fakepng.c
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/* Fake a PNG - just write it out directly.
*
* COPYRIGHT: Written by John Cunningham Bowler, 2014.
* To the extent possible under law, the author has waived all copyright and
* related or neighboring rights to this work. This work is published from:
* United States.
*
*/
#include <stdio.h>
#include <zlib.h> /* for crc32 */
void
put_uLong(uLong val)
{
putchar(val >> 24);
putchar(val >> 16);
putchar(val >> 8);
putchar(val >> 0);
}
void
put_chunk(const unsigned char *chunk, uInt length)
{
uLong crc;
put_uLong(length-4); /* Exclude the tag */
fwrite(chunk, length, 1, stdout);
crc = crc32(0, Z_NULL, 0);
put_uLong(crc32(crc, chunk, length));
}
const unsigned char signature[] =
{
137, 80, 78, 71, 13, 10, 26, 10
};
const unsigned char IHDR[] =
{
73, 72, 68, 82, /* IHDR */
0, 0, 0, 1, /* width */
0, 0, 0, 1, /* height */
1, /* bit depth */
0, /* color type: greyscale */
0, /* compression method */
0, /* filter method */
0 /* interlace method: none */
};
const unsigned char unknown[] =
{
'u', 'n', 'K', 'n' /* "unKn" - private safe to copy */
};
int
main(void)
{
fwrite(signature, sizeof signature, 1, stdout);
put_chunk(IHDR, sizeof IHDR);
for (;;)
put_chunk(unknown, sizeof unknown);
}