html5 filereader 读取图片信息

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>简单的html5 File测试 for pic2base64</title> 

<script> 
window.onload = function(){ 
var input = document.getElementById("demo_input"); 
var result= document.getElementById("result"); 
var img_area = document.getElementById("img_area"); 
if ( typeof(FileReader) === 'undefined' ){ 
        result.innerHTML = "抱歉,你的浏览器不支持 FileReader,请使用现代浏览器操作!"; 
        input.setAttribute( 'disabled','disabled' ); 
} else { 
        input.addEventListener( 'change',readFile,false );} 
} 
function readFile(){ 
        var file = this.files[0]; 
        console.log(file);
        //这里我们判断下类型如果不是图片就返回 去掉就可以上传任意文件 
        if(!/image\/\w+/.test(file.type)){ 
        alert("请确保文件为图像类型"); 
        return false; 
} 
var reader = new FileReader(); 
reader.readAsDataURL(file); 
reader.onload = function(e){ 
        //result.innerHTML = '<img src="'+this.result+'" alt=""/>'; 
        //img_area.innerHTML = '<div class="sitetip">图片img标签展示:</div><img src="'+this.result+'" alt=""/>'; 
} 
} 
</script> 
</head> 
<body> 
<input type="file" value="sdgsdg"  /> 
<textarea  rows=30 cols=300></textarea> 
<p ></p> 
</body> 
</html>