将echarts转为base64图片并且下载

var obj = document.getElementById("chartId");
var myChart = echarts.init(obj);// $obj为原生dom对象
myChart.getDataURL({
    type: 'jpeg', //png | jpeg
    pixelRatio: 2,  
    backgroundColor: '#fff' //背景色白色
});

var echartCanvas = $("#echartId").find("canvas")[0];
var image = echartCanvas.toDataURL("image/jpeg");
var a = document.createElement('a');
a.setAttribute("href", image);
a.setAttribute("download", "图片名称");
a.click();