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#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include "zlib/zlib.h"
static const char png_magic[] = {0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n'};
static const char ihdr[] = {'I', 'H', 'D', 'R'};
static const char plte[] = {'P', 'L', 'T', 'E'};
static const char idat[] = {'I', 'D', 'A', 'T'};
static const char iend[] = {'I', 'E', 'N', 'D'};
enum {
COLOR_TRUE = 2,
COLOR_INDEXED
};
static void write_chunk(FILE *f, const char*id, uint8_t *buffer, uint32_t size)
{
uint8_t tmp[4] = {size >> 24, size >> 16, size >> 8, size};
uint8_t warn = 0;
warn = warn || (sizeof(tmp) != fwrite(tmp, 1, sizeof(tmp), f));
warn = warn || (4 != fwrite(id, 1, 4, f));
if (size) {
warn = warn || (size != fwrite(buffer, 1, size, f));
}
uint32_t crc = crc32(0, NULL, 0);
crc = crc32(crc, id, 4);
if (size) {
crc = crc32(crc, buffer, size);
}
tmp[0] = crc >> 24;
tmp[1] = crc >> 16;
tmp[2] = crc >> 8;
tmp[3] = crc;
warn = warn || (sizeof(tmp) != fwrite(tmp, 1, sizeof(tmp), f));
if (warn) {
fprintf(stderr, "Failure during write of %c%c%c%c chunk\n", id[0], id[1], id[2], id[3]);
}
}
static void write_header(FILE *f, uint32_t width, uint32_t height, uint8_t color_type)
{
uint8_t chunk[13] = {
width >> 24, width >> 16, width >> 8, width,
height >> 24, height >> 16, height >> 8, height,
8, color_type, 0, 0, 0
};
if (sizeof(png_magic) != fwrite(png_magic, 1, sizeof(png_magic), f)) {
fputs("Error writing PNG magic\n", stderr);
}
write_chunk(f, ihdr, chunk, sizeof(chunk));
}
void save_png24(FILE *f, uint32_t *buffer, uint32_t width, uint32_t height, uint32_t pitch)
{
uint32_t idat_size = (1 + width*3) * height;
uint8_t *idat_buffer = malloc(idat_size);
uint32_t *pixel = buffer;
uint8_t *cur = idat_buffer;
for (uint32_t y = 0; y < height; y++)
{
//save filter type
*(cur++) = 0;
uint32_t *start = pixel;
for (uint32_t x = 0; x < width; x++, pixel++)
{
uint32_t value = *pixel;
*(cur++) = value >> 16;
*(cur++) = value >> 8;
*(cur++) = value;
}
pixel = start + pitch / sizeof(uint32_t);
}
write_header(f, width, height, COLOR_TRUE);
uLongf compress_buffer_size = idat_size + 5 * (idat_size/16383 + 1) + 3;
uint8_t *compressed = malloc(compress_buffer_size);
compress(compressed, &compress_buffer_size, idat_buffer, idat_size);
free(idat_buffer);
write_chunk(f, idat, compressed, compress_buffer_size);
write_chunk(f, iend, NULL, 0);
free(compressed);
}
void save_png(FILE *f, uint32_t *buffer, uint32_t width, uint32_t height, uint32_t pitch)
{
uint32_t palette[256];
uint8_t pal_buffer[256*3];
uint32_t num_pal = 0;
uint32_t index_size = (1 + width) * height;
uint8_t *index_buffer = malloc(index_size);
uint8_t *cur = index_buffer;
uint32_t *pixel = buffer;
for (uint32_t y = 0; y < height; y++)
{
//save filter type
*(cur++) = 0;
uint32_t *start = pixel;
for (uint32_t x = 0; x < width; x++, pixel++, cur++)
{
uint32_t value = (*pixel) & 0xFFFFFF;
uint32_t i;
for (i = 0; i < num_pal; i++)
{
if (palette[i] == value) {
break;
}
}
if (i == num_pal) {
if (num_pal == 256) {
free(index_buffer);
save_png24(f, buffer, width, height, pitch);
return;
}
palette[i] = value;
num_pal++;
}
*cur = i;
}
pixel = start + pitch / sizeof(uint32_t);
}
write_header(f, width, height, COLOR_INDEXED);
cur = pal_buffer;
for (uint32_t i = 0; i < num_pal; i++)
{
*(cur++) = palette[i] >> 16;
*(cur++) = palette[i] >> 8;
*(cur++) = palette[i];
}
write_chunk(f, plte, pal_buffer, num_pal * 3);
uLongf compress_buffer_size = index_size + 5 * (index_size/16383 + 1) + 3;
uint8_t *compressed = malloc(compress_buffer_size);
compress(compressed, &compress_buffer_size, index_buffer, index_size);
free(index_buffer);
write_chunk(f, idat, compressed, compress_buffer_size);
write_chunk(f, iend, NULL, 0);
free(compressed);
}
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