PHP生成图片缩略图函数

输出到浏览器） * @return bool */function mkThumbnail($src, $width = null, $height = null, $filename = null) {    if (!isset($width) && !isset($height))        return false;    if (isset($width) && $width <= 0)        return false;    if (isset($height) && $height <= 0)        return false;    $size = getimagesize($src);    if (!$size)        return false;    list($src_w, $src_h, $src_type) = $size;    $src_mime = $size['mime'];    switch($src_type) {        case 1 :            $img_type = 'gif';            break;        case 2 :            $img_type = 'jpeg';            break;        case 3 :            $img_type = 'png';            break;        case 15 :            $img_type = 'wbmp';            break;        default :            return false;    }    if (!isset($width))        $width = $src_w * ($height / $src_h);    if (!isset($height))        $height = $src_h * ($width / $src_w);    $imagecreatefunc = 'imagecreatefrom' . $img_type;    $src_img = $imagecreatefunc($src);    $dest_img = imagecreatetruecolor($width, $height);    imagecopyresampled($dest_img, $src_img, 0, 0, 0, 0, $width, $height, $src_w, $src_h);    $imagefunc = 'image' . $img_type;    if ($filename) {        $imagefunc($dest_img, $filename);    } else {        header('Content-Type: ' . $src_mime);        $imagefunc($dest_img);    }    imagedestroy($src_img);    imagedestroy($dest_img);    return true;}$result = mkThumbnail('./IMG_3324.JPG', 147, 147);