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/* Copyright (C) 2018 Curtis McEnroe <june@causal.agency>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <arpa/inet.h>
#include <err.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <zlib.h>
enum {
PNGGrayscale,
PNGTruecolor = 2,
PNGIndexed,
PNGAlpha,
};
enum {
PNGNone,
PNGSub,
PNGUp,
PNGAverage,
PNGPaeth,
};
static uint32_t pngCRC;
static inline void pngWrite(FILE *file, const void *ptr, size_t len) {
if (!fwrite(ptr, len, 1, file)) err(EX_IOERR, "pngWrite");
pngCRC = crc32(pngCRC, ptr, len);
}
static inline void pngInt32(FILE *file, uint32_t n) {
n = htonl(n);
pngWrite(file, &n, 4);
}
static inline void pngChunk(FILE *file, char type[static 4], uint32_t len) {
pngInt32(file, len);
pngCRC = crc32(0, Z_NULL, 0);
pngWrite(file, type, 4);
}
static inline void pngHead(
FILE *file, uint32_t width, uint32_t height, uint8_t depth, uint8_t color
) {
pngWrite(file, "\x89PNG\r\n\x1A\n", 8);
pngChunk(file, "IHDR", 13);
pngInt32(file, width);
pngInt32(file, height);
pngWrite(file, &depth, 1);
pngWrite(file, &color, 1);
pngWrite(file, "\0\0\0", 3);
pngInt32(file, pngCRC);
}
static inline void pngPalette(FILE *file, const uint8_t *pal, uint32_t len) {
pngChunk(file, "PLTE", len);
pngWrite(file, pal, len);
pngInt32(file, pngCRC);
}
static inline void pngData(FILE *file, const uint8_t *data, uint32_t len) {
uLong zlen = compressBound(len);
uint8_t *zdata = malloc(zlen);
if (!zlen) err(EX_OSERR, "malloc");
int error = compress(zdata, &zlen, data, len);
if (error != Z_OK) errx(EX_SOFTWARE, "compress: %d", error);
pngChunk(file, "IDAT", zlen);
pngWrite(file, zdata, zlen);
pngInt32(file, pngCRC);
free(zdata);
}
static inline void pngTail(FILE *file) {
pngChunk(file, "IEND", 0);
pngInt32(file, pngCRC);
}
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