<?php
 
/**
 * Steganography in PHP
 *
 * This class lets you write and read string in the least significant bit of an image, making "hide" information in an image.
 *
 * @package StreamSteganography
 * @author Pedro Vargas (deer@deerme.org) http://deerme.org
 * @version 0.1
 * @licence GNU General Public License (GPL)
 */
 
class StreamSteganography
{
 
	var $img_path;
	var $img_object = null;
 
	function StreamSteganography( $img_path , $w = 640 , $h = 480 )
	{
		if ( !is_file( $img_path ) )
		{
			if ( is_writable($img_path) )
				die("nThe image path is not writable");
			$this->img_object = imagecreatetruecolor($w,$h);
			imagepng($this->img_object, $img_path  ); 			
		}
		else
		{
			$inf = @getimagesize($img_path);
			if ( $inf == null )
				die("nThe image is not valid");
 
			if ( !	( $inf["mime"] == "image/jpeg"  OR $inf["mime"] == "image/png" OR $inf["mime"] == "image/gif" ) )
				die("nThe image must be jpeg/png/gif");
 
			if ( $inf["mime"] == "image/gif"  )
				$this->img_object = imagecreatefromgif( $img_path );
			if ( $inf["mime"] == "image/jpeg"   )
				$this->img_object = imagecreatefromjpeg( $img_path );
			if ( $inf["mime"] == "image/png"  )
				$this->img_object = imagecreatefrompng( $img_path );		
 
		}
		$this->img_path = $img_path;
	}
 
	function Write( $data )
	{
		$bits=$this->_asc2bin($data);
		$lenbit=strlen($bits);
		$nx=imagesx($this->img_object);
		$ny=imagesy($this->img_object);
		for($x=0,$bit=0; $x<$nx; $x++)
		{
			for($y=0; $y<$ny; $y++)
			{
				$pix=$this->_getcolor($this->img_object,$x,$y);
				foreach(array('R','G','B') as $C)
					$col[$C]=$bit<$lenbit?($pix[$C]|$bits[$bit])&(254|$bits[$bit++]):$pix[$C];
				imagesetpixel($this->img_object,$x,$y,$this->_setcolor($this->img_object,$col['R'],$col['G'],$col['B']));
			}
		}
		imagepng($this->img_object,$this->img_path); 
	}
 
	function Read()
	{
		$nx=imagesx($this->img_object);
		$ny=imagesy($this->img_object);
		for($x=0; $x<$nx; $x++ )
		{
			for($y=0; $y<$ny; $y++)
			{
				$pix=$this->_getcolor($this->img_object,$x,$y);		
				$data.=($pix['R']&1).($pix['G']&1).($pix['B']&1);
			}
		}
		return $this->_bin2asc($data);
	}
 
 
	function _bin2asc($str)
	{
		$len = strlen($str); 
		for ($i=0;$i<$len;$i+=8){ $ch=chr(bindec(substr($str,$i,8))); if(!ord($ch))break; $data.=$ch; }
		return $data; 
	}
 
 
	function _asc2bin($str)
	{
		$len = strlen($str);
		for($i=0;$i<$len;$i++)
			$data.=str_pad(decbin(ord($str[$i])),8,'0',STR_PAD_LEFT);	  
		return $data.'00000000';
	}
 
	function _getcolor($img,$x,$y) 
	{
		$color = imagecolorat($img,$x,$y);
		return array('R'=>($color>>16)&0xFF,'G'=>($color>>8)&0xFF,'B'=>$color&0xFF);
	} 
 
	function _setcolor($img,$r,$g,$b) 
	{
		$c=imagecolorexact($img,$r,$g,$b); if($c!=-1)return $c;
		$c=imagecolorallocate($img,$r,$g,$b); if($c!=-1)return $c;
		return imagecolorclosest($img,$r,$g,$b); 
	} 
 
 
 
}
 
// New Image
$ss = new StreamSteganography("/tmp/newimage.png");
$ss->Write("nThis message was written to ".date("Y-m-d H:i:s")."n");
// Read in Image
print $ss->Read();
// Concat Data in Image
$ss->Write(  $ss->Read(). " -  New Datan");
// Read in Image
print $ss->Read();
 
// Data in Image
$ss = new StreamSteganography("kitty.png");
$ss->Read()."n";
 
?>