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PHP PNG Library

PHP PNG Library, An attempt at creating a non-extension PNG library for PHP.

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grimpirate

16 Sep, 2008 - 11:37 AM

Post #1

D.I.C Head

Joined: 3 Aug, 2006
Posts: 187

Who Cares

Thanked 5 times

Dream Kudos: 375
My Contributions

Alright here's my idea. Some servers don't provide the gd or zlib extensions for PHP. PNG is a widely accepted internet picture format. If you don't have gd for php it's impossible to make things such as captcha images and the like. Therefore, I'm working on creating a PNG library that works using only the already available PHP functions (those that don't need a special install or directive enable). Right now the code I have is very limited. The limitations are as follows:

Images must be truecolor with alpha
No error handling
zlib is implemented using the gzcompress function of php (must remake zlib to be completely independent)
PNG output images have only been viewable thus far on Opera

If anyone can offer some help/guidance as to why these images aren't viewable on other browsers or in media editors/picture viewers please let me know what I'm doing wrong. To me the PNG stream seems compliant, but I'm no guru. I can also save the image from the browser and view it using Windows Picture and Fax Viewer and Paint surprisingly. However, Internet Explorer and Firefox won't show the image. Two PHP files work the code as of now. Here they are:
png.php

php

<?php
require_once('crcpng.php');
header("Content-type: image/png");
$png = new PNG(69, 5);
$png->line(0, 0, 3, 0);
$png->line(6, 0, 9, 0);
$png->line(12, 0, 16, 0);
$png->line(19, 0, 21, 0);
$png->line(24, 0, 28, 0);
$png->line(32, 0, 36, 0);
$png->pixel(38, 0);
$png->pixel(42, 0);
$png->line(46, 0, 50, 0);
$png->line(52, 0, 56, 0);
$png->line(58, 0, 61, 0);
$png->line(64, 0, 68, 0);
$png->pixel(0, 1);
$png->pixel(4, 1);
$png->pixel(6, 1);
$png->pixel(10, 1);
$png->pixel(12, 1);
$png->pixel(18, 1);
$png->pixel(22, 1);
$png->pixel(24, 1);
$png->pixel(26, 1);
$png->pixel(28, 1);
$png->pixel(34, 1);
$png->pixel(38, 1);
$png->pixel(39, 1);
$png->pixel(42, 1);
$png->pixel(46, 1);
$png->pixel(52, 1);
$png->pixel(56, 1);
$png->pixel(58, 1);
$png->pixel(62, 1);
$png->pixel(64, 1);
$png->pixel(0, 2);
$png->pixel(4, 2);
$png->line(6, 2, 10, 2);
$png->line(12, 2, 15, 2);
$png->pixel(18, 2);
$png->pixel(22, 2);
$png->pixel(24, 2);
$png->pixel(26, 2);
$png->pixel(28, 2);
$png->pixel(34, 2);
$png->pixel(38, 2);
$png->pixel(40, 2);
$png->pixel(42, 2);
$png->pixel(46, 2);
$png->pixel(52, 2);
$png->pixel(56, 2);
$png->pixel(58, 2);
$png->pixel(62, 2);
$png->line(64, 2, 67, 2);
$png->pixel(0, 3);
$png->pixel(4, 3);
$png->pixel(6, 3);
$png->pixel(8, 3);
$png->pixel(12, 3);
$png->line(18, 3, 22, 3);
$png->pixel(24, 3);
$png->pixel(26, 3);
$png->pixel(28, 3);
$png->pixel(34, 3);
$png->pixel(38, 3);
$png->pixel(41, 3);
$png->pixel(42, 3);
$png->pixel(46, 3);
$png->pixel(52, 3);
$png->pixel(56, 3);
$png->pixel(58, 3);
$png->pixel(62, 3);
$png->pixel(64, 3);
$png->line(0, 4, 3, 4);
$png->pixel(6, 4);
$png->pixel(9, 4);
$png->pixel(10, 4);
$png->line(12, 4, 16, 4);
$png->pixel(18, 4);
$png->pixel(22, 4);
$png->pixel(24, 4);
$png->pixel(28, 4);
$png->pixel(30, 4);
$png->line(32, 4, 36, 4);
$png->pixel(38, 4);
$png->pixel(42, 4);
$png->pixel(44, 4);
$png->line(46, 4, 50, 4);
$png->line(52, 4, 56, 4);
$png->line(58, 4, 61, 4);
$png->line(64, 4, 68, 4);
echo $png->resultantImage();

class PNG {
	var $signature;				// 8 bytes
	var $width;					// 4 bytes
	var $height;				// 4 bytes
	var $bit_depth;				// 1 byte
	var $colour_type;			// 1 byte
	var $compression_method;	// 1 byte
	var $filter_method;			// 1 byte
	var $interlace_method;		// 1 byte
	var $pixelData;				// n bytes
	
	function PNG($width, $height, $bit_depth = 8, $colour_type = 6, $compression_method = 0, $filter_method = 0, $interlace_method = 0){
		$this->signature = chr(137) . 'PNG' . chr(13) . chr(10) . chr(26) . chr(10);
		$this->width = $width;
		$this->height = $height;
		$this->bit_depth = $bit_depth;
		$this->colour_type = $colour_type;
		$this->compression_method = $compression_method;
		$this->filter_method = $filter_method;
		$this->interlace_method = $interlace_method;
		for($i = 0; $i < $height; $i++){
			$this->pixelData[] = array();
			for($j = 0; $j < $width; $j++){
				$this->pixelData[$i][] = chr(255) . chr(255) . chr(255) . chr(0);
			}
		}
	}
	
	function chunk($type){
		$chunk = array(
			'length' => null,	// 4 bytes
			'type' => null,		// 4 bytes
			'data' => null,		// n bytes
			'crc' => null		// 4 bytes
		);
		if(!strcmp('IHDR', $type)){
			$chunk['type'] = 'IHDR';
			$chunk['data'] = writableInt($this->width) . writableInt($this->height) . chr($this->bit_depth) . chr($this->colour_type) . chr($this->compression_method) . chr($this->filter_method) . chr($this->interlace_method);
		}elseif(!strcmp('IDAT', $type)){
			$chunk['type'] = 'IDAT';
			$scanlines = array_values($this->pixelData);
			$scanlines = array_map('scanser', $scanlines);
			$scanlines = gzcompress(implode('', $scanlines));
			$chunk['data'] = $scanlines;
		}elseif(!strcmp('IEND', $type)){
			$chunk['type'] = 'IEND';
		}
		$chunk['length'] = writableInt(strlen($chunk['data']));
		$chunk['crc'] = writableInt(crc($chunk['type'] . $chunk['data']));
		return implode('', $chunk);
	}
	
	function resultantImage(){
		return $this->signature . $this->chunk('IHDR') . $this->chunk('IDAT') . $this->chunk('IEND');
	}
	
	function pixel($x, $y, $r = 0, $g = 0, $b = 0, $a = 255){
		$this->pixelData[$y][$x] = chr($r) . chr($g) . chr($b) . chr($a);
	}
	
	/*
	Makes use of the Bresenham line algorithm
	http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
	*/
	function line($x0, $y0, $x1, $y1, $r = 0, $g = 0, $b = 0, $a = 255){
		$steep = abs($y1 - $y0) > abs($x1 - $x0);
		if($steep){
			$temp = $x0;
			$x0 = $y0;
			$y0 = $temp;
			$temp = $x1;
			$x1 = $y1;
			$y1 = $temp;
		}
		if($x0 > $x1){
			$temp = $x0;
			$x0 = $x1;
			$x1 = $temp;
			$temp = $y0;
			$y0 = $y1;
			$y1 = $temp;
		}
		$deltax = $x1 - $x0;
		$deltay = abs($y1 - $y0);
		$error = $deltax / 2;
		$y = $y0;
		if($y0 < $y1)
			$ystep = 1;
		else
			$ystep = -1;
		for($x = $x0; $x <= $x1; $x++){
			if($steep)
				$this->pixelData[$x][$y] = chr($r) . chr($g) . chr($b) . chr($a);
			else
				$this->pixelData[$y][$x] = chr($r) . chr($g) . chr($b) . chr($a);
			$error = $error - $deltay;
			if($error < 0){
				$y += $ystep;
				$error += $deltax;
			}
		}
	}
}

function scanser($value){
	return chr(0) . implode('', $value);
}

function writableInt($number){
	$output = '';
	for($i = 0; $i > -32; $i -= 8){
		$output .= chr(bitRotate32($number, $i) & 0x000000ff);
	}
	return strrev($output);
}
// Negatives rotate right, positives rotate left
// Made by Nina Cording from the php.net site
function bitRotate32($value, $amount){
	if ($amount > 0){
		$amount %= 32;
		$value = ($value << $amount) | ($value >> (32 - $amount));
	} elseif($amount < 0){
		$amount = (-1 * $amount) % 32;
		$value = ($value >> $amount) | ($value << (32 - $amount));
	}
	return $value;
}
?>

crcpng.php

php

<?php
$crc_table = array();

$crc_table_computed = false;

function make_crc_table(){
	global $crc_table, $crc_table_computed;
	for($n = 0; $n < 256; $n++){
		$c = $n;
		for($k = 0; $k < 8; $k++){
		if($c & 1 === 1)
			$c = 0xedb88320 ^ (($c >> 1) & 0xefffffff);
		else
			$c = ($c >> 1) & 0xefffffff;
		}
	$crc_table[] = $c;
	}
	$crc_table_computed = true;
}

function update_crc($crc, $buf){
	global $crc_table, $crc_table_computed;
	$c = $crc;

	if(!$crc_table_computed)
		make_crc_table();
	$len = strlen($buf);
	for($n = 0; $n < $len; $n++){
		$c = $crc_table[($c ^ ord(substr($buf, $n, 1))) & 0x000000ff] ^ (($c >> 8) & 0x00ffffff);
	}
	return $c;
}

function crc($buf){
	return update_crc(0xffffffff, $buf) ^ 0xffffffff;
}
?>

The output it produces on Opera is basically a small image that says DREAM.IN.CODE on it. I'm including a screencap. Thank you for any input you can provide.

Attached image(s)

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mocker	16 Sep, 2008 - 03:25 PM Post #2
D.I.C Regular Joined: 14 Oct, 2007 Posts: 256 Thanked 15 times My Contributions	I tried messing around with the php headers thinking maybe the browsers weren't interpreting it right, however IE, Firefox and Chrome all read it as an invalid PNG, so they are trying to parse it as a png and just failing. If I save the file to my computer, I can then open it up. I would check the PNG format you are writing. I am guessing something in the header information in the png data does not match the standard the browsers are expecting. Windows and Opera are probably more lax about their interpretation of the file.
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grimpirate	16 Sep, 2008 - 10:03 PM Post #3
D.I.C Head Joined: 3 Aug, 2006 Posts: 187 Thanked 5 times Dream Kudos: 375 My Contributions	I figured out the problem. It was line 143 of the png.php file. The checksum that they perform can in fact be determined with the php function crc32. I though the implementation I had coded did the exact same thing as that listed in the specifications, but apparently it is erroneous. So basically the line SHOULD become the following: CODE $chunk['crc'] = writableInt(crc32($chunk['type'] . $chunk['data'])); This change eliminates the need for the crcpng.php file. Now your png images should open up anywhere Mocker. Only thing left now is to figure out how to code zlib. T_T
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grimpirate

17 Sep, 2008 - 12:16 AM

Post #4

D.I.C Head

Joined: 3 Aug, 2006
Posts: 187

Who Cares

Thanked 5 times

Dream Kudos: 375
My Contributions

To all those that would defy me, BEHOLD MY GLORY!

php

<?php
define('DEF_BLK_SIZE', 65531);
define('ADLER_BASE', 65521);
header("Content-type: image/png");
$png = new PNG(69, 5);
$png->line(0, 0, 3, 0);
$png->line(6, 0, 9, 0);
$png->line(12, 0, 16, 0);
$png->line(19, 0, 21, 0);
$png->line(24, 0, 28, 0);
$png->line(32, 0, 36, 0);
$png->pixel(38, 0);
$png->pixel(42, 0);
$png->line(46, 0, 50, 0);
$png->line(52, 0, 56, 0);
$png->line(58, 0, 61, 0);
$png->line(64, 0, 68, 0);
$png->pixel(0, 1);
$png->pixel(4, 1);
$png->pixel(6, 1);
$png->pixel(10, 1);
$png->pixel(12, 1);
$png->pixel(18, 1);
$png->pixel(22, 1);
$png->pixel(24, 1);
$png->pixel(26, 1);
$png->pixel(28, 1);
$png->pixel(34, 1);
$png->pixel(38, 1);
$png->pixel(39, 1);
$png->pixel(42, 1);
$png->pixel(46, 1);
$png->pixel(52, 1);
$png->pixel(56, 1);
$png->pixel(58, 1);
$png->pixel(62, 1);
$png->pixel(64, 1);
$png->pixel(0, 2);
$png->pixel(4, 2);
$png->line(6, 2, 10, 2);
$png->line(12, 2, 15, 2);
$png->pixel(18, 2);
$png->pixel(22, 2);
$png->pixel(24, 2);
$png->pixel(26, 2);
$png->pixel(28, 2);
$png->pixel(34, 2);
$png->pixel(38, 2);
$png->pixel(40, 2);
$png->pixel(42, 2);
$png->pixel(46, 2);
$png->pixel(52, 2);
$png->pixel(56, 2);
$png->pixel(58, 2);
$png->pixel(62, 2);
$png->line(64, 2, 67, 2);
$png->pixel(0, 3);
$png->pixel(4, 3);
$png->pixel(6, 3);
$png->pixel(8, 3);
$png->pixel(12, 3);
$png->line(18, 3, 22, 3);
$png->pixel(24, 3);
$png->pixel(26, 3);
$png->pixel(28, 3);
$png->pixel(34, 3);
$png->pixel(38, 3);
$png->pixel(41, 3);
$png->pixel(42, 3);
$png->pixel(46, 3);
$png->pixel(52, 3);
$png->pixel(56, 3);
$png->pixel(58, 3);
$png->pixel(62, 3);
$png->pixel(64, 3);
$png->line(0, 4, 3, 4);
$png->pixel(6, 4);
$png->pixel(9, 4);
$png->pixel(10, 4);
$png->line(12, 4, 16, 4);
$png->pixel(18, 4);
$png->pixel(22, 4);
$png->pixel(24, 4);
$png->pixel(28, 4);
$png->pixel(30, 4);
$png->line(32, 4, 36, 4);
$png->pixel(38, 4);
$png->pixel(42, 4);
$png->pixel(44, 4);
$png->line(46, 4, 50, 4);
$png->line(52, 4, 56, 4);
$png->line(58, 4, 61, 4);
$png->line(64, 4, 68, 4);
echo $png->resultantImage();

class PNG {
	var $signature;				// 8 bytes
	var $width;					// 4 bytes
	var $height;				// 4 bytes
	var $bit_depth;				// 1 byte
	var $colour_type;			// 1 byte
	var $compression_method;	// 1 byte
	var $filter_method;			// 1 byte
	var $interlace_method;		// 1 byte
	var $pixelData;				// n bytes
	
	function PNG($width, $height, $bit_depth = 8, $colour_type = 6, $compression_method = 0, $filter_method = 0, $interlace_method = 0){
		$this->signature = chr(137) . 'PNG' . chr(13) . chr(10) . chr(26) . chr(10);
		$this->width = $width;
		$this->height = $height;
		$this->bit_depth = $bit_depth;
		$this->colour_type = $colour_type;
		$this->compression_method = $compression_method;
		$this->filter_method = $filter_method;
		$this->interlace_method = $interlace_method;
		for($i = 0; $i < $height; $i++){
			$this->pixelData[] = array();
			for($j = 0; $j < $width; $j++){
				$this->pixelData[$i][] = chr(255) . chr(255) . chr(255) . chr(0);
			}
		}
	}
	
	function chunk($type){
		$chunk = array(
			'length' => null,	// 4 bytes
			'type' => null,		// 4 bytes
			'data' => null,		// n bytes
			'crc' => null		// 4 bytes
		);
		if(!strcmp('IHDR', $type)){
			$chunk['type'] = 'IHDR';
			$chunk['data'] = writableInt($this->width) . writableInt($this->height) . chr($this->bit_depth) . chr($this->colour_type) . chr($this->compression_method) . chr($this->filter_method) . chr($this->interlace_method);
		}elseif(!strcmp('IDAT', $type)){
			$chunk['type'] = 'IDAT';
			$scanlines = array_values($this->pixelData);
			$scanlines = array_map('scanser', $scanlines);
			//$scanlines = gzcompress(implode('', $scanlines));
			$scanlines = defstr(implode('', $scanlines));
			$chunk['data'] = $scanlines;
		}elseif(!strcmp('IEND', $type)){
			$chunk['type'] = 'IEND';
		}
		$chunk['length'] = writableInt(strlen($chunk['data']));
		$chunk['crc'] = writableInt(crc32($chunk['type'] . $chunk['data']));
		return implode('', $chunk);
	}
	
	function resultantImage(){
		return $this->signature . $this->chunk('IHDR') . $this->chunk('IDAT') . $this->chunk('IEND');
	}
	
	function pixel($x, $y, $r = 0, $g = 0, $b = 0, $a = 255){
		$this->pixelData[$y][$x] = chr($r) . chr($g) . chr($b) . chr($a);
	}
	
	/*
	Makes use of the Bresenham line algorithm
	http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
	*/
	function line($x0, $y0, $x1, $y1, $r = 0, $g = 0, $b = 0, $a = 255){
		$steep = abs($y1 - $y0) > abs($x1 - $x0);
		if($steep){
			$temp = $x0;
			$x0 = $y0;
			$y0 = $temp;
			$temp = $x1;
			$x1 = $y1;
			$y1 = $temp;
		}
		if($x0 > $x1){
			$temp = $x0;
			$x0 = $x1;
			$x1 = $temp;
			$temp = $y0;
			$y0 = $y1;
			$y1 = $temp;
		}
		$deltax = $x1 - $x0;
		$deltay = abs($y1 - $y0);
		$error = $deltax / 2;
		$y = $y0;
		if($y0 < $y1)
			$ystep = 1;
		else
			$ystep = -1;
		for($x = $x0; $x <= $x1; $x++){
			if($steep)
				$this->pixelData[$x][$y] = chr($r) . chr($g) . chr($b) . chr($a);
			else
				$this->pixelData[$y][$x] = chr($r) . chr($g) . chr($b) . chr($a);
			$error = $error - $deltay;
			if($error < 0){
				$y += $ystep;
				$error += $deltax;
			}
		}
	}
}

function defstr($string){
	$adler = writableInt(adler32($string));
	$output = chr(120) . chr(1);
	$len = strlen($string);
	$div = floor($len / DEF_BLK_SIZE);
	if($div != 0){
		for($i = 0; $i < $div; $i++){
			$output .= chr(0);
			$output .= strrev(substr(writableInt(DEF_BLK_SIZE), 2));
			$output .= strrev(substr(writableInt(DEF_BLK_SIZE ^ 0xffffffff), 2));
			$output .= substr($string, 0, DEF_BLK_SIZE);
			$string = substr($string, DEF_BLK_SIZE);
		}
	}
	$len = strlen($string);
	$output .= chr(1);
	$output .= strrev(substr(writableInt($len), 2));
	$output .= strrev(substr(writableInt($len ^ 0xffffffff), 2));
	$output .= $string;
	$output .= $adler;
	return $output;
}
function adler32($buf){
	return update_adler32(1, $buf);
}

function update_adler32($adler, $buf){
	$s1 = $adler & 0x0000ffff;
	$s2 = ($adler >> 16) & 0x0000ffff;
	$len = strlen($buf);
	for($n = 0; $n < $len; $n++){
		$s1 = ($s1 + ord(substr($buf, $n, 1))) % ADLER_BASE;
		$s2 = ($s2 + $s1) % ADLER_BASE;
	}
	return ($s2 << 16) + $s1;
}
function scanser($value){
	return chr(0) . implode('', $value);
}

function writableInt($number){
	$output = '';
	for($i = 0; $i > -32; $i -= 8){
		$output .= chr(bitRotate32($number, $i) & 0x000000ff);
	}
	return strrev($output);
}
// Negatives rotate right, positives rotate left
// Made by Nina Cording from the php.net site
function bitRotate32($value, $amount){
	if ($amount > 0){
		$amount %= 32;
		$value = ($value << $amount) | ($value >> (32 - $amount));
	} elseif($amount < 0){
		$amount = (-1 * $amount) % 32;
		$value = ($value >> $amount) | ($value << (32 - $amount));
	}
	return $value;
}

?>

DREAM.IN.CODE generated from the ground up without any outside libraries! BWAHAHAHA! NEXT THE WORLD!

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grimpirate	17 Sep, 2008 - 06:55 PM Post #5
D.I.C Head Joined: 3 Aug, 2006 Posts: 187 Thanked 5 times Dream Kudos: 375 My Contributions	As my specialty is not compression algorithms. I will likely be keeping this as is. Uncompressed true color with alpha images as the only applicable PNG setting. Currently, I'm working on trying to implement a Xiaolin Wu line drawing algorithm. Once I get that working I'll see about working out line thicknesses and polygon drawing and other such 2d graphical constructs. If anyone has any pointers or useful info to assist me with that I'd be appreciative.
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