protected function inputId()
    {
        // If we're editing an already existing image, return it's Image id
        if (($image = $this->image()) && $image->id) {
            return $image->id;
        }

        // Otherwise, use the name of the field, which should be unique compared
        // to other image fields on the page.
        if (!$this->input_id) {
            $this->input_id = '_'.preg_replace('#[^\w]#', '', $this->name);
        }

        return $this->input_id;
    }