nodejs远程获取图片

if(require("http")) {
            var http = require("http");
            http.get(url,function (res) {
                res.setEncoding('binary');//二进制（binary）
                var re ='';
                res.on('data',function (data) {
                    re += data;
                    // collect the data chunks to the variable named "html"

                }).on('end', function () {
                        //console.log(re);
                        var key = getKeyByURL(url);
                        var b = new Buffer(re);
                        var imageData =toArrayBuffer(b)
                         getCanvasData(key, imageData, order);
                    })
            }).on('error', function (e) {
                    console.log("Got error: " + e.message);
                });
        }

    };

function getCanvasData (key, buffer, order) {
        createCanvas();
        var _blob = new Blob(new Array(buffer), { type: "image/jpeg" });
        var _url = URL.createObjectURL(_blob);
        var _img = new Image();
        var imgData = undefined;
        _img.onload = function () {
            ctx.clearRect(0, 0, 256, 256);
            ctx.drawImage(this, 0, 0);
            URL.revokeObjectURL(_url);
            imgData = ctx.getImageData(0, 0, 256, 256);
            cache[order](key, imgData);
            exeCheckCallback(key, imgData);
        };
        _img.onerror = function () {
            exeCheckCallback(key, imgData);
        };
        _img.src = _url;
    };

function createCanvas() {
        if (!canvas) {
            canvas = document.createElement('canvas');
            canvas.width = 256;
            canvas.height = 256;
            ctx = canvas.getContext('2d');
        }
    }