function getImgBase64(path, callback) {    var img = new Image();    img.src = path;    //图片加载完成后触发    img.onload = function () {        var canvas = document.createElement("canvas");        //获取绘画上下文        ctx = canvas.getContext("2d");        // 获取图片宽高        var imgWidth = img.width;        var imgHeight = img.height;        //设置画布宽高与图片宽高相同        canvas.width = imgWidth;        canvas.height = imgHeight;        //绘制图片        ctx.drawImage(img, 0, 0, imgWidth, imgHeight);        //图片展示的 data URI        var dataUrl = canvas.toDataURL('image/jpeg');        callback ? callback(dataUrl) : '';    };}getImgBase64('wood.png', function (dataUrl) {    console.log(dataUrl);});