一、准备工作
1.默认素材：Img_add.png
2 使用window.FileReader ：预览
二、以默认图片覆盖input：type="file"元素。浏览图片，实现预览
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="initial-scale=1.0, user-scalable=no, width=device-width">
<title>测试图片</title>
</head>
<body>
<div class="FileDiv" style="position:relative;left:0;top:0;width:150px; height:150px;" >
<input style="position:absolute;width:0px; height:0px;display:none;" type="file" accept="image/*" id="file" name="file" onchange="showPreview(this)" />
<img style="position:absolute;left:0;top:0;width:150px; height:150px;z-index:0;" width="150" height="150" id="portrait" src="Images/Img_add.png" onclick="document.getElementById('file').click()">
</div>
</body>
</html>
<script type="text/javascript">
function showPreview(source) {
var file = source.files[0];
if (!/image\/\w+/.test(file.type)) {
alert("请确保文件为图像类型");
return false;
}
if (window.FileReader) {
var fr = new FileReader();
fr.onloadend = function (e) {
document.getElementById("portrait").src = e.target.result;
document.getElementById("portrait").style.display = " inline-block";
};
fr.readAsDataURL(file);
}
}
</script>