class ImageManipulation
{

	protected $im = null;
	protected $width = 0;
	protected $height = 0;

	public function __construct($file)
	{
		// put gd in $this->im
	}

	public function get_gd()
	{
		return $this->im;
	}

	public function get_rgb_channels()
	{
		$width=imageSX($im);
		$height=imageSY($im);
		$red_channel = imagecreate($width, $height);
		imagecopy($red_channel,$im,0,0,0,0,$width,$height);
		$green_channel = imagecreate($width, $height);
		imagecopy($green_channel,$im,0,0,0,0,$width,$height);
		$blue_channel = imagecreate($width, $height);
		imagecopy($blue_channel,$im,0,0,0,0,$width,$height);
		for ($x = 0; $x < $width; $x++)
		{
			for ($y = 0; $y < $width; $y++)
			{
				$index = imagecolorat($this->im, $x, $y);
				$color = imagecolorsforindex($this->im, $index);
				$red = $color['red'];
				$green = $color['green'];
				$blue = $color['blue'];
				$red_index = imagecolorat($red_channel, $x, $y);
				$green_index = imagecolorat($green_channel, $x, $y);
				$blue_index = imagecolorat($blue_channel, $x, $y);
				$red_color = imagecolorallocate($red_channel, $red, 0, 0);
				$green_color = imagecolorallocate($green_channel, 0, $green, 0);
				$blue_color = imagecolorallocate($blue_channel, 0, 0, $blue);
				imagesetpixel($red_channel,$x,$y,$red_color);
				imagesetpixel($green_channel,$x,$y,$green_color);
				imagesetpixel($blue_channel,$x,$y,$blue_color);
			}
		}
		return array('red'=>$red_channel,'green'=>$green_channel,'blue'=>$blue_channel);
	}

	public function resize($width,$height)
	{
		$im = imagecreate($width, $height);
		imagecopyresized($im, $this->im, 0, 0, 0, 0, $width, $height, $this->width, $this->height);
		$this->im = $im;
		$this->width = $width;
		$this->height=$height;
		return $this->im;
	}

	public function crop($left, $right, $top, $bottom)
	{
		$width = $this->width - $left - $right;
		$height = $this->height - $top - $bottom;
		$temp = imagecreate($width,$height);
		imagecopy( $temp, $this->im, $right, $bottom, $left, $top, $width, $height );
		$this->im = $temp;
		$this->width=$width;
		$this->height=$height;
		return $temp;
	}

}