JS 实现图片直接下载

<a href="picName.jpg"   id=pic1 onclick="savepic();return false;"style="cursor:hand">点击下载</a>    

1. <script type="text/javascript"> 
   
2. function savepic() {  
3.             if (document.all.a1 == null) {  
4.                 objIframe = document.createElement("IFRAME");  
5.                 document.body.insertBefore(objIframe);  
6.                 objIframe.outerHTML = "<iframe name=a1 style='width:400px;hieght:300px' src=" + imageName.href + "></iframe>";  
7.                 re = setTimeout("savepic()", 1)  
8.             }  
9.             else {  
10.                 clearTimeout(re)  
11.                 pic = window.open(imageName.href, "a1")  
12.                 pic.document.execCommand("SaveAs")  
13.                 document.all.a1.removeNode(true)  
14.             }  
15.         }   
16. </script>  
17.