given in Poynton's ColorFAQ of 1998-01-04 at
* <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
* versions dated 1998 through November 2002 have been archived at
* http://web.archive.org/web/20000816232553/http://www.inforamp.net/
* ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
* Charles Poynton poynton at poynton.com
*
* Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
*
* which can be expressed with integers as
*
* Y = (6969 * R + 23434 * G + 2365 * B)/32768
*
* Poynton's current link (as of January 2003 through July 2011):
* <http://www.poynton.com/notes/colour_and_gamma/>
* has changed the numbers slightly:
*
* Y = 0.2126*R + 0.7152*G + 0.0722*B
*
* which can be expressed with integers as
*
* Y = (6966 * R + 23436 * G + 2366 * B)/32768
*
* Historically, however, libpng uses numbers derived from the ITU-R Rec 709
* end point chromaticities and the D65 white point. Depending on the
* precision used for the D65 white point this produces a variety of different
* numbers, however if the four decimal place value used in ITU-R Rec 709 is
* used (0.3127,0.3290) the Y calculation would be:
*
* Y = (6968 * R + 23435 * G + 2366 * B)/32768
*
* While this is correct the rounding results in an overflow for white, because
* the sum of the rounded coefficients is 32769, not 32768. Consequently
* libpng uses, instead, the closest non-overflowing approximation:
*
* Y = (6968 * R + 23434 * G + 2366 * B)/32768
*
* Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
* (including an sRGB chunk) then the chromaticities are used to calculate the
* coefficients. See the chunk handling in pngrutil.c for more information.
*
* In all cases the calculation is to be done in a linear colorspace. If no
* gamma information is available to correct the encoding of the original RGB
* values this results in an implicit assumption that the original PNG RGB
* values were linear.
*
* Other integer coefficents can be used via png_set_rgb_to_gray(). Because
* the API takes just red and green coefficients the blue coefficient is
* calculated to make the sum 32768. This will result in different rounding
* to that used above.
*/
int /* PRIVATE */
png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
{
int rgb_error = 0;
png_debug(1, "in png_do_rgb_to_gray");
if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
(row_info->color_type & PNG_COLOR_MASK_COLOR))
{
PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
PNG_CONST png_uint_32 bc = 32768 - rc - gc;
PNG_CONST png_uint_32 row_width = row_info->width;
PNG_CONST int have_alpha =
(row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
if (row_info->bit_depth == 8)
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
/* Notice that gamma to/from 1 are not necessarily inverses (if
* there is an overall gamma correction). Prior to 1.5.5 this code
* checked the linearized values for equality; this doesn't match
* the documentation, the original values must be checked.
*/
if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
if (red != green || red != blue)
{
red = png_ptr->gamma_to_1[red];
green = png_ptr->gamma_to_1[green];
blue = png_ptr->gamma_to_1[blue];
rgb_error |= 1;
*(dp++) = png_ptr->gamma_from_1[
(rc*red + gc*green + bc*blue + 16384)>>15];
}
else
{
/* If there is no overall correction the table will not be
* set.
*/
if (png_ptr->gamma_table != NULL)
red = png_ptr->gamma_table[red];
*(dp++) = red;
}
if (have_alpha)
*(dp++) = *(sp++);
}
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_byte red = *(sp++);
png_byte green = *(sp++);
png_byte blue = *(sp++);
if (red != green || red != blue)
{
rgb_error |= 1;
/* NOTE: this is the historical approach which simply
* truncates the results.
*/
*(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
}
else
*(dp++) = red;
if (have_alpha)
*(dp++) = *(sp++);
}
}
}
else /* RGB bit_depth == 16 */
{
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_uint_16 red, green, blue, w;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red == green && red == blue)
{
if (png_ptr->gamma_16_table != NULL)
w = png_ptr->gamma_16_table[(red&0xff)
>> png_ptr->gamma_shift][red>>8];
else
w = red;
}
else
{
png_uint_16 red_1 = png_ptr->gamma_16_to_1[(red&0xff)
>> png_ptr->gamma_shift][red>>8];
png_uint_16 green_1 =
png_ptr->gamma_16_to_1[(green&0xff) >>
png_ptr->gamma_shift][green>>8];
png_uint_16 blue_1 = png_ptr->gamma_16_to_1[(blue&0xff)
>> png_ptr->gamma_shift][blue>>8];
png_uint_16 gray16 = (png_uint_16)((rc*red_1 + gc*green_1
+ bc*blue_1 + 16384)>>15);
w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
png_ptr->gamma_shift][gray16 >> 8];
rgb_error |= 1;
}
*(dp++) = (png_byte)((w>>8) & 0xff);
*(dp++) = (png_byte)(w & 0xff);
if (have_alpha)
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
}
}
}
else
#endif
{
png_bytep sp = row;
png_bytep dp = row;
png_uint_32 i;
for (i = 0; i < row_width; i++)
{
png_uint_16 red, green, blue, gray16;
red = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
blue = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
if (red != green || red != blue)
rgb_error |= 1;
/* From 1.5.5 in the 16 bit case do the accurate conversion even
* in the 'fast' case - this is because this is where the code
* ends up when handling linear 16 bit data.
*/
gray16 = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
15);
*(dp++) = (png_byte)((gray16>>8) & 0xff);
*(dp++) = (png_byte)(gray16 & 0xff);
if (have_alpha)
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
}
}
}
}
row_info->channels = (png_byte)(row_info->channels - 2);
row_info->color_type = (png_byte)(row_info->color_type &
~PNG_COLOR_MASK_COLOR);
row_info->pixel_depth = (png_byte)(row_info->channels *
row_info->bit_depth);
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
}
return rgb_error;
}
#endif
#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
/* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
* large of png_color. This lets grayscale images be treated as
* paletted. Most useful for gamma correction and simplification
* of code. This API is not used internally.
*/
void PNGAPI
png_build_grayscale_palette(int bit_depth, png_colorp palette)
{
int num_palette;
int color_inc;
int i;
int v;
png_debug(1, "in png_do_build_grayscale_palette");
if (palette == NULL)
return;
switch (bit_depth)
{
case 1:
num_palette = 2;
color_inc = 0xff;
break;
case 2:
num_palette = 4;
color_inc = 0x55;
break;
case 4:
num_palette = 16;
color_inc = 0x11;
break;
case 8:
num_palette = 256;
color_inc = 1;
break;
default:
num_palette = 0;
color_inc = 0;
break;
}
for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
{
palette[i].red = (png_byte)v;
palette[i].green = (png_byte)v;
palette[i].blue = (png_byte)v;
}
}
#endif
#ifdef PNG_READ_TRANSFORMS_SUPPORTED
#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
(defined PNG_READ_ALPHA_MODE_SUPPORTED)
/* Replace any alpha or transparency with the supplied background color.
* "background" is already in the screen gamma, while "background_1" is
* at a gamma of 1.0. Paletted files have already been taken care of.
*/
void /* PRIVATE */
png_do_compose(png_row_infop row_info, png_bytep row, png_structp png_ptr)
{
#ifdef PNG_READ_GAMMA_SUPPORTED
png_const_bytep gamma_table = png_ptr->gamma_table;
png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
int gamma_shift = png_ptr->gamma_shift;
#endif
png_bytep sp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
int shift;
png_debug(1, "in png_do_compose");
{
switch (row_info->color_type)
{
case PNG_COLOR_TYPE_GRAY:
{
switch (row_info->bit_depth)
{
case 1:
{
sp = row;
shift = 7;
for (i = 0; i < row_width; i++)
{
if ((png_uint_16)((*sp >> shift) & 0x01)
== png_ptr->trans_color.gray)
{
*sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
*sp |= (png_byte)(png_ptr->background.gray << shift);
}
if (!shift)
{
shift = 7;
sp++;
}
else
shift--;
}
break;
}
case 2:
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_table != NULL)
{
sp = row;
shift = 6;
for (i = 0; i < row_width; i++)
{
if ((png_uint_16)((*sp >> shift) & 0x03)
== png_ptr->trans_color.gray)
{
*sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
*sp |= (png_byte)(png_ptr->background.gray << shift);
}
else
{
png_byte p = (png_byte)((*sp >> shift) & 0x03);
png_byte g = (png_byte)((gamma_table [p | (p << 2) |
(p << 4) | (p << 6)] >> 6) & 0x03);
*sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
*sp |= (png_byte)(g << shift);
}
if (!shift)
{
shift = 6;
sp++;
}
else
shift -= 2;
}
}
else
#endif
{
sp = row;
shift = 6;
for (i = 0; i < row_width; i++)
{
if ((png_uint_16)((*sp >> shift) & 0x03)
== png_ptr->trans_color.gray)
{
*sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
*sp |= (png_byte)(png_ptr->background.gray << shift);
}
if (!shift)
{
shift = 6;
sp++;
}
else
shift -= 2;
}
}
break;
}
case 4:
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_table != NULL)
{
sp = row;
shift = 4;
for (i = 0; i < row_width; i++)
{
if ((png_uint_16)((*sp >> shift) & 0x0f)
== png_ptr->trans_color.gray)
{
*sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
*sp |= (png_byte)(png_ptr->background.gray << shift);
}
else
{
png_byte p = (png_byte)((*sp >> shift) & 0x0f);
png_byte g = (png_byte)((gamma_table[p |
(p << 4)] >> 4) & 0x0f);
*sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
*sp |= (png_byte)(g << shift);
}
if (!shift)
{
shift = 4;
sp++;
}
else
shift -= 4;
}
}
else
#endif
{
sp = row;
shift = 4;
for (i = 0; i < row_width; i++)
{
if ((png_uint_16)((*sp >> shift) & 0x0f)
== png_ptr->trans_color.gray)
{
*sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
*sp |= (png_byte)(png_ptr->background.gray << shift);
}
if (!shift)
{
shift = 4;
sp++;
}
else
shift -= 4;
}
}
break;
}
case 8:
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_table != NULL)
{
sp = row;
for (i = 0; i < row_width; i++, sp++)
{
if (*sp == png_ptr->trans_color.gray)
*sp = (png_byte)png_ptr->background.gray;
else
*sp = gamma_table[*sp];
}
}
else
#endif
{
sp = row;
for (i = 0; i < row_width; i++, sp++)
{
if (*sp == png_ptr->trans_color.gray)
*sp = (png_byte)png_ptr->background.gray;
}
}
break;
}
case 16:
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_16 != NULL)
{
sp = row;
for (i = 0; i < row_width; i++, sp += 2)
{
png_uint_16 v;
v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
if (v == png_ptr->trans_color.gray)
{
/* Background is already in screen gamma */
*sp = (png_byte)((png_ptr->background.gray >> 8)
& 0xff);
*(sp + 1) = (png_byte)(png_ptr->background.gray
& 0xff);
}
else
{
v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
*sp = (png_byte)((v >> 8) & 0xff);
*(sp + 1) = (png_byte)(v & 0xff);
}
}
}
else
#endif
{
sp = row;
for (i = 0; i < row_width; i++, sp += 2)
{
png_uint_16 v;
v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
if (v == png_ptr->trans_color.gray)
{
*sp = (png_byte)((png_ptr->background.gray >> 8)
& 0xff);
*(sp + 1) = (png_byte)(png_ptr->background.gray
& 0xff);
}
}
}
break;
}
default:
break;
}
break;
}
case PNG_COLOR_TYPE_RGB:
{
if (row_info->bit_depth == 8)
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_table != NULL)
{
sp = row;
for (i = 0; i < row_width; i++, sp += 3)
{
if (*sp == png_ptr->trans_color.red &&
*(sp + 1) == png_ptr->trans_color.green &&
*(sp + 2) == png_ptr->trans_color.blue)
{
*sp = (png_byte)png_ptr->background.red;
*(sp + 1) = (png_byte)png_ptr->background.green;
*(sp + 2) = (png_byte)png_ptr->background.blue;
}
else
{
*sp = gamma_table[*sp];
*(sp + 1) = gamma_table[*(sp + 1)];
*(sp + 2) = gamma_table[*(sp + 2)];
}
}
}
else
#endif
{
sp = row;
for (i = 0; i < row_width; i++, sp += 3)
{
if (*sp == png_ptr->trans_color.red &&
*(sp + 1) == png_ptr->trans_color.green &&
*(sp + 2) == png_ptr->trans_color.blue)
{
*sp = (png_byte)png_ptr->background.red;
*(sp + 1) = (png_byte)png_ptr->background.green;
*(sp + 2) = (png_byte)png_ptr->background.blue;
}
}
}
}
else /* if (row_info->bit_depth == 16) */
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_16 != NULL)
{
sp = row;
for (i = 0; i < row_width; i++, sp += 6)
{
png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
+ *(sp + 3));
png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
+ *(sp + 5));
if (r == png_ptr->trans_color.red &&
g == png_ptr->trans_color.green &&
b == png_ptr->trans_color.blue)
{
/* Background is already in screen gamma */
*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
& 0xff);
*(sp + 3) = (png_byte)(png_ptr->background.green
& 0xff);
*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
& 0xff);
*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
}
else
{
png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
*sp = (png_byte)((v >> 8) & 0xff);
*(sp + 1) = (png_byte)(v & 0xff);
v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
*(sp + 2) = (png_byte)((v >> 8) & 0xff);
*(sp + 3) = (png_byte)(v & 0xff);
v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
*(sp + 4) = (png_byte)((v >> 8) & 0xff);
*(sp + 5) = (png_byte)(v & 0xff);
}
}
}
else
#endif
{
sp = row;
for (i = 0; i < row_width; i++, sp += 6)
{
png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
+ *(sp + 3));
png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
+ *(sp + 5));
if (r == png_ptr->trans_color.red &&
g == png_ptr->trans_color.green &&
b == png_ptr->trans_color.blue)
{
*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
& 0xff);
*(sp + 3) = (png_byte)(png_ptr->background.green
& 0xff);
*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
& 0xff);
*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
}
}
}
}
break;
}
case PNG_COLOR_TYPE_GRAY_ALPHA:
{
if (row_info->bit_depth == 8)
{
#ifdef PNG_READ_GAMMA_SUPPORTED
if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
gamma_table != NULL)
{
sp = row;
for (i = 0; i < row_width; i++, sp += 2)
{
png_uint_16 a = *(sp + 1);
if (a == 0xff)
*sp = gamma_table[*sp];
else if (a == 0)
{
/* Background is already in screen gamma */
*sp = (png_byte)png_ptr->background.gray;
}
else
{
png_byte v, w;
v = gamma_to_1[*sp];
png_composite(w, v, a, png_ptr->background_1.gray);
if (!optimize)
w = gamma_from_1[w];
*sp = w;
}
}
}
else