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pngrtran.c
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/* pngrtran.c - transforms the data in a row for PNG readers
*
* Last changed in libpng 1.2.45 [July 7, 2011]
* Copyright (c) 1998-2011 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.
*/
#define PNG_INTERNAL
#define PNG_NO_PEDANTIC_WARNINGS
#include "png.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;
}
}
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
defined(PNG_FLOATING_POINT_SUPPORTED)
/* Handle alpha and tRNS via a background color */
void PNGAPI
png_set_background(png_structp png_ptr,
png_color_16p background_color, int background_gamma_code,
int need_expand, double background_gamma)
{
png_debug(1, "in png_set_background");
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_BACKGROUND;
png_memcpy(&(png_ptr->background), background_color,
png_sizeof(png_color_16));
png_ptr->background_gamma = (float)background_gamma;
png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
}
#endif
#ifdef PNG_READ_16_TO_8_SUPPORTED
/* Strip 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->flags |= PNG_FLAG_STRIP_ALPHA;
}
#endif
#ifdef PNG_READ_DITHER_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_dither" indicates
* whether we need a dithering 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_dither(png_structp png_ptr, png_colorp palette,
int num_palette, int maximum_colors, png_uint_16p histogram,
int full_dither)
{
png_debug(1, "in png_set_dither");
if (png_ptr == NULL)
return;
png_ptr->transformations |= PNG_DITHER;
if (!full_dither)
{
int i;
png_ptr->dither_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->dither_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->dither_sort = (png_bytep)png_malloc(png_ptr,
(png_uint_32)(num_palette * png_sizeof(png_byte)));
/* Initialize the dither_sort array */
for (i = 0; i < num_palette; i++)
png_ptr->dither_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->dither_sort[j]]
< histogram[png_ptr->dither_sort[j + 1]])
{
png_byte t;
t = png_ptr->dither_sort[j];
png_ptr->dither_sort[j] = png_ptr->dither_sort[j + 1];
png_ptr->dither_sort[j + 1] = t;
done = 0;
}
}
if (done)
break;
}
/* Swap the palette around, and set up a table, if necessary */
if (full_dither)
{
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->dither_sort[i] >= maximum_colors)
{
do
j--;
while ((int)png_ptr->dither_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->dither_sort[i] >= maximum_colors)
{
png_color tmp_color;
do
j--;
while ((int)png_ptr->dither_sort[j] >= maximum_colors);
tmp_color = palette[j];
palette[j] = palette[i];
palette[i] = tmp_color;
/* Indicate where the color went */
png_ptr->dither_index[j] = (png_byte)i;
png_ptr->dither_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->dither_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->dither_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->dither_index[i] = (png_byte)min_k;
}
}
}
png_free(png_ptr, png_ptr->dither_sort);
png_ptr->dither_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_dither)
{
int k;
for (k = 0; k < num_palette; k++)
{
if (png_ptr->dither_index[k] ==
png_ptr->index_to_palette[j])
png_ptr->dither_index[k] =
png_ptr->index_to_palette[next_j];
if ((int)png_ptr->dither_index[k] ==
num_new_palette)
png_ptr->dither_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_dither)
{
int i;
png_bytep distance;
int total_bits = PNG_DITHER_RED_BITS + PNG_DITHER_GREEN_BITS +
PNG_DITHER_BLUE_BITS;
int num_red = (1 << PNG_DITHER_RED_BITS);
int num_green = (1 << PNG_DITHER_GREEN_BITS);
int num_blue = (1 << PNG_DITHER_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_DITHER_RED_BITS));
int g = (palette[i].green >> (8 - PNG_DITHER_GREEN_BITS));
int b = (palette[i].blue >> (8 - PNG_DITHER_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_DITHER_BLUE_BITS +
PNG_DITHER_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_DITHER_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
#if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
/* Transform the image from the file_gamma to the screen_gamma. We
* 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.
*
* We will turn off gamma transformation later if no semitransparent entries
* are present in the tRNS array for palette images. We can't do it here
* because we don't necessarily have the tRNS chunk yet.
*/
void PNGAPI
png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
{
png_debug(1, "in png_set_gamma");
if (png_ptr == NULL)
return;
if ((fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD) ||
(png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
(png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
png_ptr->transformations |= PNG_GAMMA;
png_ptr->gamma = (float)file_gamma;
png_ptr->screen_gamma = (float)scrn_gamma;
}
#endif
#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;
}
#ifndef PNG_1_0_X
/* 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;
}
#endif
#if defined(PNG_1_0_X) || defined(PNG_1_2_X)
/* Expand grayscale images of less than 8-bit depth to 8 bits. */
/* Deprecated as of libpng-1.2.9 */
void PNGAPI
png_set_gray_1_2_4_to_8(png_structp png_ptr)
{
png_debug(1, "in png_set_gray_1_2_4_to_8");
if (png_ptr == NULL)
return;
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
}
#endif
/* 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_GRAY_TO_RGB_SUPPORTED
void PNGAPI
png_set_gray_to_rgb(png_structp png_ptr)
{
png_debug(1, "in png_set_gray_to_rgb");
png_ptr->transformations |= PNG_GRAY_TO_RGB;
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
}
#endif
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
#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)
{
int red_fixed, green_fixed;
if (png_ptr == NULL)
return;
if (red > 21474.83647 || red < -21474.83648 ||
green > 21474.83647 || green < -21474.83648)
{
png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
red_fixed = -1;
green_fixed = -1;
}
else
{
red_fixed = (int)((float)red*100000.0 + 0.5);
green_fixed = (int)((float)green*100000.0 + 0.5);
}
png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed);
}
#endif
void PNGAPI
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 1: png_ptr->transformations |= PNG_RGB_TO_GRAY;
break;
case 2: png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
break;
case 3: png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
}
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
{
png_uint_16 red_int, green_int;
if (red < 0 || green < 0)
{
red_int = 6968; /* .212671 * 32768 + .5 */
green_int = 23434; /* .715160 * 32768 + .5 */
}
else if (red + green < 100000L)
{
red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
}
else
{
png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
red_int = 6968;
green_int = 23434;
}
png_ptr->rgb_to_gray_red_coeff = red_int;
png_ptr->rgb_to_gray_green_coeff = green_int;
png_ptr->rgb_to_gray_blue_coeff =
(png_uint_16)(32768 - red_int - green_int);
}
}
#endif
#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
defined(PNG_LEGACY_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
#ifdef PNG_LEGACY_SUPPORTED
if (read_user_transform_fn)
png_warning(png_ptr,
"This version of libpng does not support user transforms");
#endif
}
#endif
/* Initialize everything needed for the read. This includes modifying
* the palette.
*/
void /* PRIVATE */
png_init_read_transformations(png_structp png_ptr)
{
png_debug(1, "in png_init_read_transformations");
#ifdef PNG_USELESS_TESTS_SUPPORTED
if (png_ptr != NULL)
#endif
{
#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_SHIFT_SUPPORTED) || \
defined(PNG_READ_GAMMA_SUPPORTED)
int color_type = png_ptr->color_type;
#endif
#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
#ifdef 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.
*/
if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
!(color_type & PNG_COLOR_MASK_COLOR))
{
png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
} else if ((png_ptr->transformations & PNG_BACKGROUND) &&
!(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
(png_ptr->transformations & PNG_GRAY_TO_RGB) &&
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
if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
(png_ptr->transformations & PNG_EXPAND))
{
if (!(color_type & PNG_COLOR_MASK_COLOR)) /* i.e., GRAY or GRAY_ALPHA */
{
/* Expand background and tRNS chunks */
switch (png_ptr->bit_depth)
{
case 1:
png_ptr->background.gray *= (png_uint_16)0xff;
png_ptr->background.red = png_ptr->background.green
= png_ptr->background.blue = png_ptr->background.gray;
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
{
png_ptr->trans_values.gray *= (png_uint_16)0xff;
png_ptr->trans_values.red = png_ptr->trans_values.green
= png_ptr->trans_values.blue = png_ptr->trans_values.gray;
}
break;
case 2:
png_ptr->background.gray *= (png_uint_16)0x55;
png_ptr->background.red = png_ptr->background.green
= png_ptr->background.blue = png_ptr->background.gray;
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
{
png_ptr->trans_values.gray *= (png_uint_16)0x55;
png_ptr->trans_values.red = png_ptr->trans_values.green
= png_ptr->trans_values.blue = png_ptr->trans_values.gray;
}
break;
case 4:
png_ptr->background.gray *= (png_uint_16)0x11;
png_ptr->background.red = png_ptr->background.green
= png_ptr->background.blue = png_ptr->background.gray;
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
{
png_ptr->trans_values.gray *= (png_uint_16)0x11;
png_ptr->trans_values.red = png_ptr->trans_values.green
= png_ptr->trans_values.blue = png_ptr->trans_values.gray;
}
break;
case 8:
case 16:
png_ptr->background.red = png_ptr->background.green
= png_ptr->background.blue = png_ptr->background.gray;
break;
}
}
else if (color_type == PNG_COLOR_TYPE_PALETTE)
{
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)
{
#ifdef PNG_READ_EXPAND_SUPPORTED
if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
#endif
{
/* Invert the alpha channel (in tRNS) unless the pixels are
* going to be expanded, in which case leave it for later
*/
int i, istop;
istop=(int)png_ptr->num_trans;
for (i=0; i<istop; i++)
png_ptr->trans[i] = (png_byte)(255 - png_ptr->trans[i]);
}
}
#endif
}
}
#endif
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
png_ptr->background_1 = png_ptr->background;
#endif
#if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
if ((color_type == PNG_COLOR_TYPE_PALETTE && png_ptr->num_trans != 0)
&& (fabs(png_ptr->screen_gamma * png_ptr->gamma - 1.0)
< PNG_GAMMA_THRESHOLD))
{
int i, k;
k=0;
for (i=0; i<png_ptr->num_trans; i++)
{
if (png_ptr->trans[i] != 0 && png_ptr->trans[i] != 0xff)
k=1; /* Partial transparency is present */
}
if (k == 0)
png_ptr->transformations &= ~PNG_GAMMA;
}
if ((png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY)) &&
png_ptr->gamma != 0.0)
{
png_build_gamma_table(png_ptr);
#ifdef PNG_READ_BACKGROUND_SUPPORTED
if (png_ptr->transformations & PNG_BACKGROUND)
{
if (color_type == PNG_COLOR_TYPE_PALETTE)
{
/* Could skip if no transparency */
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
{
double g, gs;
switch (png_ptr->background_gamma_type)
{
case PNG_BACKGROUND_GAMMA_SCREEN:
g = (png_ptr->screen_gamma);
gs = 1.0;
break;
case PNG_BACKGROUND_GAMMA_FILE:
g = 1.0 / (png_ptr->gamma);
gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
break;
case PNG_BACKGROUND_GAMMA_UNIQUE:
g = 1.0 / (png_ptr->background_gamma);
gs = 1.0 / (png_ptr->background_gamma *
png_ptr->screen_gamma);
break;
default:
g = 1.0; /* back_1 */
gs = 1.0; /* back */
}
if ( fabs(gs - 1.0) < PNG_GAMMA_THRESHOLD)
{
back.red = (png_byte)png_ptr->background.red;
back.green = (png_byte)png_ptr->background.green;
back.blue = (png_byte)png_ptr->background.blue;
}
else
{
back.red = (png_byte)(pow(
(double)png_ptr->background.red/255, gs) * 255.0 + .5);
back.green = (png_byte)(pow(
(double)png_ptr->background.green/255, gs) * 255.0
+ .5);
back.blue = (png_byte)(pow(
(double)png_ptr->background.blue/255, gs) * 255.0 + .5);
}
back_1.red = (png_byte)(pow(
(double)png_ptr->background.red/255, g) * 255.0 + .5);
back_1.green = (png_byte)(pow(
(double)png_ptr->background.green/255, g) * 255.0 + .5);
back_1.blue = (png_byte)(pow(
(double)png_ptr->background.blue/255, g) * 255.0 + .5);
}