网络图片转base64格式

// 定义网络图转base64的方法
function getBase64(url, ext, callback) {
    var canvas = document.createElement("canvas");   //创建canvas DOM元素
    var ctx = canvas.getContext("2d");
    var img = new Image;
    img.crossOrigin = 'Anonymous';
    img.src = url;
    img.onload = function () {
        canvas.width = img.width; //指定画板的宽度，自定义
        canvas.height = img.height; //指定画板的高度,自定义
        ctx.drawImage(img, 0, 0, img.width, img.height); //参数可自定义
        var dataURL = canvas.toDataURL("image/" + ext);
        callback.call(this, dataURL); //回掉函数获取Base64编码
        canvas = null;
    };
}

var imgUrl = 'http://124.205.255.18:8003/sstbk/xpkpsmsz/getEwm_open?uuid=2188d0406784467a97d6d12ef6851fdc&je=4.00&isClient=true';
getBase64(imgUrl, 'png', function(base64){
    // 给原生img对象的src属性赋值
    img.src = base64;
})