let url = this.codes[0].qrImgUrl

this.getBase64(url).then(function(base64){

　　let save_link = document.createElementNS('http://www.w3.org/1999/xhtml', 'a');

　　save_link.href = base64;

　　if(that.pageType=='mediaIds'){

　　　　save_link.download = that.data[0].mediaNo+'.jpg';

　　}else{

　　　　save_link.download = that.data[0].salesmanName+that.data[0].accNo+'.jpg';

　　}

　　let event = document.createEvent('MouseEvents');

　　event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);

　　save_link.dispatchEvent(event);

},function(err){

});

getBase64(img){

　　let that = this

　　let image = new Image();

　　image.crossOrigin = '';

　　image.src = img;

　　let deferred=$.Deferred();

　　if(img){

　　　　image.onload =function (){

　　　　deferred.resolve(that.getBase64Image(image));//将base64传给done上传处理

　　}

　　return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']

　　}

},

getBase64Image(img,width,height) {//width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小

let canvas = document.createElement("canvas");

canvas.width = width ? width : img.width;

canvas.height = height ? height : img.height;

let ctx = canvas.getContext("2d");

ctx.drawImage(img, 0, 0, canvas.width, canvas.height);

let dataURL = canvas.toDataURL();

return dataURL;

},