public function initialiseImageMap(
        $Name = "pChart",
        $StorageMode = IMAGE_MAP_STORAGE_SESSION,
        $UniqueID = "imageMap",
        $StorageFolder = "tmp"
    ) {
        $this->ImageMapIndex = $Name;
        $this->ImageMapStorageMode = $StorageMode;

        if ($StorageMode == IMAGE_MAP_STORAGE_SESSION) {
            if (!isset($_SESSION)) {
                session_start();
            }
            $_SESSION[$this->ImageMapIndex] = null;
        } elseif ($StorageMode == IMAGE_MAP_STORAGE_FILE) {
            $this->ImageMapFileName = $UniqueID;
            $this->ImageMapStorageFolder = $StorageFolder;

            $path = sprintf("%s/%s.map", $StorageFolder, $UniqueID);
            if (file_exists($path)) {
                unlink($path);
            }
        }
    }