PHP等比例生成缩略图

/**
	* 生成缩略图
	* $imgSrc			图片源路径
	* $resize_width		图片宽度
	* $resize_height	图片高度
	* $dstimg			缩略图路径
	* $isCut			是否剪切图片
	*/
	public function reSizeImg($imgSrc, $resize_width, $resize_height, $dstimg, $isCut = false) {
        //图片的类型
        $type = substr(strrchr($imgSrc, "."), 1);
        //初始化图象
        if ($type == "jpg" || $type == "jpeg") {
            $im = imagecreatefromjpeg($imgSrc);
        }
        if ($type == "gif") {
            $im = imagecreatefromgif($imgSrc);
        }
        if ($type == "png") {
            $im = imagecreatefrompng($imgSrc);
        }

        $width = imagesx($im);
        $height = imagesy($im);

        //生成图象
        //改变后的图象的比例
        $resize_ratio = ($resize_width) / ($resize_height);
        //实际图象的比例
        $ratio = ($width) / ($height);
        if (($isCut) == 1) {
            if ($ratio >= $resize_ratio) {
				//高度优先
                $newimg = imagecreatetruecolor($resize_width, $resize_height);
                imagecopyresampled($newimg, $im, 0, 0, 0, 0, $resize_width, $resize_height, (($height) * $resize_ratio), $height);
                ImageJpeg($newimg, $dstimg);
            }
            if ($ratio < $resize_ratio) {
				//宽度优先
                $newimg = imagecreatetruecolor($resize_width, $resize_height);
                imagecopyresampled($newimg, $im, 0, 0, 0, 0, $resize_width, $resize_height, $width, (($width) / $resize_ratio));
                ImageJpeg($newimg, $dstimg);
            }
        } else {
            if ($ratio >= $resize_ratio) {
                $newimg = imagecreatetruecolor($resize_width, ($resize_width) / $ratio);
                imagecopyresampled($newimg, $im, 0, 0, 0, 0, $resize_width, ($resize_width) / $ratio, $width, $height);
                ImageJpeg($newimg, $dstimg);
            }
            if ($ratio < $resize_ratio) {
                $newimg = imagecreatetruecolor(($resize_height) * $ratio, $resize_height);
                imagecopyresampled($newimg, $im, 0, 0, 0, 0, ($resize_height) * $ratio, $resize_height, $width, $height);
                ImageJpeg($newimg, $dstimg);
            }
        }
        ImageDestroy($im);
    }