protected function crop($newWidth, $newHeight, $sourceX = 0, $sourceY = 0)
{
$this->imageResized = imagecreatetruecolor($newWidth, $newHeight);
imagecopyresampled($this->imageResized, $this->image, 0, 0, $sourceX, $sourceY, $this->width, $this->height, $this->width, $this->height);
return $this;
}