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c08cae1c22
libpng/pngvalid.c
Glenn Randers-Pehrson c08cae1c22 [devel] Revised pngvalid.c to use cexcept.h for error handling.
2010-08-20 09:55:01 -05:00

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/* pngvalid.c - validate libpng by constructing then reading png files.
*
* Last changed in libpng 1.5.0 [August 11, 2010]
* Copyright (c) 2010 Glenn Randers-Pehrson
* Written by John C. Bowler
*
* 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 <math.h> /* For floor */
/* Unused formal parameter errors are removed using the following macro which is
* expected to have no bad effects on performance.
*/
#ifndef UNUSED
# define UNUSED(param) param = param;
#endif
/***************************** EXCEPTION HANDLING *****************************/
#include "contrib/visupng/cexcept.h"
define_exception_type(struct png_store*);
/* The following is a macro to reduce typing everywhere where the well known
* name 'the_exception_context' must be defined.
*/
#define context(ps,fault) struct exception_context *the_exception_context = \
&(ps)->exception_context; png_store *fault
/******************************* ERROR UTILITIES ******************************/
static size_t safecat(char *buffer, size_t bufsize, size_t pos,
PNG_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 PNG_CONST char invalid[] = "invalid";
static PNG_CONST char sep[] = ": ";
/* NOTE: this is indexed by ln2(bit_depth)! */
static PNG_CONST char *bit_depths[8] =
{
"1", "2", "4", "8", "16", invalid, invalid, invalid
};
static PNG_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;
}
*bit_depth = (png_byte)(*bit_depth << 1);
/* Palette images are restricted to 8 bit depth */
if (*bit_depth <= 8 || (*colour_type != 3 && *bit_depth <= 16))
return 1;
/* Move to the next color type, or return 0 at the end. */
switch (*colour_type)
{
case 0:
*colour_type = 2;
*bit_depth = 8;
return 1;
case 2:
*colour_type = 3;
*bit_depth = 1;
return 1;
case 3:
*colour_type = 4;
*bit_depth = 8;
return 1;
case 4:
*colour_type = 6;
*bit_depth = 8;
return 1;
default:
return 0;
}
}
static unsigned int
sample(png_byte *row, png_byte colour_type, png_byte bit_depth, png_uint_32 x,
unsigned int 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_store 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 STORE_BUFFER_SIZE 500 /* arbitrary */
typedef struct png_store_buffer
{
struct png_store_buffer* prev; /* NOTE: stored in reverse order */
png_byte buffer[STORE_BUFFER_SIZE];
} png_store_buffer;
typedef struct png_store_file
{
struct png_store_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_store_buffer data; /* Last buffer in file */
} png_store_file;
typedef struct png_store
{
/* For cexcept.h exception handling - simply store one of these;
* the context is a self pointer but it may point to a different
* png_store (in fact it never does in this program.)
*/
struct exception_context
exception_context;
unsigned int verbose :1;
unsigned int treat_warnings_as_errors :1;
unsigned int expect_error :1;
unsigned int expect_warning :1;
unsigned int saw_warning :1;
int nerrors;
int nwarnings;
char test[64]; /* Name of test */
char error[128];
/* Read fields */
png_structp pread; /* Used to read a saved file */
png_infop piread;
png_store_file* current; /* Set when reading */
png_store_buffer* next; /* Set when reading */
png_size_t readpos; /* Position in *next */
/* Write fields */
png_store_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_store_buffer new; /* The end of the new PNG file being written. */
} png_store;
/* Initialization and cleanup */
static void
store_init(png_store* ps)
{
memset(ps, 0, sizeof *ps);
ps->verbose = 0;
ps->treat_warnings_as_errors = 0;
ps->expect_error = 0;
ps->expect_warning = 0;
ps->saw_warning = 0;
ps->nerrors = ps->nwarnings = 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
store_freebuffer(png_store_buffer* psb)
{
if (psb->prev)
{
store_freebuffer(psb->prev);
free(psb->prev);
psb->prev = NULL;
}
}
static void
store_freenew(png_store *ps)
{
store_freebuffer(&ps->new);
ps->writepos = 0;
}
static void
store_storenew(png_store *ps)
{
png_store_buffer *pb;
if (ps->writepos != STORE_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;
}
/* Currently unused: */
#if 0
static void
store_freefile(png_store_file *pf)
{
if (pf->next)
store_freefile(pf->next);
pf->next = NULL;
store_freebuffer(&pf->data);
pf->datacount = 0;
free(pf);
}
#endif
/* Main interface to file storeage, after writing a new PNG file (see the API
* below) call store_storefile to store the result with the given name and id.
*/
static void
store_storefile(png_store *ps, png_uint_32 id)
{
png_store_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
store_message(png_structp pp, char *buffer, size_t bufsize, PNG_CONST char *msg)
{
size_t pos = 0;
png_store *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);
pos = safecat(buffer, bufsize, pos, sep);
}
else
{
/* Neither reading nor writing */
pos = safecat(buffer, bufsize, pos, "pngvalid: ");
}
pos = safecat(buffer, bufsize, pos, ps->test);
pos = safecat(buffer, bufsize, pos, sep);
pos = safecat(buffer, bufsize, pos, msg);
return pos;
}
/* Functions to use as PNG callbacks. */
static void
store_error(png_structp pp, png_const_charp message) /* PNG_NORETURN */
{
png_store *ps = png_get_error_ptr(pp);
if (!ps->expect_error)
{
char buffer[256];
store_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);
}
/* And finally throw an exception. */
{
struct exception_context *the_exception_context = &ps->exception_context;
Throw ps;
}
}
static void
store_warning(png_structp pp, png_const_charp message)
{
png_store *ps = png_get_error_ptr(pp);
if (!ps->expect_warning)
{
char buffer[256];
store_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);
}
else
ps->saw_warning = 1;
}
static void
store_write(png_structp pp, png_bytep pb, png_size_t st)
{
png_store *ps = png_get_io_ptr(pp);
if (ps->pwrite != pp)
png_error(pp, "store state damaged");
while (st > 0)
{
size_t cb;
if (ps->writepos >= STORE_BUFFER_SIZE)
store_storenew(ps);
cb = st;
if (cb > STORE_BUFFER_SIZE - ps->writepos)
cb = STORE_BUFFER_SIZE - ps->writepos;
memcpy(ps->new.buffer + ps->writepos, pb, cb);
pb += cb;
st -= cb;
ps->writepos += cb;
}
}
static void
store_flush(png_structp pp)
{
pp = pp;
/*DOES NOTHING*/
}
static size_t
store_read_buffer_size(png_store *ps)
{
/* Return the bytes available for read in the current buffer. */
if (ps->next != &ps->current->data)
return STORE_BUFFER_SIZE;
return ps->current->datacount;
}
static int
store_read_buffer_next(png_store *ps)
{
png_store_buffer *pbOld = ps->next;
png_store_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
store_read(png_structp pp, png_bytep pb, png_size_t st)
{
png_store *ps = png_get_io_ptr(pp);
if (ps->pread != pp || ps->current == NULL || ps->next == NULL)
png_error(pp, "store state damaged");
while (st > 0)
{
size_t cbAvail = store_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 (!store_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
store_write_reset(png_store *ps)
{
if (ps->pwrite != NULL)
{
png_destroy_write_struct(&ps->pwrite, &ps->piwrite);
ps->pwrite = NULL;
ps->piwrite = NULL;
}
store_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
* store_storefile above to record this file after it has been written. The
* returned libpng structures as destroyed by store_write_reset above.
*/
static png_structp
set_store_for_write(png_store *ps, png_infopp ppi,
PNG_CONST char * volatile name)
{
context(ps,fault);
png_structp result = NULL;
Try
{
if (ps->pwrite != NULL)
png_error(ps->pwrite, "store already in use");
store_write_reset(ps);
safecat(ps->wname, sizeof ps->wname, 0, name);
ps->pwrite = png_create_write_struct(PNG_LIBPNG_VER_STRING, ps,
store_error, store_warning);
png_set_write_fn(ps->pwrite, ps, store_write, store_flush);
if (ppi != NULL)
*ppi = ps->piwrite = png_create_info_struct(ps->pwrite);
result = ps->pwrite;
}
Catch(fault)
{
if (fault != ps) Throw fault;
}
return result;
}
/* Cleanup when finished reading (either due to error or in the success case. )
*/
static void
store_read_reset(png_store *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
store_read_set(png_store *ps, png_uint_32 id)
{
png_store_file *pf = ps->saved;
while (pf != NULL)
{
if (pf->id == id)
{
ps->current = pf;
ps->next = NULL;
store_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 store_read_reset above.
*/
static png_structp
set_store_for_read(png_store *ps, png_infopp ppi, png_uint_32 id,
PNG_CONST char *name)
{
context(ps, fault);
png_structp result = NULL;
/* NOTE: reference to 'name' must be outside the Try block or GCC can
* optimized it away.
*/
safecat(ps->test, sizeof ps->test, 0, name);
Try
{
if (ps->pread != NULL)
png_error(ps->pread, "store already in use");
store_read_reset(ps);
ps->pread = png_create_read_struct(PNG_LIBPNG_VER_STRING, ps, store_error,
store_warning);
store_read_set(ps, id);
png_set_read_fn(ps->pread, ps, store_read);
if (ppi != NULL)
*ppi = ps->piread = png_create_info_struct(ps->pread);
result = ps->pread;
}
Catch(fault)
{
if (ps != fault) Throw fault;
}
return result;
}
/*********************** PNG FILE MODIFICATION ON READ ************************/
/* Files may be modified on read. The following structure contains a complete
* png_store 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_store. There is a special read function, set_modifier_for_read, which
* replaces set_store_for_read.
*/
typedef struct png_modifier
{
png_store this; /* I am a png_store */
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 int ngammas;
/* Lowest sbit to test (libpng fails for sbit < 8) */
png_byte sbitlow;
/* Error control - these are the limits on errors accepted by the gamma tests
* below.
*/
double maxout8; /* Maximum output value error */
double maxabs8; /* Absolute 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: */
unsigned int use_input_precision :1;
unsigned int use_input_precision_sbit :1;
unsigned int use_input_precision_16to8 :1;
unsigned 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);
store_init(&pm->this);
pm->modifications = NULL;
pm->state = modifier_start;
pm->sbitlow = 1U;
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;
unsigned int modified :1; /* Chunk was modified */
unsigned int added :1; /* Chunk was added */
unsigned 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)
{
store_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:
store_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:
store_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;
case modifier_IHDR:
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;
store_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
store_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)
{
store_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 store, 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,
PNG_CONST char *name)
{
volatile png_structp ppSafe = set_store_for_read(&pm->this, ppi, id, name);
if (ppSafe != NULL)
{
context(&pm->this, fault);
Try
{
png_set_read_fn(ppSafe, 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;
}
Catch(fault)
{
store_read_reset(&pm->this);
if (fault != &pm->this) Throw fault;
ppSafe = NULL;
}
}
return ppSafe;
}
/***************************** 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)& 0x7U)
#define DEPTH_FROM_ID(id) (((id) >> 3) & 0x1fU)
#define STD_WIDTH 128U
#define STD_ROWMAX (STD_WIDTH*8U)
static unsigned int
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;
}
/* standard_wdith(pp, colour_type, bit_depth) current returns the same number
* every time, so just use a macro:
*/
#define standard_width(pp, colour_type, bit_depth) 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. */
default:
return 0; /* Error, will be caught later */
}
}
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;
default:
break;
}
png_error(pp, "internal error");
}
/* This is just to do the right cast - could be changed to a function to check
* 'bd' but there isn't much point.
*/
#define DEPTH(bd) ((png_byte)(1U << (bd)))
static void
make_standard(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
int PNG_CONST bdloIn, int PNG_CONST bdhi)
{
volatile int bdlo = bdloIn;
for (; bdlo <= bdhi; ++bdlo)
{
context(ps, fault);
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_store_for_write(ps, &pi, name);
}
if (pp == NULL)
return;
/* Do the honourable write stuff, protected by a local catch */
Try
{
png_byte bit_depth = DEPTH(bdlo);
png_uint_32 h = standard_height(pp, colour_type, bit_depth), y;
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 */
{
unsigned int i = 0;
png_color pal[256];
do
pal[i].red = pal[i].green = pal[i].blue = (png_byte)i;
while(++i < 256U);
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. */
store_storefile(ps, FILEID(colour_type, bit_depth));
store_write_reset(ps);
}
Catch(fault)
{
store_write_reset(ps);
if (ps != fault) Throw fault;
}
}
}
static void
make_standard_images(png_store *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 */
/* Like 'make_standard' but errors are deliberately introduced into the calls
* to ensure that they get detected - it should not be possible to write an
* invalid image with libpng!
*/
static void
sBIT0_error_fn(png_structp pp, png_infop pi)
{
/* 0 is invalid... */
png_color_8 bad;
bad.red = bad.green = bad.blue = bad.gray = bad.alpha = 0;
png_set_sBIT(pp, pi, &bad);
}
static void
sBIT_error_fn(png_structp pp, png_infop pi)
{
png_byte bit_depth;
png_color_8 bad;
if (png_get_color_type(pp, pi) == PNG_COLOR_TYPE_PALETTE)
bit_depth = 8;
else
bit_depth = png_get_bit_depth(pp, pi);
/* Now we know the bit depth we can easily generate an invalid sBIT entry */
bad.red = bad.green = bad.blue = bad.gray = bad.alpha =
(png_byte)(bit_depth+1);
png_set_sBIT(pp, pi, &bad);
}
static struct
{
void (*fn)(png_structp, png_infop);
PNG_CONST char *msg;
unsigned int warning :1; /* the error is a warning... */
} error_test[] =
{
{ sBIT0_error_fn, "sBIT(0): failed to detect error", 1 },
{ sBIT_error_fn, "sBIT(too big): failed to detect error", 1 },
};
static void
make_error(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
int PNG_CONST bdloIn, int PNG_CONST bdhi)
{
volatile int bdlo = bdloIn;
volatile unsigned int test;
for (; bdlo <= bdhi; ++bdlo)
for (test=0; test<(sizeof error_test)/(sizeof error_test[0]); ++test)
{
context(ps, fault);
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_store_for_write(ps, &pi, name);
}
if (pp == NULL)
return;
Try
{
png_byte bit_depth = DEPTH(bdlo);
volatile png_uint_32
h = standard_height(pp, colour_type, bit_depth),
y;
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 */
{
unsigned int i = 0;
png_color pal[256];
do
pal[i].red = pal[i].green = pal[i].blue = (png_byte)i;
while(++i < 256U);
png_set_PLTE(pp, pi, pal, 256);
}
/* Time for a few errors, these are in various optional chunks,
* the standard tests test the standard chunks pretty well.
*/
Try
{
/* Expect this to throw: */
ps->expect_error = !error_test[test].warning;
ps->expect_warning = error_test[test].warning;
ps->saw_warning = 0;
error_test[test].fn(pp, pi);
/* Normally the error is only detected here: */
png_write_info(pp, pi);
/* And handle the case where it was only a warning: */
if (ps->expect_warning && ps->saw_warning)
Throw ps;
/* If we get here there is a problem, we have success, however the
* Throw within the png_error will take control back to the Catch
* below, and the loop will continue.
*/
ps->expect_error = 0;
ps->expect_warning = 0;
png_error(pp, error_test[test].msg);
}
Catch (fault)
{
ps->expect_error = 0;
ps->expect_warning = 0;
if (ps != fault) Throw fault;
}
ps->expect_error = 0; /* safety */
ps->expect_warning = 0;
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);
store_write_reset(ps);
}
Catch(fault)
{
/* This is not expected because we catch the errors (maybe)
* above.
*/
ps->expect_error = 0;
store_write_reset(ps);
if (ps != fault)
Throw fault;
}
}
}
static void
perform_error_test(png_modifier *pm)
{
/* Need to do this here because we just write in this test. */
safecat(pm->this.test, sizeof pm->this.test, 0, "error test");
make_error(&pm->this, 0, 0, 4);
if (fail(pm))
return;
make_error(&pm->this, 2, 3, 4);
if (fail(pm))
return;
make_error(&pm->this, 3, 0, 3);
if (fail(pm))
return;
make_error(&pm->this, 4, 3, 4);
if (fail(pm))
return;
make_error(&pm->this, 6, 3, 4);
}
static void
test_standard(png_store* PNG_CONST ps, png_byte PNG_CONST colour_type,
int PNG_CONST bdloIn, int PNG_CONST bdhi)
{
volatile int bdlo = bdloIn;
for (; bdlo <= bdhi; ++bdlo)
{
context(ps, fault);
PNG_CONST png_byte bit_depth = DEPTH(bdlo);
png_structp pp;
png_infop pi;
/* Get a png_struct for writing the image. */
pp = set_store_for_read(ps, &pi, FILEID(colour_type, bit_depth),
"standard");
if (pp == NULL)
return;
/* Do the honourable write stuff, protected by a local catch */
Try
{
png_uint_32 h = standard_height(pp, colour_type, bit_depth), y;
size_t cb;
/* 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);
store_read_reset(ps);
}
Catch(fault)
{
store_read_reset(ps);
if (ps != fault) Throw fault;
}
}
}
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. */
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)
{
UNUSED(pp);
UNUSED(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)
{
double g;
modification_init(&me->this);
me->this.chunk = CHUNK_gAMA;
me->this.modify_fn = gamma_modify;
me->this.add = CHUNK_PLTE;
g = floor(gamma * 100000 + .5);
me->gamma = (png_fixed_point)g;
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)
{
UNUSED(pp);
UNUSED(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, PNG_CONST png_byte colour_type,
PNG_CONST png_byte bit_depth, PNG_CONST double file_gamma,
PNG_CONST double screen_gamma, PNG_CONST png_byte sbit,
PNG_CONST int threshold_test, PNG_CONST char *name, PNG_CONST int speed,
PNG_CONST int use_input_precision, PNG_CONST int strip16)
{
context(&pm->this, fault);
Try
{
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, if this fails just given up by
* doing a Throw to get to the Catch below.
*/
pp = set_modifier_for_read(pm, &pi, FILEID(colour_type, bit_depth), name);
if (pp == NULL) Throw &pm->this;
/* 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);
{
PNG_CONST png_byte out_ct = png_get_color_type(pp, pi);
PNG_CONST png_byte out_bd = png_get_bit_depth(pp, pi);
PNG_CONST unsigned int outmax = (1U<<out_bd)-1;
PNG_CONST png_uint_32 w = png_get_image_width(pp, pi);
PNG_CONST png_uint_32 h = png_get_image_height(pp, pi);
PNG_CONST size_t cb = png_get_rowbytes(pp, pi); /* For memcmp below. */
PNG_CONST double maxabs = abserr(pm, out_bd);
PNG_CONST double maxout = outerr(pm, out_bd);
PNG_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.
*/
PNG_CONST int processing = (fabs(screen_gamma*file_gamma-1) >=
PNG_GAMMA_THRESHOLD && !threshold_test && !speed && colour_type !=
3) || bit_depth != out_bd;
PNG_CONST unsigned int samples_per_pixel = (out_ct & 2U) ? 3U : 1U;
PNG_CONST double gamma = 1/(file_gamma*screen_gamma); /* Overall */
for (y=0; y<h; ++y) /* just one pass - no interlacing */
{
unsigned int 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: */
PNG_CONST unsigned int
id = sample(std, colour_type, bit_depth, x, s);
PNG_CONST unsigned int
od = sample(display, out_ct, out_bd, x, s);
PNG_CONST unsigned int
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 (nevertheless 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)
{
/* There 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 1:
break;
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;
default:
png_error(pp, "bad bit depth (internal: 1)");
}
}
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;
default:
png_error(pp, "bad bit depth (internal: 2)");
}
}
}
Catch(fault)
{
modifier_reset(pm);
if (fault != &pm->this)
Throw fault;
}
}
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,
PNG_CONST png_byte colour_type, PNG_CONST png_byte bit_depth,
PNG_CONST double file_gamma, PNG_CONST double screen_gamma,
PNG_CONST png_byte sbit, PNG_CONST int speed,
PNG_CONST int use_input_precision, PNG_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)
{
unsigned 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)
{
unsigned 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 conversion 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.
*/
unsigned 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 < 8U)
{
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 < 8U)
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, PNG_CONST char **argv)
{
volatile int summary = 1; /* Print the error sumamry at the end */
volatile int speed = 0; /* Speed test only (for gamma stuff) */
/* Create the given output file on success: */
PNG_CONST char *volatile touch = NULL;
/* 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;
context(&pm.this, fault);
modifier_init(&pm);
/* Default to error on warning: */
pm.this.treat_warnings_as_errors = 1;
/* Store the test gammas */
pm.gammas = gammas;
pm.ngammas = 3U; /* for speed */
pm.sbitlow = 8U; /* because libpng doesn't do sBIT below 8! */
pm.use_input_precision_16to8 = 1U; /* 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)
summary = pm.this.verbose = pm.log = 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 = (png_byte)atoi(*++argv);
else if (argc >= 1 && strcmp(*argv, "--touch") == 0)
--argc, touch = *++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);
}
}
Try
{
/* Make useful base images */
make_standard_images(&pm.this);
/* Perform the standard and gamma tests. */
if (!speed)
{
perform_standard_test(&pm);
perform_error_test(&pm);
}
perform_gamma_test(&pm, speed != 0, summary && !speed);
}
Catch(fault)
{
fprintf(stderr, "pngvalid: test aborted\n");
exit(1);
}
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);
}
/* Success case. */
if (touch != NULL)
{
FILE *fsuccess = fopen(touch, "wt");
if (fsuccess != NULL)
{
int error = 0;
fprintf(fsuccess, "PNG validation succeeded\n");
fflush(fsuccess);
error = ferror(fsuccess);
if (fclose(fsuccess) || error)
{
fprintf(stderr, "%s: write failed\n", touch);
exit(1);
}
}
}
return 0;
}
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