share/png/contrib/libtests/fakepng.c

   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 }