html5使用canvas实现图片下载功能的示例代码分析

<a href="图片src" download="下载海报">
下载海报
</a>

img.crossOrigin = 'anonymous';

canvas.toDataURL("image/png")

 var save_link = document.createElement('a');
   save_link.href = image;
   save_link.download ='测试.png';
              
 var clickevent = document.createEvent('MouseEvents');
   clickevent.initEvent('click', true, false);
   save_link.dispatchEvent(clickevent);

var canvas = $('.canvas');
var cxt = canvas[0].getContext("2d");
function save(){
  var img = new Image();
  img.crossOrigin = 'anonymous';
  img.onload = function(){
    var _w = img.naturalWidth;
    var _h = img.naturalHeight;
    canvas.attr({width:_w,height:_h});
    cxt.drawImage(img,0,0);
    var image = canvas[0].toDataURL("image/png")
    var save_link = document.createElement('a');
    save_link.href = image;
    save_link.download ='测试.png';
              
    var clickevent = document.createEvent('MouseEvents');
      clickevent.initEvent('click', true, false);
      save_link.dispatchEvent(clickevent);
  };
  img.src = 'http://n.sinaimg.cn/sports/transform/20170825/NZI3-  fykiufe6650492.jpg';
}