将画布上的图像转化为base64字符串

绘制图片

    var b = document.createElement("canvas");    var j = b.getContext("2d");    var i = b.width;    var d = b.height;    var a = $("#photo");    var k = a[0].width;    var e = a[0].height;    j.drawImage(a[0], 0, 0)   //在画布上原样输出图片    j.drawImage(a[0], 0, 0, k, e, 0, 0, i, d);  //在画布上将图片拉伸

将图像转为base64字符串

 var base64=b.toDataURL();