Belirlenen Bir Renkte Görüntü Oluşturmak

<?php
class piksel {
    var $r;
    var $g;
    var $b;
  function piksel(){
        extract($_REQUEST);
        if(isset($r) and isset($g) and isset($b)){
            $this->r=(int)(abs($r)%255);
            $this->g=(int)(abs($g)%255);
            $this->b=(int)(abs($b)%255);
        }elseif(isset($s)){
            $this->renksec($s);
        }
    }
  function cikti($genislik,$yukseklik){
        $im = imagecreatetruecolor($genislik,$yukseklik);
        $renk = imagecolorallocate($im,$this->r,$this->g,$this->b);
        imagefill($im,0,0,$renk);
        header('Content-type: image/png');
        imagepng($im);
        imagedestroy($im);
  }
    function renksec($renk) {
        switch ($renk) {
            case 'black': $this->r=0;$this->g=0;$this->b=0;break;
            case 'white': $this->r=255;$this->g=255;$this->b=255;break;
            case 'pink': $this->r=255;$this->g=0;$this->b=255;break;
            case 'red': $this->r=255;$this->g=0;$this->b=0;break;
            case 'blue': $this->r=0;$this->g=0;$this->b=255;break;
            default:$this->r=255;$this->g=0;$this->b=255;
        } 
    }  
}
$a=new piksel;
echo $a->cikti(100,100);
?>
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX