constructor( template, width, height, expiration ) {
		this.template = template;
		this.expiration = expiration;

		this.url = template
			? template.replace( reWidth, width ).replace( reHeight, height )
			: null;
		this.time = null;
	}
@param {string} template
@param {number} width
@param {number} height
@param {number} expiration