switch($this->format) {
                case 'GIF':
                    $this->oldImage = ImageCreateFromGif($this->fileName);
                    break;
                case 'JPG':
                    $this->oldImage = ImageCreateFromJpeg($this->fileName);
                    break;
                case 'PNG':
                    $this->oldImage = ImageCreateFromPng($this->fileName);
   
				
$result = $this->oldImage;
ImageAlphaBlending($result, true); // true by default, but still...
ImageSaveAlpha($result, true);
ImageFill($result, 0, 0, IMG_COLOR_TRANSPARENT);
ImagePNG($result);


                    break;
            }