<!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>Firefox3,IE6,IE7,IE8上传图片预览</title>
<style type=”text/css”>
#preview_wrapper{
display:inline-block;
width:300px;
height:300px;
background-color:#CCC;
}
#preview_fake{ /* 该对象用于在IE下显示预览图片 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
#preview_size_fake{ /* 该对象只用来在IE下获得图片的原始尺寸，无其它用途 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);
visibility:hidden;
}
#preview{ /* 该对象用于在FF下显示预览图片 */
width:300px;
height:300px;
}
</style>
<script type=”text/javascript”>
function onUploadImgChange(sender){
var filePath = sender.value;
var fileExt = filePath.substring(filePath.lastIndexOf(“.”)).toLowerCase();
if(!checkFileExt(fileExt))
{
alert(“您上传的文件不是图片,请重新上传！”);
return;
}
var objPreview = document.getElementById( ‘preview’ );
var objPreviewFake = document.getElementById( ‘preview_fake’ );
var objPreviewSizeFake = document.getElementById( ‘preview_size_fake’ );
try{
if( sender.files && sender.files[0] ){
objPreview.style.display = ‘block’;
objPreview.style.width = ‘auto’;
objPreview.style.height = ‘auto’;
// Firefox 因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
objPreview.src = sender.files[0].getAsDataURL();
//读取图片文件大小
fileSize = sender.files[0].fileSize;
checkFileSize(sender,fileSize);
}else if( objPreviewFake.filters ){
// IE7,IE8 在设置本地图片地址为 img.src 时出现莫名其妙的后果
//（相同环境有时能显示，有时不显示），因此只能用滤镜来解决
// IE7, IE8因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
sender.select();
var imgSrc = document.selection.createRange().text;
objPreviewFake.filters.item(
‘DXImageTransform.Microsoft.AlphaImageLoader’).src = imgSrc;
objPreviewSizeFake.filters.item(
‘DXImageTransform.Microsoft.AlphaImageLoader’).src = imgSrc;
autoSizePreview( objPreviewFake,
objPreviewSizeFake.offsetWidth, objPreviewSizeFake.offsetHeight );
objPreview.style.display = ‘none’;
//读取图片文件大小
var sh = setInterval(
function(){
var img = document.createElement(“img”);
img.src = imgSrc;
fileSize = img.fileSize;
if (fileSize > 0){ checkFileSize(sender,fileSize);clearInterval(sh);}
img = null;
}
,100);
}
}catch(e)
{
alert(“您上传的文件过大或者不是图片,请重新上传！”);
}
}
function onPreviewLoad(sender){
autoSizePreview( sender, sender.offsetWidth, sender.offsetHeight );
}
function autoSizePreview( objPre, originalWidth, originalHeight ){
var zoomParam = clacImgZoomParam( 300, 300, originalWidth, originalHeight );
objPre.style.width = zoomParam.width + ‘px’;
objPre.style.height = zoomParam.height + ‘px’;
objPre.style.marginTop = zoomParam.top + ‘px’;
objPre.style.marginLeft = zoomParam.left + ‘px’;
}
function clacImgZoomParam( maxWidth, maxHeight, width, height ){
var param = { width:width, height:height, top:0, left:0 };
if( width>maxWidth || height>maxHeight ){
rateWidth = width / maxWidth;
rateHeight = height / maxHeight;
if( rateWidth > rateHeight ){
param.width = maxWidth;
param.height = height / rateWidth;
}else{
param.width = width / rateHeight;
param.height = maxHeight;
}
}
param.left = (maxWidth – param.width) / 2;
param.top = (maxHeight – param.height) / 2;
return param;
}
function checkFileSize(sender,fileSize)
{
if(fileSize > 3145728)
{
alert(“您上传的文件过大,请上传小于3M的图片！”);
return false;
}
return true;
}
function checkFileExt(ext)
{
if (!ext.match(/.jpg|.gif|.png|.bmp/i)) {
return false;
}
return true;
}
</script>
</head>
<body>
<div id=”preview_wrapper”>
<div id=”preview_fake”>
<img id=”preview” οnlοad=”onPreviewLoad(this)”/>
</div>
</div>
<br/>
<input id=”upload_img” type=”file” οnchange=”onUploadImgChange(this)”/>
<br/>
<img id=”preview_size_fake”/>
</body>
</html>
代码二：
<html xmlns=”http://www.w3.org/1999/xhtml” xml:lang=”en” lang=”en”>
<head>
<title></title>
</head>
<body>
系统允许的大小:<input type=”text” size=”4″ value=”10″ name=”fileSizeLimit” id=”fileSizeLimit”/> K
<input type=”file” name=”file1″ id=”file1″ size=”40″ οnchange=”changeSrc(this)”/>
<img src=”about:blank” id=”fileChecker” alt=”test” height=”180″/> <!–巧妙之处–>
<script type=”text/javascript”>
var oFileChecker = document.getElementById(“fileChecker”);
function changeSrc(filePicker)
{
if(window.addEventListener){ // FF
oFileChecker.src = document.getElementById(‘file1’).files[0].getAsDataURL();
oFileChecker.addEventListener(‘load’, function(){isFFCompleted(document.getElementById(‘file1’).files[0]);}, false);
}else{ // IE
oFileChecker.src = filePicker.value;
oFileChecker.attachEvent(“onreadystatechange”, function(){isIECompleted(oFileChecker);});
}
}
function isIECompleted(fileObj){
if (oFileChecker.readyState == “complete”)
{
checkSize(fileObj);
}
}
function isFFCompleted(fileObj){
if ( oFileChecker.complete )
{
checkSize(fileObj);
}
}
function checkSize(fileObj)
{
var limit = document.getElementById(“fileSizeLimit”).value * 1024;
if (fileObj.fileSize > limit)
{
alert(“文件太大”);
}
else
{
alert(“文件正确”);
}
}
</script>
</body>
</html>
代码三：
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd”>
<html xmlns=”http://www.w3.org/1999/xhtml”>
<body>
<input type=file name=”doc” id=”doc” οnchange=”javascript:setImagePreview();”>
<p>
<div id=”localImag”><img id=”preview” width=-1 height=-1 style=”diplay:none” /></div>
</p>
<script>
function setImagePreview() {
var docObj=document.getElementById(“doc”);
var fileName = docObj.value;
var imgObjPreview=document.getElementById(“preview”);
if(docObj.files && docObj.files[0]){
//火狐下，直接设img属性
imgObjPreview.style.display = ‘block’;
imgObjPreview.style.width = ‘150px’;
imgObjPreview.style.height = ‘120px’;
imgObjPreview.src = docObj.files[0].getAsDataURL();
}else{
//IE下，使用滤镜
docObj.select();
var imgSrc = document.selection.createRange().text;
var localImagId = document.getElementById(“localImag”);
//必须设置初始大小
localImagId.style.width = “150px”;
localImagId.style.height = “120px”;
//图片异常的捕捉，防止用户修改后缀来伪造图片
try{
localImagId.style.filter=”progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)”;
localImagId.filters.item(“DXImageTransform.Microsoft.AlphaImageLoader”).src = imgSrc;
}catch(e){
alert(“您上传的图片格式不正确，请重新选择!”);
return false;
}
imgObjPreview.style.display = ‘none’;
document.selection.empty();
}
return true;
}
</script>
</body>
</html>