Gazelle/classes/imagetools.class.php

<?php
declare(strict_types=1);

/**
 * 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)
    {
        $ENV = ENV::go();
        $Psk = $ENV->getPriv('IMAGE_PSK');

        if (!$Url) {
            return '';
        }
        
        if (preg_match('/^https:\/\/('.$ENV->SITE_DOMAIN.'|'.$ENV->IMAGE_DOMAIN.')\//', $Url) || $Url[0] === '/') {
            if (strpos($Url, '?') === false) {
                $Url .= '?';
            }
            return $Url;
        } else {
            return 'https://'
            . $ENV->IMAGE_DOMAIN
            . ($Thumb?"/$Thumb/":'/')
            . '?h='
            . rawurlencode(base64_encode(hash_hmac('sha256', $Url, $Psk, true)))
            . '&i='
            . urlencode($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;
    }
}