blob: 96a5a1b4b4714bac813c99144ae3bc783cc7b132 [file] [log] [blame]
/* pngread.c - read a PNG file
*
* Last changed in libpng 1.7.0 [(PENDING RELEASE)]
* Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* This file contains routines that an application calls directly to
* read a PNG file or stream.
*/
#include "pngpriv.h"
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
# include <errno.h>
#endif
#define PNG_SRC_FILE PNG_SRC_FILE_pngread
#ifdef PNG_READ_SUPPORTED
/* Create a PNG structure for reading, and allocate any memory needed. */
PNG_FUNCTION(png_structp,PNGAPI
png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
{
#ifndef PNG_USER_MEM_SUPPORTED
png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
error_fn, warn_fn, NULL, NULL, NULL);
#else
return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
warn_fn, NULL, NULL, NULL);
}
/* Alternate create PNG structure for reading, and allocate any memory
* needed.
*/
PNG_FUNCTION(png_structp,PNGAPI
png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
{
png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
#endif /* USER_MEM */
if (png_ptr != NULL)
{
png_ptr->read_struct = 1;
png_ptr->critical_crc = crc_error_quit;
png_ptr->ancillary_crc = crc_warn_discard;
# ifdef PNG_BENIGN_ERRORS_SUPPORTED
# if !PNG_RELEASE_BUILD
/* Always quit on error prior to release */
png_ptr->benign_error_action = PNG_ERROR;
png_ptr->app_warning_action = PNG_WARN;
png_ptr->app_error_action = PNG_ERROR;
# else /* RELEASE_BUILD */
/* Allow benign errors on read, subject to app control. */
png_ptr->benign_error_action = PNG_WARN;
# ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
png_ptr->app_error_action = PNG_WARN;
png_ptr->app_warning_action = PNG_WARN;
# else /* !BENIGN_READ_ERRORS */
/* libpng build without benign error support; the application
* author has to be assumed to be correct, so:
*/
png_ptr->app_warning_action = PNG_WARN;
png_ptr->app_error_action = PNG_ERROR;
# endif /* !BENIGN_READ_ERRORS */
# endif /* RELEASE_BUILD */
/* This is always png_error unless explicitly changed: */
png_ptr->IDAT_error_action = PNG_ERROR;
# endif /* BENIGN_ERRORS */
# ifdef PNG_SEQUENTIAL_READ_SUPPORTED
png_ptr->IDAT_size = PNG_IDAT_READ_SIZE;
# endif /* SEQUENTIAL_READ */
# ifdef PNG_READ_GAMMA_SUPPORTED
/* Default gamma correction values: */
# if 0 /*NYI*/
png_ptr->gamma_accuracy = PNG_DEFAULT_GAMMA_ACCURACY;
# endif /*NYI*/
png_ptr->gamma_threshold = PNG_GAMMA_THRESHOLD_FIXED;
# endif /* READ_GAMMA */
}
return png_ptr;
}
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read the chunk header (length + type name).
* Put the type name into png_ptr->chunk_name, and return the length.
*/
static void
png_read_chunk_header(png_structrp png_ptr)
{
png_byte buf[8];
#ifdef PNG_IO_STATE_SUPPORTED
png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
#endif
/* Read the length and the chunk name.
* This must be performed in a single I/O call.
*/
png_read_data(png_ptr, buf, 8);
/* Put the chunk name into png_ptr->chunk_name. */
png_ptr->chunk_length = png_get_uint_31(png_ptr, buf);
png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
png_debug2(0, "Reading %lx chunk, length = %lu",
(unsigned long)png_ptr->chunk_name,
(unsigned long)png_ptr->chunk_length);
/* Reset the crc and run it over the chunk name. */
png_reset_crc(png_ptr, buf + 4);
#ifdef PNG_IO_STATE_SUPPORTED
png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
#endif
}
static void
png_read_sequential_unknown(png_structrp png_ptr, png_inforp info_ptr)
{
#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
/* Read the data for an unknown chunk. The read buffer is used: */
png_bytep buffer = png_read_buffer(png_ptr, png_ptr->chunk_length,
PNG_CHUNK_ANCILLARY(png_ptr->chunk_name)); /* error if critical */
if (buffer != NULL)
{
if (png_ptr->chunk_length > 0U)
png_crc_read(png_ptr, buffer, png_ptr->chunk_length);
png_crc_finish(png_ptr, 0);
png_handle_unknown(png_ptr, info_ptr, buffer);
}
else /* out of memory on an ancillary chunk; skip the chunk */
#else /* !READ_UNKNOWN_CHUNKS */
/* or, no support for reading unknown chunks, so just skip it. */
PNG_UNUSED(info_ptr)
#endif /* !READ_UNKNOWN_CHUNKS */
png_crc_finish(png_ptr, png_ptr->chunk_length);
}
/* Read the information before the actual image data. This has been
* changed in v0.90 to allow reading a file that already has the magic
* bytes read from the stream. You can tell libpng how many bytes have
* been read from the beginning of the stream (up to the maximum of 8)
* via png_set_sig_bytes(), and we will only check the remaining bytes
* here. The application can then have access to the signature bytes we
* read if it is determined that this isn't a valid PNG file.
*/
void PNGAPI
png_read_info(png_structrp png_ptr, png_inforp info_ptr)
{
png_debug(1, "in png_read_info");
if (png_ptr == NULL || info_ptr == NULL)
return;
/* Read and check the PNG file signature (this may do nothing if it has
* already been read.)
*/
png_read_sig(png_ptr, info_ptr);
/* Loop reading chunks until an IDAT is encountered or we reach the end of
* the stream (IEND).
*
* Prior to 1.7.0 this function behaved very weirdly if called after the
* IDATs had been read; it would keep on reading chunks util it found
* another IDAT. This could cause it to read beyond IEND, damaging the
* state in the host stream. This is now caught by the check below.
*/
while ((png_ptr->mode & (PNG_HAVE_IEND|PNG_HAVE_IDAT)) == 0)
{
png_read_chunk_header(png_ptr);
switch (png_find_chunk_op(png_ptr))
{
default:
impossible("invalid chunk op");
/* FALL THROUGH */
case png_chunk_skip:
png_crc_finish(png_ptr, png_ptr->chunk_length);
break;
case png_chunk_unknown:
png_read_sequential_unknown(png_ptr, info_ptr);
break;
case png_chunk_process_all:
png_handle_chunk(png_ptr, info_ptr);
break;
case png_chunk_process_part:
debug(png_ptr->mode & PNG_HAVE_IDAT);
return;
}
}
/* The loop was ended by IDAT or IEND, but if an IEND was seen the read code
* (png_handle_position in pngrutil.c) should have errored out, therefore:
*/
#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
affirm(png_ptr->chunk_name == png_IDAT && ((png_ptr->known_unknown)&1U));
#else
debug(png_ptr->chunk_name == png_IDAT);
impossible("unknown IDAT");
#endif
/* And the code cannot have left it unread; it must have called one of the
* handlers, so we are skipping IDAT.
*/
}
/* Initialize palette, background, etc, after transformations
* are set, but before any reading takes place. This allows
* the user to obtain a gamma-corrected palette, for example.
* If the user doesn't call this, we will do it ourselves.
*/
void PNGAPI
png_start_read_image(png_structrp png_ptr)
{
png_debug(1, "in png_start_read_image");
if (png_ptr != NULL)
{
if (png_ptr->zowner != png_IDAT)
png_read_start_IDAT(png_ptr);
/* New in 1.6.0 this avoids the bug of doing the initializations twice,
* it could be a warning but in practice it indicates that the app may
* have made png_get_ calls on png_ptr assuming that it hadn't been
* 'started'.
*/
else
png_app_error(png_ptr,
"png_start_read_image/png_read_update_info: duplicate call");
}
}
static void
png_read_IDAT(png_structrp png_ptr)
{
/* Read more input data, up to png_struct::IDAT_size, stop at the end of the
* IDAT stream. pngset.c checks png_struct::IDAT_size to ensure that it will
* fit in a uInt.
*/
const uInt buffer_size = (uInt)/*SAFE*/png_ptr->IDAT_size;
uInt IDAT_size = 0;
png_bytep buffer =
png_read_buffer(png_ptr, buffer_size, 0/*error*/);
png_ptr->zstream.next_in = buffer;
while (png_ptr->chunk_name == png_IDAT && IDAT_size < buffer_size)
{
png_uint_32 l = png_ptr->chunk_length;
while (l == 0) /* end of this IDAT */
{
png_crc_finish(png_ptr, 0);
png_read_chunk_header(png_ptr);
if (png_ptr->chunk_name != png_IDAT) /* end of all IDAT */
{
png_ptr->mode |= PNG_AFTER_IDAT;
goto done;
}
l = png_ptr->chunk_length;
}
/* Read from the IDAT chunk into the buffer, up to png_struct::IDAT_size:
*/
if (l > buffer_size - IDAT_size) /* SAFE: while check */
l = buffer_size - IDAT_size;
png_crc_read(png_ptr, buffer+IDAT_size, l);
IDAT_size += (uInt)/*SAFE*/l;
png_ptr->chunk_length -= l;
}
done:
/* IDAT_size may be zero if the compressed image stream is truncated;
* this is likely given a broken PNG.
*/
png_ptr->zstream.next_in = buffer;
png_ptr->zstream.avail_in = IDAT_size;
}
void PNGAPI
png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
/* It is valid to call this API with both 'row' and 'dsp_row' NULL, all
* the processing gets done. This is only useful for, either, performance
* testing (but it skips png_combine_row) or if there is a user transform
* or user row callback which actually uses the row data.
*/
{
if (png_ptr == NULL)
return;
png_debug2(1, "in png_read_row (row %lu, pass %d)",
(unsigned long)png_ptr->row_number, png_ptr->pass);
/* Check the row number; if png_read_process_IDAT is called too many times
* if issues an affirm, but, while this is appropriate for the progressive
* reader, it is an app error if it happens here.
*
* Note that when the app does the interlace handling the last row will
* typically be before the last row in the image.
*/
if (png_ptr->read_started &&
(png_ptr->interlaced == PNG_INTERLACE_NONE ?
png_ptr->row_number == png_ptr->height-1U : (
# ifdef PNG_READ_INTERLACING_SUPPORTED
png_ptr->do_interlace ?
png_ptr->pass == 6U && png_ptr->row_number == png_ptr->height-1U :
# endif /* READ_INTERLACING */
png_ptr->pass == PNG_LAST_PASS(png_ptr->width, png_ptr->height) &&
PNG_LAST_PASS_ROW(png_ptr->row_number, png_ptr->pass,
png_ptr->height)
)
))
{
png_app_error(png_ptr, "Too many calls to png_read_row");
return;
}
/* Check this right at the start; functions like png_read_process_IDAT
* regard this condition as an internal error:
*/
if (png_ptr->zowner != png_IDAT)
png_read_start_IDAT(png_ptr);
/* So reading has started: */
png_ptr->read_started = 1;
for (;;)
{
if (png_ptr->zstream.avail_in == 0)
png_read_IDAT(png_ptr);
/* So... zstream.next_in may still be 0, but this may be enough for the
* next row if zlib is storing enough output state (it only need be enough
* for one byte, because png_read_process_IDAT keeps the next filter byte,
* so on the last row of the image only one byte might be required.)
*
* png_read_process_IDAT handles the case where the input has ended; mode
* has PNG_AFTER_IDAT set, by either doing png_error or using 0 bytes for
* the data (after issuing a warning.)
*/
switch (png_read_process_IDAT(png_ptr, row, dsp_row, 0/*no save*/))
{
case png_row_incomplete:
/* more IDAT data needed for row */
debug(png_ptr->zstream.avail_in == 0);
continue;
case png_row_repeat:
/* row not in this pass, but the existing row in row_buffer or (if
* transforms are happening) png_struct::transformed_row is
* available from a previous row.
*/
/* FALL THROUGH */
case png_row_skip:
/* row not in pass and no appropriate data; skip this row, nothing
* more need be done, except the read_row_fn and then only if libpng
* is doing the interlace handling (this is the historical
* behavior!)
*/
# ifdef PNG_READ_INTERLACING_SUPPORTED
if (!png_ptr->do_interlace) continue;
# else /* !do_interlace */
continue;
# endif /* !do_interlace */
/* FALL THROUGH */
case png_row_process:
/* png_read_process_IDAT has done everything we need, the only extra
* required is to call the application row callback.
*/
if (png_ptr->read_row_fn != NULL)
png_ptr->read_row_fn(png_ptr, png_ptr->row_number,
png_ptr->pass);
/* And return now because the next row has been processed; so there
* is exactly one read_row_fn callback for each call to
* png_read_process_IDAT.
*/
return;
default:
impossible("not reached");
}
}
}
/* Read one or more rows of image data. If the image is interlaced,
* and png_set_interlace_handling() has been called, the rows need to
* contain the contents of the rows from the previous pass. If the
* image has alpha or transparency, and png_handle_alpha()[*] has been
* called, the rows contents must be initialized to the contents of the
* screen.
*
* "row" holds the actual image, and pixels are placed in it
* as they arrive. If the image is displayed after each pass, it will
* appear to "sparkle" in. "display_row" can be used to display a
* "chunky" progressive image, with finer detail added as it becomes
* available. If you do not want this "chunky" display, you may pass
* NULL for display_row. If you do not want the sparkle display, and
* you have not called png_handle_alpha(), you may pass NULL for rows.
* If you have called png_handle_alpha(), and the image has either an
* alpha channel or a transparency chunk, you must provide a buffer for
* rows. In this case, you do not have to provide a display_row buffer
* also, but you may. If the image is not interlaced, or if you have
* not called png_set_interlace_handling(), the display_row buffer will
* be ignored, so pass NULL to it.
*
* [*] png_handle_alpha() does not exist yet, as of this version of libpng
*/
void PNGAPI
png_read_rows(png_structrp png_ptr, png_bytepp row,
png_bytepp display_row, png_uint_32 num_rows)
{
png_uint_32 i;
png_bytepp rp;
png_bytepp dp;
png_debug(1, "in png_read_rows");
if (png_ptr == NULL)
return;
rp = row;
dp = display_row;
if (rp != NULL && dp != NULL)
for (i = 0; i < num_rows; i++)
{
png_bytep rptr = *rp++;
png_bytep dptr = *dp++;
png_read_row(png_ptr, rptr, dptr);
}
else if (rp != NULL)
for (i = 0; i < num_rows; i++)
{
png_bytep rptr = *rp;
png_read_row(png_ptr, rptr, NULL);
rp++;
}
else if (dp != NULL)
for (i = 0; i < num_rows; i++)
{
png_bytep dptr = *dp;
png_read_row(png_ptr, NULL, dptr);
dp++;
}
}
#endif /* SEQUENTIAL_READ */
#ifdef PNG_READ_IMAGE_SUPPORTED
/* Read the entire image. If the image has an alpha channel or a tRNS
* chunk, and you have called png_handle_alpha()[*], you will need to
* initialize the image to the current image that PNG will be overlaying.
* We set the num_rows again here, in case it was incorrectly set in
* png_read_start_IDAT() by a call to png_read_update_info() or
* png_start_read_image() if png_set_interlace_handling() wasn't called
* prior to either of these functions like it should have been. You can
* only call this function once. If you desire to have an image for
* each pass of a interlaced image, use png_read_rows() instead.
*
* [*] png_handle_alpha() does not exist yet, as of this version of libpng
*/
void PNGAPI
png_read_image(png_structrp png_ptr, png_bytepp image)
{
png_uint_32 image_height;
int pass, j;
png_debug(1, "in png_read_image");
if (png_ptr == NULL)
return;
if (png_ptr->zowner != png_IDAT)
pass = png_set_interlace_handling(png_ptr);
else
{
if (png_ptr->interlaced == 0)
pass = 1;
else
pass = PNG_INTERLACE_ADAM7_PASSES;
}
for (j = 0, image_height = png_ptr->height; j < pass; ++j)
{
png_bytepp rp = image;
png_uint_32 i;
for (i = 0; i < image_height; i++)
{
png_read_row(png_ptr, *rp, NULL);
rp++;
}
}
}
#endif /* READ_IMAGE */
#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read the end of the PNG file. Will not read past the end of the
* file, will verify the end is accurate, and will read any comments
* or time information at the end of the file, if info is not NULL.
*/
void PNGAPI
png_read_end(png_structrp png_ptr, png_inforp info_ptr)
{
png_debug(1, "in png_read_end");
if (png_ptr == NULL)
return;
/* When this routine is entered it is possible that an IDAT chunk still
* remains to be read. There are three conditions:
*
* 1) The app decided to handle IDAT as unknown, libpng will have consumed
* the first IDAT in png_read_info, the rest will be consumed as normal
* chunks by calls to png_handle_chunk below.
*
* 2) The app did not start to read an image, so png_read_start_IDAT was
* not called and png_struct::zowner is not png_IDAT. The first IDAT
* must still be skipped then the code below will skip the remainder.
*
* 3) The app did start to read the image. png_struct::zowner is png_IDAT
* and we need to close down the IDAT reading code. There may also be
* pending IDAT chunks, these are passed to png_read_finish_IDAT here so
* that error detection happens. If the app didn't read all the rows
* libpng will issue an 'extra compressed data' error, we could supress
* that by warning that not all the rows have been read and setting
* png_struct::zstream_error if necessary.
*/
# ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
if (!(png_ptr->known_unknown & 1U))
# endif
{
if (png_ptr->zowner == png_IDAT)
{
/* Normal case: read to the end of the IDAT chunks. In about
* 5/PNG_IDAT_READ_SIZE cases (typically that's 1:820) zlib will have
* returned all the image data but not read up to the end of the
* Adler32 because the end of the stream had not been read. Make sure
* it gets read here:
*/
if (png_ptr->zstream.avail_in == 0)
png_read_IDAT(png_ptr);
while (!png_read_finish_IDAT(png_ptr)) {
/* This will adjust zstream.next/avail_in appropriately and if
* necessary read the next chunk. After this avail_in may still
* be zero, but if it is then PNG_AFTER_IDAT should be set.
*/
debug(png_ptr->zstream.avail_in == 0);
png_read_IDAT(png_ptr);
debug(png_ptr->zstream.avail_in > 0 ||
(png_ptr->mode & PNG_AFTER_IDAT) != 0);
}
debug(png_ptr->zstream.avail_in == 0 && png_ptr->zowner == 0);
/* If this is still an IDAT then it hasn't been finished; at least
* the CRC has not been read. If there is data left in it then
* an error may need to be output. Note that the code below handles
* any additional chunks.
*/
if (png_ptr->chunk_name == png_IDAT)
{
if (png_ptr->chunk_length > 0 && !png_ptr->zstream_error)
{
png_chunk_benign_error(png_ptr, "too much IDAT data (read)");
png_ptr->zstream_error = 1;
}
png_crc_finish(png_ptr, png_ptr->chunk_length);
png_read_chunk_header(png_ptr);
}
}
else if (png_ptr->chunk_name == png_IDAT)
{
/* This IDAT has not been processed, the remainder will be finished
* in the loop. This is the case where IDAT is being skipped because
* the rows weren't read, this is OK, but warn anyway.
*/
png_crc_finish(png_ptr, png_ptr->chunk_length);
png_app_warning(png_ptr, "image reading skipped");
png_ptr->zstream_error = 1; /* Prevent 'too much IDAT' errors */
png_read_chunk_header(png_ptr);
}
else /* This might work, if the signature was read, but just in case: */
png_app_error(png_ptr, "Missing call to png_read_info");
}
# ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
else
{
/* IDAT is unknown, the chunk that terminated the loop must be an IDAT
* and it has been processed. Get a new chunk header.
*/
if (png_ptr->chunk_name == png_IDAT)
png_read_chunk_header(png_ptr);
else
png_app_error(png_ptr,
"Missing call to png_read_info with unknown IDAT");
}
# endif
if ((png_ptr->mode & PNG_HAVE_IEND) == 0) for (;;)
{
switch (png_find_chunk_op(png_ptr))
{
default:
impossible("invalid chunk op");
/* FALL THROUGH */
case png_chunk_skip:
png_crc_finish(png_ptr, png_ptr->chunk_length);
break;
case png_chunk_unknown:
png_read_sequential_unknown(png_ptr, info_ptr);
break;
case png_chunk_process_all:
png_handle_chunk(png_ptr, info_ptr);
break;
case png_chunk_process_part:
debug(png_ptr->chunk_name == png_IDAT);
debug(!(png_ptr->mode & PNG_AFTER_IDAT));
if (png_ptr->chunk_length > 0 && !png_ptr->zstream_error)
{
png_chunk_benign_error(png_ptr, "too many IDAT chunks");
png_ptr->zstream_error = 1;
}
/* Skip it: */
png_crc_finish(png_ptr, png_ptr->chunk_length);
return;
}
if ((png_ptr->mode & PNG_HAVE_IEND) != 0)
break;
png_read_chunk_header(png_ptr);
}
}
#endif /* SEQUENTIAL_READ */
/* Free all memory used in the read struct */
static void
png_read_destroy(png_structrp png_ptr)
{
png_debug(1, "in png_read_destroy");
png_read_free_row_buffers(png_ptr);
png_free(png_ptr, png_ptr->read_buffer);
png_ptr->read_buffer = NULL;
if (png_ptr->palette != NULL)
{
png_free(png_ptr, png_ptr->palette);
png_ptr->num_palette = 0;
png_ptr->palette = NULL;
}
#ifdef PNG_READ_tRNS_SUPPORTED
if (png_ptr->trans_alpha != NULL)
{
png_free(png_ptr, png_ptr->trans_alpha);
png_ptr->num_trans = 0;
png_ptr->trans_alpha = NULL;
}
#endif
if (png_ptr->zstream.state != NULL)
{
int ret = inflateEnd(&png_ptr->zstream);
if (ret != Z_OK)
{
png_zstream_error(&png_ptr->zstream, ret);
png_warning(png_ptr, png_ptr->zstream.msg);
}
}
#ifdef PNG_TRANSFORM_MECH_SUPPORTED
png_transform_free(png_ptr, &png_ptr->transform_list);
#endif
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
png_free(png_ptr, png_ptr->save_buffer);
png_ptr->save_buffer = NULL;
#endif
#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
png_free(png_ptr, png_ptr->chunk_list);
png_ptr->chunk_list = NULL;
#endif
/* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
* callbacks are still set at this point. They are required to complete the
* destruction of the png_struct itself.
*/
}
/* Free all memory used by the read */
void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
png_infopp end_info_ptr_ptr)
{
png_structrp png_ptr = NULL;
png_debug(1, "in png_destroy_read_struct");
if (png_ptr_ptr != NULL)
png_ptr = *png_ptr_ptr;
if (png_ptr == NULL)
return;
/* libpng 1.6.0: use the API to destroy info structs to ensure consistent
* behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
* The extra was, apparently, unnecessary yet this hides memory leak bugs.
*/
png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
png_destroy_info_struct(png_ptr, info_ptr_ptr);
*png_ptr_ptr = NULL;
png_read_destroy(png_ptr);
png_destroy_png_struct(png_ptr);
}
void PNGAPI
png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
{
if (png_ptr == NULL)
return;
png_ptr->read_row_fn = read_row_fn;
}
#ifdef PNG_READ_PNG_SUPPORTED
#ifdef __GNUC__
/* This exists solely to work round a warning from GNU C. */
static int /* PRIVATE */
png_gt(size_t a, size_t b)
{
return a > b;
}
#else
# define png_gt(a,b) ((a) > (b))
#endif
void PNGAPI
png_read_png(png_structrp png_ptr, png_inforp info_ptr, int transforms,
voidp params)
{
if (png_ptr == NULL || info_ptr == NULL)
return;
/* png_read_info() gives us all of the information from the
* PNG file before the first IDAT (image data chunk).
*/
png_read_info(png_ptr, info_ptr);
if (png_gt(info_ptr->height, PNG_SIZE_MAX/(sizeof (png_bytep))))
png_error(png_ptr, "Image is too high to process with png_read_png()");
/* -------------- image transformations start here ------------------- */
/* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
* is not implemented. This will only happen in de-configured (non-default)
* libpng builds. The results can be unexpected - png_read_png may return
* short or mal-formed rows because the transform is skipped.
*/
/* Tell libpng to strip 16-bit/color files down to 8 bits per color.
*/
if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
/* Added at libpng-1.5.4. "strip_16" produces the same result that it
* did in earlier versions, while "scale_16" is now more accurate.
*/
#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
png_set_scale_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
#endif
/* If both SCALE and STRIP are required pngrtran will effectively cancel the
* latter by doing SCALE first. This is ok and allows apps not to check for
* which is supported to get the right answer.
*/
if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
png_set_strip_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
#endif
/* Strip alpha bytes from the input data without combining with
* the background (not recommended).
*/
if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
png_set_strip_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
#endif
/* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
* byte into separate bytes (useful for paletted and grayscale images).
*/
if ((transforms & PNG_TRANSFORM_PACKING) != 0)
#ifdef PNG_READ_PACK_SUPPORTED
png_set_packing(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
#endif
/* Change the order of packed pixels to least significant bit first
* (not useful if you are using png_set_packing).
*/
if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
#ifdef PNG_READ_PACKSWAP_SUPPORTED
png_set_packswap(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
#endif
/* Expand paletted colors into true RGB triplets
* Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
* Expand paletted or RGB images with transparency to full alpha
* channels so the data will be available as RGBA quartets.
*/
if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
#ifdef PNG_READ_EXPAND_SUPPORTED
png_set_expand(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
#endif
/* We don't handle background color, gamma transformation, or quantizing. */
/* Invert monochrome files to have 0 as white and 1 as black */
if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
#ifdef PNG_READ_INVERT_SUPPORTED
png_set_invert_mono(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
#endif
/* If you want to shift the pixel values from the range [0,255] or
* [0,65535] to the original [0,7] or [0,31], or whatever range the
* colors were originally in:
*/
if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
#ifdef PNG_READ_SHIFT_SUPPORTED
if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
png_set_shift(png_ptr, &info_ptr->sig_bit);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
#endif
/* Flip the RGB pixels to BGR (or RGBA to BGRA) */
if ((transforms & PNG_TRANSFORM_BGR) != 0)
#ifdef PNG_READ_BGR_SUPPORTED
png_set_bgr(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
#endif
/* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
png_set_swap_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
#endif
/* Swap bytes of 16-bit files to least significant byte first */
if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
#ifdef PNG_READ_SWAP_SUPPORTED
png_set_swap(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
#endif
/* Added at libpng-1.2.41 */
/* Invert the alpha channel from opacity to transparency */
if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
png_set_invert_alpha(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
#endif
/* Added at libpng-1.2.41 */
/* Expand grayscale image to RGB */
if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
png_set_gray_to_rgb(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
#endif
/* Added at libpng-1.5.4 */
if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
#ifdef PNG_READ_EXPAND_16_SUPPORTED
png_set_expand_16(png_ptr);
#else
png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
#endif
/* We don't handle adding filler bytes */
/* We use png_read_image and rely on that for interlace handling, but we also
* call png_read_update_info therefore must turn on interlace handling now:
*/
(void)png_set_interlace_handling(png_ptr);
/* Optional call to gamma correct and add the background to the palette
* and update info structure. REQUIRED if you are expecting libpng to
* update the palette for you (i.e., you selected such a transform above).
*/
png_read_update_info(png_ptr, info_ptr);
/* -------------- image transformations end here ------------------- */
png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
if (info_ptr->row_pointers == NULL)
{
png_uint_32 iptr;
png_alloc_size_t rowbytes = png_get_rowbytes(png_ptr, info_ptr);
info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
info_ptr->height * (sizeof (png_bytep))));
for (iptr=0; iptr<info_ptr->height; iptr++)
info_ptr->row_pointers[iptr] = NULL;
info_ptr->free_me |= PNG_FREE_ROWS;
for (iptr = 0; iptr < info_ptr->height; iptr++)
info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
png_malloc(png_ptr, rowbytes));
}
png_read_image(png_ptr, info_ptr->row_pointers);
info_ptr->valid |= PNG_INFO_IDAT;
/* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
png_read_end(png_ptr, info_ptr);
PNG_UNUSED(params)
}
#endif /* READ_PNG */
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
/* SIMPLIFIED READ
*
* This code currently relies on the sequential reader, though it could easily
* be made to work with the progressive one.
*/
/* Arguments to png_image_finish_read: */
/* Encoding of PNG data (used by the color-map code) */
# define P_NOTSET 0 /* File encoding not yet known */
# define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
# define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
# define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
# define P_LINEAR8 4 /* 8-bit linear: only from a file value */
# define P_FILE8 5 /* 8-bit encoded to file gamma but not significant bits */
/* Color-map processing: after libpng has run on the PNG image further
* processing may be needed to convert the data to color-map indices.
*/
#define PNG_CMAP_NONE 0
#define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
#define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
#define PNG_CMAP_RGB 3 /* Process RGB data */
#define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
/* The following document where the background is for each processing case. */
#define PNG_CMAP_NONE_BACKGROUND 256
#define PNG_CMAP_GA_BACKGROUND 231
#define PNG_CMAP_TRANS_BACKGROUND 254
#define PNG_CMAP_RGB_BACKGROUND 256
#define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
typedef struct
{
/* Arguments: */
png_imagep image;
png_voidp buffer;
ptrdiff_t row_stride;
png_voidp colormap;
png_const_colorp background;
/* Local variables: */
png_voidp local_row;
png_voidp first_row;
ptrdiff_t row_bytes; /* step between rows */
int file_encoding; /* E_ values above */
png_fixed_point file_to_sRGB; /* Cached correction factor */
int colormap_processing; /* PNG_CMAP_ values above */
png_byte sBIT[4]; /* Significant bits for channels */
} png_image_read_control;
/* Do all the *safe* initialization - 'safe' means that png_error won't be
* called, so setting up the jmp_buf is not required. This means that anything
* called from here must *not* call png_malloc - it has to call png_malloc_warn
* instead so that control is returned safely back to this routine.
*/
static int
png_image_read_init(png_imagep image)
{
if (image->opaque == NULL)
{
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
png_safe_error, png_safe_warning);
/* And set the rest of the structure to NULL to ensure that the various
* fields are consistent.
*/
memset(image, 0, (sizeof *image));
image->version = PNG_IMAGE_VERSION;
if (png_ptr != NULL)
{
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr != NULL)
{
png_controlp control = png_voidcast(png_controlp,
png_malloc_warn(png_ptr, (sizeof *control)));
if (control != NULL)
{
memset(control, 0, (sizeof *control));
control->png_ptr = png_ptr;
control->info_ptr = info_ptr;
control->for_write = 0;
image->opaque = control;
return 1;
}
/* Error clean up */
png_destroy_info_struct(png_ptr, &info_ptr);
}
png_destroy_read_struct(&png_ptr, NULL, NULL);
}
return png_image_error(image, "png_image_read: out of memory");
}
return png_image_error(image, "png_image_read: opaque pointer not NULL");
}
/* Utility to find the base format of a PNG file from a png_struct. */
static png_uint_32
png_image_format(png_structrp png_ptr)
{
png_uint_32 format = 0;
if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
format |= PNG_FORMAT_FLAG_COLOR;
if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
format |= PNG_FORMAT_FLAG_ALPHA;
/* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
* sets the png_struct fields; that's all we are interested in here. The
* precise interaction with an app call to png_set_tRNS and PNG file reading
* is unclear.
*/
else if (png_ptr->num_trans > 0)
format |= PNG_FORMAT_FLAG_ALPHA;
if (png_ptr->bit_depth == 16)
format |= PNG_FORMAT_FLAG_LINEAR;
if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
format |= PNG_FORMAT_FLAG_COLORMAP;
return format;
}
/* Is the given gamma significantly different from sRGB?
*/
static int
png_gamma_not_sRGB(png_fixed_point g)
{
/* An uninitialized gamma is assumed to be sRGB for the simplified API. */
return g != 0 && !PNG_GAMMA_IS_sRGB(g);
}
/* Do the main body of a 'png_image_begin_read' function; read the PNG file
* header and fill in all the information. This is executed in a safe context,
* unlike the init routine above.
*/
static int
png_image_read_header(png_voidp argument)
{
png_imagep image = png_voidcast(png_imagep, argument);
png_structrp png_ptr = image->opaque->png_ptr;
png_inforp info_ptr = image->opaque->info_ptr;
#ifdef PNG_BENIGN_ERRORS_SUPPORTED
png_set_benign_errors(png_ptr, 1/*warn*/);
#endif
png_read_info(png_ptr, info_ptr);
/* Do this the fast way; just read directly out of png_struct. */
image->width = png_ptr->width;
image->height = png_ptr->height;
{
png_uint_32 format = png_image_format(png_ptr);
image->format = format;
#ifdef PNG_COLORSPACE_SUPPORTED
/* Does the colorspace match sRGB? If there is no color endpoint
* (colorant) information assume yes, otherwise require the
* 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
* colorspace has been determined to be invalid ignore it.
*/
if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
& (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
#endif
}
/* We need the maximum number of entries regardless of the format the
* application sets here.
*/
{
png_uint_32 cmap_entries;
switch (png_ptr->color_type)
{
case PNG_COLOR_TYPE_GRAY:
cmap_entries = 1U << png_ptr->bit_depth;
break;
case PNG_COLOR_TYPE_PALETTE:
cmap_entries = png_ptr->num_palette;
break;
default:
cmap_entries = 256;
break;
}
if (cmap_entries > 256)
cmap_entries = 256;
image->colormap_entries = cmap_entries;
}
return 1;
}
static void
png_image_get_sBIT(png_image_read_control *display)
/* Utility to cache the sBIT values. This uses the information from the
* png_struct not png_info because it may be needed after the sBIT
* information in png_info has been invalidated.
*/
{
if (display->sBIT[0] == 0)
{
const png_const_structrp png_ptr = display->image->opaque->png_ptr;
const unsigned int color_type = png_ptr->color_type;
const png_byte bit_depth =
(color_type & PNG_COLOR_MASK_PALETTE) ? 8U : png_ptr->bit_depth;
memset(display->sBIT, bit_depth, sizeof display->sBIT);
if (color_type & PNG_COLOR_MASK_COLOR)
{
if (png_ptr->sig_bit.red > 0 && png_ptr->sig_bit.red < bit_depth)
display->sBIT[0] = png_ptr->sig_bit.red;
if (png_ptr->sig_bit.green > 0 && png_ptr->sig_bit.green < bit_depth)
display->sBIT[1] = png_ptr->sig_bit.green;
if (png_ptr->sig_bit.blue > 0 && png_ptr->sig_bit.blue < bit_depth)
display->sBIT[2] = png_ptr->sig_bit.blue;
}
else
{
if (png_ptr->sig_bit.gray > 0 && png_ptr->sig_bit.gray < bit_depth)
display->sBIT[2] = display->sBIT[1] = display->sBIT[0] =
png_ptr->sig_bit.gray;
}
if (color_type & PNG_COLOR_MASK_ALPHA)
{
if (png_ptr->sig_bit.alpha > 0 && png_ptr->sig_bit.alpha < bit_depth)
display->sBIT[3] = png_ptr->sig_bit.alpha;
}
}
}
#ifdef PNG_STDIO_SUPPORTED
int PNGAPI
png_image_begin_read_from_stdio(png_imagep image, FILE* file)
{
if (image != NULL && image->version == PNG_IMAGE_VERSION)
{
if (file != NULL)
{
if (png_image_read_init(image) != 0 &&
png_image_init_io(image, file) != 0)
return png_safe_execute(image, png_image_read_header, image);
}
else
return png_image_error(image,
"png_image_begin_read_from_stdio: invalid argument");
}
else if (image != NULL)
return png_image_error(image,
"png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
return 0;
}
int PNGAPI
png_image_begin_read_from_file(png_imagep image, const char *file_name)
{
if (image != NULL && image->version == PNG_IMAGE_VERSION)
{
if (file_name != NULL)
{
FILE *fp = fopen(file_name, "rb");
if (fp != NULL)
{
if (png_image_read_init(image) != 0 &&
png_image_init_io(image, fp) != 0)
{
image->opaque->owned_file = 1;
return png_safe_execute(image, png_image_read_header, image);
}
/* Clean up: just the opened file. */
(void)fclose(fp);
}
else
return png_image_error(image, strerror(errno));
}
else
return png_image_error(image,
"png_image_begin_read_from_file: invalid argument");
}
else if (image != NULL)
return png_image_error(image,
"png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
return 0;
}
#endif /* STDIO */
static void PNGCBAPI
png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
{
if (png_ptr != NULL)
{
png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
if (image != NULL)
{
png_controlp cp = image->opaque;
if (cp != NULL)
{
png_const_bytep memory = cp->memory;
png_size_t size = cp->size;
if (memory != NULL && size >= need)
{
memcpy(out, memory, need);
cp->memory = memory + need;
cp->size = size - need;
return;
}
png_error(png_ptr, "read beyond end of data");
}
}
png_error(png_ptr, "invalid memory read");
}
}
static int
image_init_memory_io(png_voidp param)
/* Set the read function and pointer for a memory read, the io pointer is
* just the imagep so it is passed in directly.
*/
{
png_imagep image = png_voidcast(png_imagep, param);
png_set_read_fn(image->opaque->png_ptr, image, png_image_memory_read);
return 1;
}
int PNGAPI
png_image_begin_read_from_memory(png_imagep image, png_const_voidp memory,
png_size_t size)
{
if (image != NULL && image->version == PNG_IMAGE_VERSION)
{
if (memory != NULL && size > 0)
{
if (png_image_read_init(image) != 0)
{
/* Now set the IO functions to read from the memory buffer and
* store it into io_ptr. Again do this in-place to avoid calling a
* libpng function that requires error handling.
*/
image->opaque->memory = png_voidcast(png_const_bytep, memory);
image->opaque->size = size;
return png_safe_execute(image, image_init_memory_io, image) &&
png_safe_execute(image, png_image_read_header, image);
}
}
else
return png_image_error(image,
"png_image_begin_read_from_memory: invalid argument");
}
else if (image != NULL)
return png_image_error(image,
"png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
return 0;
}
/* Utility function to skip chunks that are not used by the simplified image
* read functions and an appropriate macro to call it.
*/
#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
static void
png_image_skip_unused_chunks(png_structrp png_ptr)
{
/* Prepare the reader to ignore all recognized chunks whose data will not
* be used, i.e., all chunks recognized by libpng except for those
* involved in basic image reading:
*
* IHDR, PLTE, IDAT, IEND
*
* Or image data handling:
*
* tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
*
* This provides a small performance improvement and eliminates any
* potential vulnerability to security problems in the unused chunks.
*
* At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
* too. This allows the simplified API to be compiled without iCCP support,
* however if the support is there the chunk is still checked to detect
* errors (which are unfortunately quite common.)
*/
{
static PNG_CONST png_byte chunks_to_process[] = {
98, 75, 71, 68, '\0', /* bKGD */
99, 72, 82, 77, '\0', /* cHRM */
103, 65, 77, 65, '\0', /* gAMA */
# ifdef PNG_READ_iCCP_SUPPORTED
105, 67, 67, 80, '\0', /* iCCP */
# endif
115, 66, 73, 84, '\0', /* sBIT */
115, 82, 71, 66, '\0', /* sRGB */
};
/* Ignore unknown chunks and all other chunks except for the
* IHDR, PLTE, tRNS, IDAT, and IEND chunks.
*/
png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
NULL, -1);
/* But do not ignore image data handling chunks */
png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
}
}
# define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
#else
# define PNG_SKIP_CHUNKS(p) ((void)0)
#endif /* HANDLE_AS_UNKNOWN */
/* The following macro gives the exact rounded answer for all values in the
* range 0..255 (it actually divides by 51.2, but the rounding still generates
* the correct numbers 0..5
*/
#define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
/* Utility functions to make particular color-maps */
static void
set_file_encoding(png_image_read_control *display)
{
/* First test for an encoding close to linear: */
if (png_need_gamma_correction(display->image->opaque->png_ptr,
0/*PNG gamma*/, 0/*not sRGB*/))
{
png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
/* Now look for one close to sRGB: */
if (png_gamma_not_sRGB(g))
display->file_encoding = P_FILE;
else
display->file_encoding = P_sRGB;
}
else
display->file_encoding = P_LINEAR8;
}
/* For colormap entries we end up doing the gamma correction here and the
* following routines are provided to separate out the code. In all cases the
* input value is in the range 0..255 and is encoded P_FILE with the gamma value
* stored in the png_struct colorspace.
*/
static void
init_correct(png_const_structrp png_ptr, png_fixed_point *correct)
{
/* Record the convertion necessary to get from the encoding values to
* sRGB. If this overflows just store FP_1.
*
* NOTE: this code used to store, and use, a convertion factor to
* linear then use the sRGB encoding tables to get back to sRGB, but
* this smashes the low values; the ones which fall in the linear part
* of the sRGB transfer function.
*
* The new version of this code assumes an encoding which is neither
* linear nor sRGB is a power law transform of the sRGB curve, not
* linear values. This is somewhat at odds with a precise reading of
* the PNG spec, but given that we are trying to produce sRGB values
* here it is most likely to be correct.
*/
affirm(png_ptr->colorspace.gamma > 0);
if (!png_muldiv(correct, PNG_GAMMA_sRGB_INVERSE, PNG_FP_1,
png_ptr->colorspace.gamma))
*correct = PNG_FP_1;
}
static png_uint_32
update_for_sBIT(png_uint_32 value, unsigned int significant_bits,
unsigned int bit_depth)
/* Return a bit_depth value adjusted for the number of significant bits in
* the value.
*/
{
if (significant_bits < bit_depth)
{
value >>= bit_depth - significant_bits;
/* Now scale back to bit_depth, taking care not to overflow when 'value'
* is (1<<significant_bits)-1 by rounding *down* the rounding add below
* (so, e.g. rather than 2, 1 is used when significant bits is 2).
*/
value = (value * ((1U<<bit_depth)-1U) + ((1U<<(significant_bits-1U))-1U))
/ ((1U<<significant_bits)-1U);
}
return value;
}
static png_uint_32
convert_to_sRGB(png_image_read_control *display, png_uint_32 value,
unsigned int significant_bits)
{
/* Converts an 8-bit value from P_FILE to P_sRGB */
png_const_structrp png_ptr = display->image->opaque->png_ptr;
debug(value <= 255U && significant_bits <= 8U && significant_bits > 0U);
if (display->file_to_sRGB == 0)
init_correct(png_ptr, &display->file_to_sRGB);
/* Now simply apply this correction factor and scale back to 8 bits. */
if (display->file_to_sRGB != PNG_FP_1)
value = png_gamma_nxmbit_correct(value >> (8U-significant_bits),
display->file_to_sRGB, significant_bits, 8U);
else if (significant_bits < 8U)
value = update_for_sBIT(value, significant_bits, 8U);
return value;
}
static png_uint_32
convert_to_linear(png_image_read_control *display, png_uint_32 value,
unsigned int significant_bits)
{
/* Converts an 8-bit value from P_FILE to 16-bit P_LINEAR */
png_const_structrp png_ptr = display->image->opaque->png_ptr;
debug(value <= 255U && significant_bits <= 8U && significant_bits > 0U);
if (display->file_to_sRGB == 0)
init_correct(png_ptr, &display->file_to_sRGB);
/* Use this correction to get a 16-bit sRGB value: */
if (display->file_to_sRGB != PNG_FP_1)
value = png_gamma_nxmbit_correct(value >> (8U-significant_bits),
display->file_to_sRGB, significant_bits, 16U);
else
{
value *= 257U;
if (significant_bits < 8U)
value = update_for_sBIT(value, significant_bits, 16U);
}
/* Now convert this back to linear, using the correct transfer function. */
if (value <= 2650U /* 65535 * 0.04045 */)
{
/* We want to divide a 12-bit number by 12.92, do this by scaling to 32
* bits then dividing by 2^24, with rounding:
*/
value = (value * 1298546U + 649273U) >> 24;
}
else
{
/* Calculate for v in the range 0.04045..1.0 calculate:
*
* ((v + 0.055)/1.055)^2.4
*
* the gamma correction function needs a 16-bit value:
*/
value *= 62119U;
value += 223904831U+32768U; /* cannot overflow; test with 65535 */
value = png_gamma_nxmbit_correct(value >> 16, 240000, 16U, 16U);
}
return value;
}
static unsigned int
decode_gamma(png_image_read_control *display, png_uint_32 value,
unsigned int significant_bits, int encoding)
{
int do_sBIT = 0;
if (encoding == P_FILE) /* double check */
encoding = display->file_encoding, do_sBIT = 1;
if (encoding == P_NOTSET) /* must be the file encoding */
{
set_file_encoding(display);
encoding = display->file_encoding;
}
switch (encoding)
{
case P_FILE:
/* This is a file value, so the sBIT, if any, needs to be used. */
value = convert_to_linear(display, value, significant_bits);
break;
case P_sRGB:
if (do_sBIT)
value = update_for_sBIT(value, significant_bits, 8U);
value = png_sRGB_table[value];
break;
case P_LINEAR:
if (do_sBIT)
value = update_for_sBIT(value, significant_bits, 16U);
break;
case P_LINEAR8:
value *= 257;
if (do_sBIT)
value = update_for_sBIT(value, significant_bits, 16U);
break;
default:
png_impossiblepp(display->image->opaque->png_ptr,
"unexpected encoding");
break;
}
return value;
}
static png_uint_32
png_colormap_compose(png_image_read_control *display,
png_uint_32 foreground, unsigned int foreground_significant_bits,
int foreground_encoding, png_uint_32 alpha,
png_uint_32 background, int encoding)
{
/* The file value is composed on the background, the background has the given
* encoding and so does the result, the file is encoded with P_FILE and the
* file and alpha are 8-bit values. The (output) encoding will always be
* P_LINEAR or P_sRGB.
*/
png_uint_32 f = decode_gamma(display, foreground,
foreground_significant_bits, foreground_encoding);
png_uint_32 b = decode_gamma(display, background, 0U/*UNUSED*/, encoding);
/* The alpha is always an 8-bit value (it comes from the palette), the value
* scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
*/
f = f * alpha + b * (255-alpha);
if (encoding == P_LINEAR)
{
/* Scale to 65535; divide by 255, approximately (in fact this is extremely
* accurate, it divides by 255.00000005937181414556, with no overflow.)
*/
f *= 257; /* Now scaled by 65535 */
f += f >> 16;
f = (f+32768) >> 16;
}
else /* P_sRGB */
f = PNG_sRGB_FROM_LINEAR(display->image->opaque->png_ptr, f);
return f;
}
/* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
* be 8-bit.
*/
static void
png_create_colormap_entry(png_image_read_control *display,
png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
png_uint_32 alpha, int encoding)
{
png_imagep image = display->image;
# define png_ptr image->opaque->png_ptr /* for error messages */
const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
(red != green || green != blue);
int use_sBIT = encoding == P_FILE;
affirm(ip <= 255);
implies(encoding != P_LINEAR, red <= 255U && green <= 255U && blue <= 255U
&& display->sBIT[0] <= 8U && display->sBIT[1] <= 8U
&& display->sBIT[2] <= 8U && display->sBIT[3] <= 8U);
/* This is a hack for the grayscale colormap below. */
if (encoding == P_FILE8)
encoding = P_FILE;
/* Update the cache with whether the file gamma is significantly different
* from sRGB.
*/
if (encoding == P_FILE)
{
if (display->file_encoding == P_NOTSET)
set_file_encoding(display);
/* Note that the cached value may be P_FILE too. */
encoding = display->file_encoding;
if (use_sBIT)
png_image_get_sBIT(display);
}
if (encoding == P_FILE)
{
if (convert_to_Y != 0 || output_encoding == P_LINEAR)
{
red = convert_to_linear(display, red,
use_sBIT ? display->sBIT[0] : 8U);
green = convert_to_linear(display, green,
use_sBIT ? display->sBIT[1] : 8U);
blue = convert_to_linear(display, blue,
use_sBIT ? display->sBIT[2] : 8U);
alpha *= 257U;
if (use_sBIT)
alpha = update_for_sBIT(alpha, display->sBIT[3], 16U);
encoding = P_LINEAR;
use_sBIT = 0;
}
else
{
red = convert_to_sRGB(display, red,
use_sBIT ? display->sBIT[0] : 8U);
green = convert_to_sRGB(display, green,
use_sBIT ? display->sBIT[1] : 8U);
blue = convert_to_sRGB(display, blue,
use_sBIT ? display->sBIT[2] : 8U);
if (use_sBIT)
alpha = update_for_sBIT(alpha, display->sBIT[3], 8U);
encoding = P_sRGB;
use_sBIT = 0;
}
}
else if (encoding == P_LINEAR8)
{
/* This encoding corresponds to a colormap with linear RGB entries, this
* is not a very sensible encoding but it does happen with the PNGSuite
* test images.
*/
red *= 257;
green *= 257;
blue *= 257;
alpha *= 257;
if (use_sBIT)
{
red = update_for_sBIT(red, display->sBIT[0], 16U);
green = update_for_sBIT(green, display->sBIT[1], 16U);
blue = update_for_sBIT(blue, display->sBIT[2], 16U);
alpha = update_for_sBIT(alpha, display->sBIT[3], 16U);
use_sBIT = 0;
}
encoding = P_LINEAR;
}
else if (encoding == P_sRGB &&
(convert_to_Y != 0 || output_encoding == P_LINEAR))
{
/* The values are 8-bit sRGB values, but must be converted to 16-bit
* linear.
*/
if (use_sBIT)
{
red = convert_to_linear(display, red, display->sBIT[0]);
green = convert_to_linear(display, green, display->sBIT[1]);
blue = convert_to_linear(display, blue, display->sBIT[2]);
alpha = update_for_sBIT(alpha * 257U, display->sBIT[3], 16U);
use_sBIT = 0;
}
else
{
red = png_sRGB_table[red];
green = png_sRGB_table[green];
blue = png_sRGB_table[blue];
alpha *= 257;
}
encoding = P_LINEAR;
}
else if (encoding == P_sRGB && use_sBIT)
{
debug(output_encoding == P_sRGB); /* P_LINEAR handled above */
red = update_for_sBIT(red, display->sBIT[0], 8U);
green = update_for_sBIT(green, display->sBIT[1], 8U);
blue = update_for_sBIT(blue, display->sBIT[2], 8U);
alpha = update_for_sBIT(alpha, display->sBIT[3], 8U);
use_sBIT = 0;
}
debug(!use_sBIT); /* it should have been handled above */
/* This is set if the color isn't gray but the output is. */
if (encoding == P_LINEAR)
{
if (convert_to_Y != 0)
{
/* NOTE: these values are copied from png_do_rgb_to_gray */
png_uint_32 y = 6968 * red + 23434 * green + 2366 * blue;
if (output_encoding == P_LINEAR)
y = (y + 16384) >> 15;
else
{
/* y is scaled by 32768, we need it scaled by 255: */
y = (y + 128) >> 8;
y *= 255;
y = PNG_sRGB_FROM_LINEAR(png_ptr, (y + 64) >> 7);
alpha = PNG_DIV257(alpha);
encoding = P_sRGB;
}
blue = red = green = y;
}
else if (output_encoding == P_sRGB)
{
red = PNG_sRGB_FROM_LINEAR(png_ptr, red * 255);
green = PNG_sRGB_FROM_LINEAR(png_ptr, green * 255);
blue = PNG_sRGB_FROM_LINEAR(png_ptr, blue * 255);
alpha = PNG_DIV257(alpha);
encoding = P_sRGB;
}
}
if (encoding != output_encoding)
png_impossiblepp(png_ptr, "bad encoding");
/* Store the value. */
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
(image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
# else
# define afirst 0
# endif
# ifdef PNG_FORMAT_BGR_SUPPORTED
const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
# else
# define bgr 0
# endif
if (output_encoding == P_LINEAR)
{
png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
/* The linear 16-bit values must be pre-multiplied by the alpha channel
* value, if less than 65535 (this is, effectively, composite on black
* if the alpha channel is removed.)
*/
switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
{
case 4:
entry[afirst ? 0 : 3] = png_check_u16(png_ptr, alpha);
/* FALL THROUGH */
case 3:
if (alpha < 65535)
{
if (alpha > 0)
{
blue = (blue * alpha + 32767U)/65535U;
green = (green * alpha + 32767U)/65535U;
red = (red * alpha + 32767U)/65535U;
}
else
red = green = blue = 0;
}
entry[afirst + (2 ^ bgr)] = png_check_u16(png_ptr, blue);
entry[afirst + 1] = png_check_u16(png_ptr, green);
entry[afirst + bgr] = png_check_u16(png_ptr, red);
break;
case 2:
entry[1 ^ afirst] = png_check_u16(png_ptr, alpha);
/* FALL THROUGH */
case 1:
if (alpha < 65535)
{
if (alpha > 0)
green = (green * alpha + 32767U)/65535U;
else
green = 0;
}
entry[afirst] = png_check_u16(png_ptr, green);
break;
default:
break;
}
}
else /* output encoding is P_sRGB */
{
png_bytep entry = png_voidcast(png_bytep, display->colormap);
entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
png_affirmpp(png_ptr, output_encoding == P_sRGB);
switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
{
case 4:
entry[afirst ? 0 : 3] = png_check_byte(png_ptr, alpha);
case 3:
entry[afirst + (2 ^ bgr)] = png_check_byte(png_ptr, blue);
entry[afirst + 1] = png_check_byte(png_ptr, green);
entry[afirst + bgr] = png_check_byte(png_ptr, red);
break;
case 2:
entry[1 ^ afirst] = png_check_byte(png_ptr, alpha);
case 1:
entry[afirst] = png_check_byte(png_ptr, green);
break;
default:
break;
}
}
# ifdef afirst
# undef afirst
# endif
# ifdef bgr
# undef bgr
# endif
}
# undef png_ptr
}
static int
make_gray_file_colormap(png_image_read_control *display)
{
unsigned int i;
for (i=0; i<256; ++i)
png_create_colormap_entry(display, i, i, i, i, 255, P_FILE8);
return i;
}
static int
make_gray_colormap(png_image_read_control *display)
{
unsigned int i;
for (i=0; i<256; ++i)
png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
return i;
}
#define PNG_GRAY_COLORMAP_ENTRIES 256
static int
make_ga_colormap(png_image_read_control *display)
{
unsigned int i, a;
/* Alpha is retained, the output will be a color-map with entries
* selected by six levels of alpha. One transparent entry, 6 gray
* levels for all the intermediate alpha values, leaving 230 entries
* for the opaque grays. The color-map entries are the six values
* [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
* relevant entry.
*
* if (alpha > 229) // opaque
* {
* // The 231 entries are selected to make the math below work:
* base = 0;
* entry = (231 * gray + 128) >> 8;
* }
* else if (alpha < 26) // transparent
* {
* base = 231;
* entry = 0;
* }
* else // partially opaque
* {
* base = 226 + 6 * PNG_DIV51(alpha);
* entry = PNG_DIV51(gray);
* }
*/
i = 0;
while (i < 231)
{
unsigned int gray = (i * 256 + 115) / 231;
png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
}
/* 255 is used here for the component values for consistency with the code
* that undoes premultiplication in pngwrite.c.
*/
png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
for (a=1; a<5; ++a)
{
unsigned int g;
for (g=0; g<6; ++g)
png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
P_sRGB);
}
return i;
}
#define PNG_GA_COLORMAP_ENTRIES 256
static int
make_rgb_colormap(png_image_read_control *display)
{
unsigned int i, r;
/* Build a 6x6x6 opaque RGB cube */
for (i=r=0; r<6; ++r)
{
unsigned int g;
for (g=0; g<6; ++g)
{
unsigned int b;
for (b=0; b<6; ++b)
png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
P_sRGB);
}
}
return i;
}
#define PNG_RGB_COLORMAP_ENTRIES 216
/* Return a palette index to the above palette given three 8-bit sRGB values. */
#define PNG_RGB_INDEX(r,g,b) \
(png_check_byte(image->opaque->png_ptr,\
6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
static int
png_image_read_colormap(png_voidp argument)
{
png_image_read_control *display =
png_voidcast(png_image_read_control*, argument);
const png_imagep image = display->image;
const png_structrp png_ptr = image->opaque->png_ptr;
const png_uint_32 output_format = image->format;
const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
unsigned int cmap_entries;
unsigned int output_processing; /* Output processing option */
unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
/* Background information; the background color and the index of this color
* in the color-map if it exists (else 256).
*/
unsigned int background_index = 256;
png_uint_32 back_r, back_g, back_b;
/* Flags to accumulate things that need to be done to the input. */
int expand_tRNS = 0;
/* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
* very difficult to do, the results look awful, and it is difficult to see
* what possible use it is because the application can't control the
* color-map.
*/
if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
png_ptr->num_trans > 0) /* alpha in input */ &&
((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
{
if (output_encoding == P_LINEAR) /* compose on black */
back_b = back_g = back_r = 0;
else if (display->background == NULL /* no way to remove it */)
png_error(png_ptr,
"background color must be supplied to remove alpha/transparency");
/* Get a copy of the background color (this avoids repeating the checks
* below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
* output format.
*/
else
{
back_g = display->background->green;
if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
{
back_r = display->background->red;
back_b = display->background->blue;
}
else
back_b = back_r = back_g;
}
}
else if (output_encoding == P_LINEAR)
back_b = back_r = back_g = 65535;
else
back_b = back_r = back_g = 255;
/* Default the input file gamma if required - this is necessary because
* libpng assumes that if no gamma information is present the data is in the
* output format, but the simplified API deduces the gamma from the input
* format.
*/
if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
{
/* Do this directly, not using the png_colorspace functions, to ensure
* that it happens even if the colorspace is invalid (though probably if
* it is the setting will be ignored) Note that the same thing can be
* achieved at the application interface with png_set_gAMA.
*/
if (png_ptr->bit_depth == 16 &&
(image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
else
png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
/* Make sure libpng doesn't ignore the setting: */
if (png_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
png_ptr->colorspace.flags = PNG_COLORSPACE_HAVE_GAMMA;
else
png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
}
/* Decide what to do based on the PNG color type of the input data. The
* utility function png_create_colormap_entry deals with most aspects of the
* output transformations; this code works out how to produce bytes of
* color-map entries from the original format.
*/
switch (png_ptr->color_type)
{
case PNG_COLOR_TYPE_GRAY:
if (png_ptr->bit_depth <= 8)
{
/* There at most 256 colors in the output, regardless of
* transparency.
*/
unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
cmap_entries = 1U << png_ptr->bit_depth;
if (cmap_entries > image->colormap_entries)
png_error(png_ptr, "gray[8] color-map: too few entries");
step = 255 / (cmap_entries - 1);
output_processing = PNG_CMAP_NONE;
/* If there is a tRNS chunk then this either selects a transparent
* value or, if the output has no alpha, the background color.
*/
if (png_ptr->num_trans > 0)
{
trans = png_ptr->trans_color.gray;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
}
/* png_create_colormap_entry just takes an RGBA and writes the
* corresponding color-map entry using the format from 'image',
* including the required conversion to sRGB or linear as
* appropriate. The input values are always either sRGB (if the
* gamma correction flag is 0) or 0..255 scaled file encoded values
* (if the function must gamma correct them).
*/
for (i=val=0; i<cmap_entries; ++i, val += step)
{
/* 'i' is a file value. While this will result in duplicated
* entries for 8-bit non-sRGB encoded files it is necessary to
* have non-gamma corrected values to do tRNS handling.
*/
if (i != trans)
png_create_colormap_entry(display, i, val, val, val, 255,
P_FILE/*8-bit with file gamma*/);
/* Else this entry is transparent. The colors don't matter if
* there is an alpha channel (back_alpha == 0), but it does no
* harm to pass them in; the values are not set above so this
* passes in white.
*
* NOTE: this preserves the full precision of the application
* supplied background color when it is used.
*/
else
{
#ifdef __COVERITY__
/* Coverity says back_r|g|b might be 16-bit values */
png_affirmpp(png_ptr, back_r < 256 && back_g < 256 &&
back_b < 256);
#endif
png_create_colormap_entry(display, i, back_r, back_g, back_b,
back_alpha, output_encoding);
}
}
/* We need libpng to preserve the original encoding. */
data_encoding = P_FILE;
/* The rows from libpng, while technically gray values, are now also
* color-map indices; however, they may need to be expanded to 1
* byte per pixel. This is what png_set_packing does (i.e., it
* unpacks the bit values into bytes.)
*/
if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
}
else /* bit depth is 16 */
{
/* The 16-bit input values can be converted directly to 8-bit gamma
* encoded values; however, if a tRNS chunk is present 257 color-map
* entries are required. This means that the extra entry requires
* special processing; add an alpha channel, sacrifice gray level
* 254 and convert transparent (alpha==0) entries to that.
*
* Use libpng to chop the data to 8 bits. Convert it to sRGB at the
* same time to minimize quality loss. If a tRNS chunk is present
* this means libpng must handle it too; otherwise it is impossible
* to do the exact match on the 16-bit value.
*
* If the output has no alpha channel *and* the background color is
* gray then it is possible to let libpng handle the substitution by
* ensuring that the corresponding gray level matches the background
* color exactly.
*/
data_encoding = P_sRGB;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray[16] color-map: too few entries");
cmap_entries = make_gray_colormap(display);
if (png_ptr->num_trans > 0)
{
unsigned int back_alpha;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
back_alpha = 0;
else
{
if (back_r == back_g && back_g == back_b)
{
/* Background is gray; no special processing will be
* required.
*/
png_color_16 c;
png_uint_32 gray = back_g;
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(png_ptr, gray * 255);
/* And make sure the corresponding palette entry
* matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the
* sRGB value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue =
png_check_u16(png_ptr, gray);
/* NOTE: does this work without expanding tRNS to alpha?
* It should be the color->gray case below apparently
* doesn't.
*/
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_NONE;
break;
}
/* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
* here.
*/
affirm(output_encoding != P_LINEAR);
back_alpha = 255U;
}
/* output_processing means that the libpng-processed row will be
* 8-bit GA and it has to be processing to single byte color-map
* values. Entry 254 is replaced by either a completely
* transparent entry or by the background color at full
* precision (and the background color is not a simple gray
* level in this case.)
*/
expand_tRNS = 1;
output_processing = PNG_CMAP_TRANS;
background_index = 254;
/* And set (overwrite) color-map entry 254 to the actual
* background color at full precision.
*/
#ifdef __COVERITY__
/* Coverity says back_r|g|b might be 16-bit values */
png_affirmpp(png_ptr, back_r < 256 && back_g < 256 &&
back_b < 256);
#endif
png_create_colormap_entry(display, 254, back_r, back_g, back_b,
back_alpha, output_encoding);
}
else
output_processing = PNG_CMAP_NONE;
}
break;
case PNG_COLOR_TYPE_GRAY_ALPHA:
/* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
* of 65536 combinations. If, however, the alpha channel is to be
* removed there are only 256 possibilities if the background is gray.
* (Otherwise there is a subset of the 65536 possibilities defined by
* the triangle between black, white and the background color.)
*
* Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
* worry about tRNS matching - tRNS is ignored if there is an alpha
* channel.
*/
data_encoding = P_sRGB;
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray+alpha color-map: too few entries");
cmap_entries = make_ga_colormap(display);
background_index = PNG_CMAP_GA_BACKGROUND;
output_processing = PNG_CMAP_GA;
}
else /* alpha is removed */
{
/* Alpha must be removed as the PNG data is processed when the
* background is a color because the G and A channels are
* independent and the vector addition (non-parallel vectors) is a
* 2-D problem.
*
* This can be reduced to the same algorithm as above by making a
* colormap containing gray levels (for the opaque grays), a
* background entry (for a transparent pixel) and a set of four six
* level color values, one set for each intermediate alpha value.
* See the comments in make_ga_colormap for how this works in the
* per-pixel processing.
*
* If the background is gray, however, we only need a 256 entry gray
* level color map. It is sufficient to make the entry generated
* for the background color be exactly the color specified.
*/
if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
(back_r == back_g && back_g == back_b))
{
/* Background is gray; no special processing will be required. */
png_color_16 c;
png_uint_32 gray = back_g;
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "gray-alpha color-map: too few entries");
cmap_entries = make_gray_colormap(display);
if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(png_ptr, gray * 255);
/* And make sure the corresponding palette entry matches. */
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 65535, P_LINEAR);
}
/* The background passed to libpng, however, must be the sRGB
* value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue = png_check_u16(png_ptr, gray);
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_NONE;
}
else
{
png_uint_32 i, a;
/* This is the same as png_make_ga_colormap, above, except that
* the entries are all opaque.
*/
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "ga-alpha color-map: too few entries");
i = 0;
while (i < 231)
{
png_uint_32 gray = (i * 256 + 115) / 231;
png_create_colormap_entry(display, i++, gray, gray, gray,
255, P_sRGB);
}
/* NOTE: this preserves the full precision of the application
* background color.
*
* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
*/
affirm(output_encoding != P_LINEAR);
background_index = i;
png_create_colormap_entry(display, i++, back_r, back_g, back_b,
255U, output_encoding);
/* For non-opaque input composite on the sRGB background - this
* requires inverting the encoding for each component. The input
* is still converted to the sRGB encoding because this is a
* reasonable approximate to the logarithmic curve of human
* visual sensitivity, at least over the narrow range which PNG
* represents. Consequently 'G' is always sRGB encoded, while
* 'A' is linear. We need the linear background colors.
*/
if (output_encoding == P_sRGB) /* else already linear */
{
/* This may produce a value not exactly matching the
* background, but that's ok because these numbers are only
* used when alpha != 0
*/
back_r = png_sRGB_table[back_r];
back_g = png_sRGB_table[back_g];
back_b = png_sRGB_table[back_b];
}
for (a=1; a<5; ++a)
{
unsigned int g;
/* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
* by an 8-bit alpha value (0..255).
*/
png_uint_32 alpha = 51 * a;
png_uint_32 back_rx = (255-alpha) * back_r;
png_uint_32 back_gx = (255-alpha) * back_g;
png_uint_32 back_bx = (255-alpha) * back_b;
for (g=0; g<6; ++g)
{
png_uint_32 gray = png_sRGB_table[g*51] * alpha;
png_create_colormap_entry(display, i++,
PNG_sRGB_FROM_LINEAR(png_ptr, gray + back_rx),
PNG_sRGB_FROM_LINEAR(png_ptr, gray + back_gx),
PNG_sRGB_FROM_LINEAR(png_ptr, gray + back_bx),
255, P_sRGB);
}
}
cmap_entries = i;
output_processing = PNG_CMAP_GA;
}
}
break;
case PNG_COLOR_TYPE_RGB:
case PNG_COLOR_TYPE_RGB_ALPHA:
/* Exclude the case where the output is gray; we can always handle this
* with the cases above.
*/
if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
{
/* The color-map will be grayscale, so we may as well convert the
* input RGB values to a simple grayscale and use the grayscale
* code above.
*
* NOTE: calling this apparently damages the recognition of the
* transparent color in background color handling; call
* png_set_tRNS_to_alpha before png_set_background_fixed.
*/
png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
-1);
data_encoding = P_sRGB;
/* The output will now be one or two 8-bit gray or gray+alpha
* channels. The more complex case arises when the input has alpha.
*/
if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
(output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
/* Both input and output have an alpha channel, so no background
* processing is required; just map the GA bytes to the right
* color-map entry.
*/
expand_tRNS = 1;
if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[ga] color-map: too few entries");
cmap_entries = make_ga_colormap(display);
background_index = PNG_CMAP_GA_BACKGROUND;
output_processing = PNG_CMAP_GA;
}
else
{
/* Either the input or the output has no alpha channel, so there
* will be no non-opaque pixels in the color-map; it will just be
* grayscale.
*/
if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb[gray] color-map: too few entries");
/* Ideally this code would use libpng to do the gamma correction,
* but if an input alpha channel is to be removed we will hit the
* libpng bug in gamma+compose+rgb-to-gray (the double gamma
* correction bug). Fix this by dropping the gamma correction in
* this case and doing it in the palette; this will result in
* duplicate palette entries, but that's better than the
* alternative of double gamma correction.
*/
if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0) &&
png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
{
cmap_entries = make_gray_file_colormap(display);
data_encoding = P_FILE;
}
else
cmap_entries = make_gray_colormap(display);
/* But if the input has alpha or transparency it must be removed
*/
if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{
png_color_16 c;
png_uint_32 gray = back_g;
/* We need to ensure that the application background exists in
* the colormap and that completely transparent pixels map to
* it. Achieve this simply by ensuring that the entry
* selected for the background really is the background color.
*/
if (data_encoding == P_FILE) /* from the fixup above */
{
/* The app supplied a gray which is in output_encoding, we
* need to convert it to a value of the input (P_FILE)
* encoding then set this palette entry to the required
* output encoding.
*/
if (output_encoding == P_sRGB)
gray = png_sRGB_table[gray]; /* now P_LINEAR */
gray = png_gamma_nxmbit_correct(gray,
png_ptr->colorspace.gamma, 16U, 8U);
/* And make sure the corresponding palette entry contains
* exactly the required sRGB value.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, output_encoding);
}
else if (output_encoding == P_LINEAR)
{
gray = PNG_sRGB_FROM_LINEAR(png_ptr, gray * 255);
/* And make sure the corresponding palette entry matches.
*/
png_create_colormap_entry(display, gray, back_g, back_g,
back_g, 0/*unused*/, P_LINEAR);
}
/* The background passed to libpng, however, must be the
* output (normally sRGB) value.
*/
c.index = 0; /*unused*/
c.gray = c.red = c.green = c.blue =
png_check_u16(png_ptr, gray);
/* NOTE: the following is apparently a bug in libpng. Without
* it the transparent color recognition in
* png_set_background_fixed seems to go wrong.
*/
expand_tRNS = 1;
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
}
output_processing = PNG_CMAP_NONE;
}
}
else /* output is color */
{
/* We could use png_quantize here so long as there is no transparent
* color or alpha; png_quantize ignores alpha. Easier overall just
* to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
* Consequently we always want libpng to produce sRGB data.
*/
data_encoding = P_sRGB;
/* Is there any transparency or alpha? */
if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
png_ptr->num_trans > 0)
{
/* Is there alpha in the output too? If so all four channels are
* processed into a special RGB cube with alpha support.
*/
if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
{
png_uint_32 r;
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb+alpha color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
/* Add a transparent entry. */
png_create_colormap_entry(display, cmap_entries, 255, 255,
255, 0, P_sRGB);
/* This is stored as the background index for the processing
* algorithm.
*/
background_index = cmap_entries++;
/* Add 27 r,g,b entries each with alpha 0.5. */
for (r=0; r<256; r = (r << 1) | 0x7f)
{
png_uint_32 g;
for (g=0; g<256; g = (g << 1) | 0x7f)
{
png_uint_32 b;
/* This generates components with the values 0, 127 and
* 255
*/
for (b=0; b<256; b = (b << 1) | 0x7f)
png_create_colormap_entry(display, cmap_entries++,
r, g, b, 128, P_sRGB);
}
}
expand_tRNS = 1;
output_processing = PNG_CMAP_RGB_ALPHA;
}
else
{
/* Alpha/transparency must be removed. The background must
* exist in the color map (achieved by setting adding it after
* the 666 color-map). If the standard processing code will
* pick up this entry automatically that's all that is
* required; libpng can be called to do the background
* processing.
*/
unsigned int sample_size =
PNG_IMAGE_SAMPLE_SIZE(output_format);
png_uint_32 r, g, b; /* sRGB background */
if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
png_error(png_ptr, "rgb-alpha color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
png_create_colormap_entry(display, cmap_entries, back_r,
back_g, back_b, 0/*unused*/, output_encoding);
if (output_encoding == P_LINEAR)
{
r = PNG_sRGB_FROM_LINEAR(png_ptr, back_r * 255);
g = PNG_sRGB_FROM_LINEAR(png_ptr, back_g * 255);
b = PNG_sRGB_FROM_LINEAR(png_ptr, back_b * 255);
}
else
{
r = back_r;
g = back_g;
b = back_g;
}
/* Compare the newly-created color-map entry with the one the
* PNG_CMAP_RGB algorithm will use. If the two entries don't
* match, add the new one and set this as the background
* index.
*/
if (memcmp((png_const_bytep)display->colormap +
sample_size * cmap_entries,
(png_const_bytep)display->colormap +
sample_size * PNG_RGB_INDEX(r,g,b),
sample_size) != 0)
{
/* The background color must be added. */
background_index = cmap_entries++;
/* Add 27 r,g,b entries each with created by composing with
* the background at alpha 0.5.
*/
for (r=0; r<256; r = (r << 1) | 0x7f)
{
for (g=0; g<256; g = (g << 1) | 0x7f)
{
/* This generates components with the values 0, 127
* and 255
*/
for (b=0; b<256; b = (b << 1) | 0x7f)
png_create_colormap_entry(display, cmap_entries++,
png_colormap_compose(display, r, 8U, P_sRGB,
128U, back_r, output_encoding),
png_colormap_compose(display, g, 8U, P_sRGB,
128U, back_g, output_encoding),
png_colormap_compose(display, b, 8U, P_sRGB,
128U, back_b, output_encoding),
0/*unused*/, output_encoding);
}
}
expand_tRNS = 1;
output_processing = PNG_CMAP_RGB_ALPHA;
}
else /* background color is in the standard color-map */
{
png_color_16 c;
c.index = 0; /*unused*/
c.red = png_check_u16(png_ptr, back_r);
c.gray = c.green = png_check_u16(png_ptr, back_g);
c.blue = png_check_u16(png_ptr, back_b);
png_set_background_fixed(png_ptr, &c,
PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
0/*gamma: not used*/);
output_processing = PNG_CMAP_RGB;
}
}
}
else /* no alpha or transparency in the input */
{
/* Alpha in the output is irrelevant, simply map the opaque input
* pixels to the 6x6x6 color-map.
*/
if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
png_error(png_ptr, "rgb color-map: too few entries");
cmap_entries = make_rgb_colormap(display);
output_processing = PNG_CMAP_RGB;
}
}
break;
case PNG_COLOR_TYPE_PALETTE:
/* It's already got a color-map. It may be necessary to eliminate the
* tRNS entries though.
*/
{
unsigned int num_trans = png_ptr->num_trans;
png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
png_const_colorp colormap = png_ptr->palette;
const int do_background = trans != NULL &&
(output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
unsigned int i;
/* Just in case: */
if (trans == NULL)
num_trans = 0;
output_processing = PNG_CMAP_NONE;
data_encoding = P_FILE; /* Don't change from color-map indices */
cmap_entries = png_ptr->num_palette;
if (cmap_entries > 256)
cmap_entries = 256;
if (cmap_entries > image->colormap_entries)
png_error(png_ptr, "palette color-map: too few entries");
for (i=0; i < cmap_entries; ++i)
{
if (do_background != 0 && i < num_trans && trans[i] < 255)
{
if (trans[i] == 0)
png_create_colormap_entry(display, i, back_r, back_g,
back_b, 0, output_encoding);
else
{
unsigned int alpha;
/* Must compose the PNG file color in the color-map entry
* on the sRGB color in 'back'.
*/
png_image_get_sBIT(display);
alpha = update_for_sBIT(trans[i], display->sBIT[3], 8U);
/* Do the sBIT handling here because it only applies to the
* values from the colormap, not the background. Passing
* output_encoding to png_create_colormap_entry prevents
* this being duplicated.
*/
png_create_colormap_entry(display, i,
png_colormap_compose(display, colormap[i].red,
display->sBIT[0], P_FILE, alpha, back_r,
output_encoding),
png_colormap_compose(display, colormap[i].green,
display->sBIT[1], P_FILE, alpha, back_g,
output_encoding),
png_colormap_compose(display, colormap[i].blue,
display->sBIT[2], P_FILE, alpha, back_b,
output_encoding),
output_encoding == P_LINEAR ?
update_for_sBIT(alpha*257U, display->sBIT[3], 16U) :
trans[i],
output_encoding);
}
}
else
png_create_colormap_entry(display, i, colormap[i].red,
colormap[i].green, colormap[i].blue,
i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
}
/* The PNG data may have indices packed in fewer than 8 bits, it
* must be expanded if so.
*/
if (png_ptr->bit_depth < 8)
png_set_packing(png_ptr);
}
break;
default:
png_error(png_ptr, "invalid PNG color type");
/*NOT REACHED*/
}
/* Now deal with the output processing */
if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
(png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
png_set_tRNS_to_alpha(png_ptr);
switch (data_encoding)
{
default:
impossible("bad data option");
break;
case P_sRGB:
/* Change to 8-bit sRGB */
png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
/* FALL THROUGH */
case P_FILE:
if (png_ptr->bit_depth > 8)
png_set_scale_16(png_ptr);
break;
}
affirm(cmap_entries <= 256 && cmap_entries <= image->colormap_entries);
image->colormap_entries = cmap_entries;
/* Double check using the recorded background index */
switch (output_processing)
{
case PNG_CMAP_NONE:
if (background_index != PNG_CMAP_NONE_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_GA:
if (background_index != PNG_CMAP_GA_BACKGROUND)
goto bad_background;
break;
case PNG_CMAP_TRANS:
if (background_index