workbench/libs/png/contrib/libtests/fakepng.c

   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
  13 void
  14 put_uLong(uLong val)
  15 {
  16    putchar(val >> 24);
  17    putchar(val >> 16);
  18    putchar(val >>  8);
  19    putchar(val >>  0);
  20 }
  21
  22 void
  23 put_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
  35 const unsigned char signature[] =
  36 {
  37    137, 80, 78, 71, 13, 10, 26, 10
  38 };
  39
  40 const 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
  52 const unsigned char unknown[] =
  53 {
  54    'u', 'n', 'K', 'n' /* "unKn" - private safe to copy */
  55 };
  56
  57 int
  58 main(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 }