/**
* Resize an GD image
*
* @return boolean False if the target image cannot be created, otherwise true
*/
protected function executeResizeGd()
{
$sourceImage = \GdImage::fromFile($this->fileObj);
$coordinates = $this->computeResize();
$newImage = \GdImage::fromDimensions($coordinates['width'], $coordinates['height']);
$sourceImage->copyTo($newImage, $coordinates['target_x'], $coordinates['target_y'], $coordinates['target_width'], $coordinates['target_height']);
$newImage->saveToFile(TL_ROOT . '/' . $this->getCacheName());
}