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libpng/pngvalid.c
Glenn Randers-Pehrson 31aee0d0c0 [devel] 
Fixed point APIs are now supported throughout (no missing APIs).
  Internal fixed point arithmetic support exists for all internal floating
    point operations.
  sCAL validates the floating point strings it is passed.
  Safe, albeit rudimentary, Watcom support is provided by PNG_API_RULE==2
  Two new APIs exist to get the number of passes without turning on the
    PNG_INTERLACE transform and to get the number of rows in the current
    pass.
  A new test program, pngvalid.c, validates the gamma code.
  Errors in the 16 bit gamma correction (overflows) have been corrected.
  cHRM chunk testing is done consistently (previously the floating point
    API bypassed it, because the test really didn't work on FP, now the test
    is performed on the actual values to be stored in the PNG file so it
    works in the FP case too.)
  Most floating point APIs now simply call the fixed point APIs after
    converting the values to the fixed point form used in the PNG file.
  The standard headers no longer include zlib.h, which is currently only
    required for pngstruct.h and can therefore be internal.
  (Patches by John Bowler)
2010-07-29 17:39:14 -05:00

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/* pngvalid.c - validate libpng by constructing then reading png files.
*
* Last changed in libpng 1.5.0 [July 5, 2010]
* Copyright (c) 2010-2010 Glenn Randers-Pehrson
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* NOTES:
* This is a C program that is intended to be linked against libpng. It
* generates bitmaps internally, stores them as PNG files (using the
* sequential write code) then reads them back (using the sequential
* read code) and validates that the result has the correct data.
*
* The program can be modified and extended to test the correctness of
* transformations performed by libpng.
*/
#include "png.h"
#include "zlib.h" /* For crc32 */
#include <stdlib.h> /* For malloc */
#include <string.h> /* For memcpy, memset */
#include <setjmp.h> /* For jmp_buf, setjmp, longjmp */
#include <math.h> /* For floor */
/******************************* ERROR UTILITIES ******************************/
static size_t safecat(char *buffer, size_t bufsize, size_t pos, const char *cat)
{
while (pos < bufsize && cat != NULL && *cat != 0) buffer[pos++] = *cat++;
if (pos >= bufsize) pos = bufsize-1;
buffer[pos] = 0;
return pos;
}
static size_t safecatn(char *buffer, size_t bufsize, size_t pos, int n)
{
char number[64];
sprintf(number, "%d", n);
return safecat(buffer, bufsize, pos, number);
}
static size_t safecatd(char *buffer, size_t bufsize, size_t pos, double d,
int precision)
{
char number[64];
sprintf(number, "%.*f", precision, d);
return safecat(buffer, bufsize, pos, number);
}
static const char invalid[] = "invalid";
static const char sep[] = ": ";
/* NOTE: this is indexed by ln2(bit_depth)! */
static const char *bit_depths[8] =
{
"1", "2", "4", "8", "16", invalid, invalid, invalid
};
static const char *colour_types[8] =
{
"greyscale", invalid, "truecolour", "indexed-colour",
"greyscale with alpha", invalid, "truecolour with alpha", invalid
};
/* Convenience API to list valid formats: */
static int
next_format(png_bytep colour_type, png_bytep bit_depth)
{
if (*bit_depth == 0)
{
*colour_type = 0, *bit_depth = 1;
return 1;
}
else switch (*colour_type)
{
case 0:
*bit_depth <<= 1;
if (*bit_depth <= 16) return 1;
*colour_type = 2;
*bit_depth = 8;
return 1;
case 2:
*bit_depth <<= 1;
if (*bit_depth <= 16) return 1;
*colour_type = 3;
*bit_depth = 1;
return 1;
case 3:
*bit_depth <<= 1;
if (*bit_depth <= 8) return 1;
*colour_type = 4;
*bit_depth = 8;
return 1;
case 4:
*bit_depth <<= 1;
if (*bit_depth <= 16) return 1;
*colour_type = 6;
*bit_depth = 8;
return 1;
case 6:
*bit_depth <<= 1;
if (*bit_depth <= 16) return 1;
break;
}
/* Here at the end. */
return 0;
}
static inline unsigned
sample(png_byte *row, png_byte colour_type, png_byte bit_depth, png_uint_32 x,
unsigned sample)
{
png_uint_32 index, result;
/* Find a sample index for the desired sample: */
x *= bit_depth;
index = x;
if ((colour_type & 1) == 0) /* !palette */
{
if (colour_type & 2)
index *= 3, index += sample; /* Colour channels; select one */
if (colour_type & 4) index += x; /* Alpha channel */
}
/* Return the sample from the row as an integer. */
row += index >> 3;
result = *row;
if (bit_depth == 8)
return result;
else if (bit_depth > 8)
return (result << 8) + *++row;
/* Less than 8 bits per sample. */
index &= 7;
return (result >> (8-index-bit_depth)) & ((1U<<bit_depth)-1);
}
/*************************** BASIC PNG FILE WRITING ***************************/
/* A png_sucker takes data from the sequential writer or provides data
* to the sequential reader. It can also store the result of a PNG
* write for later retrieval.
*/
#define SUCKER_BUFFER_SIZE 500 /* arbitrary */
typedef struct png_sucker_buffer
{
struct png_sucker_buffer* prev; /* NOTE: stored in reverse order */
png_byte buffer[SUCKER_BUFFER_SIZE];
} png_sucker_buffer;
typedef struct png_sucker_file
{
struct png_sucker_file* next; /* as many as you like... */
char name[64]; /* textual name */
png_uint_32 id; /* as a convenience to users */
png_size_t datacount; /* In this (the last) buffer */
png_sucker_buffer data; /* Last buffer in file */
} png_sucker_file;
#define SUCKER_ERROR 0x345
typedef struct png_sucker
{
jmp_buf jmpbuf;
int verbose;
int nerrors;
int nwarnings;
int treat_warnings_as_errors;
char test[64]; /* Name of test */
char error[128];
/* Read fields */
png_structp pread; /* Used to read a saved file */
png_infop piread;
png_sucker_file* current; /* Set when reading */
png_sucker_buffer* next; /* Set when reading */
png_size_t readpos; /* Position in *next */
/* Write fields */
png_sucker_file* saved;
png_structp pwrite; /* Used when writing a new file */
png_infop piwrite;
png_size_t writepos; /* Position in .new */
char wname[64];/* Name of file being written */
png_sucker_buffer new; /* The end of the new PNG file being written. */
} png_sucker;
/* Initialization and cleanup */
static void
sucker_init(png_sucker* ps)
{
memset(ps, 0, sizeof *ps);
ps->verbose = 0;
ps->nerrors = ps->nwarnings = 0;
ps->treat_warnings_as_errors = 0;
ps->pread = NULL;
ps->piread = NULL;
ps->saved = ps->current = NULL;
ps->next = NULL;
ps->readpos = 0;
ps->pwrite = NULL;
ps->piwrite = NULL;
ps->writepos = 0;
ps->new.prev = NULL;
}
static void
sucker_freebuffer(png_sucker_buffer* psb)
{
if (psb->prev)
{
sucker_freebuffer(psb->prev);
free(psb->prev);
psb->prev = NULL;
}
}
static void
sucker_freenew(png_sucker *ps)
{
sucker_freebuffer(&ps->new);
ps->writepos = 0;
}
static void
sucker_storenew(png_sucker *ps)
{
png_sucker_buffer *pb;
if (ps->writepos != SUCKER_BUFFER_SIZE)
png_error(ps->pwrite, "invalid store call");
pb = malloc(sizeof *pb);
if (pb == NULL)
png_error(ps->pwrite, "store new: OOM");
*pb = ps->new;
ps->new.prev = pb;
ps->writepos = 0;
}
static void
sucker_freefile(png_sucker_file *pf)
{
if (pf->next)
sucker_freefile(pf->next);
pf->next = NULL;
sucker_freebuffer(&pf->data);
pf->datacount = 0;
free(pf);
}
/* Main interface to file storeage, after writing a new PNG file (see the API
* below) call sucker_storefile to store the result with the given name and id.
*/
static void
sucker_storefile(png_sucker *ps, png_uint_32 id)
{
png_sucker_file *pf = malloc(sizeof *pf);
if (pf == NULL)
png_error(ps->pwrite, "storefile: OOM");
safecat(pf->name, sizeof pf->name, 0, ps->wname);
pf->id = id;
pf->data = ps->new;
pf->datacount = ps->writepos;
ps->new.prev = NULL;
ps->writepos = 0;
/* And save it. */
pf->next = ps->saved;
ps->saved = pf;
}
/* Generate an error message (in the given buffer) */
static size_t
sucker_message(png_structp pp, char *buffer, size_t bufsize, const char *msg)
{
size_t pos = 0;
png_sucker *ps = png_get_error_ptr(pp);
if (pp == ps->pread)
{
/* Reading a file */
pos = safecat(buffer, bufsize, pos, "read: ");
if (ps->current != NULL)
{
pos = safecat(buffer, bufsize, pos, ps->current->name);
pos = safecat(buffer, bufsize, pos, sep);
}
}
else if (pp == ps->pwrite)
{
/* Writing a file */
pos = safecat(buffer, bufsize, pos, "write: ");
pos = safecat(buffer, bufsize, pos, ps->wname);
}
else
{
/* Neither reading nor writing */
pos = safecat(buffer, bufsize, pos, "pngvalid: ");
}
pos = safecat(buffer, bufsize, pos, ps->test);
pos = safecat(buffer, bufsize, pos, " ");
pos = safecat(buffer, bufsize, pos, msg);
return pos;
}
/* Functions to use as PNG callbacks. */
static void
sucker_error(png_structp pp, png_const_charp message) /* PNG_NORETURN */
{
png_sucker *ps = png_get_error_ptr(pp);
char buffer[256];
sucker_message(pp, buffer, sizeof buffer, message);
if (ps->nerrors++ == 0)
safecat(ps->error, sizeof ps->error, 0, buffer);
if (ps->verbose)
fprintf(stderr, "error: %s\n", buffer);
/* The longjmp argument is because, by UTSL, libpng calls longjmp with 1, and
* libpng is *not* expected to ever call longjmp, so this is a sanity
* check. The code below ensures that libpng gets a copy of our jmp_buf.
*/
longjmp(ps->jmpbuf, SUCKER_ERROR);
}
static void
sucker_warning(png_structp pp, png_const_charp message)
{
png_sucker *ps = png_get_error_ptr(pp);
char buffer[256];
sucker_message(pp, buffer, sizeof buffer, message);
if (ps->nwarnings++ == 0 && ps->nerrors == 0)
safecat(ps->error, sizeof ps->error, 0, buffer);
if (ps->verbose)
fprintf(stderr, "warning: %s\n", buffer);
}
static void
sucker_write(png_structp pp, png_bytep pb, png_size_t st)
{
png_sucker *ps = png_get_io_ptr(pp);
if (ps->pwrite != pp)
png_error(pp, "sucker state damaged");
while (st > 0)
{
size_t cb;
if (ps->writepos >= SUCKER_BUFFER_SIZE)
sucker_storenew(ps);
cb = st;
if (cb > SUCKER_BUFFER_SIZE - ps->writepos)
cb = SUCKER_BUFFER_SIZE - ps->writepos;
memcpy(ps->new.buffer + ps->writepos, pb, cb);
pb += cb;
st -= cb;
ps->writepos += cb;
}
}
static void
sucker_flush(png_structp pp)
{
/*DOES NOTHING*/
}
static size_t
sucker_read_buffer_size(png_sucker *ps)
{
/* Return the bytes available for read in the current buffer. */
if (ps->next != &ps->current->data)
return SUCKER_BUFFER_SIZE;
return ps->current->datacount;
}
static int
sucker_read_buffer_next(png_sucker *ps)
{
png_sucker_buffer *pbOld = ps->next;
png_sucker_buffer *pbNew = &ps->current->data;
if (pbOld != pbNew)
{
while (pbNew != NULL && pbNew->prev != pbOld)
pbNew = pbNew->prev;
if (pbNew != NULL)
{
ps->next = pbNew;
ps->readpos = 0;
return 1;
}
png_error(ps->pread, "buffer lost");
}
return 0; /* EOF or error */
}
static void
sucker_read(png_structp pp, png_bytep pb, png_size_t st)
{
png_sucker *ps = png_get_io_ptr(pp);
if (ps->pread != pp || ps->current == NULL || ps->next == NULL)
png_error(pp, "sucker state damaged");
while (st > 0)
{
size_t cbAvail = sucker_read_buffer_size(ps) - ps->readpos;
if (cbAvail > 0)
{
if (cbAvail > st) cbAvail = st;
memcpy(pb, ps->next->buffer + ps->readpos, cbAvail);
st -= cbAvail;
pb += cbAvail;
ps->readpos += cbAvail;
}
else if (!sucker_read_buffer_next(ps))
png_error(pp, "read beyond end of file");
}
}
/* Setup functions. */
/* Cleanup when aborting a write or after storing the new file. */
static void
sucker_write_reset(png_sucker *ps)
{
if (ps->pwrite != NULL)
{
png_destroy_write_struct(&ps->pwrite, &ps->piwrite);
ps->pwrite = NULL;
ps->piwrite = NULL;
}
sucker_freenew(ps);
}
/* The following is the main write function, it returns a png_struct and,
* optionally, a png)info suitable for writiing a new PNG file. Use
* sucker_storefile above to record this file after it has been written. The
* returned libpng structures as destroyed by sucker_write_reset above.
*/
static png_structp
set_sucker_for_write(png_sucker *ps, png_infopp ppi, const char name[64])
{
if (setjmp(ps->jmpbuf) != 0)
return NULL;
if (ps->pwrite != NULL)
png_error(ps->pwrite, "sucker already in use");
sucker_write_reset(ps);
safecat(ps->wname, sizeof ps->wname, 0, name);
ps->pwrite = png_create_write_struct(PNG_LIBPNG_VER_STRING, ps, sucker_error,
sucker_warning);
png_set_write_fn(ps->pwrite, ps, sucker_write, sucker_flush);
if (ppi != NULL)
*ppi = ps->piwrite = png_create_info_struct(ps->pwrite);
return ps->pwrite;
}
/* Cleanup when finished reading (either due to error or in the success case. )
*/
static void
sucker_read_reset(png_sucker *ps)
{
if (ps->pread != NULL)
{
png_destroy_read_struct(&ps->pread, &ps->piread, NULL);
ps->pread = NULL;
ps->piread = NULL;
}
ps->current = NULL;
ps->next = NULL;
ps->readpos = 0;
}
static void
sucker_read_set(png_sucker *ps, png_uint_32 id)
{
png_sucker_file *pf = ps->saved;
while (pf != NULL)
{
if (pf->id == id)
{
ps->current = pf;
ps->next = NULL;
sucker_read_buffer_next(ps);
return;
}
pf = pf->next;
}
png_error(ps->pread, "unable to find file to read");
}
/* The main interface for reading a saved file - pass the id number of the file
* to retrieve. Ids must be unique or the earlier file will be hidden. The API
* returns a png_struct and, optionally, a png_info. Both of these will be
* destroyed by sucker_read_reset above.
*/
static png_structp
set_sucker_for_read(png_sucker *ps, png_infopp ppi, png_uint_32 id,
const char *name)
{
safecat(ps->test, sizeof ps->test, 0, name);
if (setjmp(ps->jmpbuf) != 0)
return NULL;
if (ps->pread != NULL)
png_error(ps->pread, "sucker already in use");
sucker_read_reset(ps);
ps->pread = png_create_read_struct(PNG_LIBPNG_VER_STRING, ps, sucker_error,
sucker_warning);
sucker_read_set(ps, id);
png_set_read_fn(ps->pread, ps, sucker_read);
if (ppi != NULL)
*ppi = ps->piread = png_create_info_struct(ps->pread);
return ps->pread;
}
/*********************** PNG FILE MODIFICATION ON READ ************************/
/* Files may be modified on read. The following structure contains a complete
* png_sucker together with extra members to handle modification and a special
* read callback for libpng. To use this the 'modifications' field must be set
* to a list of png_modification structures that actually perform the
* modification, otherwise a png_modifier is functionally equivalent to a
* png_sucker. There is a special read function, set_modifier_for_read, which
* replaces set_sucker_for_read.
*/
typedef struct png_modifier
{
png_sucker this; /* I am a png_sucker */
struct png_modification *modifications; /* Changes to make */
enum modifier_state
{
modifier_start, /* Initial value */
modifier_signature, /* Have a signature */
modifier_IHDR /* Have an IHDR */
} state; /* My state */
/* Information from IHDR: */
png_byte bit_depth; /* From IHDR */
png_byte colour_type; /* From IHDR */
/* While handling PLTE, IDAT and IEND these chunks may be pended to allow
* other chunks to be inserted.
*/
png_uint_32 pending_len;
png_uint_32 pending_chunk;
/* Test values */
double *gammas;
unsigned ngammas;
/* Lowest sbit to test (libpng fails for sbit < 8) */
unsigned sbitlow;
/* Error control - these are the limits on errors accepted by the gamma tests
* below.
*/
double maxout8; /* Maximum output value error */
double maxabs8; /* Abosulte sample error 0..1 */
double maxpc8; /* Percentage sample error 0..100% */
double maxout16; /* Maximum output value error */
double maxabs16; /* Absolute sample error 0..1 */
double maxpc16; /* Percentage sample error 0..100% */
/* Logged 8 and 16 bit errors ('output' values): */
double error_gray_2;
double error_gray_4;
double error_gray_8;
double error_gray_16;
double error_color_8;
double error_color_16;
/* Flags: */
/* When to use the use_input_precision option: */
int use_input_precision :1;
int use_input_precision_sbit :1;
int use_input_precision_16to8 :1;
int log :1; /* Log max error */
/* Buffer information, the buffer size limits the size of the chunks that can
* be modified - they must fit (including header and CRC) into the buffer!
*/
size_t flush; /* Count of bytes to flush */
size_t buffer_count; /* Bytes in buffer */
size_t buffer_position; /* Position in buffer */
png_byte buffer[1024];
} png_modifier;
static double abserr(png_modifier *pm, png_byte bit_depth)
{
return bit_depth == 16 ? pm->maxabs16 : pm->maxabs8;
}
static double pcerr(png_modifier *pm, png_byte bit_depth)
{
return (bit_depth == 16 ? pm->maxpc16 : pm->maxpc8) * .01;
}
static double outerr(png_modifier *pm, png_byte bit_depth)
{
/* There is a serious error in the 2 and 4 bit grayscale transform because
* the gamma table value (8 bits) is simply shifted, not rouned, so the
* error in 4 bit greyscale gamma is up to the value below. This is a hack
* to allow pngvalid to succeed:
*/
if (bit_depth == 2) return .73182-.5;
if (bit_depth == 4) return .90644-.5;
if (bit_depth == 16) return pm->maxout16;
return pm->maxout8;
}
/* This returns true if the test should be stopped now because it has already
* failed and it is running silently.
*/
static int fail(png_modifier *pm)
{
return !pm->log && !pm->this.verbose && (pm->this.nerrors > 0 ||
pm->this.treat_warnings_as_errors && pm->this.nwarnings > 0);
}
static void
modifier_init(png_modifier *pm)
{
memset(pm, 0, sizeof *pm);
sucker_init(&pm->this);
pm->modifications = NULL;
pm->state = modifier_start;
pm->sbitlow = 1;
pm->maxout8 = pm->maxpc8 = pm->maxabs8 = 0;
pm->maxout16 = pm->maxpc16 = pm->maxabs16 = 0;
pm->error_gray_2 = pm->error_gray_4 = pm->error_gray_8 = 0;
pm->error_gray_16 = pm->error_color_8 = pm->error_color_16 = 0;
pm->use_input_precision = 0;
pm->use_input_precision_sbit = 0;
pm->use_input_precision_16to8 = 0;
pm->log = 0;
/* Rely on the memset for all the other fields - there are no pointers */
}
/* One modification strucutre must be provided for each chunk to be modified (in
* fact more than one can be provided if multiple separate changes are desired
* for a single chunk.) Modifications include adding a new chunk when a
* suitable chunk does not exist.
*
* The caller of modify_fn will reset the CRC of the chunk and record 'modified'
* or 'added' as appropriate if the modify_fn returns 1 (true). If the
* modify_fn is NULL the chunk is simply removed.
*/
typedef struct png_modification
{
struct png_modification *next;
png_uint_32 chunk;
/* If the following is NULL all matching chunks will be removed: */
int (*modify_fn)(png_structp pp, struct png_modifier *pm,
struct png_modification *me, int add);
/* If the following is set to PLTE, IDAT or IEND and the chunk has not been
* found and modified (and there is a modify_fn) the modify_fn will be called
* to add the chunk before the relevant chunk.
*/
png_uint_32 add;
int modified :1; /* Chunk was modified */
int added :1; /* Chunk was added */
int removed :1; /* Chunk was removed */
} png_modification;
static void modification_reset(png_modification *pmm)
{
if (pmm != NULL)
{
pmm->modified = 0;
pmm->added = 0;
pmm->removed = 0;
modification_reset(pmm->next);
}
}
static void
modification_init(png_modification *pmm)
{
memset(pmm, 0, sizeof *pmm);
pmm->next = NULL;
pmm->chunk = 0;
pmm->modify_fn = NULL;
pmm->add = 0;
modification_reset(pmm);
}
static void
modifier_reset(png_modifier *pm)
{
sucker_read_reset(&pm->this);
pm->modifications = NULL;
pm->state = modifier_start;
pm->bit_depth = pm->colour_type = 0;
pm->pending_len = pm->pending_chunk = 0;
pm->flush = pm->buffer_count = pm->buffer_position = 0;
}
/* Convenience macros. */
#define CHUNK(a,b,c,d) (((a)<<24)+((b)<<16)+((c)<<8)+(d))
#define CHUNK_IHDR CHUNK(73,72,68,82)
#define CHUNK_PLTE CHUNK(80,76,84,69)
#define CHUNK_IDAT CHUNK(73,68,65,84)
#define CHUNK_IEND CHUNK(73,69,78,68)
#define CHUNK_cHRM CHUNK(99,72,82,77)
#define CHUNK_gAMA CHUNK(103,65,77,65)
#define CHUNK_sBIT CHUNK(115,66,73,84)
#define CHUNK_sRGB CHUNK(115,82,71,66)
/* The guts of modification are performed during a read. */
static void
modifier_crc(png_bytep buffer)
{
/* Recalculate the chunk CRC - a complete chunk must be in
* the buffer, at the start.
*/
uInt datalen = png_get_uint_32(buffer);
png_save_uint_32(buffer+datalen+8, crc32(0L, buffer+4, datalen+4));
}
static void
modifier_setbuffer(png_modifier *pm)
{
modifier_crc(pm->buffer);
pm->buffer_count = png_get_uint_32(pm->buffer)+12;
pm->buffer_position = 0;
}
static void
modifier_read(png_structp pp, png_bytep pb, png_size_t st)
{
png_modifier *pm = png_get_io_ptr(pp);
while (st > 0)
{
size_t cb;
png_uint_32 len, chunk;
png_modification *mod;
if (pm->buffer_position >= pm->buffer_count) switch (pm->state)
{
static png_byte sign[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };
case modifier_start:
sucker_read(pp, pm->buffer, 8); /* size of signature. */
pm->buffer_count = 8;
pm->buffer_position = 0;
if (memcmp(pm->buffer, sign, 8) != 0)
png_error(pp, "invalid PNG file signature");
pm->state = modifier_signature;
break;
case modifier_signature:
sucker_read(pp, pm->buffer, 13+12); /* size of IHDR */
pm->buffer_count = 13+12;
pm->buffer_position = 0;
if (png_get_uint_32(pm->buffer) != 13 ||
png_get_uint_32(pm->buffer+4) != CHUNK_IHDR)
png_error(pp, "invalid IHDR");
/* Check the list of modifiers for modifications to the IHDR. */
mod = pm->modifications;
while (mod != NULL)
{
if (mod->chunk == CHUNK_IHDR && mod->modify_fn &&
(*mod->modify_fn)(pp, pm, mod, 0))
{
mod->modified = 1;
modifier_setbuffer(pm);
}
/* Ignore removal or add if IHDR! */
mod = mod->next;
}
/* Cache information from the IHDR (the modified one.) */
pm->bit_depth = pm->buffer[8+8];
pm->colour_type = pm->buffer[8+8+1];
pm->state = modifier_IHDR;
pm->flush = 0;
break;
default:
/* Read a new chunk and process it until we see PLTE, IDAT or
* IEND. 'flush' indicates that there is still some data to
* output from the preceding chunk.
*/
if ((cb = pm->flush) > 0)
{
if (cb > st) cb = st;
pm->flush -= cb;
sucker_read(pp, pb, cb);
pb += cb;
st -= cb;
if (st <= 0) return;
}
/* No more bytes to flush, read a header, or handle a pending
* chunk.
*/
if (pm->pending_chunk != 0)
{
png_save_uint_32(pm->buffer, pm->pending_len);
png_save_uint_32(pm->buffer+4, pm->pending_chunk);
pm->pending_len = 0;
pm->pending_chunk = 0;
}
else
sucker_read(pp, pm->buffer, 8);
pm->buffer_count = 8;
pm->buffer_position = 0;
/* Check for something to modify or a terminator chunk. */
len = png_get_uint_32(pm->buffer);
chunk = png_get_uint_32(pm->buffer+4);
/* Terminators first, they may have to be delayed for added
* chunks
*/
if (chunk == CHUNK_PLTE || chunk == CHUNK_IDAT || chunk == CHUNK_IEND)
{
mod = pm->modifications;
while (mod != NULL)
{
if ((mod->add == chunk ||
mod->add == CHUNK_PLTE && chunk == CHUNK_IDAT) &&
mod->modify_fn != NULL && !mod->modified && !mod->added)
{
/* Regardless of what the modify function does do not run this
* again.
*/
mod->added = 1;
if ((*mod->modify_fn)(pp, pm, mod, 1/*add*/))
{
/* Reset the CRC on a new chunk */
if (pm->buffer_count > 0)
modifier_setbuffer(pm);
else
{
pm->buffer_position = 0;
mod->removed = 1;
}
/* The buffer has been filled with something (we assume) so
* output this. Pend the current chunk.
*/
pm->pending_len = len;
pm->pending_chunk = chunk;
break; /* out of while */
}
}
mod = mod->next;
}
/* Don't do any further processing if the buffer was modified -
* otherwise the code will end up modifying a chunk that was just
* added.
*/
if (mod != NULL)
break; /* out of switch */
}
/* If we get to here then this chunk may need to be modified. To do
* this is must be less than 1024 bytes in total size, otherwise
* it just gets flushed.
*/
if (len+12 <= sizeof pm->buffer)
{
sucker_read(pp, pm->buffer+pm->buffer_count,
len+12-pm->buffer_count);
pm->buffer_count = len+12;
/* Check for a modification, else leave it be. */
mod = pm->modifications;
while (mod != NULL)
{
if (mod->chunk == chunk)
{
if (mod->modify_fn == NULL)
{
/* Remove this chunk */
pm->buffer_count = pm->buffer_position = 0;
mod->removed = 1;
break; /* Terminate the while loop */
}
else if ((*mod->modify_fn)(pp, pm, mod, 0))
{
mod->modified = 1;
/* The chunk may have been removed: */
if (pm->buffer_count == 0)
{
pm->buffer_position = 0;
break;
}
modifier_setbuffer(pm);
}
}
mod = mod->next;
}
}
else
pm->flush = len+12 - pm->buffer_count; /* data + crc */
/* Take the data from the buffer (if there is any). */
break;
}
/* Here to read from the modifier buffer (not directly from
* the sucker, as in the flush case above.)
*/
cb = pm->buffer_count - pm->buffer_position;
if (cb > st) cb = st;
memcpy(pb, pm->buffer + pm->buffer_position, cb);
st -= cb;
pb += cb;
pm->buffer_position += cb;
}
}
/* Set up a modifier. */
static png_structp
set_modifier_for_read(png_modifier *pm, png_infopp ppi, png_uint_32 id,
const char *name)
{
png_structp pp = set_sucker_for_read(&pm->this, ppi, id, name);
if (pp != NULL)
{
if (setjmp(pm->this.jmpbuf) == 0)
{
png_set_read_fn(pp, pm, modifier_read);
pm->state = modifier_start;
pm->bit_depth = 0;
pm->colour_type = 255;
pm->pending_len = 0;
pm->pending_chunk = 0;
pm->flush = 0;
pm->buffer_count = 0;
pm->buffer_position = 0;
}
else
{
sucker_read_reset(&pm->this);
pp = NULL;
}
}
return pp;
}
/***************************** STANDARD PNG FILES *****************************/
/* Standard files - write and save standard files. */
/* The standard files are constructed with rows which fit into a 1024 byte row
* buffer. This makes allocation easier below. Further regardless of the file
* format every file has 128 pixels (giving 1024 bytes for 64bpp formats).
*
* Files are stored with no gAMA or sBIT chunks, with a PLTE only when needed
* and with an ID derived from the colour type and bit depth as follows:
*/
#define FILEID(col, depth) ((png_uint_32)((col) + ((depth)<<3)))
#define COL_FROM_ID(id) ((id)& 0x7)
#define DEPTH_FROM_ID(id) (((id) >> 3) & 0x1f)
#define STD_WIDTH 128
#define STD_ROWMAX (STD_WIDTH*8)
static unsigned
bit_size(png_structp pp, png_byte colour_type, png_byte bit_depth)
{
switch (colour_type)
{
case 0: return bit_depth;
case 2: return 3*bit_depth;
case 3: return bit_depth;
case 4: return 2*bit_depth;
case 6: return 4*bit_depth;
default: png_error(pp, "invalid color type");
}
}
static size_t
standard_rowsize(png_structp pp, png_byte colour_type, png_byte bit_depth)
{
return (STD_WIDTH * bit_size(pp, colour_type, bit_depth)) / 8;
}
static png_uint_32
standard_width(png_structp pp, png_byte colour_type, png_byte bit_depth)
{
return STD_WIDTH;
}
static png_uint_32
standard_height(png_structp pp, png_byte colour_type, png_byte bit_depth)
{
switch (bit_size(pp, colour_type, bit_depth))
{
case 1:
case 2:
case 4:
return 1; /* Total of 128 pixels */
case 8:
return 2; /* Total of 256 pixels/bytes */
case 16:
return 512; /* Total of 65536 pixels */
case 24:
case 32:
return 512; /* 65536 pixels */
case 48:
case 64:
return 2048;/* 4 x 65536 pixels. */
}
}
static void
standard_row(png_structp pp, png_byte buffer[STD_ROWMAX], png_byte colour_type,
png_byte bit_depth, png_uint_32 y)
{
png_uint_32 v = y << 7;
png_uint_32 i = 0;
switch (bit_size(pp, colour_type, bit_depth))
{
case 1:
while (i<128/8) buffer[i] = v & 0xff, v += 17, ++i;
return;
case 2:
while (i<128/4) buffer[i] = v & 0xff, v += 33, ++i;
return;
case 4:
while (i<128/2) buffer[i] = v & 0xff, v += 65, ++i;
return;
case 8:
/* 256 bytes total, 128 bytes in each row set as follows: */
while (i<128) buffer[i] = v & 0xff, ++v, ++i;
return;
case 16:
/* Generate all 65536 pixel values in order, this includes the 8 bit GA
* case as we as the 16 bit G case.
*/
while (i<128)
buffer[2*i] = (v>>8) & 0xff, buffer[2*i+1] = v & 0xff, ++v, ++i;
return;
case 24:
/* 65535 pixels, but rotate the values. */
while (i<128)
{
/* Three bytes per pixel, r, g, b, make b by r^g */
buffer[3*i+0] = (v >> 8) & 0xff;
buffer[3*i+1] = v & 0xff;
buffer[3*i+2] = ((v >> 8) ^ v) & 0xff;
++v;
++i;
}
return;
case 32:
/* 65535 pixels, r, g, b, a; just replicate */
while (i<128)
{
buffer[4*i+0] = (v >> 8) & 0xff;
buffer[4*i+1] = v & 0xff;
buffer[4*i+2] = (v >> 8) & 0xff;
buffer[4*i+3] = v & 0xff;
++v;
++i;
}
return;
case 48:
/* y is maximum 2047, giving 4x65536 pixels, make 'r' increase by 1 at
* each pixel, g increase by 257 (0x101) and 'b' by 0x1111:
*/
while (i<128)
{
png_uint_32 t = v++;
buffer[6*i+0] = (t >> 8) & 0xff;
buffer[6*i+1] = t & 0xff;
t *= 257;
buffer[6*i+2] = (t >> 8) & 0xff;
buffer[6*i+3] = t & 0xff;
t *= 17;
buffer[6*i+4] = (t >> 8) & 0xff;
buffer[6*i+5] = t & 0xff;
++i;
}
return;
case 64:
/* As above in the 32 bit case. */
while (i<128)
{
png_uint_32 t = v++;
buffer[8*i+0] = (t >> 8) & 0xff;
buffer[8*i+1] = t & 0xff;
buffer[8*i+4] = (t >> 8) & 0xff;
buffer[8*i+5] = t & 0xff;
t *= 257;
buffer[8*i+2] = (t >> 8) & 0xff;
buffer[8*i+3] = t & 0xff;
buffer[8*i+6] = (t >> 8) & 0xff;
buffer[8*i+7] = t & 0xff;
++i;
}
return;
}
png_error(pp, "internal error");
}
static void
make_standard(png_sucker* ps, png_byte colour_type, int bdlo, int bdhi)
{
for (; bdlo <= bdhi; ++bdlo)
{
png_byte bit_depth = 1U << bdlo;
png_uint_32 h, y;
png_structp pp;
png_infop pi;
{
size_t pos;
char name[64]; /* Same size as the buffer in a file. */
/* Build a name */
pos = safecat(name, sizeof name, 0, bit_depths[bdlo]);
pos = safecat(name, sizeof name, pos, "bit ");
pos = safecat(name, sizeof name, pos, colour_types[colour_type]);
/* Get a png_struct for writing the image. */
pp = set_sucker_for_write(ps, &pi, name);
}
if (pp == NULL) return;
/* Do the honourable write stuff, protected by a local setjmp */
if (setjmp(ps->jmpbuf) != 0)
{
sucker_write_reset(ps);
continue;
}
h = standard_height(pp, colour_type, bit_depth),
png_set_IHDR(pp, pi, standard_width(pp, colour_type, bit_depth), h,
bit_depth, colour_type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
PNG_FILTER_TYPE_BASE);
if (colour_type == 3) /* palette */
{
int i;
png_color pal[256];
for (i=0; i<256; ++i) pal[i].red = pal[i].green = pal[i].blue = i;
png_set_PLTE(pp, pi, pal, 256);
}
png_write_info(pp, pi);
if (png_get_rowbytes(pp, pi) !=
standard_rowsize(pp, colour_type, bit_depth))
png_error(pp, "row size incorrect");
else for (y=0; y<h; ++y)
{
png_byte buffer[STD_ROWMAX];
standard_row(pp, buffer, colour_type, bit_depth, y);
png_write_row(pp, buffer);
}
png_write_end(pp, pi);
/* And store this under the appropriate id, then clean up. */
sucker_storefile(ps, FILEID(colour_type, bit_depth));
sucker_write_reset(ps);
}
}
static void
make_standard_images(png_sucker *ps)
{
/* Arguments are colour_type, low bit depth, high bit depth */
make_standard(ps, 0, 0, 4);
make_standard(ps, 2, 3, 4);
make_standard(ps, 3, 0, 3);
make_standard(ps, 4, 3, 4);
make_standard(ps, 6, 3, 4);
}
/* Tests - individual test cases */
static void
test_standard(png_sucker* ps, png_byte colour_type, int bdlo, int bdhi)
{
for (; bdlo <= bdhi; ++bdlo)
{
png_byte bit_depth = 1U << bdlo;
png_uint_32 h, y;
size_t cb;
png_structp pp;
png_infop pi;
/* Get a png_struct for writing the image. */
pp = set_sucker_for_read(ps, &pi, FILEID(colour_type, bit_depth),
"standard");
if (pp == NULL) return;
/* Do the honourable write stuff, protected by a local setjmp */
if (setjmp(ps->jmpbuf) != 0)
{
sucker_read_reset(ps);
continue;
}
h = standard_height(pp, colour_type, bit_depth);
/* Check the header values: */
png_read_info(pp, pi);
if (png_get_image_width(pp, pi) !=
standard_width(pp, colour_type, bit_depth))
png_error(pp, "validate: image width changed");
if (png_get_image_height(pp, pi) != h)
png_error(pp, "validate: image height changed");
if (png_get_bit_depth(pp, pi) != bit_depth)
png_error(pp, "validate: bit depth changed");
if (png_get_color_type(pp, pi) != colour_type)
png_error(pp, "validate: color type changed");
if (png_get_filter_type(pp, pi) != PNG_FILTER_TYPE_BASE)
png_error(pp, "validate: filter type changed");
if (png_get_interlace_type(pp, pi) != PNG_INTERLACE_NONE)
png_error(pp, "validate: interlacing changed");
if (png_get_compression_type(pp, pi) != PNG_COMPRESSION_TYPE_BASE)
png_error(pp, "validate: compression type changed");
if (png_set_interlace_handling(pp) != 1)
png_error(pp, "validate: interlacing unexpected");
if (colour_type == 3) /* palette */
{
png_colorp pal;
int num;
if (png_get_PLTE(pp, pi, &pal, &num) & PNG_INFO_PLTE)
{
int i;
if (num != 256)
png_error(pp, "validate: color type 3 PLTE chunk size changed");
for (i=0; i<num; ++i)
if (pal[i].red != i || pal[i].green != i || pal[i].blue != i)
png_error(pp, "validate: color type 3 PLTE chunk changed");
}
else
png_error(pp, "validate: missing PLTE with color type 3");
}
cb = standard_rowsize(pp, colour_type, bit_depth);
png_start_read_image(pp);
if (png_get_rowbytes(pp, pi) != cb)
png_error(pp, "validate: row size changed");
else for (y=0; y<h; ++y)
{
png_byte std[STD_ROWMAX];
png_byte read[STD_ROWMAX];
png_byte display[STD_ROWMAX];
standard_row(pp, std, colour_type, bit_depth, y);
png_read_row(pp, read, display);
if (memcmp(std, read, cb) != 0)
{
char msg[64];
sprintf(msg, "validate: PNG image row %d (of %d) changed", y,
h);
png_error(pp, msg);
}
if (memcmp(std, display, cb) != 0)
{
char msg[64];
sprintf(msg, "validate: transformed row %d (of %d) changed", y, h);
png_error(pp, msg);
}
}
png_read_end(pp, pi);
sucker_read_reset(ps);
}
}
static void
perform_standard_test(png_modifier *pm)
{
test_standard(&pm->this, 0, 0, 4);
if (fail(pm)) return;
test_standard(&pm->this, 2, 3, 4);
if (fail(pm)) return;
test_standard(&pm->this, 3, 0, 3);
if (fail(pm)) return;
test_standard(&pm->this, 4, 3, 4);
if (fail(pm)) return;
test_standard(&pm->this, 6, 3, 4);
}
/********************************* GAMMA TESTS ********************************/
/* Gamma test images. */
static void
make_gamma_images(png_sucker *ps)
{
/* Do nothing - the standard greyscale images are used. */
}
typedef struct gamma_modification
{
png_modification this;
png_fixed_point gamma;
}
gamma_modification;
static int
gamma_modify(png_structp pp, png_modifier *pm, png_modification *me, int add)
{
/* This simply dumps the given gamma value into the buffer. */
png_save_uint_32(pm->buffer, 4);
png_save_uint_32(pm->buffer+4, CHUNK_gAMA);
png_save_uint_32(pm->buffer+8, ((gamma_modification*)me)->gamma);
return 1;
}
static void
gamma_modification_init(gamma_modification *me, png_modifier *pm, double gamma)
{
modification_init(&me->this);
me->this.chunk = CHUNK_gAMA;
me->this.modify_fn = gamma_modify;
me->this.add = CHUNK_PLTE;
me->gamma = floor(gamma * 100000 + .5);
me->this.next = pm->modifications;
pm->modifications = &me->this;
}
typedef struct srgb_modification
{
png_modification this;
png_byte intent;
}
srgb_modification;
static int
srgb_modify(png_structp pp, png_modifier *pm, png_modification *me, int add)
{
/* As above, ignore add and just make a new chunk */
png_save_uint_32(pm->buffer, 1);
png_save_uint_32(pm->buffer+4, CHUNK_sRGB);
pm->buffer[8] = ((srgb_modification*)me)->intent;
return 1;
}
static void
srgb_modification_init(srgb_modification *me, png_modifier *pm, png_byte intent)
{
modification_init(&me->this);
me->this.chunk = CHUNK_sBIT;
if (intent <= 3) /* if valid, else *delete* sRGB chunks */
{
me->this.modify_fn = srgb_modify;
me->this.add = CHUNK_PLTE;
me->intent = intent;
}
else
{
me->this.modify_fn = 0;
me->this.add = 0;
me->intent = 0;
}
me->this.next = pm->modifications;
pm->modifications = &me->this;
}
typedef struct sbit_modification
{
png_modification this;
png_byte sbit;
}
sbit_modification;
static int
sbit_modify(png_structp pp, png_modifier *pm, png_modification *me, int add)
{
png_byte sbit = ((sbit_modification*)me)->sbit;
if (pm->bit_depth > sbit)
{
int cb = 0;
switch (pm->colour_type)
{
case 0: cb = 1; break;
case 2:
case 3: cb = 3; break;
case 4: cb = 2; break;
case 6: cb = 4; break;
default:
png_error(pp, "unexpected colour type in sBIT modification");
}
png_save_uint_32(pm->buffer, cb);
png_save_uint_32(pm->buffer+4, CHUNK_sBIT);
while (cb > 0)
(pm->buffer+8)[--cb] = sbit;
return 1;
}
else if (!add)
{
/* Remove the sBIT chunk */
pm->buffer_count = pm->buffer_position = 0;
return 1;
}
else
return 0; /* do nothing */
}
static void
sbit_modification_init(sbit_modification *me, png_modifier *pm, png_byte sbit)
{
modification_init(&me->this);
me->this.chunk = CHUNK_sBIT;
me->this.modify_fn = sbit_modify;
me->this.add = CHUNK_PLTE;
me->sbit = sbit;
me->this.next = pm->modifications;
pm->modifications = &me->this;
}
/* maxabs: maximum absolute error as a fraction
* maxout: maximum output error in the output units
* maxpc: maximum percentage error (as a percentage)
*/
static void
gamma_test(png_modifier *pm, const png_byte colour_type,
const png_byte bit_depth, const double file_gamma, const double screen_gamma,
const png_byte sbit, const int threshold_test, const char *name,
const int speed, const int use_input_precision, const int strip16)
{
png_structp pp;
png_infop pi;
double maxerrout = 0, maxerrpc = 0, maxerrabs = 0;
gamma_modification gamma_mod;
srgb_modification srgb_mod;
sbit_modification sbit_mod;
/* Make an appropriate modifier to set the PNG file gamma to the
* given gamma value and the sBIT chunk to the given precision.
*/
pm->modifications = NULL;
gamma_modification_init(&gamma_mod, pm, file_gamma);
srgb_modification_init(&srgb_mod, pm, 127/*delete*/);
sbit_modification_init(&sbit_mod, pm, sbit);
modification_reset(pm->modifications);
/* Get a png_struct for writing the image. */
pp = set_modifier_for_read(pm, &pi, FILEID(colour_type, bit_depth), name);
if (pp == NULL) return;
/* Do the honourable write stuff, protected by a local setjmp */
if (setjmp(pm->this.jmpbuf) != 0)
{
modifier_reset(pm);
return;
}
/* Set up gamma processing. */
png_set_gamma(pp, screen_gamma, file_gamma);
/* Check the header values: */
png_read_info(pp, pi);
/* If requested strip 16 to 8 bits - this is handled automagically below
* because the output bit depth is read from the library. Note that there
* are interactions with sBIT but, internally, libpng makes sbit at most
* PNG_MAX_GAMMA_8 when doing the following.
*/
if (strip16)
png_set_strip_16(pp);
if (png_set_interlace_handling(pp) != 1)
png_error(pp, "gamma: interlaced images not supported");
png_read_update_info(pp, pi);
{
const png_byte out_ct = png_get_color_type(pp, pi);
const png_byte out_bd = png_get_bit_depth(pp, pi);
const unsigned outmax = (1U<<out_bd)-1;
const png_uint_32 w = png_get_image_width(pp, pi);
const png_uint_32 h = png_get_image_height(pp, pi);
const size_t cb = png_get_rowbytes(pp, pi); /* For the memcmp below. */
const double maxabs = abserr(pm, out_bd);
const double maxout = outerr(pm, out_bd);
const double maxpc = pcerr(pm, out_bd);
png_uint_32 y;
/* There are three sources of error, firstly the quantization in the file
* encoding, determined by sbit and/or the file depth, secondly the output
* (screen) gamma and thirdly the output file encoding. Since this API
* receives the screen and file gamma in double precision it is possible
* to calculate an exact answer given an input pixel value. Therefore we
* assume that the *input* value is exact - sample/maxsample - calculate
* the corresponding gamma corrected output to the limits of double
* precision arithmetic and compare with what libpng returns.
*
* Since the library must quantise the output to 8 or 16 bits there is a
* fundamental limit on the accuracy of the output of +/-.5 - this
* quantisation limit is included in addition to the other limits
* specified by the paramaters to the API. (Effectively, add .5
* everywhere.)
*
* The behavior of the 'sbit' paramter is defined by section 12.5 (sample
* depth scaling) of the PNG spec. That section forces the decoder to
* assume that the PNG values have been scaled if sBIT is presence:
*
* png-sample = floor( input-sample * (max-out/max-in) + .5 );
*
* This means that only a subset of the possible PNG values should appear
* in the input, however the spec allows the encoder to use a variety of
* approximations to the above and doesn't require any restriction of the
* values produced.
*
* Nevertheless the spec requires that the upper 'sBIT' bits of the value
* stored in a PNG file be the original sample bits. Consequently the
* code below simply scales the top sbit bits by (1<<sbit)-1 to obtain an
* original sample value.
*
* Because there is limited precision in the input it is arguable that an
* acceptable result is any valid result from input-.5 to input+.5. The
* basic tests below do not do this, however if 'use_input_precision' is
* set a subsequent test is performed below.
*/
const int processing = (fabs(screen_gamma*file_gamma-1) >=
PNG_GAMMA_THRESHOLD && !threshold_test && !speed && colour_type != 3)
|| bit_depth != out_bd;
const int samples_per_pixel = (out_ct & 2) ? 3 : 1;
const double gamma = 1/(file_gamma*screen_gamma); /* Overall correction */
for (y=0; y<h; ++y) /* just one pass - no interlacing */
{
unsigned s, x;
png_byte std[STD_ROWMAX];
png_byte display[STD_ROWMAX];
standard_row(pp, std, colour_type, bit_depth, y);
png_read_row(pp, NULL, display);
if (processing) for (x=0; x<w; ++x) for (s=0; s<samples_per_pixel; ++s)
{
/* Input sample values: */
const unsigned id = sample(std, colour_type, bit_depth, x, s);
const unsigned od = sample(display, out_ct, out_bd, x, s);
const unsigned isbit = id >> (bit_depth-sbit);
double i, sample, encoded_sample, output, encoded_error, error;
double es_lo, es_hi;
/* First check on the 'perfect' result obtained from the digitized
* input value, id, and compare this against the actual digitized
* result, 'od'. 'i' is the input result in the range 0..1:
*
* NOTE: sbit should be taken into account here but isn't, as
* described above.
*/
i = isbit; i /= (1U<<sbit)-1;
/* Then get the gamma corrected version of 'i' and compare to 'od',
* any error less than .5 is insignificant - just quantization of
* the output value to the nearest digital value (neverthelss the
* error is still recorded - it's interesting ;-)
*/
encoded_sample = pow(i, gamma) * outmax;
encoded_error = fabs(od-encoded_sample);
if (encoded_error > maxerrout)
maxerrout = encoded_error;
if (encoded_error < .5+maxout)
continue;
/* There may be an error, calculate the actual sample values -
* unencoded light intensity values. Note that in practice these
* are not unencoded because they include a 'viewing correction' to
* decrease or (normally) increase the perceptual contrast of the
* image. There's nothing we can do about this - we don't know what
* it is - so assume the unencoded value is perceptually linear.
*/
sample = pow(i, 1/file_gamma); /* In range 0..1 */
output = od;
output /= outmax;
output = pow(output, screen_gamma);
/* Now we have the numbers for real errors, both absolute values as
* as a percentage of the correct value (output):
*/
error = fabs(sample-output);
if (error > maxerrabs)
maxerrabs = error;
/* The following is an attempt to ignore the tendency of
* quantization to dominate the percentage errors for low output
* sample values:
*/
if (sample*maxpc > .5+maxabs)
{
double pcerr = error/sample;
if (pcerr > maxerrpc) maxerrpc = pcerr;
}
/* Now calculate the digitization limits for 'encoded_sample' using
* the 'max' values. Note that maxout is in the encoded space but
* maxpc and maxabs are in linear light space.
*
* First find the maximum error in linear light space, range 0..1:
*/
{
double tmp = sample * maxpc;
if (tmp < maxabs) tmp = maxabs;
/* Low bound - the minimum of the three: */
es_lo = encoded_sample - maxout;
if (es_lo > 0 && sample-tmp > 0)
{
double l = outmax * pow(sample-tmp, 1/screen_gamma);
if (l < es_lo) es_lo = l;
}
else
es_lo = 0;
es_hi = encoded_sample + maxout;
if (es_hi < outmax && sample+tmp < 1)
{
double h = outmax * pow(sample+tmp, 1/screen_gamma);
if (h > es_hi) es_hi = h;
}
else
es_hi = outmax;
}
/* The primary test is that the final encoded value returned by the
* library should be between the two limits (inclusive) that were
* calculated above. At this point quantization of the output must
* be taken into account.
*/
if (od+.5 < es_lo || od-.5 > es_hi)
{
/* Thee has been an error in processing. */
double is_lo, is_hi;
if (use_input_precision)
{
/* Ok, something is wrong - this actually happens in current
* libpng sbit processing. Assume that the input value (id,
* adjusted for sbit) can be anywhere between value-.5 and
* value+.5 - quite a large range if sbit is low.
*/
double tmp = (isbit - .5)/((1U<<sbit)-1);
if (tmp > 0)
{
is_lo = outmax * pow(tmp, gamma) - maxout;
if (is_lo < 0) is_lo = 0;
}
else
is_lo = 0;
tmp = (isbit + .5)/((1U<<sbit)-1);
if (tmp < 1)
{
is_hi = outmax * pow(tmp, gamma) + maxout;
if (is_hi > outmax) is_hi = outmax;
}
else
is_hi = outmax;
if (!(od+.5 < is_lo || od-.5 > is_hi))
continue;
}
{
char msg[256];
sprintf(msg,
"error: %.3f; %u{%u;%u} -> %u not %.2f (%.1f-%.1f)",
od-encoded_sample, id, sbit, isbit, od, encoded_sample,
use_input_precision ? is_lo : es_lo,
use_input_precision ? is_hi : es_hi);
png_warning(pp, msg);
}
}
}
else if (!speed && memcmp(std, display, cb) != 0)
{
char msg[64];
/* No transform is expected on the threshold tests. */
sprintf(msg, "gamma: below threshold row %d (of %d) changed", y, h);
png_error(pp, msg);
}
}
}
png_read_end(pp, pi);
modifier_reset(pm);
if (pm->log && !threshold_test && !speed)
fprintf(stderr, "%d bit %s %s: max error %f (%.2g, %2g%%)\n", bit_depth,
colour_types[colour_type], name, maxerrout, maxerrabs, 100*maxerrpc);
/* Log the summary values too. */
if (colour_type == 0 || colour_type == 4) switch (bit_depth)
{
case 2:
if (maxerrout > pm->error_gray_2) pm->error_gray_2 = maxerrout; break;
case 4:
if (maxerrout > pm->error_gray_4) pm->error_gray_4 = maxerrout; break;
case 8:
if (maxerrout > pm->error_gray_8) pm->error_gray_8 = maxerrout; break;
case 16:
if (maxerrout > pm->error_gray_16) pm->error_gray_16 = maxerrout; break;
}
else if (colour_type == 2 || colour_type == 6) switch (bit_depth)
{
case 8:
if (maxerrout > pm->error_color_8) pm->error_color_8 = maxerrout; break;
case 16:
if (maxerrout > pm->error_color_16) pm->error_color_16 = maxerrout; break;
}
}
static void gamma_threshold_test(png_modifier *pm, png_byte colour_type,
png_byte bit_depth, double file_gamma, double screen_gamma)
{
size_t pos = 0;
char name[64];
pos = safecat(name, sizeof name, pos, "threshold ");
pos = safecatd(name, sizeof name, pos, file_gamma, 3);
pos = safecat(name, sizeof name, pos, "/");
pos = safecatd(name, sizeof name, pos, screen_gamma, 3);
(void)gamma_test(pm, colour_type, bit_depth, file_gamma, screen_gamma,
bit_depth, 1, name, 0/*speed*/, 0/*no input precision*/, 0/*no strip16*/);
}
static void
perform_gamma_threshold_tests(png_modifier *pm)
{
png_byte colour_type = 0;
png_byte bit_depth = 0;
while (next_format(&colour_type, &bit_depth))
{
double gamma = 1.0;
while (gamma >= .4)
{
gamma_threshold_test(pm, colour_type, bit_depth, gamma, 1/gamma);
gamma *= .95;
}
/* And a special test for sRGB */
gamma_threshold_test(pm, colour_type, bit_depth, .45455, 2.2);
if (fail(pm)) return;
}
}
static void gamma_transform_test(png_modifier *pm, const png_byte colour_type,
const png_byte bit_depth, const double file_gamma, const double screen_gamma,
const png_byte sbit, const int speed, const int use_input_precision,
const int strip16)
{
size_t pos = 0;
char name[64];
if (sbit != bit_depth)
{
pos = safecat(name, sizeof name, pos, "sbit(");
pos = safecatn(name, sizeof name, pos, sbit);
pos = safecat(name, sizeof name, pos, ") ");
}
else
pos = safecat(name, sizeof name, pos, "gamma ");
if (strip16)
pos = safecat(name, sizeof name, pos, "16to8 ");
pos = safecatd(name, sizeof name, pos, file_gamma, 3);
pos = safecat(name, sizeof name, pos, "->");
pos = safecatd(name, sizeof name, pos, screen_gamma, 3);
gamma_test(pm, colour_type, bit_depth, file_gamma, screen_gamma, sbit, 0,
name, speed, use_input_precision, strip16);
}
static void perform_gamma_transform_tests(png_modifier *pm, int speed)
{
png_byte colour_type = 0;
png_byte bit_depth = 0;
/* Ignore palette images - the gamma correction happens on the palette entry,
* haven't got the tests for this yet.
*/
while (next_format(&colour_type, &bit_depth)) if (colour_type != 3)
{
int i, j;
for (i=0; i<pm->ngammas; ++i) for (j=0; j<pm->ngammas; ++j) if (i != j)
{
gamma_transform_test(pm, colour_type, bit_depth, 1/pm->gammas[i],
pm->gammas[j], bit_depth, speed, pm->use_input_precision,
0/*do not strip16*/);
if (fail(pm)) return;
}
}
}
static void perform_gamma_sbit_tests(png_modifier *pm, int speed)
{
png_byte sbit;
/* The only interesting cases are colour and grayscale, alpha is ignored here
* for overall speed. Only bit depths 8 and 16 are tested.
*/
for (sbit=pm->sbitlow; sbit<16; ++sbit)
{
int i, j;
for (i=0; i<pm->ngammas; ++i) for (j=0; j<pm->ngammas; ++j)
if (i != j)
{
if (sbit < 8)
{
gamma_transform_test(pm, 0, 8, 1/pm->gammas[i], pm->gammas[j], sbit,
speed, pm->use_input_precision_sbit, 0/*strip16*/);
if (fail(pm)) return;
gamma_transform_test(pm, 2, 8, 1/pm->gammas[i], pm->gammas[j], sbit,
speed, pm->use_input_precision_sbit, 0/*strip16*/);
if (fail(pm)) return;
}
gamma_transform_test(pm, 0, 16, 1/pm->gammas[i], pm->gammas[j], sbit,
speed, pm->use_input_precision_sbit, 0/*strip16*/);
if (fail(pm)) return;
gamma_transform_test(pm, 2, 16, 1/pm->gammas[i], pm->gammas[j], sbit,
speed, pm->use_input_precision_sbit, 0/*strip16*/);
if (fail(pm)) return;
}
}
}
static void perform_gamma_strip16_tests(png_modifier *pm, int speed)
{
# ifndef PNG_MAX_GAMMA_8
# define PNG_MAX_GAMMA_8 11
# endif
/* Include the alpha cases here, not that sbit matches the internal value
* used by the library - otherwise we will get spurious errors from the
* internal sbit style approximation.
*
* The threshold test is here because otherwise the 16 to 8 convertion will
* proceed *without* gamma correction, and the tests above will fail (but not
* by much) - this could be fixed, it only appears with the -g option.
*/
int i, j;
for (i=0; i<pm->ngammas; ++i) for (j=0; j<pm->ngammas; ++j)
if (i != j && fabs(pm->gammas[j]/pm->gammas[i]-1) >= PNG_GAMMA_THRESHOLD)
{
gamma_transform_test(pm, 0, 16, 1/pm->gammas[i], pm->gammas[j],
PNG_MAX_GAMMA_8, speed, pm->use_input_precision_16to8, 1/*strip16*/);
if (fail(pm)) return;
gamma_transform_test(pm, 2, 16, 1/pm->gammas[i], pm->gammas[j],
PNG_MAX_GAMMA_8, speed, pm->use_input_precision_16to8, 1/*strip16*/);
if (fail(pm)) return;
gamma_transform_test(pm, 4, 16, 1/pm->gammas[i], pm->gammas[j],
PNG_MAX_GAMMA_8, speed, pm->use_input_precision_16to8, 1/*strip16*/);
if (fail(pm)) return;
gamma_transform_test(pm, 6, 16, 1/pm->gammas[i], pm->gammas[j],
PNG_MAX_GAMMA_8, speed, pm->use_input_precision_16to8, 1/*strip16*/);
if (fail(pm)) return;
}
}
static void
perform_gamma_test(png_modifier *pm, int speed, int summary)
{
/* First some arbitrary no-transform tests: */
if (!speed)
{
perform_gamma_threshold_tests(pm);
if (fail(pm)) return;
}
/* Now some real transforms. */
perform_gamma_transform_tests(pm, speed);
if (summary)
{
printf("Gamma correction error summary (output value error):\n");
printf(" 2 bit gray: %.5f\n", pm->error_gray_2);
printf(" 4 bit gray: %.5f\n", pm->error_gray_4);
printf(" 8 bit gray: %.5f\n", pm->error_gray_8);
printf(" 16 bit gray: %.5f\n", pm->error_gray_16);
printf(" 8 bit color: %.5f\n", pm->error_color_8);
printf(" 16 bit color: %.5f\n", pm->error_color_16);
}
/* The sbit tests produce much larger errors: */
pm->error_gray_2 = pm->error_gray_4 = pm->error_gray_8 = pm->error_gray_16 =
pm->error_color_8 = pm->error_color_16 = 0;
perform_gamma_sbit_tests(pm, speed);
if (summary)
{
printf("Gamma correction with sBIT:\n");
if (pm->sbitlow < 8)
{
printf(" 2 bit gray: %.5f\n", pm->error_gray_2);
printf(" 4 bit gray: %.5f\n", pm->error_gray_4);
printf(" 8 bit gray: %.5f\n", pm->error_gray_8);
}
printf(" 16 bit gray: %.5f\n", pm->error_gray_16);
if (pm->sbitlow < 8)
printf(" 8 bit color: %.5f\n", pm->error_color_8);
printf(" 16 bit color: %.5f\n", pm->error_color_16);
}
/* The 16 to 8 bit strip operations: */
pm->error_gray_2 = pm->error_gray_4 = pm->error_gray_8 = pm->error_gray_16 =
pm->error_color_8 = pm->error_color_16 = 0;
perform_gamma_strip16_tests(pm, speed);
if (summary)
{
printf("Gamma correction with 16 to 8 bit reduction:\n");
printf(" 16 bit gray: %.5f\n", pm->error_gray_16);
printf(" 16 bit color: %.5f\n", pm->error_color_16);
}
}
/* main program */
int main(int argc, const char **argv)
{
int summary = 1; /* Print the error sumamry at the end */
int speed = 0; /* Speed test only (for gamma stuff) */
/* This is an array of standard gamma values (believe it or not I've seen
* every one of these mentioned somewhere.)
*
* In the following list the most useful values are first!
*/
static double gammas[]={2.2, 1.0, 2.2/1.45, 1.8, 1.5, 2.4, 2.5, 2.62, 2.9};
png_modifier pm;
modifier_init(&pm);
/* Default to error on warning: */
pm.this.treat_warnings_as_errors = 1;
/* Store the test gammas */
pm.gammas = gammas;
pm.ngammas = 3; /* for speed */
pm.sbitlow = 8; /* because libpng doesn't do sbit below 8! */
pm.use_input_precision_16to8 = 1; /* Because of the way libpng does it */
/* Some default values (set the behavior for 'make check' here) */
pm.maxout8 = .1; /* Arithmetic error in *encoded* value */
pm.maxabs8 = .00005; /* 1/20000 */
pm.maxpc8 = .499; /* I.e. .499% fractional error */
pm.maxout16 = .499; /* Error in *encoded* value */
pm.maxabs16 = .00005;/* 1/20000 */
/* NOTE: this is a reasonable perceptual limit, we assume that humans can
* perceive light level differences of 1% over a 100:1 range, so we need to
* maintain 1 in 10000 accuracy (in linear light space), this is what the
* following guarantees. It also allows significantly higher errors at
* higher 16 bit values, which is important for performance. The actual
* maximum 16 bit error is about +/-1.9 in the fixed point implementation but
* this is only allowed for values >38149 by the following:
*/
pm.maxpc16 = .005; /* I.e. 1/200% - 1/20000 */
/* Now parse the command line options. */
while (--argc >= 1)
if (strcmp(*++argv, "-v") == 0)
pm.this.verbose = 1;
else if (strcmp(*argv, "-l") == 0)
pm.log = 1;
else if (strcmp(*argv, "-q") == 0)
pm.this.verbose = pm.log = summary = 0;
else if (strcmp(*argv, "-g") == 0)
pm.ngammas = (sizeof gammas)/(sizeof gammas[0]);
else if (strcmp(*argv, "-w") == 0)
pm.this.treat_warnings_as_errors = 0;
else if (strcmp(*argv, "-speed") == 0)
speed = 1, pm.ngammas = (sizeof gammas)/(sizeof gammas[0]);
else if (argc >= 1 && strcmp(*argv, "-sbitlow") == 0)
--argc, pm.sbitlow = atol(*++argv);
else if (argc >= 1 && strncmp(*argv, "-max", 4) == 0)
{
--argc;
if (strcmp(4+*argv, "abs8") == 0)
pm.maxabs8 = atof(*++argv);
else if (strcmp(4+*argv, "abs16") == 0)
pm.maxabs16 = atof(*++argv);
else if (strcmp(4+*argv, "out8") == 0)
pm.maxout8 = atof(*++argv);
else if (strcmp(4+*argv, "out16") == 0)
pm.maxout16 = atof(*++argv);
else if (strcmp(4+*argv, "pc8") == 0)
pm.maxpc8 = atof(*++argv);
else if (strcmp(4+*argv, "pc16") == 0)
pm.maxpc16 = atof(*++argv);
else
{
fprintf(stderr, "pngvalid: %s: unknown 'max' option\n", *argv);
exit(1);
}
}
else
{
fprintf(stderr, "pngvalid: %s: unknown argument\n", *argv);
exit(1);
}
/* Make useful base images */
make_standard_images(&pm.this);
make_gamma_images(&pm.this);
/* Perform the standard and gamma tests. */
if (!speed)
perform_standard_test(&pm);
perform_gamma_test(&pm, speed, summary && !speed);
if (summary && !speed)
printf("Results using %s point arithmetic %s\n",
#if defined(PNG_FLOATING_ARITHMETIC_SUPPORTED) || PNG_LIBPNG_VER < 10500
"floating",
#else
"fixed",
#endif
(pm.this.nerrors || pm.this.treat_warnings_as_errors &&
pm.this.nwarnings) ? "(errors)" : (pm.this.nwarnings ?
"(warnings)" : "(no errors or warnings)")
);
/* Error exit if there are any errors, and maybe if there are any
* warnings.
*/
if (pm.this.nerrors || pm.this.treat_warnings_as_errors && pm.this.nwarnings)
{
if (!pm.this.verbose)
fprintf(stderr, "pngvalid: %s\n", pm.this.error);
fprintf(stderr, "pngvalid: %d errors, %d warnings\n", pm.this.nerrors,
pm.this.nwarnings);
exit(1);
}
return 0;
}
/* vim: set sw=3 ts=8 tw=80: */
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