图片链接转成base64

一半需要我的图像转换为base64字符串，这样我们可以把我的形象到服务器。现在我们提供一个js：

function convertImgToBase64(url, callback, outputFormat){var canvas = document.createElement('CANVAS'), ctx = canvas.getContext('2d'), img =newImage; img.crossOrigin ='Anonymous'; img.onload =function(){ canvas.height = img.height; canvas.width = img.width; ctx.drawImage(img,0,0);var dataURL = canvas.toDataURL(outputFormat ||'image/png'); callback.call(this, dataURL); canvas =null;}; img.src = url;} convertImgToBase64('http://bit.ly/18g0VNp',function(base64Img){// Base64DataURL});