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#include <stdio.h>
#include <stdlib.h>
#include <png.h>
#if 0
#define LOG(x...) fprintf(stderr,"error: " x)
#else
#define LOG(x...) do {} while (0)
#endif
void *loadpng(const char *fn, unsigned *_width, unsigned *_height)
{
FILE *fp = 0;
unsigned char header[8];
unsigned char *data = 0;
unsigned char **rowptrs = 0;
png_structp p = 0;
png_infop pi = 0;
png_uint_32 width, height;
int bitdepth, colortype, imethod, cmethod, fmethod, i;
p = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if(p == 0) {
LOG("%s: failed to allocate png read struct\n", fn);
return 0;
}
pi = png_create_info_struct(p);
if(pi == 0) {
LOG("%s: failed to allocate png info struct\n", fn);
goto oops;
}
fp = fopen(fn, "rb");
if(fp == 0) {
LOG("%s: failed to open file\n", fn);
return 0;
}
if(fread(header, 8, 1, fp) != 1) {
LOG("%s: failed to read header\n", fn);
goto oops;
}
if(png_sig_cmp(header, 0, 8)) {
LOG("%s: header is not a PNG header\n", fn);
goto oops;
}
if(setjmp(png_jmpbuf(p))) {
LOG("%s: png library error\n", fn);
oops:
png_destroy_read_struct(&p, &pi, 0);
if(fp != 0) fclose(fp);
if(data != 0) free(data);
if(rowptrs != 0) free(rowptrs);
return 0;
}
png_init_io(p, fp);
png_set_sig_bytes(p, 8);
png_read_info(p, pi);
png_get_IHDR(p, pi, &width, &height, &bitdepth, &colortype,
&imethod, &cmethod, &fmethod);
// printf("PNG: %d x %d (d=%d, c=%d)\n",
// width, height, bitdepth, colortype);
switch(colortype){
case PNG_COLOR_TYPE_PALETTE:
png_set_palette_to_rgb(p);
break;
case PNG_COLOR_TYPE_RGB:
if(png_get_valid(p, pi, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(p);
} else {
png_set_filler(p, 0xff, PNG_FILLER_AFTER);
}
break;
case PNG_COLOR_TYPE_RGB_ALPHA:
break;
case PNG_COLOR_TYPE_GRAY:
if(bitdepth < 8) {
png_set_gray_1_2_4_to_8(p);
}
default:
LOG("%s: unsupported (grayscale?) color type\n");
goto oops;
}
if(bitdepth == 16) {
png_set_strip_16(p);
}
data = (unsigned char*) malloc((width * 4) * height);
rowptrs = (unsigned char **) malloc(sizeof(unsigned char*) * height);
if((data == 0) || (rowptrs == 0)){
LOG("could not allocate data buffer\n");
goto oops;
}
for(i = 0; i < height; i++) {
rowptrs[i] = data + ((width * 4) * i);
}
png_read_image(p, rowptrs);
png_destroy_read_struct(&p, &pi, 0);
fclose(fp);
if(rowptrs != 0) free(rowptrs);
*_width = width;
*_height = height;
return (void*) data;
}
typedef struct
{
const unsigned char* base;
const unsigned char* end;
const unsigned char* cursor;
} PngReader;
static void
png_reader_read_data( png_structp png_ptr,
png_bytep data,
png_size_t length )
{
PngReader* reader = png_get_io_ptr(png_ptr);
png_size_t avail = (png_size_t)(reader->end - reader->cursor);
if (avail > length)
avail = length;
memcpy( data, reader->cursor, avail );
reader->cursor += avail;
}
void *readpng(const unsigned char *base, size_t size, unsigned *_width, unsigned *_height)
{
PngReader reader;
unsigned char *data = 0;
unsigned char **rowptrs = 0;
png_structp p = 0;
png_infop pi = 0;
png_uint_32 width, height;
int bitdepth, colortype, imethod, cmethod, fmethod, i;
p = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if(p == 0) {
LOG("%s: failed to allocate png read struct\n", fn);
return 0;
}
pi = png_create_info_struct(p);
if(pi == 0) {
LOG("%s: failed to allocate png info struct\n", fn);
goto oops;
}
reader.base = base;
reader.end = base + size;
reader.cursor = base;
if(size < 8 || png_sig_cmp((unsigned char*)base, 0, 8)) {
LOG("%s: header is not a PNG header\n", fn);
goto oops;
}
reader.cursor += 8;
if(setjmp(png_jmpbuf(p))) {
LOG("%s: png library error\n", fn);
oops:
png_destroy_read_struct(&p, &pi, 0);
if(data != 0) free(data);
if(rowptrs != 0) free(rowptrs);
return 0;
}
png_set_read_fn (p, &reader, png_reader_read_data);
png_set_sig_bytes(p, 8);
png_read_info(p, pi);
png_get_IHDR(p, pi, &width, &height, &bitdepth, &colortype,
&imethod, &cmethod, &fmethod);
// printf("PNG: %d x %d (d=%d, c=%d)\n",
// width, height, bitdepth, colortype);
switch(colortype){
case PNG_COLOR_TYPE_PALETTE:
png_set_palette_to_rgb(p);
break;
case PNG_COLOR_TYPE_RGB:
if(png_get_valid(p, pi, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(p);
} else {
png_set_filler(p, 0xff, PNG_FILLER_AFTER);
}
break;
case PNG_COLOR_TYPE_RGB_ALPHA:
break;
case PNG_COLOR_TYPE_GRAY:
if(bitdepth < 8) {
png_set_gray_1_2_4_to_8(p);
}
default:
LOG("%s: unsupported (grayscale?) color type\n");
goto oops;
}
if(bitdepth == 16) {
png_set_strip_16(p);
}
data = (unsigned char*) malloc((width * 4) * height);
rowptrs = (unsigned char **) malloc(sizeof(unsigned char*) * height);
if((data == 0) || (rowptrs == 0)){
LOG("could not allocate data buffer\n");
goto oops;
}
for(i = 0; i < height; i++) {
rowptrs[i] = data + ((width * 4) * i);
}
png_read_image(p, rowptrs);
png_destroy_read_struct(&p, &pi, 0);
if(rowptrs != 0) free(rowptrs);
*_width = width;
*_height = height;
return (void*) data;
}
#if 0
int main(int argc, char **argv)
{
unsigned w,h;
unsigned char *data;
if(argc < 2) return 0;
data = loadpng(argv[1], &w, &h);
if(data != 0) {
printf("w: %d h: %d\n", w, h);
}
return 0;
}
#endif
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