276 lines
8.4 KiB
C
276 lines
8.4 KiB
C
/*---------------------------------------------------------------------------
|
|
|
|
rpng - simple PNG display program readpng.c
|
|
|
|
---------------------------------------------------------------------------
|
|
|
|
Copyright (c) 1998-1999 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 <stdio.h>
|
|
#include <stdlib.h>
|
|
|
|
#include "png.h" /* libpng header; includes zlib.h */
|
|
#include "readpng.h" /* typedefs, common macros, public prototypes */
|
|
|
|
|
|
static png_structp png_ptr = NULL;
|
|
static png_infop info_ptr = NULL;
|
|
|
|
png_uint_32 width, height;
|
|
int bit_depth, color_type;
|
|
uch *image_data = NULL;
|
|
|
|
|
|
void readpng_version_info()
|
|
{
|
|
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);
|
|
}
|
|
|
|
|
|
/* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */
|
|
|
|
int readpng_init(FILE *infile, long *pWidth, long *pHeight)
|
|
{
|
|
uch sig[8];
|
|
|
|
|
|
/* first do a quick check that the file really is a PNG image; could
|
|
* have used slightly more general png_sig_cmp() function instead */
|
|
|
|
fread(sig, 1, 8, infile);
|
|
if (!png_check_sig(sig, 8))
|
|
return 1; /* bad signature */
|
|
|
|
|
|
/* could pass pointers to user-defined error handlers instead of NULLs: */
|
|
|
|
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, 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 */
|
|
|
|
if (setjmp(png_jmp_env(png_ptr))) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
return 2;
|
|
}
|
|
|
|
|
|
png_init_io(png_ptr, infile);
|
|
png_set_sig_bytes(png_ptr, 8); /* we already read the 8 signature bytes */
|
|
|
|
png_read_info(png_ptr, info_ptr); /* read all PNG info up to image data */
|
|
|
|
|
|
/* alternatively, could make separate calls to png_get_image_width(),
|
|
* etc., but want bit_depth and color_type for later [don't care about
|
|
* compression_type and filter_type => NULLs] */
|
|
|
|
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
|
|
NULL, NULL, NULL);
|
|
*pWidth = width;
|
|
*pHeight = height;
|
|
|
|
|
|
/* OK, that's all we need for now; return happy */
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
|
|
/* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error;
|
|
* scales values to 8-bit if necessary */
|
|
|
|
int readpng_get_bgcolor(uch *red, uch *green, uch *blue)
|
|
{
|
|
png_color_16p pBackground;
|
|
|
|
|
|
/* setjmp() must be called in every function that calls a PNG-reading
|
|
* libpng function */
|
|
|
|
if (setjmp(png_jmp_env(png_ptr))) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
return 2;
|
|
}
|
|
|
|
|
|
if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
|
|
return 1;
|
|
|
|
/* 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) {
|
|
*red = pBackground->red >> 8;
|
|
*green = pBackground->green >> 8;
|
|
*blue = pBackground->blue >> 8;
|
|
} else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
|
|
if (bit_depth == 1)
|
|
*red = *green = *blue = pBackground->gray? 255 : 0;
|
|
else if (bit_depth == 2)
|
|
*red = *green = *blue = (255/3) * pBackground->gray;
|
|
else /* bit_depth == 4 */
|
|
*red = *green = *blue = (255/15) * pBackground->gray;
|
|
} else {
|
|
*red = (uch)pBackground->red;
|
|
*green = (uch)pBackground->green;
|
|
*blue = (uch)pBackground->blue;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
|
|
/* display_exponent == LUT_exponent * CRT_exponent */
|
|
|
|
uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes)
|
|
{
|
|
double gamma;
|
|
png_uint_32 i, rowbytes;
|
|
png_bytepp row_pointers = NULL;
|
|
|
|
|
|
/* setjmp() must be called in every function that calls a PNG-reading
|
|
* libpng function */
|
|
|
|
if (setjmp(png_jmp_env(png_ptr))) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
return NULL;
|
|
}
|
|
|
|
|
|
/* 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 example in the libpng documentation, we have *no* idea where
|
|
* this file may have come from--so if it doesn't have a file gamma, don't
|
|
* do any correction ("do no harm") */
|
|
|
|
if (png_get_gAMA(png_ptr, info_ptr, &gamma))
|
|
png_set_gamma(png_ptr, display_exponent, gamma);
|
|
|
|
|
|
/* all transformations have been registered; now update info_ptr data,
|
|
* get rowbytes and channels, and allocate image memory */
|
|
|
|
png_read_update_info(png_ptr, info_ptr);
|
|
|
|
*pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr);
|
|
*pChannels = (int)png_get_channels(png_ptr, info_ptr);
|
|
|
|
if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
return NULL;
|
|
}
|
|
if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
free(image_data);
|
|
image_data = NULL;
|
|
return NULL;
|
|
}
|
|
|
|
Trace((stderr, "readpng_get_image: rowbytes = %ld, height = %ld\n", rowbytes, height));
|
|
|
|
|
|
/* set the individual row_pointers to point at the correct offsets */
|
|
|
|
for (i = 0; i < height; ++i)
|
|
row_pointers[i] = image_data + i*rowbytes;
|
|
|
|
|
|
/* now we can go ahead and just read the whole image */
|
|
|
|
png_read_image(png_ptr, row_pointers);
|
|
|
|
|
|
/* and we're done! (png_read_end() can be omitted if no processing of
|
|
* post-IDAT text/time/etc. is desired) */
|
|
|
|
free(row_pointers);
|
|
row_pointers = NULL;
|
|
|
|
png_read_end(png_ptr, NULL);
|
|
|
|
return image_data;
|
|
}
|
|
|
|
|
|
void readpng_cleanup(int free_image_data)
|
|
{
|
|
if (free_image_data && image_data) {
|
|
free(image_data);
|
|
image_data = NULL;
|
|
}
|
|
|
|
if (png_ptr && info_ptr) {
|
|
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
|
|
png_ptr = NULL;
|
|
info_ptr = NULL;
|
|
}
|
|
}
|