Chris Craik | ca2bf81 | 2013-07-29 15:28:30 -0700 | [diff] [blame] | 1 | /* Fake a PNG - just write it out directly. */ |
| 2 | #include <stdio.h> |
| 3 | #include <zlib.h> /* for crc32 */ |
| 4 | |
| 5 | void |
| 6 | put_uLong(uLong val) |
| 7 | { |
| 8 | putchar(val >> 24); |
| 9 | putchar(val >> 16); |
| 10 | putchar(val >> 8); |
| 11 | putchar(val >> 0); |
| 12 | } |
| 13 | |
| 14 | void |
| 15 | put_chunk(const unsigned char *chunk, uInt length) |
| 16 | { |
| 17 | uLong crc; |
| 18 | |
| 19 | put_uLong(length-4); /* Exclude the tag */ |
| 20 | |
| 21 | fwrite(chunk, length, 1, stdout); |
| 22 | |
| 23 | crc = crc32(0, Z_NULL, 0); |
| 24 | put_uLong(crc32(crc, chunk, length)); |
| 25 | } |
| 26 | |
| 27 | const unsigned char signature[] = |
| 28 | { |
| 29 | 137, 80, 78, 71, 13, 10, 26, 10 |
| 30 | }; |
| 31 | |
| 32 | const unsigned char IHDR[] = |
| 33 | { |
| 34 | 73, 72, 68, 82, /* IHDR */ |
| 35 | 0, 0, 0, 1, /* width */ |
| 36 | 0, 0, 0, 1, /* height */ |
| 37 | 1, /* bit depth */ |
| 38 | 0, /* color type: greyscale */ |
| 39 | 0, /* compression method */ |
| 40 | 0, /* filter method */ |
| 41 | 0 /* interlace method: none */ |
| 42 | }; |
| 43 | |
| 44 | const unsigned char unknown[] = |
| 45 | { |
| 46 | 'u', 'n', 'K', 'n' /* "unKn" - private safe to copy */ |
| 47 | }; |
| 48 | |
| 49 | int |
| 50 | main(void) |
| 51 | { |
| 52 | fwrite(signature, sizeof signature, 1, stdout); |
| 53 | put_chunk(IHDR, sizeof IHDR); |
| 54 | |
| 55 | for(;;) |
| 56 | put_chunk(unknown, sizeof unknown); |
| 57 | } |