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<?php
/**
* BCGDrawPNG.php
*--------------------------------------------------------------------
*
* Image Class to draw PNG images with possibility to set DPI
*
*--------------------------------------------------------------------
* Revision History
* v2.1.0 8 nov 2009 Jean-Sébastien Goupil
*--------------------------------------------------------------------
* $Id: BCGDrawPNG.php,v 1.1 2009/11/09 04:14:37 jsgoupil Exp $
*--------------------------------------------------------------------
* Copyright (C) Jean-Sebastien Goupil
* http://www.barcodephp.com
*/
include_once('BCGDraw.php');
if (!function_exists('file_put_contents')) {
function file_put_contents($filename, $data) {
$f = @fopen($filename, 'w');
if (!$f) {
return false;
} else {
$bytes = fwrite($f, $data);
fclose($f);
return $bytes;
}
}
}
class BCGDrawPNG extends BCGDraw {
private $dpi;
/**
* Constructor
*
* @param resource $im
*/
public function __construct($im) {
parent::__construct($im);
}
/**
* Sets the DPI
*
* @param int $dpi
*/
public function setDPI($dpi) {
if(is_numeric($dpi)) {
$this->dpi = max(1, $dpi);
} else {
$this->dpi = null;
}
}
/**
* Draws the PNG on the screen or in a file
*/
public function draw() {
ob_start();
imagepng($this->im);
$bin = ob_get_contents();
ob_end_clean();
$this->setInternalProperties($bin);
if (empty($this->filename)) {
echo $bin;
} else {
file_put_contents($this->filename, $bin);
}
}
private function setInternalProperties(&$bin) {
// Scan all the ChunkType
if(strcmp(substr($bin, 0, 8), pack('H*', '89504E470D0A1A0A')) === 0) {
$chunks = $this->detectChunks($bin);
$this->internalSetDPI($bin, $chunks);
$this->internalSetC($bin, $chunks);
}
}
private function detectChunks($bin) {
$data = substr($bin, 8);
$chunks = array();
$c = strlen($data);
$offset = 0;
while($offset < $c) {
$packed = unpack('Nsize/a4chunk', $data);
$size = $packed['size'];
$chunk = $packed['chunk'];
$chunks[] = array('offset'=>$offset + 8, 'size'=>$size, 'chunk'=>$chunk);
$jump = $size + 12;
$offset += $jump;
$data = substr($data, $jump);
}
return $chunks;
}
private function internalSetDPI(&$bin, &$chunks) {
if($this->dpi !== null) {
$meters = (int)($this->dpi * 39.37007874);
$found = -1;
$c = count($chunks);
for($i = 0; $i < $c; $i++) {
// We already have a pHYs
if($chunks[$i]['chunk'] === 'pHYs') {
$found = $i;
break;
}
}
$data = 'pHYs' . pack('NNC', $meters, $meters, 0x01);
$crc = self::crc($data, 13);
$cr = pack('Na13N', 9, $data, $crc);
// We didn't have a pHYs
if($found == -1) {
// Don't do anything if we have a bad PNG
if($c >= 2 && $chunk[0]['chunk'] = 'IHDR') {
array_splice($chunks, 1, 0, array(array('offset'=>33, 'size'=>9, 'chunk'=>'pHYs')));
// Push the data
for($i = 2; $i < $c; $i++) {
$chunks[$i]['offset'] += 21;
}
$firstPart = substr($bin, 0, 33);
$secondPart = substr($bin, 33);
$bin = $firstPart;
$bin .= $cr;
$bin .= $secondPart;
}
} else {
$bin = substr_replace($bin, $cr, $chunks[$i]['offset'], 21);
}
}
}
private function internalSetC(&$bin, &$chunks) {
if(count($chunks) >= 2 && $chunk[0]['chunk'] = 'IHDR') {
$firstPart = substr($bin, 0, 33);
$secondPart = substr($bin, 33);
$cr = pack('H*', '0000004C74455874436F707972696768740047656E657261746564207769746820426172636F64652047656E657261746F7220666F722050485020687474703A2F2F7777772E626172636F64657068702E636F6D597F70B8');
$bin = $firstPart;
$bin .= $cr;
$bin .= $secondPart;
}
// Chunks is dirty!! But we are done.
}
private static $crc_table = array();
private static $crc_table_computed = false;
private static function make_crc_table() {
for($n = 0; $n < 256; $n++) {
$c = $n;
for ($k = 0; $k < 8; $k++) {
if (($c & 1) == 1) {
$c = 0xedb88320 ^ (self::SHR($c, 1));
} else {
$c = self::SHR($c, 1);
}
}
self::$crc_table[$n] = $c;
}
self::$crc_table_computed = true;
}
private static function SHR($x, $n) {
$mask = 0x40000000;
if ($x < 0) {
$x &= 0x7FFFFFFF;
$mask = $mask >> ($n - 1);
return ($x >> $n) | $mask;
}
return (int)$x >> (int)$n;
}
private static function update_crc($crc, $buf, $len) {
$c = $crc;
if (!self::$crc_table_computed) {
self::make_crc_table();
}
for($n = 0; $n < $len; $n++) {
$c = self::$crc_table[($c ^ ord($buf[$n])) & 0xff] ^ (self::SHR($c, 8));
}
return $c;
}
private static function crc($data, $len) {
return self::update_crc(-1, $data, $len) ^ -1;
}
}
?>
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