将图片转canvas

js代码：

var canvas = document.createElement('canvas');
var context = canvas.getContext('2d');

var img = new Image();
img.crossOrigin = '';  //图片转canvas
img.onload = function () {
    context.drawImage(this, 0, 0);
    context.getImageData(0, 0, this.width, this.height);
   document.body.appendChild(canvas);
};
img.src = "https://pic4.zhimg.com/869cf812c5a1beb827d723e6332748a1_m.jpg";

　　

　　在图片onload以后生成并添加到body里面