function create_png($gzimage, $width, $height)
{
// SIG
$image = pack('C8', 137, 80, 78, 71, 13, 10, 26, 10);
// IHDR
$raw = pack('C4', $width >> 24, $width >> 16, $width >> 8, $width);
$raw .= pack('C4', $height >> 24, $height >> 16, $height >> 8, $height);
$raw .= pack('C5', 8, 0, 0, 0, 0);
$image .= png_chunk(13, 'IHDR', $raw);
// IDAT
$image .= png_chunk(strlen($gzimage), 'IDAT', $gzimage);
// IEND
$image .= png_chunk(0, 'IEND', '');
return $image;
}
function create_png($raw_image, $width, $height)
{
// SIG
$image = pack('C8', 137, 80, 78, 71, 13, 10, 26, 10);
// IHDR
$raw = pack('C4', $width >> 24, $width >> 16, $width >> 8, $width);
$raw .= pack('C4', $height >> 24, $height >> 16, $height >> 8, $height);
$raw .= pack('C5', 8, 0, 0, 0, 0);
$image .= png_chunk(13, 'IHDR', $raw);
if (@extension_loaded('zlib')) {
$raw_image = gzcompress($raw_image);
$length = strlen($raw_image);
} else {
// The total length of this image, uncompressed, is just a calculation of pixels
$length = ($width + 1) * $height;
// Adler-32 hash generation
// Optimized Adler-32 loop ported from the GNU Classpath project
$temp_length = $length;
$s1 = 1;
$s2 = $index = 0;
while ($temp_length > 0) {
// We can defer the modulo operation:
// s1 maximally grows from 65521 to 65521 + 255 * 3800
// s2 maximally grows by 3800 * median(s1) = 2090079800 < 2^31
$substract_value = $temp_length < 3800 ? $temp_length : 3800;
$temp_length -= $substract_value;
while (--$substract_value >= 0) {
$s1 += ord($raw_image[$index]);
$s2 += $s1;
$index++;
}
$s1 %= 65521;
$s2 %= 65521;
}
$adler_hash = pack('N', $s2 << 16 | $s1);
// This is the same thing as gzcompress($raw_image, 0) but does not need zlib
$raw_image = pack('C3v2', 0x78, 0x1, 0x1, $length, ~$length) . $raw_image . $adler_hash;
// The Zlib header + Adler hash make us add on 11
$length += 11;
}
// IDAT
$image .= png_chunk($length, 'IDAT', $raw_image);
// IEND
$image .= png_chunk(0, 'IEND', '');
return $image;
}
