How to resample images?

/**
	 * Size of preferred thumbnail
	 * @int unknown_type
	 */
	var $preferred_size = 200;
	
	/**
	 * Color Red
	 * @int color
	 */
	var $red = 255;
	
	/**
	 * Color Green
	 * @int color
	 */
	var $green = 255;
	
	/**
	 * Color Blue
	 * @int color
	 */
	var $blue = 239;


...

function resizeImage($img) {
		//Get size for thumbnail
		$width=imagesx($img); $height=imagesy($img);
		if ($width>$height) { $n_height=$height*($this->preferred_size/$width); $n_width=$this->preferred_size; } else { $n_width=$width*($this->preferred_size/$height); $n_height=$this->preferred_size; }
		
		$x=0;$y=0;
		if ($n_width<$this->preferred_size) $x=round(($this->preferred_size-$n_width)/2);
		if ($n_height<$this->preferred_size) $y=round(($this->preferred_size-$n_height)/2);
		
		$thumb=imagecreatetruecolor($this->preferred_size,$this->preferred_size);
		
		#Background colour fix by:
		#Ben Lancaster ([email protected])
		$bgcolor = imagecolorallocate($thumb,$this->red, $this->green, $this->blue);
		imagefill($thumb, 0, 0, $bgcolor);
		
		if (function_exists("imagecopyresampled")) {
			if (!($result=@imagecopyresampled($thumb,$img,$x,$y,0,0,$n_width,$n_height,$width,$height))) {
				$result=imagecopyresized($thumb,$img,$x,$y,0,0,$n_width,$n_height,$width,$height);
			}	
		} else {
			$result=imagecopyresized($thumb,$img,$x,$y,0,0,$n_width,$n_height,$width,$height);
		}

		return ($result)?$thumb:false;
	}

function Thumbnail($fckphp_config,$type,$cwd) {
...
$this->real_cwd=str_replace("//","/",($this->fckphp_config['basedir']."/".$this->actual_cwd));
...
}
...
var $cwd;
	var $actual_cwd;
	var $filename;
...
function run() {
		//$mimeIcon=getMimeIcon($mime);
		$fullfile=$this->real_cwd.'/'.$this->filename;
		$thumbfile=$this->real_cwd.'/.thumb_'.$this->filename;
...
}