在node.js中如何实现下载图片

var request=require("request");
var fs=require("fs");
function download1(url,filename,fn){
request(url).pipe(fs.createWriteStream(filename).on("close",function(err,res){
if(err){
console.log(err);
}else{
fn&&fn();
}
}))
}
function download2(url,filename,fn){
request.get({uri:url, encoding:'binary'},function(err,res){
if(!err){
fs.writeFile(filename,res.body,"binary",function(err,res){
if(!err){
fn&&fn();
}else{
console.log(err);
}
})
}
})
}

var express = require('express');
var request = require('request');
var http = require('http');
var url = require('url');
var fs = require("fs");
var router = express.Router();
/* GET home page. */
router.get('/', function (req, res, next) {
  var url = "http://www.valu.cn/images/1.gif";
  //request('http://www.valu.cn/images/1.gif').pipe(fs.createWriteStream('./public/upload/downImg/logonew.png'));
  var req = http.get(url, function (res) {
    var imgData = "";
    res.setEncoding("binary"); //一定要设置response的编码为binary否则会下载下来的图片打不开
    res.on("data", function (chunk) {
      imgData += chunk;
    });
    res.on("end", function () {
      fs.writeFile("./public/upload/downImg/logonew.png", imgData, "binary", function (err) {
        if (err) {
          console.log("保存失败");
        }
        console.log("保存成功");
      });
    });
    res.on("error", function (err) {
      console.log("请求失败");
    });
  });
  req.on('error', function (err) {
    console.log("请求失败2" + err.message);
  });
  res.render('index', {title: '首页2'});
});
module.exports = router;