<?
//***********************************************
//*         Copyright © Stefan Saftescu         *
//*          Bucharest, Romania, 2006           *
//*            All rights reserved.             *
//*         Free for non-comercial use.         *
//*                                             *
//*  More info about Stereo Anaglyph Images at  *
//* http://en.wikipedia.org/wiki/Anaglyph_image *
//***********************************************


class StereoImage
{
	var $leftImg;
	var $rightImg;
	var $leftImgContents = false;
	var $rightImgContents = false;
	var $stereoImg = false;
	var $errors = array();
	var $error = false;
	var $i = 0;
	
	function setImages($left, $right)
	{
		$this->leftImg = $left;
		$this->rightImg = $right;
	}
	function loadImages()
	{
		if(!is_file($this->leftImg))
		{
			$this->errors[$this->i++] = $this->leftImg . " could not be found.";
			$this->error = true;
		}
		if(!is_file($this->rightImg))
		{
			$this->errors[$this->i++] = $this->rightImg . " could not be found.";
			$this->error = true;
		}
		if(!$this->error)
		{
			$this->leftImgContents = @imagecreatefromstring(file_get_contents($this->leftImg));
			if($this->leftImgContents === false)
			{
				$this->errors[$this->i++] = $this->leftImg . " is not a valid image.";
				$this->error = true;
			} else {
				imagealphablending($this->leftImgContents, false);
				imagesavealpha($this->leftImgContents, true);
				$this->rightImgContents = @imagecreatefromstring(file_get_contents($this->rightImg));
				if($this->leftImgContents === false)
				{
					$this->errors[$this->i++] = $this->rightImg . " is not a valid image.";
					$this->error = true;
				} else {
					imagealphablending($this->rightImgContents, true);
					imagesavealpha($this->rightImgContents, true);
				}
			}
		}
	}
	
	function &createStereoImage()
	{
		if(!$this->error)
		{
			$leftX;
			$leftY;
			$rightX;
			$rightY;
			
			$leftX = imagesx($this->leftImgContents);
			$leftY = imagesy($this->leftImgContents);
			$rightX = imagesx($this->rightImgContents);
			$rightY = imagesy($this->rightImgContents);
			
			if(($leftX != $rightX) || ($leftY != $rightY))
			{
				$this->errors[$i++] = "The images aren't the same size.";
				$this->error = true;
				return $this->stereoImg; //false
			}
			$this->stereoImg = imagecreatetruecolor($leftX, $leftY);
			imagealphablending($this->stereoImg, false);
			imagesavealpha($this->stereoImg, true);
			for($x=1; $x<=$leftX; $x++)
			{
				for($y=1; $y<=$leftY; $y++)
				{
					//the pixel's red channel of the stereo image will be the grayscale pixel of the left image
					//0.299, 0.587 and 0.114 are corrections made for the human eye
					$r = min(255, max(0, //the red amount of color is limited between 0 and 255 
					((imagecolorat($this->leftImgContents, $x, $y) >> 16) & 255) * 0.299 //red channel to grayscale
					+ ((imagecolorat($this->leftImgContents, $x, $y) >> 8) & 255) * 0.587 //green channel to grayscale
					+ ((imagecolorat($this->leftImgContents, $x, $y)) & 255) * 0.114)); // blue channel to grayscale
					
					//the pixel's green and blue channels will be the pixel's green and blue channel of the right image
					$g = (imagecolorat($this->rightImgContents, $x, $y) >> 8) & 255;
					$b = (imagecolorat($this->rightImgContents, $x, $y)) & 255;
					
					//mix the red, green, and blue channels into a color
					$color = imagecolorallocate($this->stereoImg, $r, $g, $b);
					
					//finally, draw the pixel
					imagesetpixel($this->stereoImg, $x, $y, $color);
				}
			}
		} 
		return $this->stereoImg;
		@imagedestroy($this->rightImgContents);
		@imagedestroy($this->leftImgContents);
	}
}
?>