mirror of
https://git.code.sf.net/p/libpng/code.git
synced 2025-07-10 18:04:09 +02:00
425 lines
14 KiB
C
425 lines
14 KiB
C
/*---------------------------------------------------------------------------
|
|
|
|
rpng2 - progressive-model PNG display program readpng2.c
|
|
|
|
---------------------------------------------------------------------------
|
|
|
|
Copyright (c) 1998-2000 Greg Roelofs. All rights reserved.
|
|
|
|
This software is provided "as is," without warranty of any kind,
|
|
express or implied. In no event shall the author or contributors
|
|
be held liable for any damages arising in any way from the use of
|
|
this software.
|
|
|
|
Permission is granted to anyone to use this software for any purpose,
|
|
including commercial applications, and to alter it and redistribute
|
|
it freely, subject to the following restrictions:
|
|
|
|
1. Redistributions of source code must retain the above copyright
|
|
notice, disclaimer, and this list of conditions.
|
|
2. Redistributions in binary form must reproduce the above copyright
|
|
notice, disclaimer, and this list of conditions in the documenta-
|
|
tion and/or other materials provided with the distribution.
|
|
3. All advertising materials mentioning features or use of this
|
|
software must display the following acknowledgment:
|
|
|
|
This product includes software developed by Greg Roelofs
|
|
and contributors for the book, "PNG: The Definitive Guide,"
|
|
published by O'Reilly and Associates.
|
|
|
|
---------------------------------------------------------------------------*/
|
|
|
|
|
|
#include <stdlib.h> /* for exit() prototype */
|
|
|
|
#include "png.h" /* libpng header; includes zlib.h and setjmp.h */
|
|
#include "readpng2.h" /* typedefs, common macros, public prototypes */
|
|
|
|
|
|
/* local prototypes */
|
|
|
|
static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr);
|
|
static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
|
|
png_uint_32 row_num, int pass);
|
|
static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr);
|
|
static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg);
|
|
|
|
|
|
|
|
|
|
void readpng2_version_info(void)
|
|
{
|
|
fprintf(stderr, " Compiled with libpng %s; using libpng %s.\n",
|
|
PNG_LIBPNG_VER_STRING, png_libpng_ver);
|
|
fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n",
|
|
ZLIB_VERSION, zlib_version);
|
|
}
|
|
|
|
|
|
|
|
|
|
int readpng2_check_sig(uch *sig, int num)
|
|
{
|
|
return png_check_sig(sig, num);
|
|
}
|
|
|
|
|
|
|
|
|
|
/* returns 0 for success, 2 for libpng problem, 4 for out of memory */
|
|
|
|
int readpng2_init(mainprog_info *mainprog_ptr)
|
|
{
|
|
png_structp png_ptr; /* note: temporary variables! */
|
|
png_infop info_ptr;
|
|
|
|
|
|
/* could also replace libpng warning-handler (final NULL), but no need: */
|
|
|
|
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
|
|
readpng2_error_handler, NULL);
|
|
if (!png_ptr)
|
|
return 4; /* out of memory */
|
|
|
|
info_ptr = png_create_info_struct(png_ptr);
|
|
if (!info_ptr) {
|
|
png_destroy_read_struct(&png_ptr, NULL, NULL);
|
|
return 4; /* out of memory */
|
|
}
|
|
|
|
|
|
/* we could create a second info struct here (end_info), but it's only
|
|
* useful if we want to keep pre- and post-IDAT chunk info separated
|
|
* (mainly for PNG-aware image editors and converters) */
|
|
|
|
|
|
/* setjmp() must be called in every function that calls a PNG-reading
|
|
* libpng function, unless an alternate error handler was installed--
|
|
* but compatible error handlers must either use longjmp() themselves
|
|
* (as in this program) or exit immediately, so here we are: */
|
|
|
|
if (setjmp(mainprog_ptr->jmpbuf)) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
return 2;
|
|
}
|
|
|
|
|
|
/* instead of doing png_init_io() here, now we set up our callback
|
|
* functions for progressive decoding */
|
|
|
|
png_set_progressive_read_fn(png_ptr, mainprog_ptr,
|
|
readpng2_info_callback, readpng2_row_callback, readpng2_end_callback);
|
|
|
|
|
|
/* make sure we save our pointers for use in readpng2_decode_data() */
|
|
|
|
mainprog_ptr->png_ptr = png_ptr;
|
|
mainprog_ptr->info_ptr = info_ptr;
|
|
|
|
|
|
/* and that's all there is to initialization */
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
|
|
/* returns 0 for success, 2 for libpng (longjmp) problem */
|
|
|
|
int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length)
|
|
{
|
|
png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
|
|
png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
|
|
|
|
|
|
/* setjmp() must be called in every function that calls a PNG-reading
|
|
* libpng function */
|
|
|
|
if (setjmp(mainprog_ptr->jmpbuf)) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
mainprog_ptr->png_ptr = NULL;
|
|
mainprog_ptr->info_ptr = NULL;
|
|
return 2;
|
|
}
|
|
|
|
|
|
/* hand off the next chunk of input data to libpng for decoding */
|
|
|
|
png_process_data(png_ptr, info_ptr, rawbuf, length);
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
|
|
static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr)
|
|
{
|
|
mainprog_info *mainprog_ptr;
|
|
int color_type, bit_depth;
|
|
double gamma;
|
|
|
|
|
|
/* setjmp() doesn't make sense here, because we'd either have to exit(),
|
|
* longjmp() ourselves, or return control to libpng, which doesn't want
|
|
* to see us again. By not doing anything here, libpng will instead jump
|
|
* to readpng2_decode_data(), which can return an error value to the main
|
|
* program. */
|
|
|
|
|
|
/* retrieve the pointer to our special-purpose struct, using the png_ptr
|
|
* that libpng passed back to us (i.e., not a global this time--there's
|
|
* no real difference for a single image, but for a multithreaded browser
|
|
* decoding several PNG images at the same time, one needs to avoid mixing
|
|
* up different images' structs) */
|
|
|
|
mainprog_ptr = png_get_progressive_ptr(png_ptr);
|
|
|
|
if (mainprog_ptr == NULL) { /* we be hosed */
|
|
fprintf(stderr,
|
|
"readpng2 error: main struct not recoverable in info_callback.\n");
|
|
fflush(stderr);
|
|
return;
|
|
/*
|
|
* Alternatively, we could call our error-handler just like libpng
|
|
* does, which would effectively terminate the program. Since this
|
|
* can only happen if png_ptr gets redirected somewhere odd or the
|
|
* main PNG struct gets wiped, we're probably toast anyway. (If
|
|
* png_ptr itself is NULL, we would not have been called.)
|
|
*/
|
|
}
|
|
|
|
|
|
/* this is just like in the non-progressive case */
|
|
|
|
png_get_IHDR(png_ptr, info_ptr, &mainprog_ptr->width,
|
|
&mainprog_ptr->height, &bit_depth, &color_type, NULL, NULL, NULL);
|
|
|
|
|
|
/* since we know we've read all of the PNG file's "header" (i.e., up
|
|
* to IDAT), we can check for a background color here */
|
|
|
|
if (mainprog_ptr->need_bgcolor &&
|
|
png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
|
|
{
|
|
png_color_16p pBackground;
|
|
|
|
/* it is not obvious from the libpng documentation, but this function
|
|
* takes a pointer to a pointer, and it always returns valid red,
|
|
* green and blue values, regardless of color_type: */
|
|
png_get_bKGD(png_ptr, info_ptr, &pBackground);
|
|
|
|
/* however, it always returns the raw bKGD data, regardless of any
|
|
* bit-depth transformations, so check depth and adjust if necessary */
|
|
if (bit_depth == 16) {
|
|
mainprog_ptr->bg_red = pBackground->red >> 8;
|
|
mainprog_ptr->bg_green = pBackground->green >> 8;
|
|
mainprog_ptr->bg_blue = pBackground->blue >> 8;
|
|
} else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
|
|
if (bit_depth == 1)
|
|
mainprog_ptr->bg_red = mainprog_ptr->bg_green =
|
|
mainprog_ptr->bg_blue = pBackground->gray? 255 : 0;
|
|
else if (bit_depth == 2)
|
|
mainprog_ptr->bg_red = mainprog_ptr->bg_green =
|
|
mainprog_ptr->bg_blue = (255/3) * pBackground->gray;
|
|
else /* bit_depth == 4 */
|
|
mainprog_ptr->bg_red = mainprog_ptr->bg_green =
|
|
mainprog_ptr->bg_blue = (255/15) * pBackground->gray;
|
|
} else {
|
|
mainprog_ptr->bg_red = (uch)pBackground->red;
|
|
mainprog_ptr->bg_green = (uch)pBackground->green;
|
|
mainprog_ptr->bg_blue = (uch)pBackground->blue;
|
|
}
|
|
}
|
|
|
|
|
|
/* as before, let libpng expand palette images to RGB, low-bit-depth
|
|
* grayscale images to 8 bits, transparency chunks to full alpha channel;
|
|
* strip 16-bit-per-sample images to 8 bits per sample; and convert
|
|
* grayscale to RGB[A] */
|
|
|
|
if (color_type == PNG_COLOR_TYPE_PALETTE)
|
|
png_set_expand(png_ptr);
|
|
if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
|
|
png_set_expand(png_ptr);
|
|
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
|
|
png_set_expand(png_ptr);
|
|
if (bit_depth == 16)
|
|
png_set_strip_16(png_ptr);
|
|
if (color_type == PNG_COLOR_TYPE_GRAY ||
|
|
color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
|
|
png_set_gray_to_rgb(png_ptr);
|
|
|
|
|
|
/* Unlike the basic viewer, which was designed to operate on local files,
|
|
* this program is intended to simulate a web browser--even though we
|
|
* actually read from a local file, too. But because we are pretending
|
|
* that most of the images originate on the Internet, we follow the recom-
|
|
* mendation of the sRGB proposal and treat unlabelled images (no gAMA
|
|
* chunk) as existing in the sRGB color space. That is, we assume that
|
|
* such images have a file gamma of 0.45455, which corresponds to a PC-like
|
|
* display system. This change in assumptions will have no effect on a
|
|
* PC-like system, but on a Mac, SGI, NeXT or other system with a non-
|
|
* identity lookup table, it will darken unlabelled images, which effec-
|
|
* tively favors images from PC-like systems over those originating on
|
|
* the local platform. Note that mainprog_ptr->display_exponent is the
|
|
* "gamma" value for the entire display system, i.e., the product of
|
|
* LUT_exponent and CRT_exponent. */
|
|
|
|
if (png_get_gAMA(png_ptr, info_ptr, &gamma))
|
|
png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma);
|
|
else
|
|
png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455);
|
|
|
|
|
|
/* we'll let libpng expand interlaced images, too */
|
|
|
|
mainprog_ptr->passes = png_set_interlace_handling(png_ptr);
|
|
|
|
|
|
/* all transformations have been registered; now update info_ptr data and
|
|
* then get rowbytes and channels */
|
|
|
|
png_read_update_info(png_ptr, info_ptr);
|
|
|
|
mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr);
|
|
mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr);
|
|
|
|
|
|
/* Call the main program to allocate memory for the image buffer and
|
|
* initialize windows and whatnot. (The old-style function-pointer
|
|
* invocation is used for compatibility with a few supposedly ANSI
|
|
* compilers that nevertheless barf on "fn_ptr()"-style syntax.) */
|
|
|
|
(*mainprog_ptr->mainprog_init)();
|
|
|
|
|
|
/* and that takes care of initialization */
|
|
|
|
return;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
|
|
png_uint_32 row_num, int pass)
|
|
{
|
|
mainprog_info *mainprog_ptr;
|
|
|
|
|
|
/* first check whether the row differs from the previous pass; if not,
|
|
* nothing to combine or display */
|
|
|
|
if (!new_row)
|
|
return;
|
|
|
|
|
|
/* retrieve the pointer to our special-purpose struct so we can access
|
|
* the old rows and image-display callback function */
|
|
|
|
mainprog_ptr = png_get_progressive_ptr(png_ptr);
|
|
|
|
|
|
/* save the pass number for optional use by the front end */
|
|
|
|
mainprog_ptr->pass = pass;
|
|
|
|
|
|
/* have libpng either combine the new row data with the existing row data
|
|
* from previous passes (if interlaced) or else just copy the new row
|
|
* into the main program's image buffer */
|
|
|
|
png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num],
|
|
new_row);
|
|
|
|
|
|
/* finally, call the display routine in the main program with the number
|
|
* of the row we just updated */
|
|
|
|
(*mainprog_ptr->mainprog_display_row)(row_num);
|
|
|
|
|
|
/* and we're ready for more */
|
|
|
|
return;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr)
|
|
{
|
|
mainprog_info *mainprog_ptr;
|
|
|
|
|
|
/* retrieve the pointer to our special-purpose struct */
|
|
|
|
mainprog_ptr = png_get_progressive_ptr(png_ptr);
|
|
|
|
|
|
/* let the main program know that it should flush any buffered image
|
|
* data to the display now and set a "done" flag or whatever, but note
|
|
* that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do
|
|
* NOT call readpng2_cleanup() either here or in the finish_display()
|
|
* routine; wait until control returns to the main program via
|
|
* readpng2_decode_data() */
|
|
|
|
(*mainprog_ptr->mainprog_finish_display)();
|
|
|
|
|
|
/* all done */
|
|
|
|
return;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
void readpng2_cleanup(mainprog_info *mainprog_ptr)
|
|
{
|
|
png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
|
|
png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
|
|
|
|
if (png_ptr && info_ptr)
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
|
|
mainprog_ptr->png_ptr = NULL;
|
|
mainprog_ptr->info_ptr = NULL;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg)
|
|
{
|
|
mainprog_info *mainprog_ptr;
|
|
|
|
/* This function, aside from the extra step of retrieving the "error
|
|
* pointer" (below) and the fact that it exists within the application
|
|
* rather than within libpng, is essentially identical to libpng's
|
|
* default error handler. The second point is critical: since both
|
|
* setjmp() and longjmp() are called from the same code, they are
|
|
* guaranteed to have compatible notions of how big a jmp_buf is,
|
|
* regardless of whether _BSD_SOURCE or anything else has (or has not)
|
|
* been defined. */
|
|
|
|
fprintf(stderr, "readpng2 libpng error: %s\n", msg);
|
|
fflush(stderr);
|
|
|
|
mainprog_ptr = png_get_error_ptr(png_ptr);
|
|
if (mainprog_ptr == NULL) { /* we are completely hosed now */
|
|
fprintf(stderr,
|
|
"readpng2 severe error: jmpbuf not recoverable; terminating.\n");
|
|
fflush(stderr);
|
|
exit(99);
|
|
}
|
|
|
|
longjmp(mainprog_ptr->jmpbuf, 1);
|
|
}
|