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}