跨域图片下载

var downloadIamge = function(imgsrc, name) {
  let image = new Image();
  // 解决跨域 Canvas 污染问题
  image.setAttribute("crossOrigin", "anonymous");
  image.onload = function() {
  let canvas = document.createElement("canvas");
  canvas.width = image.width;
       canvas.height = image.height;
       let context = canvas.getContext("2d");
       context.drawImage(image, 0, 0, image.width, image.height);
       let url = canvas.toDataURL("image/png"); 
       let a = document.createElement("a"); 
       let event = new MouseEvent("click");
       a.download = name || "photo"; 
       a.href = url; 
       a.dispatchEvent(event);
 };
 image.src = imgsrc;
}