html之input tye=file标签 --- 图片的上传、预览
<!DOCTYPE html>
<html lang="en">
<head>
<title></title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<div style="border:2px dashed red;">
<p>
图片上传前预览：<input type="file" id="xdaTanFileImg" onchange="xmTanUploadImg(this)" accept="image/*"/>
<input type="button" value="隐藏图片" onclick="document.getElementById('xmTanImg').style.display = 'none';"/>
<input type="button" value="显示图片" onclick="document.getElementById('xmTanImg').style.display = 'block';"/>
</p>
<img id="xmTanImg" width="50%"/>
<div id="xmTanDiv"></div>
</div>
<hr />
<script type="text/javascript">
//判断浏览器是否支持FileReader接口
if (typeof FileReader == 'undefined') {
document.getElementById("xmTanDiv").InnerHTML = "<h1>当前浏览器不支持FileReader接口</h1>";
//使选择控件不可操作
document.getElementById("xdaTanFileImg").setAttribute("disabled", "disabled");
}
//选择图片，马上预览
function xmTanUploadImg(obj) {
var file = obj.files[0];
console.log(obj);
console.log(file);
console.log("file.size = " + file.size); //file.size 单位为byte
var reader = new FileReader();
reader.readAsDataURL(file)
//读取文件过程方法
reader.onloadstart = function (e) {
console.log("开始读取....");
}
reader.onprogress = function (e) {
console.log("正在读取中....");
}
reader.onabort = function (e) {
console.log("中断读取....");
}
reader.onerror = function (e) {
console.log("读取异常....");
}
reader.onload = function (e) {
console.log("成功读取....");
var img = document.getElementById("xmTanImg");
img.src = e.target.result;
//或者 img.src = this.result; //e.target == this
}
}
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<title></title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<script type="text/javascript">
//判断浏览器是否支持FileReader接口
if (typeof FileReader == 'undefined') {
document.getElementById("xmTanContentDiv").InnerHTML = "<p>当前浏览器不支持FileReader接口！</p>";
document.getElementById("xmTanFile").setAttribute("disabled", "disabled");
}
//选择文件
function xmTanUploadFile(obj){
if (obj.files.length < 1) return;
var file = obj.files[0];
if (file.size > 1024 * 1024) {
alert("文件大于1M， 太大了，小点吧！");
obj.value = "";
return;
}
}
//读取文件为二进制
function readAsBinaryString() {
var obj = document.getElementById("xmTanFile");
if (obj.files.length < 1) return;
var file = obj.files[0];
var reader = new FileReader();
//将文件以二进制形式读入页面
reader.readAsBinaryString(file);
reader.onload = function (f) {
document.getElementById("xmTanContentDiv").innerHTML = this.result;
}
}
//读取文件为文本
function readAsText() {
var obj = document.getElementById("xmTanFile");
if (obj.files.length < 1) return;
var file = obj.files[0];
var reader = new FileReader();
//将文件以文本形式读入页面
reader.readAsText(file);
reader.onload = function (f) {
document.getElementById("xmTanContentDiv").innerHTML = this.result;
}
}
</script>
<div style="border: 2px dashed red; padding: 20px 0px;">
<label>选择文件：</label>
<input type="file" id="xmTanFile" accept=".html,.js,.css,.txt,.cs,.xml" onchange="xmTanUploadFile(this)"/>
<input type="button" value="读取成二进制数据" onclick="readAsBinaryString()" />
<input type="button" value="读取成文本数据" onclick="readAsText()" />
<input type="button" value="隐藏读取内容" onclick="document.getElementById('xmTanContentDiv').style.display = 'none';"/>
<input type="button" value="显示读取内容" onclick="document.getElementById('xmTanContentDiv').style.display = 'block';"/>
<div id="xmTanContentDiv"></div>
</div>
</body>
</html>
设置a标签href为图片链接，再设置download属性，点此链接可以直接下载图片
<div style="text-align:center; padding: 5px 20px;width: 70%;">
<img id="xmTanShowImg" src=""/>
<h1><a href="javascript:void()" download="girl.jpg" id="xmTanDownload">点此下载</a></h1>
</div>
<script type="text/javascript">
//图片转成base64位字符串数据
var imgData = "data:image/png;base64,.........";
//或直接设置图片链接： var imgData = "images/picture.png";
document.getElementById("xmTanShowImg").setAttribute("src", imgData); //给图片标签设置src
document.getElementById("xmTanDownload").setAttribute("href", imgData); //给a标签设置href
</script>