/**
 * 图片格式化
 * @param  {[String]} url
 * @param  {[Number]} width
 * @param  {[Number]} height
 * @param  {[String]} mode
 * @return {[boolen]}
 */
module.exports = function(url, width, height, mode) {
    mode = parseInt(mode, 10) ? mode : 2;
    url = url || '';
    return url.replace(/{width}/g, width).replace(/{height}/g, height).replace(/{mode}/g, mode);
};