在线图片资源转换成Base64格式

function getBase64Image(img) {
        var canvas = document.createElement("canvas");
        canvas.width = img.width;
        canvas.height = img.height;
        var ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, img.width, img.height);
        var dataURL = canvas.toDataURL("image/png"); // 可选其他值 image/jpeg
        return dataURL;
    }

    function main(src, cb) {
        var image = new Image();
        image.src = src + \'?v=\' + Math.random(); // 处理缓存
        image.crossOrigin = "*"; // 支持跨域图片
        image.onload = function () {
            var base64 = getBase64Image(image);
            cb && cb(base64);
        }
    }

    main(\'http://192.168.0.204:8082/rest/v1/newdip/web/background/15.jpg\', function (base64) {
        // console.log(base64);
        document.querySelector(".box").style.backgroundImage = `url(${base64})`;
    });

原文地址：http://www.cnblogs.com/minigrasshopper/p/9042686.html