Gazelle/classes/imagetools.class.php

<?php

/**
 * ImageTools Class
 * Thumbnail aide, mostly
 */
class ImageTools
{

  /**
   * Determine the image URL. This takes care of the image proxy and thumbnailing.
   * @param string $Url
   * @param string $Thumb image proxy scale profile to use
   * @return string
   */
    public static function process($Url = '', $Thumb = false)
    {
        if (!$Url) {
            return '';
        }
        if (preg_match('/^https:\/\/('.SITE_DOMAIN.'|'.IMAGE_DOMAIN.')\//', $Url) || $Url[0]=='/') {
            if (strpos($Url, '?') === false) {
                $Url .= '?';
            }
            return $Url;
        } else {
            return 'https://'.IMAGE_DOMAIN.($Thumb?"/$Thumb/":'/').'?h='.rawurlencode(base64_encode(hash_hmac('sha256', $Url, IMAGE_PSK, true))).'&i='.urlencode($Url);
        }
    }

    /**
     * Checks if a link's host is (not) good, otherwise displays an error.
     * @param string $Url Link to an image
     * @return boolean
     */
    public static function blacklisted($Url, $ShowError = true)
    {
        $Blacklist = ['tinypic.com'];
        foreach ($Blacklist as $Value) {
            if (stripos($Url, $Value) !== false) {
                if ($ShowError) {
                    error($Value . ' is not an allowed image host. Please use a different host.');
                }
                return true;
            }
        }
        return false;
    }
}