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#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.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_GRAY,
COLOR_TRUE = 2,
COLOR_INDEXED,
COLOR_GRAY_ALPHA,
COLOR_TRUE_ALPHA=6
};
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);
}
typedef uint8_t (*filter_fun)(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x);
typedef uint32_t (*pixel_fun)(uint8_t **cur, uint8_t **last, uint8_t bpp, uint32_t x, filter_fun);
static uint8_t filter_none(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x)
{
return *cur;
}
static uint8_t filter_sub(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x)
{
if (x) {
return *cur + *(cur - bpp);
} else {
return *cur;
}
}
static uint8_t filter_up(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x)
{
if (last) {
return *cur + *last;
} else {
return *cur;
}
}
static uint8_t filter_avg(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x)
{
uint8_t prev = x ? *(cur - bpp) : 0;
uint8_t prior = last ? *last : 0;
return *cur + ((prev + prior) >> 1);
}
static uint8_t paeth(uint8_t a, uint8_t b, uint8_t c)
{
int32_t p = a + b - c;
int32_t pa = abs(p - a);
int32_t pb = abs(p - b);
int32_t pc = abs(p - c);
if (pa <= pb && pa <= pc) {
return a;
}
if (pb <= pc) {
return b;
}
return c;
}
static uint8_t filter_paeth(uint8_t *cur, uint8_t *last, uint8_t bpp, uint32_t x)
{
uint8_t prev, prev_prior;
if (x) {
prev = *(cur - bpp);
prev_prior = *(last - bpp);
} else {
prev = prev_prior = 0;
}
uint8_t prior = last ? *last : 0;
return *cur + paeth(prev, prior, prev_prior);
}
static uint32_t pixel_gray(uint8_t **cur, uint8_t **last, uint8_t bpp, uint32_t x, filter_fun filter)
{
uint8_t value = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
return 0xFF000000 | value << 16 | value << 8 | value;
}
static uint32_t pixel_true(uint8_t **cur, uint8_t **last, uint8_t bpp, uint32_t x, filter_fun filter)
{
uint8_t red = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t green = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t blue = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
return 0xFF000000 | red << 16 | green << 8 | blue;
}
static uint32_t pixel_gray_alpha(uint8_t **cur, uint8_t **last, uint8_t bpp, uint32_t x, filter_fun filter)
{
uint8_t value = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t alpha = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
return alpha << 24 | value << 16 | value << 8 | value;
}
static uint32_t pixel_true_alpha(uint8_t **cur, uint8_t **last, uint8_t bpp, uint32_t x, filter_fun filter)
{
uint8_t red = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t green = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t blue = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
uint8_t alpha = filter(*cur, *last, bpp, x);
(*cur)++;
if (*last) {
(*last)++;
}
return alpha << 24 | red << 16 | green << 8 | blue;
}
static filter_fun filters[] = {filter_none, filter_sub, filter_up, filter_avg, filter_paeth};
#define MIN_CHUNK_SIZE 12
#define MIN_IHDR_SIZE 0xD
#define MAX_SUPPORTED_DIM 32767 //chosen to avoid possibility of overflow when calculating uncompressed size
uint32_t *load_png(uint8_t *buffer, uint32_t buf_size, uint32_t *width, uint32_t *height)
{
if (buf_size < sizeof(png_magic) || memcmp(buffer, png_magic, sizeof(png_magic))) {
return NULL;
}
uint32_t cur = sizeof(png_magic);
uint8_t has_header = 0;
uint8_t bits, color_type, comp_type, filter_type, interlace;
uint8_t *idat_buf = NULL;
uint8_t idat_needs_free = 0;
uint32_t idat_size;
uint32_t *out = NULL;
uint32_t *palette = NULL;
while(cur + MIN_CHUNK_SIZE <= buf_size)
{
uint32_t chunk_size = buffer[cur++] << 24;
chunk_size |= buffer[cur++] << 16;
chunk_size |= buffer[cur++] << 8;
chunk_size |= buffer[cur++];
if (!memcmp(ihdr, buffer + cur, sizeof(ihdr))) {
if (chunk_size < MIN_IHDR_SIZE || cur + MIN_IHDR_SIZE > buf_size) {
return NULL;
}
cur += sizeof(ihdr);
*width = buffer[cur++] << 24;
*width |= buffer[cur++] << 16;
*width |= buffer[cur++] << 8;
*width |= buffer[cur++];
*height = buffer[cur++] << 24;
*height |= buffer[cur++] << 16;
*height |= buffer[cur++] << 8;
*height |= buffer[cur++];
if (*width > MAX_SUPPORTED_DIM || *height > MAX_SUPPORTED_DIM) {
return NULL;
}
bits = buffer[cur++];
if (bits != 8) {
//only support 8-bits per element for now
return NULL;
}
color_type = buffer[cur++];
if (color_type > COLOR_TRUE_ALPHA || color_type == 1 || color_type == 5) {
//reject invalid color type
return NULL;
}
comp_type = buffer[cur++];
if (comp_type) {
//only compression type 0 is defined by the spec
return NULL;
}
filter_type = buffer[cur++];
interlace = buffer[cur++];
if (interlace) {
//interlacing not supported for now
return NULL;
}
cur += chunk_size - MIN_IHDR_SIZE;
has_header = 1;
} else {
if (!has_header) {
//IHDR is required to be the first chunk, fail if it isn't
break;
}
if (!memcmp(plte, buffer + cur, sizeof(plte))) {
//TODO: implement paletted images
} else if (!memcmp(idat, buffer + cur, sizeof(idat))) {
cur += sizeof(idat);
if (idat_buf) {
if (idat_needs_free) {
idat_buf = realloc(idat_buf, idat_size + chunk_size);
} else {
uint8_t *tmp = idat_buf;
idat_buf = malloc(idat_size + chunk_size);
memcpy(idat_buf, tmp, idat_size);
}
memcpy(idat_buf + idat_size, buffer + cur, chunk_size);
idat_size += chunk_size;
} else {
idat_buf = buffer + cur;
idat_size = chunk_size;
}
cur += chunk_size;
} else if (!memcmp(iend, buffer + cur, sizeof(iend))) {
if (!idat_buf) {
break;
}
if (!palette && color_type == COLOR_INDEXED) {
//indexed color, but no PLTE chunk found
return NULL;
}
uLongf uncompressed_size = *width * *height;
uint8_t bpp;
pixel_fun pixel;
switch (color_type)
{
case COLOR_GRAY:
uncompressed_size *= bits / 8;
bpp = bits/8;
pixel = pixel_gray;
break;
case COLOR_TRUE:
uncompressed_size *= 3 * bits / 8;
bpp = 3 * bits/8;
pixel = pixel_true;
break;
case COLOR_INDEXED: {
uint32_t pixels_per_byte = 8 / bits;
uncompressed_size = (*width / pixels_per_byte) * *height;
if (*width % pixels_per_byte) {
uncompressed_size += *height;
}
bpp = 1;
break;
}
case COLOR_GRAY_ALPHA:
uncompressed_size *= bits / 4;
bpp = bits / 4;
pixel = pixel_gray_alpha;
break;
case COLOR_TRUE_ALPHA:
uncompressed_size *= bits / 2;
bpp = bits / 2;
pixel = pixel_true_alpha;
break;
}
//add filter type byte
uncompressed_size += *height;
uint8_t *decomp_buffer = malloc(uncompressed_size);
if (Z_OK != uncompress(decomp_buffer, &uncompressed_size, idat_buf, idat_size)) {
free(decomp_buffer);
break;
}
out = calloc(*width * *height, sizeof(uint32_t));
uint32_t *cur_pixel = out;
uint8_t *cur_byte = decomp_buffer;
uint8_t *last_line = NULL;
for (uint32_t y = 0; y < *height; y++)
{
uint8_t filter_type = *(cur_byte++);
if (filter_type >= sizeof(filters)/sizeof(*filters)) {
free(out);
out = NULL;
free(decomp_buffer);
break;
}
filter_fun filter = filters[filter_type];
uint8_t *line_start = cur_byte;
for (uint32_t x = 0; x < *width; x++)
{
*(cur_pixel++) = pixel(&cur_byte, &last_line, bpp, x, filter);
}
last_line = line_start;
}
free(decomp_buffer);
} else {
//skip uncrecognized chunks
cur += 4 + chunk_size;
}
}
//skip CRC for now
cur += sizeof(uint32_t);
}
if (idat_needs_free) {
free(idat_buf);
}
free(palette);
return out;
}
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