html5使用canvas实现图片下载功能的示例代码-爱站

一开始考虑使用a标签的download属性进行下载：

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

但是通过测试，发现再safari中，下载的文件不能带上拓展名，所以只好换一个思路，使用canvas进行处理。

1.图片需要添加crossOrigin=’anonymous’设置图像的跨域属性

img.crossOrigin = 'anonymous';

2.使用toDataURL把图片转换成base64格式

canvas.toDataURL("image/png")

3.使用模拟点击事件，触发下载

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);

完整代码：

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';
}