php使用imagecopyresized压缩图片

function imageresize($goods_pic){
		$newwidth = 50;
		$newheight = 50;
		$filename = 'images/' . $goods_pic;
		$newname = 'images/small_images/' . $goods_pic;
		if(!empty($goods_pic) && file_exists($filename)){
			list($width, $height) = getimagesize($filename);
			$thumb = imagecreatetruecolor($newwidth, $newheight);
			
			$suffix = strrchr($filename,'.');
			switch($suffix){
				case '.gif':
					$source = imagecreatefromgif($filename);
					imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
					imagegif($thumb,$newname);
				break;
				case '.png':
					$source = imagecreatefrompng($filename);
					imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
					imagepng($thumb,$newname);
				break;
				case '.jpg':
					$source = imagecreatefromjpeg($filename);
					imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
					imagejpeg($thumb,$newname);
				break;
				case '.bmp':
					$source = imagecreatefromwbmp($filename);
					imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
					imagewbmp($thumb,$newname);
				break;
			}
			
			imagedestroy($thumb);
		}
	}