js绝对地址图片转换成base64的方法

//将图片转换成base64
        function getBase64Image(url, callback){
          var canvas = document.createElement('canvas'),
              ctx = canvas.getContext('2d'),
              img = new Image();
          //为了解决跨域，可以直接img.crossOrigin=''就能解决图片跨域问题
          img.crossOrigin = 'xes';
          img.onload = function(){
              canvas.height = img.height;
              canvas.width = img.width;
              ctx.drawImage(img,0,0);
              var dataURL = canvas.toDataURL('image/png');
              callback.call(this, dataURL);
              canvas = null; 
          }
          img.src = url;
        } 
        getBase64Image('http://app1.xesimg.com/roommsg/9071347a804c1b2f9b27ee4198f4e738_small.jpg', function(base64Img){
           console.log(base64Img)
        });