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/*-
* pngstest.c
*
* Copyright (c) 2013-2015 John Cunningham Bowler
*
* Last changed in libpng 1.6.18 [July 23, 2015]
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* Test for the PNG 'simplified' APIs.
*/
#define _ISOC90_SOURCE 1
#define MALLOC_CHECK_ 2/*glibc facility: turn on debugging*/
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <math.h>
#if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
# include <config.h>
#endif
/* Define the following to use this test against your installed libpng, rather
* than the one being built here:
*/
#ifdef PNG_FREESTANDING_TESTS
# include <png.h>
#else
# include "../../png.h"
#endif
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED /* Else nothing can be done */
#include "../tools/sRGB.h"
/* KNOWN ISSUES
*
* These defines switch on alternate algorithms for format conversions to match
* the current libpng implementation; they are set to allow pngstest to pass
* even though libpng is producing answers that are not as correct as they
* should be.
*/
#define ALLOW_UNUSED_GPC 0
/* If true include unused static GPC functions and declare an external array
* of them to hide the fact that they are unused. This is for development
* use while testing the correct function to use to take into account libpng
* misbehavior, such as using a simple power law to correct sRGB to linear.
*/
/* The following is to support direct compilation of this file as C++ */
#ifdef __cplusplus
# define voidcast(type, value) static_cast<type>(value)
# define aligncastconst(type, value) \
static_cast<type>(static_cast<const void*>(value))
#else
# define voidcast(type, value) (value)
# define aligncastconst(type, value) ((const void*)(value))
#endif /* __cplusplus */
/* During parallel runs of pngstest each temporary file needs a unique name,
* this is used to permit uniqueness using a command line argument which can be
* up to 22 characters long.
*/
static char tmpf[23] = "TMP";
/* Generate random bytes. This uses a boring repeatable algorithm and it
* is implemented here so that it gives the same set of numbers on every
* architecture. It's a linear congruential generator (Knuth or Sedgewick
* "Algorithms") but it comes from the 'feedback taps' table in Horowitz and
* Hill, "The Art of Electronics".
*/
static void
make_random_bytes(png_uint_32* seed, void* pv, size_t size)
{
png_uint_32 u0 = seed[0], u1 = seed[1];
png_bytep bytes = voidcast(png_bytep, pv);
/* There are thirty three bits, the next bit in the sequence is bit-33 XOR
* bit-20. The top 1 bit is in u1, the bottom 32 are in u0.
*/
size_t i;
for (i=0; i<size; ++i)
{
/* First generate 8 new bits then shift them in at the end. */
png_uint_32 u = ((u0 >> (20-8)) ^ ((u1 << 7) | (u0 >> (32-7)))) & 0xff;
u1 <<= 8;
u1 |= u0 >> 24;
u0 <<= 8;
u0 |= u;
*bytes++ = (png_byte)u;
}
seed[0] = u0;
seed[1] = u1;
}
static void
random_color(png_colorp color)
{
static png_uint_32 color_seed[2] = { 0x12345678, 0x9abcdef };
make_random_bytes(color_seed, color, sizeof *color);
}
/* Math support - neither Cygwin nor Visual Studio have C99 support and we need
* a predictable rounding function, so make one here:
*/
static double
closestinteger(double x)
{
return floor(x + .5);
}
/* Cast support: remove GCC whines. */
static png_byte
u8d(double d)
{
d = closestinteger(d);
return (png_byte)d;
}
static png_uint_16
u16d(double d)
{
d = closestinteger(d);
return (png_uint_16)d;
}
/* sRGB support: use exact calculations rounded to the nearest int, see the
* fesetround() call in main(). sRGB_to_d optimizes the 8 to 16-bit conversion.
*/
static double sRGB_to_d[256];
static double g22_to_d[256];
static void
init_sRGB_to_d(void)
{
int i;
sRGB_to_d[0] = 0;
for (i=1; i<255; ++i)
sRGB_to_d[i] = linear_from_sRGB(i/255.);
sRGB_to_d[255] = 1;
g22_to_d[0] = 0;
for (i=1; i<255; ++i)
g22_to_d[i] = pow(i/255., 1/.45455);
g22_to_d[255] = 1;
}
static png_byte
sRGB(double linear /*range 0.0 .. 1.0*/)
{
return u8d(255 * sRGB_from_linear(linear));
}
static png_byte
isRGB(int fixed_linear)
{
return sRGB(fixed_linear / 65535.);
}
#if 0 /* not used */
static png_byte
unpremultiply(int component, int alpha)
{
if (alpha <= component)
return 255; /* Arbitrary, but consistent with the libpng code */
else if (alpha >= 65535)
return isRGB(component);
else
return sRGB((double)component / alpha);
}
#endif
static png_uint_16
ilinear(int fixed_srgb)
{
return u16d(65535 * sRGB_to_d[fixed_srgb]);
}
static png_uint_16
ilineara(int fixed_srgb, int alpha)
{
return u16d((257 * alpha) * sRGB_to_d[fixed_srgb]);
}
static png_uint_16
ilinear_g22(int fixed_srgb)
{
return u16d(65535 * g22_to_d[fixed_srgb]);
}
#if ALLOW_UNUSED_GPC
static png_uint_16
ilineara_g22(int fixed_srgb, int alpha)
{
return u16d((257 * alpha) * g22_to_d[fixed_srgb]);
}
#endif
static double
YfromRGBint(int ir, int ig, int ib)
{
double r = ir;
double g = ig;
double b = ib;
return YfromRGB(r, g, b);
}
#if 0 /* unused */
/* The error that results from using a 2.2 power law in place of the correct
* sRGB transform, given an 8-bit value which might be either sRGB or power-law.
*/
static int
power_law_error8(int value)
{
if (value > 0 && value < 255)
{
double vd = value / 255.;
double e = fabs(
pow(sRGB_to_d[value], 1/2.2) - sRGB_from_linear(pow(vd, 2.2)));
/* Always allow an extra 1 here for rounding errors */
e = 1+floor(255 * e);
return (int)e;
}
return 0;
}
static int error_in_sRGB_roundtrip = 56; /* by experiment */
static int
power_law_error16(int value)
{
if (value > 0 && value < 65535)
{
/* Round trip the value through an 8-bit representation but using
* non-matching to/from conversions.
*/
double vd = value / 65535.;
double e = fabs(
pow(sRGB_from_linear(vd), 2.2) - linear_from_sRGB(pow(vd, 1/2.2)));
/* Always allow an extra 1 here for rounding errors */
e = error_in_sRGB_roundtrip+floor(65535 * e);
return (int)e;
}
return 0;
}
static int
compare_8bit(int v1, int v2, int error_limit, int multiple_algorithms)
{
int e = abs(v1-v2);
int ev1, ev2;
if (e <= error_limit)
return 1;
if (!multiple_algorithms)
return 0;
ev1 = power_law_error8(v1);
if (e <= ev1)
return 1;
ev2 = power_law_error8(v2);
if (e <= ev2)
return 1;
return 0;
}
static int
compare_16bit(int v1, int v2, int error_limit, int multiple_algorithms)
{
int e = abs(v1-v2);
int ev1, ev2;
if (e <= error_limit)
return 1;
/* "multiple_algorithms" in this case means that a color-map has been
* involved somewhere, so we can deduce that the values were forced to 8-bit
* (like the via_linear case for 8-bit.)
*/
if (!multiple_algorithms)
return 0;
ev1 = power_law_error16(v1);
if (e <= ev1)
return 1;
ev2 = power_law_error16(v2);
if (e <= ev2)
return 1;
return 0;
}
#endif /* unused */
#define READ_FILE 1 /* else memory */
#define USE_STDIO 2 /* else use file name */
#define STRICT 4 /* fail on warnings too */
#define VERBOSE 8
#define KEEP_TMPFILES 16 /* else delete temporary files */
#define KEEP_GOING 32
#define ACCUMULATE 64
#define FAST_WRITE 128
#define sRGB_16BIT 256
static void
print_opts(png_uint_32 opts)
{
if (opts & READ_FILE)
printf(" --file");
if (opts & USE_STDIO)
printf(" --stdio");
if (opts & STRICT)
printf(" --strict");
if (opts & VERBOSE)
printf(" --verbose");
if (opts & KEEP_TMPFILES)
printf(" --preserve");
if (opts & KEEP_GOING)
printf(" --keep-going");
if (opts & ACCUMULATE)
printf(" --accumulate");
if (!(opts & FAST_WRITE)) /* --fast is currently the default */
printf(" --slow");
if (opts & sRGB_16BIT)
printf(" --sRGB-16bit");
}
#define FORMAT_NO_CHANGE 0x80000000 /* additional flag */
/* A name table for all the formats - defines the format of the '+' arguments to
* pngstest.
*/
#define FORMAT_COUNT 64
#define FORMAT_MASK 0x3f
static PNG_CONST char * PNG_CONST format_names[FORMAT_COUNT] =
{
"sRGB-gray",
"sRGB-gray+alpha",
"sRGB-rgb",
"sRGB-rgb+alpha",
"linear-gray",
"linear-gray+alpha",
"linear-rgb",
"linear-rgb+alpha",
"color-mapped-sRGB-gray",
"color-mapped-sRGB-gray+alpha",
"color-mapped-sRGB-rgb",
"color-mapped-sRGB-rgb+alpha",
"color-mapped-linear-gray",
"color-mapped-linear-gray+alpha",
"color-mapped-linear-rgb",
"color-mapped-linear-rgb+alpha",
"sRGB-gray",
"sRGB-gray+alpha",
"sRGB-bgr",
"sRGB-bgr+alpha",
"linear-gray",
"linear-gray+alpha",
"linear-bgr",
"linear-bgr+alpha",
"color-mapped-sRGB-gray",
"color-mapped-sRGB-gray+alpha",
"color-mapped-sRGB-bgr",
"color-mapped-sRGB-bgr+alpha",
"color-mapped-linear-gray",
"color-mapped-linear-gray+alpha",
"color-mapped-linear-bgr",
"color-mapped-linear-bgr+alpha",
"sRGB-gray",
"alpha+sRGB-gray",
"sRGB-rgb",
"alpha+sRGB-rgb",
"linear-gray",
"alpha+linear-gray",
"linear-rgb",
"alpha+linear-rgb",
"color-mapped-sRGB-gray",
"color-mapped-alpha+sRGB-gray",
"color-mapped-sRGB-rgb",
"color-mapped-alpha+sRGB-rgb",
"color-mapped-linear-gray",
"color-mapped-alpha+linear-gray",
"color-mapped-linear-rgb",
"color-mapped-alpha+linear-rgb",
"sRGB-gray",
"alpha+sRGB-gray",
"sRGB-bgr",
"alpha+sRGB-bgr",
"linear-gray",
"alpha+linear-gray",
"linear-bgr",
"alpha+linear-bgr",
"color-mapped-sRGB-gray",
"color-mapped-alpha+sRGB-gray",
"color-mapped-sRGB-bgr",
"color-mapped-alpha+sRGB-bgr",
"color-mapped-linear-gray",
"color-mapped-alpha+linear-gray",
"color-mapped-linear-bgr",
"color-mapped-alpha+linear-bgr",
};
/* Decode an argument to a format number. */
static png_uint_32
formatof(const char *arg)
{
char *ep;
unsigned long format = strtoul(arg, &ep, 0);
if (ep > arg && *ep == 0 && format < FORMAT_COUNT)
return (png_uint_32)format;
else for (format=0; format < FORMAT_COUNT; ++format)
{
if (strcmp(format_names[format], arg) == 0)
return (png_uint_32)format;
}
fprintf(stderr, "pngstest: format name '%s' invalid\n", arg);
return FORMAT_COUNT;
}
/* Bitset/test functions for formats */
#define FORMAT_SET_COUNT (FORMAT_COUNT / 32)
typedef struct
{
png_uint_32 bits[FORMAT_SET_COUNT];
}
format_list;
static void format_init(format_list *pf)
{
int i;
for (i=0; i<FORMAT_SET_COUNT; ++i)
pf->bits[i] = 0; /* All off */
}
#if 0 /* currently unused */
static void format_clear(format_list *pf)
{
int i;
for (i=0; i<FORMAT_SET_COUNT; ++i)
pf->bits[i] = 0;
}
#endif
static int format_is_initial(format_list *pf)
{
int i;
for (i=0; i<FORMAT_SET_COUNT; ++i)
if (pf->bits[i] != 0)
return 0;
return 1;
}
static int format_set(format_list *pf, png_uint_32 format)
{
if (format < FORMAT_COUNT)
return pf->bits[format >> 5] |= ((png_uint_32)1) << (format & 31);
return 0;
}
#if 0 /* currently unused */
static int format_unset(format_list *pf, png_uint_32 format)
{
if (format < FORMAT_COUNT)
return pf->bits[format >> 5] &= ~((png_uint_32)1) << (format & 31);
return 0;
}
#endif
static int format_isset(format_list *pf, png_uint_32 format)
{
return format < FORMAT_COUNT &&
(pf->bits[format >> 5] & (((png_uint_32)1) << (format & 31))) != 0;
}
static void format_default(format_list *pf, int redundant)
{
if (redundant)
{
int i;
/* set everything, including flags that are pointless */
for (i=0; i<FORMAT_SET_COUNT; ++i)
pf->bits[i] = ~(png_uint_32)0;
}
else
{
png_uint_32 f;
for (f=0; f<FORMAT_COUNT; ++f)
{
/* Eliminate redundant and unsupported settings. */
# ifdef PNG_FORMAT_BGR_SUPPORTED
/* BGR is meaningless if no color: */
if ((f & PNG_FORMAT_FLAG_COLOR) == 0 &&
(f & PNG_FORMAT_FLAG_BGR) != 0)
# else
if ((f & 0x10U/*HACK: fixed value*/) != 0)
# endif
continue;
/* AFIRST is meaningless if no alpha: */
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if ((f & PNG_FORMAT_FLAG_ALPHA) == 0 &&
(f & PNG_FORMAT_FLAG_AFIRST) != 0)
# else
if ((f & 0x20U/*HACK: fixed value*/) != 0)
# endif
continue;
format_set(pf, f);
}
}
}
/* THE Image STRUCTURE */
/* The super-class of a png_image, contains the decoded image plus the input
* data necessary to re-read the file with a different format.
*/
typedef struct
{
png_image image;
png_uint_32 opts;
const char *file_name;
int stride_extra;
FILE *input_file;
png_voidp input_memory;
png_size_t input_memory_size;
png_bytep buffer;
ptrdiff_t stride;
png_size_t bufsize;
png_size_t allocsize;
char tmpfile_name[32];
png_uint_16 colormap[256*4];
}
Image;
/* Initializer: also sets the permitted error limit for 16-bit operations. */
static void
newimage(Image *image)
{
memset(image, 0, sizeof *image);
}
/* Reset the image to be read again - only needs to rewind the FILE* at present.
*/
static void
resetimage(Image *image)
{
if (image->input_file != NULL)
rewind(image->input_file);
}
/* Free the image buffer; the buffer is re-used on a re-read, this is just for
* cleanup.
*/
static void
freebuffer(Image *image)
{
if (image->buffer) free(image->buffer);
image->buffer = NULL;
image->bufsize = 0;
image->allocsize = 0;
}
/* Delete function; cleans out all the allocated data and the temporary file in
* the image.
*/
static void
freeimage(Image *image)
{
freebuffer(image);
png_image_free(&image->image);
if (image->input_file != NULL)
{
fclose(image->input_file);
image->input_file = NULL;
}
if (image->input_memory != NULL)
{
free(image->input_memory);
image->input_memory = NULL;
image->input_memory_size = 0;
}
if (image->tmpfile_name[0] != 0 && (image->opts & KEEP_TMPFILES) == 0)
{
(void)remove(image->tmpfile_name);
image->tmpfile_name[0] = 0;
}
}
/* This is actually a re-initializer; allows an image structure to be re-used by
* freeing everything that relates to an old image.
*/
static void initimage(Image *image, png_uint_32 opts, const char *file_name,
int stride_extra)
{
freeimage(image);
memset(&image->image, 0, sizeof image->image);
image->opts = opts;
image->file_name = file_name;
image->stride_extra = stride_extra;
}
/* Make sure the image buffer is big enough; allows re-use of the buffer if the
* image is re-read.
*/
#define BUFFER_INIT8 73
static void
allocbuffer(Image *image)
{
png_size_t size = PNG_IMAGE_BUFFER_SIZE(image->image, image->stride);
if (size+32 > image->bufsize)
{
freebuffer(image);
image->buffer = voidcast(png_bytep, malloc(size+32));
if (image->buffer == NULL)
{
fflush(stdout);
fprintf(stderr,
"simpletest: out of memory allocating %lu(+32) byte buffer\n",
(unsigned long)size);
exit(1);
}
image->bufsize = size+32;
}
memset(image->buffer, 95, image->bufsize);
memset(image->buffer+16, BUFFER_INIT8, size);
image->allocsize = size;
}
/* Make sure 16 bytes match the given byte. */
static int
check16(png_const_bytep bp, int b)
{
int i = 16;
do
if (*bp != b) return 1;
while (--i);
return 0;
}
/* Check for overwrite in the image buffer. */
static void
checkbuffer(Image *image, const char *arg)
{
if (check16(image->buffer, 95))
{
fflush(stdout);
fprintf(stderr, "%s: overwrite at start of image buffer\n", arg);
exit(1);
}
if (check16(image->buffer+16+image->allocsize, 95))
{
fflush(stdout);
fprintf(stderr, "%s: overwrite at end of image buffer\n", arg);
exit(1);
}
}
/* ERROR HANDLING */
/* Log a terminal error, also frees the libpng part of the image if necessary.
*/
static int
logerror(Image *image, const char *a1, const char *a2, const char *a3)
{
fflush(stdout);
if (image->image.warning_or_error)
fprintf(stderr, "%s%s%s: %s\n", a1, a2, a3, image->image.message);
else
fprintf(stderr, "%s%s%s\n", a1, a2, a3);
if (image->image.opaque != NULL)
{
fprintf(stderr, "%s: image opaque pointer non-NULL on error\n",
image->file_name);
png_image_free(&image->image);
}
return 0;
}
/* Log an error and close a file (just a utility to do both things in one
* function call.)
*/
static int
logclose(Image *image, FILE *f, const char *name, const char *operation)
{
int e = errno;
fclose(f);
return logerror(image, name, operation, strerror(e));
}
/* Make sure the png_image has been freed - validates that libpng is doing what
* the spec says and freeing the image.
*/
static int
checkopaque(Image *image)
{
if (image->image.opaque != NULL)
{
png_image_free(&image->image);
return logerror(image, image->file_name, ": opaque not NULL", "");
}
else if (image->image.warning_or_error != 0 && (image->opts & STRICT) != 0)
return logerror(image, image->file_name, " --strict", "");
else
return 1;
}
/* IMAGE COMPARISON/CHECKING */
/* Compare the pixels of two images, which should be the same but aren't. The
* images must have been checked for a size match.
*/
typedef struct
{
/* The components, for grayscale images the gray value is in 'g' and if alpha
* is not present 'a' is set to 255 or 65535 according to format.
*/
int r, g, b, a;
} Pixel;
typedef struct
{
/* The background as the original sRGB 8-bit value converted to the final
* integer format and as a double precision linear value in the range 0..1
* for with partially transparent pixels.
*/
int ir, ig, ib;
double dr, dg, db; /* linear r,g,b scaled to 0..1 */
} Background;
/* Basic image formats; control the data but not the layout thereof. */
#define BASE_FORMATS\
(PNG_FORMAT_FLAG_ALPHA|PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_LINEAR)
/* Read a Pixel from a buffer. The code below stores the correct routine for
* the format in a function pointer, these are the routines:
*/
static void
gp_g8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = p->g = p->b = pp[0];
p->a = 255;
}
static void
gp_ga8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = p->g = p->b = pp[0];
p->a = pp[1];
}
#ifdef PNG_FORMAT_AFIRST_SUPPORTED
static void
gp_ag8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = p->g = p->b = pp[1];
p->a = pp[0];
}
#endif
static void
gp_rgb8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[0];
p->g = pp[1];
p->b = pp[2];
p->a = 255;
}
#ifdef PNG_FORMAT_BGR_SUPPORTED
static void
gp_bgr8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[2];
p->g = pp[1];
p->b = pp[0];
p->a = 255;
}
#endif
static void
gp_rgba8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[0];
p->g = pp[1];
p->b = pp[2];
p->a = pp[3];
}
#ifdef PNG_FORMAT_BGR_SUPPORTED
static void
gp_bgra8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[2];
p->g = pp[1];
p->b = pp[0];
p->a = pp[3];
}
#endif
#ifdef PNG_FORMAT_AFIRST_SUPPORTED
static void
gp_argb8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[1];
p->g = pp[2];
p->b = pp[3];
p->a = pp[0];
}
#endif
#if defined(PNG_FORMAT_AFIRST_SUPPORTED) && defined(PNG_FORMAT_BGR_SUPPORTED)
static void
gp_abgr8(Pixel *p, png_const_voidp pb)
{
png_const_bytep pp = voidcast(png_const_bytep, pb);
p->r = pp[3];
p->g = pp[2];
p->b = pp[1];
p->a = pp[0];
}
#endif
static void
gp_g16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = p->g = p->b = pp[0];
p->a = 65535;
}
static void
gp_ga16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = p->g = p->b = pp[0];
p->a = pp[1];
}
#ifdef PNG_FORMAT_AFIRST_SUPPORTED
static void
gp_ag16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = p->g = p->b = pp[1];
p->a = pp[0];
}
#endif
static void
gp_rgb16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[0];
p->g = pp[1];
p->b = pp[2];
p->a = 65535;
}
#ifdef PNG_FORMAT_BGR_SUPPORTED
static void
gp_bgr16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[2];
p->g = pp[1];
p->b = pp[0];
p->a = 65535;
}
#endif
static void
gp_rgba16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[0];
p->g = pp[1];
p->b = pp[2];
p->a = pp[3];
}
#ifdef PNG_FORMAT_BGR_SUPPORTED
static void
gp_bgra16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[2];
p->g = pp[1];
p->b = pp[0];
p->a = pp[3];
}
#endif
#ifdef PNG_FORMAT_AFIRST_SUPPORTED
static void
gp_argb16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[1];
p->g = pp[2];
p->b = pp[3];
p->a = pp[0];
}
#endif
#if defined(PNG_FORMAT_AFIRST_SUPPORTED) && defined(PNG_FORMAT_BGR_SUPPORTED)
static void
gp_abgr16(Pixel *p, png_const_voidp pb)
{
png_const_uint_16p pp = voidcast(png_const_uint_16p, pb);
p->r = pp[3];
p->g = pp[2];
p->b = pp[1];
p->a = pp[0];
}
#endif
/* Given a format, return the correct one of the above functions. */
static void (*
get_pixel(png_uint_32 format))(Pixel *p, png_const_voidp pb)
{
/* The color-map flag is irrelevant here - the caller of the function
* returned must either pass the buffer or, for a color-mapped image, the
* correct entry in the color-map.
*/
if (format & PNG_FORMAT_FLAG_LINEAR)
{
if (format & PNG_FORMAT_FLAG_COLOR)
{
# ifdef PNG_FORMAT_BGR_SUPPORTED
if (format & PNG_FORMAT_FLAG_BGR)
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_abgr16;
else
# endif
return gp_bgra16;
}
else
return gp_bgr16;
}
else
# endif
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_argb16;
else
# endif
return gp_rgba16;
}
else
return gp_rgb16;
}
}
else
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_ag16;
else
# endif
return gp_ga16;
}
else
return gp_g16;
}
}
else
{
if (format & PNG_FORMAT_FLAG_COLOR)
{
# ifdef PNG_FORMAT_BGR_SUPPORTED
if (format & PNG_FORMAT_FLAG_BGR)
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_abgr8;
else
# endif
return gp_bgra8;
}
else
return gp_bgr8;
}
else
# endif
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_argb8;
else
# endif
return gp_rgba8;
}
else
return gp_rgb8;
}
}
else
{
if (format & PNG_FORMAT_FLAG_ALPHA)
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
if (format & PNG_FORMAT_FLAG_AFIRST)
return gp_ag8;
else
# endif
return gp_ga8;
}
else
return gp_g8;
}
}
}
/* Convertion between pixel formats. The code above effectively eliminates the
* component ordering changes leaving three basic changes:
*
* 1) Remove an alpha channel by pre-multiplication or compositing on a
* background color. (Adding an alpha channel is a no-op.)
*
* 2) Remove color by mapping to grayscale. (Grayscale to color is a no-op.)
*
* 3) Convert between 8-bit and 16-bit components. (Both directtions are
* relevant.)
*
* This gives the following base format conversion matrix:
*
* OUT: ----- 8-bit ----- ----- 16-bit -----
* IN G GA RGB RGBA G GA RGB RGBA
* 8 G . . . . lin lin lin lin
* 8 GA bckg . bckc . pre' pre pre' pre
* 8 RGB g8 g8 . . glin glin lin lin
* 8 RGBA g8b g8 bckc . gpr' gpre pre' pre
* 16 G sRGB sRGB sRGB sRGB . . . .
* 16 GA b16g unpg b16c unpc A . A .
* 16 RGB sG sG sRGB sRGB g16 g16 . .
* 16 RGBA gb16 sGp cb16 sCp g16 g16' A .
*
* 8-bit to 8-bit:
* bckg: composite on gray background
* bckc: composite on color background
* g8: convert sRGB components to sRGB grayscale
* g8b: convert sRGB components to grayscale and composite on gray background
*
* 8-bit to 16-bit:
* lin: make sRGB components linear, alpha := 65535
* pre: make sRGB components linear and premultiply by alpha (scale alpha)
* pre': as 'pre' but alpha := 65535
* glin: make sRGB components linear, convert to grayscale, alpha := 65535
* gpre: make sRGB components grayscale and linear and premultiply by alpha
* gpr': as 'gpre' but alpha := 65535
*
* 16-bit to 8-bit:
* sRGB: convert linear components to sRGB, alpha := 255
* unpg: unpremultiply gray component and convert to sRGB (scale alpha)
* unpc: unpremultiply color components and convert to sRGB (scale alpha)
* b16g: composite linear onto gray background and convert the result to sRGB
* b16c: composite linear onto color background and convert the result to sRGB
* sG: convert linear RGB to sRGB grayscale
* sGp: unpremultiply RGB then convert to sRGB grayscale
* sCp: unpremultiply RGB then convert to sRGB
* gb16: composite linear onto background and convert to sRGB grayscale
* (order doesn't matter, the composite and grayscale operations permute)
* cb16: composite linear onto background and convert to sRGB
*
* 16-bit to 16-bit:
* A: set alpha to 65535
* g16: convert linear RGB to linear grayscale (alpha := 65535)
* g16': as 'g16' but alpha is unchanged
*/
/* Simple copy: */
static void
gpc_noop(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = in->r;
out->g = in->g;
out->b = in->b;
out->a = in->a;
}
#if ALLOW_UNUSED_GPC
static void
gpc_nop8(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a == 0)
out->r = out->g = out->b = 255;
else
{
out->r = in->r;
out->g = in->g;
out->b = in->b;
}
out->a = in->a;
}
#endif
#if ALLOW_UNUSED_GPC
static void
gpc_nop6(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a == 0)
out->r = out->g = out->b = 65535;
else
{
out->r = in->r;
out->g = in->g;
out->b = in->b;
}
out->a = in->a;
}
#endif
/* 8-bit to 8-bit conversions */
/* bckg: composite on gray background */
static void
gpc_bckg(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
out->r = out->g = out->b = back->ig;
else if (in->a >= 255)
out->r = out->g = out->b = in->g;
else
{
double a = in->a / 255.;
out->r = out->g = out->b = sRGB(sRGB_to_d[in->g] * a + back->dg * (1-a));
}
out->a = 255;
}
/* bckc: composite on color background */
static void
gpc_bckc(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
{
out->r = back->ir;
out->g = back->ig;
out->b = back->ib;
}
else if (in->a >= 255)
{
out->r = in->r;
out->g = in->g;
out->b = in->b;
}
else
{
double a = in->a / 255.;
out->r = sRGB(sRGB_to_d[in->r] * a + back->dr * (1-a));
out->g = sRGB(sRGB_to_d[in->g] * a + back->dg * (1-a));
out->b = sRGB(sRGB_to_d[in->b] * a + back->db * (1-a));
}
out->a = 255;
}
/* g8: convert sRGB components to sRGB grayscale */
static void
gpc_g8(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = in->g;
else
out->r = out->g = out->b =
sRGB(YfromRGB(sRGB_to_d[in->r], sRGB_to_d[in->g], sRGB_to_d[in->b]));
out->a = in->a;
}
/* g8b: convert sRGB components to grayscale and composite on gray background */
static void
gpc_g8b(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
out->r = out->g = out->b = back->ig;
else if (in->a >= 255)
{
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = in->g;
else
out->r = out->g = out->b = sRGB(YfromRGB(
sRGB_to_d[in->r], sRGB_to_d[in->g], sRGB_to_d[in->b]));
}
else
{
double a = in->a/255.;
out->r = out->g = out->b = sRGB(a * YfromRGB(sRGB_to_d[in->r],
sRGB_to_d[in->g], sRGB_to_d[in->b]) + back->dg * (1-a));
}
out->a = 255;
}
/* 8-bit to 16-bit conversions */
/* lin: make sRGB components linear, alpha := 65535 */
static void
gpc_lin(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilinear(in->r);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilinear(in->b);
}
else
{
out->g = ilinear(in->g);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilinear(in->b);
}
out->a = 65535;
}
/* pre: make sRGB components linear and premultiply by alpha (scale alpha) */
static void
gpc_pre(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilineara(in->r, in->a);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilineara(in->b, in->a);
}
else
{
out->g = ilineara(in->g, in->a);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilineara(in->b, in->a);
}
out->a = in->a * 257;
}
/* pre': as 'pre' but alpha := 65535 */
static void
gpc_preq(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilineara(in->r, in->a);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilineara(in->b, in->a);
}
else
{
out->g = ilineara(in->g, in->a);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilineara(in->b, in->a);
}
out->a = 65535;
}
/* glin: make sRGB components linear, convert to grayscale, alpha := 65535 */
static void
gpc_glin(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilinear(in->g);
else
out->r = out->g = out->b = u16d(65535 *
YfromRGB(sRGB_to_d[in->r], sRGB_to_d[in->g], sRGB_to_d[in->b]));
out->a = 65535;
}
/* gpre: make sRGB components grayscale and linear and premultiply by alpha */
static void
gpc_gpre(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilineara(in->g, in->a);
else
out->r = out->g = out->b = u16d(in->a * 257 *
YfromRGB(sRGB_to_d[in->r], sRGB_to_d[in->g], sRGB_to_d[in->b]));
out->a = 257 * in->a;
}
/* gpr': as 'gpre' but alpha := 65535 */
static void
gpc_gprq(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilineara(in->g, in->a);
else
out->r = out->g = out->b = u16d(in->a * 257 *
YfromRGB(sRGB_to_d[in->r], sRGB_to_d[in->g], sRGB_to_d[in->b]));
out->a = 65535;
}
/* 8-bit to 16-bit conversions for gAMA 45455 encoded values */
/* Lin: make gAMA 45455 components linear, alpha := 65535 */
static void
gpc_Lin(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilinear_g22(in->r);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilinear_g22(in->b);
}
else
{
out->g = ilinear_g22(in->g);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilinear_g22(in->b);
}
out->a = 65535;
}
#if ALLOW_UNUSED_GPC
/* Pre: make gAMA 45455 components linear and premultiply by alpha (scale alpha)
*/
static void
gpc_Pre(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilineara_g22(in->r, in->a);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilineara_g22(in->b, in->a);
}
else
{
out->g = ilineara_g22(in->g, in->a);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilineara_g22(in->b, in->a);
}
out->a = in->a * 257;
}
#endif
#if ALLOW_UNUSED_GPC
/* Pre': as 'Pre' but alpha := 65535 */
static void
gpc_Preq(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = ilineara_g22(in->r, in->a);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = ilineara_g22(in->b, in->a);
}
else
{
out->g = ilineara_g22(in->g, in->a);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = ilineara_g22(in->b, in->a);
}
out->a = 65535;
}
#endif
#if ALLOW_UNUSED_GPC
/* Glin: make gAMA 45455 components linear, convert to grayscale, alpha := 65535
*/
static void
gpc_Glin(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilinear_g22(in->g);
else
out->r = out->g = out->b = u16d(65535 *
YfromRGB(g22_to_d[in->r], g22_to_d[in->g], g22_to_d[in->b]));
out->a = 65535;
}
#endif
#if ALLOW_UNUSED_GPC
/* Gpre: make gAMA 45455 components grayscale and linear and premultiply by
* alpha.
*/
static void
gpc_Gpre(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilineara_g22(in->g, in->a);
else
out->r = out->g = out->b = u16d(in->a * 257 *
YfromRGB(g22_to_d[in->r], g22_to_d[in->g], g22_to_d[in->b]));
out->a = 257 * in->a;
}
#endif
#if ALLOW_UNUSED_GPC
/* Gpr': as 'Gpre' but alpha := 65535 */
static void
gpc_Gprq(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->r == in->g && in->g == in->b)
out->r = out->g = out->b = ilineara_g22(in->g, in->a);
else
out->r = out->g = out->b = u16d(in->a * 257 *
YfromRGB(g22_to_d[in->r], g22_to_d[in->g], g22_to_d[in->b]));
out->a = 65535;
}
#endif
/* 16-bit to 8-bit conversions */
/* sRGB: convert linear components to sRGB, alpha := 255 */
static void
gpc_sRGB(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = isRGB(in->r);
if (in->g == in->r)
{
out->g = out->r;
if (in->b == in->r)
out->b = out->r;
else
out->b = isRGB(in->b);
}
else
{
out->g = isRGB(in->g);
if (in->b == in->r)
out->b = out->r;
else if (in->b == in->g)
out->b = out->g;
else
out->b = isRGB(in->b);
}
out->a = 255;
}
/* unpg: unpremultiply gray component and convert to sRGB (scale alpha) */
static void
gpc_unpg(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a <= 128)
{
out->r = out->g = out->b = 255;
out->a = 0;
}
else
{
out->r = out->g = out->b = sRGB((double)in->g / in->a);
out->a = u8d(in->a / 257.);
}
}
/* unpc: unpremultiply color components and convert to sRGB (scale alpha) */
static void
gpc_unpc(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a <= 128)
{
out->r = out->g = out->b = 255;
out->a = 0;
}
else
{
out->r = sRGB((double)in->r / in->a);
out->g = sRGB((double)in->g / in->a);
out->b = sRGB((double)in->b / in->a);
out->a = u8d(in->a / 257.);
}
}
/* b16g: composite linear onto gray background and convert the result to sRGB */
static void
gpc_b16g(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
out->r = out->g = out->b = back->ig;
else
{
double a = in->a/65535.;
double a1 = 1-a;
a /= 65535;
out->r = out->g = out->b = sRGB(in->g * a + back->dg * a1);
}
out->a = 255;
}
/* b16c: composite linear onto color background and convert the result to sRGB*/
static void
gpc_b16c(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
{
out->r = back->ir;
out->g = back->ig;
out->b = back->ib;
}
else
{
double a = in->a/65535.;
double a1 = 1-a;
a /= 65535;
out->r = sRGB(in->r * a + back->dr * a1);
out->g = sRGB(in->g * a + back->dg * a1);
out->b = sRGB(in->b * a + back->db * a1);
}
out->a = 255;
}
/* sG: convert linear RGB to sRGB grayscale */
static void
gpc_sG(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = out->g = out->b = sRGB(YfromRGBint(in->r, in->g, in->b)/65535);
out->a = 255;
}
/* sGp: unpremultiply RGB then convert to sRGB grayscale */
static void
gpc_sGp(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a <= 128)
{
out->r = out->g = out->b = 255;
out->a = 0;
}
else
{
out->r = out->g = out->b = sRGB(YfromRGBint(in->r, in->g, in->b)/in->a);
out->a = u8d(in->a / 257.);
}
}
/* sCp: unpremultiply RGB then convert to sRGB */
static void
gpc_sCp(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
if (in->a <= 128)
{
out->r = out->g = out->b = 255;
out->a = 0;
}
else
{
out->r = sRGB((double)in->r / in->a);
out->g = sRGB((double)in->g / in->a);
out->b = sRGB((double)in->b / in->a);
out->a = u8d(in->a / 257.);
}
}
/* gb16: composite linear onto background and convert to sRGB grayscale */
/* (order doesn't matter, the composite and grayscale operations permute) */
static void
gpc_gb16(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
out->r = out->g = out->b = back->ig;
else if (in->a >= 65535)
out->r = out->g = out->b = isRGB(in->g);
else
{
double a = in->a / 65535.;
double a1 = 1-a;
a /= 65535;
out->r = out->g = out->b = sRGB(in->g * a + back->dg * a1);
}
out->a = 255;
}
/* cb16: composite linear onto background and convert to sRGB */
static void
gpc_cb16(Pixel *out, const Pixel *in, const Background *back)
{
if (in->a <= 0)
{
out->r = back->ir;
out->g = back->ig;
out->b = back->ib;
}
else if (in->a >= 65535)
{
out->r = isRGB(in->r);
out->g = isRGB(in->g);
out->b = isRGB(in->b);
}
else
{
double a = in->a / 65535.;
double a1 = 1-a;
a /= 65535;
out->r = sRGB(in->r * a + back->dr * a1);
out->g = sRGB(in->g * a + back->dg * a1);
out->b = sRGB(in->b * a + back->db * a1);
}
out->a = 255;
}
/* 16-bit to 16-bit conversions */
/* A: set alpha to 65535 */
static void
gpc_A(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = in->r;
out->g = in->g;
out->b = in->b;
out->a = 65535;
}
/* g16: convert linear RGB to linear grayscale (alpha := 65535) */
static void
gpc_g16(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = out->g = out->b = u16d(YfromRGBint(in->r, in->g, in->b));
out->a = 65535;
}
/* g16': as 'g16' but alpha is unchanged */
static void
gpc_g16q(Pixel *out, const Pixel *in, const Background *back)
{
(void)back;
out->r = out->g = out->b = u16d(YfromRGBint(in->r, in->g, in->b));
out->a = in->a;
}
#if ALLOW_UNUSED_GPC
/* Unused functions (to hide them from GCC unused function warnings) */
void (* const gpc_unused[])
(Pixel *out, const Pixel *in, const Background *back) =
{
gpc_Pre, gpc_Preq, gpc_Glin, gpc_Gpre, gpc_Gprq, gpc_nop8, gpc_nop6
};
#endif
/* OUT: ----- 8-bit ----- ----- 16-bit -----
* IN G GA RGB RGBA G GA RGB RGBA
* 8 G . . . . lin lin lin lin
* 8 GA bckg . bckc . pre' pre pre' pre
* 8 RGB g8 g8 . . glin glin lin lin
* 8 RGBA g8b g8 bckc . gpr' gpre pre' pre
* 16 G sRGB sRGB sRGB sRGB . . . .
* 16 GA b16g unpg b16c unpc A . A .
* 16 RGB sG sG sRGB sRGB g16 g16 . .
* 16 RGBA gb16 sGp cb16 sCp g16 g16' A .
*
* The matrix is held in an array indexed thus:
*
* gpc_fn[out_format & BASE_FORMATS][in_format & BASE_FORMATS];
*/
/* This will produce a compile time error if the FORMAT_FLAG values don't
* match the above matrix!
*/
#if PNG_FORMAT_FLAG_ALPHA == 1 && PNG_FORMAT_FLAG_COLOR == 2 &&\
PNG_FORMAT_FLAG_LINEAR == 4
static void (* const gpc_fn[8/*in*/][8/*out*/])
(Pixel *out, const Pixel *in, const Background *back) =
{
/*out: G-8 GA-8 RGB-8 RGBA-8 G-16 GA-16 RGB-16 RGBA-16 */
{gpc_noop,gpc_noop,gpc_noop,gpc_noop, gpc_Lin, gpc_Lin, gpc_Lin, gpc_Lin },
{gpc_bckg,gpc_noop,gpc_bckc,gpc_noop, gpc_preq,gpc_pre, gpc_preq,gpc_pre },
{gpc_g8, gpc_g8, gpc_noop,gpc_noop, gpc_glin,gpc_glin,gpc_lin, gpc_lin },
{gpc_g8b, gpc_g8, gpc_bckc,gpc_noop, gpc_gprq,gpc_gpre,gpc_preq,gpc_pre },
{gpc_sRGB,gpc_sRGB,gpc_sRGB,gpc_sRGB, gpc_noop,gpc_noop,gpc_noop,gpc_noop},
{gpc_b16g,gpc_unpg,gpc_b16c,gpc_unpc, gpc_A, gpc_noop,gpc_A, gpc_noop},
{gpc_sG, gpc_sG, gpc_sRGB,gpc_sRGB, gpc_g16, gpc_g16, gpc_noop,gpc_noop},
{gpc_gb16,gpc_sGp, gpc_cb16,gpc_sCp, gpc_g16, gpc_g16q,gpc_A, gpc_noop}
};
/* The array is repeated for the cases where both the input and output are color
* mapped because then different algorithms are used.
*/
static void (* const gpc_fn_colormapped[8/*in*/][8/*out*/])
(Pixel *out, const Pixel *in, const Background *back) =
{
/*out: G-8 GA-8 RGB-8 RGBA-8 G-16 GA-16 RGB-16 RGBA-16 */
{gpc_noop,gpc_noop,gpc_noop,gpc_noop, gpc_lin, gpc_lin, gpc_lin, gpc_lin },
{gpc_bckg,gpc_noop,gpc_bckc,gpc_noop, gpc_preq,gpc_pre, gpc_preq,gpc_pre },
{gpc_g8, gpc_g8, gpc_noop,gpc_noop, gpc_glin,gpc_glin,gpc_lin, gpc_lin },
{gpc_g8b, gpc_g8, gpc_bckc,gpc_noop, gpc_gprq,gpc_gpre,gpc_preq,gpc_pre },
{gpc_sRGB,gpc_sRGB,gpc_sRGB,gpc_sRGB, gpc_noop,gpc_noop,gpc_noop,gpc_noop},
{gpc_b16g,gpc_unpg,gpc_b16c,gpc_unpc, gpc_A, gpc_noop,gpc_A, gpc_noop},
{gpc_sG, gpc_sG, gpc_sRGB,gpc_sRGB, gpc_g16, gpc_g16, gpc_noop,gpc_noop},
{gpc_gb16,gpc_sGp, gpc_cb16,gpc_sCp, gpc_g16, gpc_g16q,gpc_A, gpc_noop}
};
/* The error arrays record the error in the same matrix; 64 entries, however
* the different algorithms used in libpng for colormap and direct conversions
* mean that four separate matrices are used (for each combination of
* colormapped and direct.)
*
* In some cases the conversion between sRGB formats goes via a linear
* intermediate; an sRGB to linear conversion (as above) is followed by a simple
* linear to sRGB step with no other conversions. This is done by a separate
* error array from an arbitrary 'in' format to one of the four basic outputs
* (since final output is always sRGB not colormapped).
*
* These arrays may be modified if the --accumulate flag is set during the run;
* then instead of logging errors they are simply added in.
*
* The three entries are currently for transparent, partially transparent and
* opaque input pixel values. Notice that alpha should be exact in each case.
*
* Errors in alpha should only occur when converting from a direct format
* to a colormapped format, when alpha is effectively smashed (so large
* errors can occur.) There should be no error in the '0' and 'opaque'
* values. The fourth entry in the array is used for the alpha error (and it
* should always be zero for the 'via linear' case since this is never color
* mapped.)
*
* Mapping to a colormap smashes the colors, it is necessary to have separate
* values for these cases because they are much larger; it is very much
* impossible to obtain a reasonable result, these are held in
* gpc_error_to_colormap.
*/
#if PNG_FORMAT_FLAG_COLORMAP == 8 /* extra check also required */
/* START MACHINE GENERATED */
static png_uint_16 gpc_error[16/*in*/][16/*out*/][4/*a*/] =
{
{ /* input: sRGB-gray */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 372, 0 }, { 0, 0, 372, 0 }, { 0, 0, 372, 0 }, { 0, 0, 372, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: sRGB-gray+alpha */
{ 0, 18, 0, 0 }, { 0, 0, 0, 0 }, { 0, 20, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 897, 788, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: sRGB-rgb */
{ 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 893, 0 }, { 0, 0, 893, 0 }, { 0, 0, 811, 0 }, { 0, 0, 811, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: sRGB-rgb+alpha */
{ 0, 4, 13, 0 }, { 0, 14, 13, 0 }, { 0, 19, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 832, 764, 0 }, { 0, 832, 764, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: linear-gray */
{ 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: linear-gray+alpha */
{ 0, 74, 9, 0 }, { 0, 20, 9, 0 }, { 0, 74, 9, 0 }, { 0, 20, 9, 0 },
{ 0, 0, 0, 0 }, { 0, 1, 0, 0 }, { 0, 0, 0, 0 }, { 0, 1, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: linear-rgb */
{ 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 },
{ 0, 0, 4, 0 }, { 0, 0, 4, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: linear-rgb+alpha */
{ 0, 126, 143, 0 }, { 0, 9, 7, 0 }, { 0, 74, 9, 0 }, { 0, 16, 9, 0 },
{ 0, 4, 4, 0 }, { 0, 5, 4, 0 }, { 0, 0, 0, 0 }, { 0, 1, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-sRGB-gray */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-sRGB-gray+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-sRGB-rgb */
{ 0, 0, 13, 0 }, { 0, 0, 13, 0 }, { 0, 0, 8, 0 }, { 0, 0, 8, 0 },
{ 0, 0, 673, 0 }, { 0, 0, 673, 0 }, { 0, 0, 674, 0 }, { 0, 0, 674, 0 },
{ 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 460, 0 }, { 0, 0, 460, 0 }, { 0, 0, 263, 0 }, { 0, 0, 263, 0 }
}, { /* input: color-mapped-sRGB-rgb+alpha */
{ 0, 6, 8, 0 }, { 0, 7, 8, 0 }, { 0, 75, 8, 0 }, { 0, 9, 8, 0 },
{ 0, 585, 427, 0 }, { 0, 585, 427, 0 }, { 0, 717, 409, 0 }, { 0, 717, 409, 0 },
{ 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 13323, 460, 0 }, { 0, 334, 460, 0 }, { 0, 16480, 263, 0 }, { 0, 243, 263, 0 }
}, { /* input: color-mapped-linear-gray */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 282, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-gray+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 253, 282, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-rgb */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 265, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-rgb+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 243, 265, 0 }
}
};
static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
{
{ /* input: sRGB-gray */
{ 0, 0, 7, 0 }, { 0, 0, 7, 0 }, { 0, 0, 7, 0 }, { 0, 0, 7, 0 }
}, { /* input: sRGB-gray+alpha */
{ 0, 15, 15, 0 }, { 0, 186, 15, 0 }, { 0, 15, 15, 0 }, { 0, 186, 15, 0 }
}, { /* input: sRGB-rgb */
{ 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 15, 0 }, { 0, 0, 15, 0 }
}, { /* input: sRGB-rgb+alpha */
{ 0, 12, 14, 0 }, { 0, 180, 14, 0 }, { 0, 14, 15, 0 }, { 0, 186, 15, 0 }
}, { /* input: linear-gray */
{ 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }
}, { /* input: linear-gray+alpha */
{ 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }
}, { /* input: linear-rgb */
{ 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }
}, { /* input: linear-rgb+alpha */
{ 0, 1, 1, 0 }, { 0, 8, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }
}, { /* input: color-mapped-sRGB-gray */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-sRGB-gray+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-sRGB-rgb */
{ 0, 0, 13, 0 }, { 0, 0, 13, 0 }, { 0, 0, 14, 0 }, { 0, 0, 14, 0 }
}, { /* input: color-mapped-sRGB-rgb+alpha */
{ 0, 4, 8, 0 }, { 0, 9, 8, 0 }, { 0, 8, 3, 0 }, { 0, 32, 3, 0 }
}, { /* input: color-mapped-linear-gray */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-gray+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-rgb */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}, { /* input: color-mapped-linear-rgb+alpha */
{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
}
};
static png_uint_16 gpc_error_to_colormap[8/*i*/][8/*o*/][4] =
{
{ /* input: sRGB-gray */
{ 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 },
{ 0, 0, 560, 0 }, { 0, 0, 560, 0 }, { 0, 0, 560, 0 }, { 0, 0, 560, 0 }
}, { /* input: sRGB-gray+alpha */
{ 0, 19, 2, 0 }, { 0, 255, 2, 25 }, { 0, 88, 2, 0 }, { 0, 255, 2, 25 },
{ 0, 1012, 745, 0 }, { 0, 16026, 745, 6425 }, { 0, 1012, 745, 0 }, { 0, 16026, 745, 6425 }
}, { /* input: sRGB-rgb */
{ 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 25, 0 }, { 0, 0, 25, 0 },
{ 0, 0, 937, 0 }, { 0, 0, 937, 0 }, { 0, 0, 13677, 0 }, { 0, 0, 13677, 0 }
}, { /* input: sRGB-rgb+alpha */
{ 0, 63, 77, 0 }, { 0, 255, 19, 25 }, { 0, 220, 25, 0 }, { 0, 255, 25, 67 },
{ 0, 17534, 18491, 0 }, { 0, 15614, 2824, 6425 }, { 0, 14019, 13677, 0 }, { 0, 48573, 13677, 17219 }
}, { /* input: linear-gray */
{ 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 73, 0 },
{ 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }
}, { /* input: linear-gray+alpha */
{ 0, 74, 74, 0 }, { 0, 255, 74, 25 }, { 0, 97, 74, 0 }, { 0, 255, 74, 25 },
{ 0, 18919, 18907, 0 }, { 0, 24549, 18907, 6552 }, { 0, 18919, 18907, 0 }, { 0, 24549, 18907, 6552 }
}, { /* input: linear-rgb */
{ 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 98, 0 }, { 0, 0, 98, 0 },
{ 0, 0, 18664, 0 }, { 0, 0, 18664, 0 }, { 0, 0, 24998, 0 }, { 0, 0, 24998, 0 }
}, { /* input: linear-rgb+alpha */
{ 0, 181, 196, 0 }, { 0, 255, 61, 25 }, { 206, 187, 98, 0 }, { 0, 255, 98, 67 },
{ 0, 18141, 18137, 0 }, { 0, 17494, 17504, 6553 }, { 0, 24979, 24992, 0 }, { 0, 46509, 24992, 17347 }
}
};
/* END MACHINE GENERATED */
#endif /* COLORMAP flag check */
#endif /* flag checks */
typedef struct
{
/* Basic pixel information: */
Image* in_image; /* Input image */
const Image* out_image; /* Output image */
/* 'background' is the value passed to the gpc_ routines, it may be NULL if
* it should not be used (*this* program has an error if it crashes as a
* result!)
*/
Background background_color;
const Background* background;
/* Precalculated values: */
int in_opaque; /* Value of input alpha that is opaque */
int is_palette; /* Sample values come from the palette */
int accumulate; /* Accumlate component errors (don't log) */
int output_8bit; /* Output is 8 bit (else 16 bit) */
void (*in_gp)(Pixel*, png_const_voidp);
void (*out_gp)(Pixel*, png_const_voidp);
void (*transform)(Pixel *out, const Pixel *in, const Background *back);
/* A function to perform the required transform */
void (*from_linear)(Pixel *out, const Pixel *in, const Background *back);
/* For 'via_linear' transforms the final, from linear, step, else NULL */
png_uint_16 error[4];
/* Three error values for transparent, partially transparent and opaque
* input pixels (in turn).
*/
png_uint_16 *error_ptr;
/* Where these are stored in the static array (for 'accumulate') */
}
Transform;
/* Return a 'transform' as above for the given format conversion. */
static void
transform_from_formats(Transform *result, Image *in_image,
const Image *out_image, png_const_colorp background, int via_linear)
{
png_uint_32 in_format, out_format;
png_uint_32 in_base, out_base;
memset(result, 0, sizeof *result);
/* Store the original images for error messages */
result->in_image = in_image;
result->out_image = out_image;
in_format = in_image->image.format;
out_format = out_image->image.format;
if (in_format & PNG_FORMAT_FLAG_LINEAR)
result->in_opaque = 65535;
else
result->in_opaque = 255;
result->output_8bit = (out_format & PNG_FORMAT_FLAG_LINEAR) == 0;
result->is_palette = 0; /* set by caller if required */
result->accumulate = (in_image->opts & ACCUMULATE) != 0;
/* The loaders (which need the ordering information) */
result->in_gp = get_pixel(in_format);
result->out_gp = get_pixel(out_format);
/* Remove the ordering information: */
in_format &= BASE_FORMATS | PNG_FORMAT_FLAG_COLORMAP;
in_base = in_format & BASE_FORMATS;
out_format &= BASE_FORMATS | PNG_FORMAT_FLAG_COLORMAP;
out_base = out_format & BASE_FORMATS;
if (via_linear)
{
/* Check for an error in this program: */
if (out_format & (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLORMAP))
{
fprintf(stderr, "internal transform via linear error 0x%x->0x%x\n",
in_format, out_format);
exit(1);
}
result->transform = gpc_fn[in_base][out_base | PNG_FORMAT_FLAG_LINEAR];
result->from_linear = gpc_fn[out_base | PNG_FORMAT_FLAG_LINEAR][out_base];
result->error_ptr = gpc_error_via_linear[in_format][out_format];
}
else if (~in_format & out_format & PNG_FORMAT_FLAG_COLORMAP)
{
/* The input is not colormapped but the output is, the errors will
* typically be large (only the grayscale-no-alpha case permits preserving
* even 8-bit values.)
*/
result->transform = gpc_fn[in_base][out_base];
result->from_linear = NULL;
result->error_ptr = gpc_error_to_colormap[in_base][out_base];
}
else
{
/* The caller handles the colormap->pixel value conversion, so the
* transform function just gets a pixel value, however because libpng
* currently contains a different implementation for mapping a colormap if
* both input and output are colormapped we need different conversion
* functions to deal with errors in the libpng implementation.
*/
if (in_format & out_format & PNG_FORMAT_FLAG_COLORMAP)
result->transform = gpc_fn_colormapped[in_base][out_base];
else
result->transform = gpc_fn[in_base][out_base];
result->from_linear = NULL;
result->error_ptr = gpc_error[in_format][out_format];
}
/* Follow the libpng simplified API rules to work out what to pass to the gpc
* routines as a background value, if one is not required pass NULL so that
* this program crashes in the even of a programming error.
*/
result->background = NULL; /* default: not required */
/* Rule 1: background only need be supplied if alpha is to be removed */
if (in_format & ~out_format & PNG_FORMAT_FLAG_ALPHA)
{
/* The input value is 'NULL' to use the background and (otherwise) an sRGB
* background color (to use a solid color). The code above uses a fixed
* byte value, BUFFER_INIT8, for buffer even for 16-bit output. For
* linear (16-bit) output the sRGB background color is ignored; the
* composition is always on the background (so BUFFER_INIT8 * 257), except
* that for the colormap (i.e. linear colormapped output) black is used.
*/
result->background = &result->background_color;
if (out_format & PNG_FORMAT_FLAG_LINEAR || via_linear)
{
if (out_format & PNG_FORMAT_FLAG_COLORMAP)
{
result->background_color.ir =
result->background_color.ig =
result->background_color.ib = 0;
result->background_color.dr =
result->background_color.dg =
result->background_color.db = 0;
}
else
{
result->background_color.ir =
result->background_color.ig =
result->background_color.ib = BUFFER_INIT8 * 257;
result->background_color.dr =
result->background_color.dg =
result->background_color.db = 0;
}
}
else /* sRGB output */
{
if (background != NULL)
{
if (out_format & PNG_FORMAT_FLAG_COLOR)
{
result->background_color.ir = background->red;
result->background_color.ig = background->green;
result->background_color.ib = background->blue;
/* TODO: sometimes libpng uses the power law conversion here, how
* to handle this?
*/
result->background_color.dr = sRGB_to_d[background->red];
result->background_color.dg = sRGB_to_d[background->green];
result->background_color.db = sRGB_to_d[background->blue];
}
else /* grayscale: libpng only looks at 'g' */
{
result->background_color.ir =
result->background_color.ig =
result->background_color.ib = background->green;
/* TODO: sometimes libpng uses the power law conversion here, how
* to handle this?
*/
result->background_color.dr =
result->background_color.dg =
result->background_color.db = sRGB_to_d[background->green];
}
}
else if ((out_format & PNG_FORMAT_FLAG_COLORMAP) == 0)
{
result->background_color.ir =
result->background_color.ig =
result->background_color.ib = BUFFER_INIT8;
/* TODO: sometimes libpng uses the power law conversion here, how
* to handle this?
*/
result->background_color.dr =
result->background_color.dg =
result->background_color.db = sRGB_to_d[BUFFER_INIT8];
}
/* Else the output is colormapped and a background color must be
* provided; if pngstest crashes then that is a bug in this program
* (though libpng should png_error as well.)
*/
else
result->background = NULL;
}
}
if (result->background == NULL)
{
result->background_color.ir =
result->background_color.ig =
result->background_color.ib = -1; /* not used */
result->background_color.dr =
result->background_color.dg =
result->background_color.db = 1E30; /* not used */
}
/* Copy the error values into the Transform: */
result->error[0] = result->error_ptr[0];
result->error[1] = result->error_ptr[1];
result->error[2] = result->error_ptr[2];
result->error[3] = result->error_ptr[3];
}
/* Compare two pixels.
*
* OLD error values:
static int error_to_linear = 811; * by experiment *
static int error_to_linear_grayscale = 424; * by experiment *
static int error_to_sRGB = 6; * by experiment *
static int error_to_sRGB_grayscale = 17; * libpng error by calculation +
2 by experiment *
static int error_in_compose = 2; * by experiment *
static int error_in_premultiply = 1;
*
* The following is *just* the result of a round trip from 8-bit sRGB to linear
* then back to 8-bit sRGB when it is done by libpng. There are two problems:
*
* 1) libpng currently uses a 2.2 power law with no linear segment, this results
* in instability in the low values and even with 16-bit precision sRGB(1) ends
* up mapping to sRGB(0) as a result of rounding in the 16-bit representation.
* This gives an error of 1 in the handling of value 1 only.
*
* 2) libpng currently uses an intermediate 8-bit linear value in gamma
* correction of 8-bit values. This results in many more errors, the worse of
* which is mapping sRGB(14) to sRGB(0).
*
* The general 'error_via_linear' is more complex because of pre-multiplication,
* this compounds the 8-bit errors according to the alpha value of the pixel.
* As a result 256 values are pre-calculated for error_via_linear.
*/
#if 0
static int error_in_libpng_gamma;
static int error_via_linear[256]; /* Indexed by 8-bit alpha */
static void
init_error_via_linear(void)
{
int alpha;
error_via_linear[0] = 255; /* transparent pixel */
for (alpha=1; alpha<=255; ++alpha)
{
/* 16-bit values less than 128.5 get rounded to 8-bit 0 and so the worst
* case error arises with 16-bit 128.5, work out what sRGB
* (non-associated) value generates 128.5; any value less than this is
* going to map to 0, so the worst error is floor(value).
*
* Note that errors are considerably higher (more than a factor of 2)
* because libpng uses a simple power law for sRGB data at present.
*
* Add .1 for arithmetic errors inside libpng.
*/
double v = floor(255*pow(.5/*(128.5 * 255 / 65535)*/ / alpha, 1/2.2)+.1);
error_via_linear[alpha] = (int)v;
}
/* This is actually 14.99, but, despite the closeness to 15, 14 seems to work
* ok in this case.
*/
error_in_libpng_gamma = 14;
}
#endif
static void
print_pixel(char string[64], const Pixel *pixel, png_uint_32 format)
{
switch (format & (PNG_FORMAT_FLAG_ALPHA|PNG_FORMAT_FLAG_COLOR))
{
case 0:
sprintf(string, "%s(%d)", format_names[format], pixel->g);
break;
case PNG_FORMAT_FLAG_ALPHA:
sprintf(string, "%s(%d,%d)", format_names[format], pixel->g,
pixel->a);
break;
case PNG_FORMAT_FLAG_COLOR:
sprintf(string, "%s(%d,%d,%d)", format_names[format],
pixel->r, pixel->g, pixel->b);
break;