1/* Fake a PNG - just write it out directly. 2 * 3 * COPYRIGHT: Written by John Cunningham Bowler, 2014. 4 * To the extent possible under law, the author has waived all copyright and 5 * related or neighboring rights to this work. This work is published from: 6 * United States. 7 * 8 */ 9 10#include <stdio.h> 11#include <zlib.h> /* for crc32 */ 12 13void 14put_uLong(uLong val) 15{ 16 putchar(val >> 24); 17 putchar(val >> 16); 18 putchar(val >> 8); 19 putchar(val >> 0); 20} 21 22void 23put_chunk(const unsigned char *chunk, uInt length) 24{ 25 uLong crc; 26 27 put_uLong(length-4); /* Exclude the tag */ 28 29 fwrite(chunk, length, 1, stdout); 30 31 crc = crc32(0, Z_NULL, 0); 32 put_uLong(crc32(crc, chunk, length)); 33} 34 35const unsigned char signature[] = 36{ 37 137, 80, 78, 71, 13, 10, 26, 10 38}; 39 40const unsigned char IHDR[] = 41{ 42 73, 72, 68, 82, /* IHDR */ 43 0, 0, 0, 1, /* width */ 44 0, 0, 0, 1, /* height */ 45 1, /* bit depth */ 46 0, /* color type: greyscale */ 47 0, /* compression method */ 48 0, /* filter method */ 49 0 /* interlace method: none */ 50}; 51 52const unsigned char unknown[] = 53{ 54 'u', 'n', 'K', 'n' /* "unKn" - private safe to copy */ 55}; 56 57int 58main(void) 59{ 60 fwrite(signature, sizeof signature, 1, stdout); 61 put_chunk(IHDR, sizeof IHDR); 62 63 for (;;) 64 put_chunk(unknown, sizeof unknown); 65} 66