/**
* Extract info from a PNG file without using the GD library.
* @param $file (string) image file to parse
* @return array structure containing the image data
* @public static
*/
public static function _parsepng($file)
{
$f = fopen($file, 'rb');
if ($f === false) {
// Can't open image file
return false;
}
//Check signature
if (fread($f, 8) != chr(137) . 'PNG' . chr(13) . chr(10) . chr(26) . chr(10)) {
// Not a PNG file
return false;
}
//Read header chunk
fread($f, 4);
if (fread($f, 4) != 'IHDR') {
//Incorrect PNG file
return false;
}
$w = TcpdfStatic::_freadint($f);
$h = TcpdfStatic::_freadint($f);
$bpc = ord(fread($f, 1));
$ct = ord(fread($f, 1));
if ($ct == 0) {
$colspace = 'DeviceGray';
} elseif ($ct == 2) {
$colspace = 'DeviceRGB';
} elseif ($ct == 3) {
$colspace = 'Indexed';
} else {
// alpha channel
fclose($f);
return 'pngalpha';
}
if (ord(fread($f, 1)) != 0) {
// Unknown compression method
fclose($f);
return false;
}
if (ord(fread($f, 1)) != 0) {
// Unknown filter method
fclose($f);
return false;
}
if (ord(fread($f, 1)) != 0) {
// Interlacing not supported
fclose($f);
return false;
}
fread($f, 4);
$channels = $ct == 2 ? 3 : 1;
$parms = '/DecodeParms << /Predictor 15 /Colors ' . $channels . ' /BitsPerComponent ' . $bpc . ' /Columns ' . $w . ' >>';
//Scan chunks looking for palette, transparency and image data
$pal = '';
$trns = '';
$data = '';
$icc = false;
do {
$n = TcpdfStatic::_freadint($f);
$type = fread($f, 4);
if ($type == 'PLTE') {
// read palette
$pal = TcpdfStatic::rfread($f, $n);
fread($f, 4);
} elseif ($type == 'tRNS') {
// read transparency info
$t = TcpdfStatic::rfread($f, $n);
if ($ct == 0) {
$trns = array(ord($t[1]));
} elseif ($ct == 2) {
$trns = array(ord($t[1]), ord($t[3]), ord($t[5]));
} else {
$pos = strpos($t, chr(0));
if ($pos !== false) {
$trns = array($pos);
}
}
fread($f, 4);
} elseif ($type == 'IDAT') {
// read image data block
$data .= TcpdfStatic::rfread($f, $n);
fread($f, 4);
} elseif ($type == 'iCCP') {
// skip profile name
$len = 0;
while (ord(fread($f, 1)) > 0 and $len < 80) {
++$len;
}
// skip null separator
fread($f, 1);
// get compression method
if (ord(fread($f, 1)) != 0) {
// Unknown filter method
fclose($f);
return false;
}
// read ICC Color Profile
$icc = TcpdfStatic::rfread($f, $n - $len - 2);
// decompress profile
$icc = gzuncompress($icc);
fread($f, 4);
} elseif ($type == 'IEND') {
break;
} else {
TcpdfStatic::rfread($f, $n + 4);
}
} while ($n);
if ($colspace == 'Indexed' and empty($pal)) {
// Missing palette
fclose($f);
return false;
}
fclose($f);
return array('w' => $w, 'h' => $h, 'ch' => $channels, 'icc' => $icc, 'cs' => $colspace, 'bpc' => $bpc, 'f' => 'FlateDecode', 'parms' => $parms, 'pal' => $pal, 'trns' => $trns, 'data' => $data);
}
