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4284 lines (3985 loc) · 143 KB
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/* pngrtran.c - transforms the data in a row for PNG readers
*
* Last changed in libpng 1.2.22 [October 13, 2007]
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1998-2007 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 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
#include "png.h"
#if defined(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\n");
/* Tell libpng how we react to CRC errors in critical chunks */
if(png_ptr == NULL) return;
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;
}
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\n");
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
#if defined(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\n");
if(png_ptr == NULL) return;
png_ptr->transformations |= PNG_16_TO_8;
}
#endif
#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
void PNGAPI
png_set_strip_alpha(png_structp png_ptr)
{
png_debug(1, "in png_set_strip_alpha\n");
if(png_ptr == NULL) return;
png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
}
#endif
#if defined(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\n");
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_malloc(png_ptr, (png_uint_32)(769 *
png_sizeof (png_dsortp)));
for (i = 0; i < 769; i++)
hash[i] = NULL;
/* png_memset(hash, 0, 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_malloc(png_ptr,
(png_uint_32)(num_entries * png_sizeof (png_byte)));
png_memset(png_ptr->palette_lookup, 0, 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\n");
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
#if defined(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\n");
if(png_ptr == NULL) return;
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
#ifdef PNG_WARN_UNINITIALIZED_ROW
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
#endif
}
/* 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-1.4.0, png_set_gray_1_2_4_to_8() was modified
* to expand only the sample depth but not to expand the tRNS to alpha.
*/
/* 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\n");
if(png_ptr == NULL) return;
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
#ifdef PNG_WARN_UNINITIALIZED_ROW
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
#endif
}
#if !defined(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\n");
if(png_ptr == NULL) return;
png_ptr->transformations |= PNG_EXPAND;
#ifdef PNG_WARN_UNINITIALIZED_ROW
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
#endif
}
#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\n");
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\n");
png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
#ifdef PNG_WARN_UNINITIALIZED_ROW
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
#endif
}
#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
#if defined(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\n");
png_ptr->transformations |= PNG_GRAY_TO_RGB;
#ifdef PNG_WARN_UNINITIALIZED_ROW
png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
#endif
}
#endif
#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
#if defined(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 = (int)((float)red*100000.0 + 0.5);
int green_fixed = (int)((float)green*100000.0 + 0.5);
if(png_ptr == NULL) return;
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\n");
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)
#if defined(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_WRITE_USER_TRANSFORM_SUPPORTED) || \
defined(PNG_LEGACY_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\n");
if(png_ptr == NULL) return;
#if defined(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\n");
#if defined(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)
#if 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.
*/
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;
#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
if (png_ptr->transformations & PNG_INVERT_ALPHA)
{
#if defined(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);
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
if (png_ptr->transformations & PNG_BACKGROUND)
{
if (color_type == PNG_COLOR_TYPE_PALETTE)
{
/* could skip if no transparency and
*/
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);
}
for (i = 0; i < num_palette; i++)
{
if (i < (int)png_ptr->num_trans && png_ptr->trans[i] != 0xff)
{
if (png_ptr->trans[i] == 0)
{
palette[i] = back;
}
else /* if (png_ptr->trans[i] != 0xff) */
{
png_byte v, w;
v = png_ptr->gamma_to_1[palette[i].red];
png_composite(w, v, png_ptr->trans[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[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[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];
}
}
}
/* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
else
/* color_type != PNG_COLOR_TYPE_PALETTE */
{
double m = (double)(((png_uint_32)1 << png_ptr->bit_depth) - 1);
double g = 1.0;
double gs = 1.0;
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;
}
png_ptr->background_1.gray = (png_uint_16)(pow(
(double)png_ptr->background.gray / m, g) * m + .5);
png_ptr->background.gray = (png_uint_16)(pow(
(double)png_ptr->background.gray / m, gs) * m + .5);
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))