php:在缓存之前调整图像大小

此脚本将加载一个映像，然后保存一个本地副本以缓存

header('Content-Type: image/png');
            $imgpochette = $_GET['i'];
            $ENABLE_CACHE = true;
            $CACHE_TIME_HOURS = 744;
            $CACHE_FILE_PATH = "pochette_album/$imgpochette.png";
            if($ENABLE_CACHE && file_exists($CACHE_FILE_PATH) && (time() - filemtime($CACHE_FILE_PATH) < ($CACHE_TIME_HOURS * 60 * 60))) {
              echo @file_get_contents($CACHE_FILE_PATH);
            } else {
                    // Load the requested image
                    $imgdisplay = "http://www.pirate-punk.com/pochette.php?i=$imgpochette&display=1";
                    $image = imagecreatefromstring(file_get_contents($imgdisplay));
$width = "30";
$height = "30";
$new_image = imagecreatetruecolor($width, $height);
imagecopyresampled($new_image, $image, 0, 0, 0, 0, $width, $height, $image.getWidth(), $image.getHeight());
                    // Send the image
                    imagejpeg($image, $CACHE_FILE_PATH);
                    exit();
              @file_put_contents($CACHE_FILE_PATH, $output);
              echo $output;
            }

如何在保存之前将图像调整为300x300px？