效果如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>简单的html5 File测试 for pic2base64</title>
<style>
*{margin: 0; padding:0;}
#result{ width: 800px; height: 100px; margin-top: 20px; display: block; }
#box{position: fixed; width: 100%; height: 100%; background-color: rgba(0,0,0,.4); top: 0; left: 0; text-align: center; line-height: 100%; padding-top: 30%; display: none;}
</style>
</head>
<body>
将图片转成base64：<input type="file" value="sdgsdg" />';
box.style.display = 'none';
}
}
})();
</script>
</body>
</html>
转の-----http://www.2cto.com/kf/201308/232916.html