1、設置Internet選項：安全-自定義級別-將文件上傳到服務器時包含本地目錄路徑-啟用
2、在加入head中加入
<style type="text/css">
#PreviewImg
{
FILTER: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)
}
</style>
<script type="text/javascript">
function ShowImg(obj)
{
var AllowExt = ".jpg|.gif|.bmp|";
var FileExt = obj.value.substr(obj.value.lastIndexOf(".")).toLowerCase();
if (AllowExt != 0 && AllowExt.indexOf(FileExt + "|") == -1) //判斷文件類型是否允許上傳
{
alert("您上傳的不是圖片！");
}
else
{
var newPreview = document.getElementById("PreviewImg");
newPreview.innerHTML = "";
newPreview.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = obj.value;
newPreview.style.width = "100px";
newPreview.style.height = "100px";
}
}
</script>
3、頁面中控件：
<asp:FileUpload ID="ZhuCSBUpload" runat="server" Width="200px" onchange='ShowImg(this)' />
<div id="PreviewImg" style="width: 100px; height: 100px">
</div>
以下方法兼容IE7,IE8,FF，你只要看清了頁面所有元素，給個空白頁面，再將以下內容全加進去就能運行了
<!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上傳圖片預覽</title>
<style type="text/css">
#preview_wrapper{
display:inline-block;
width:300px;
height:300px;
background-color:#CCC;
}
#preview_fake{ /* 該對象用戶在IE下顯示預覽圖片 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
#preview_size_fake{ /* 該對象只用來在IE下獲得圖片的原始尺寸，無其它用途 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);
visibility:hidden;
}
#preview{ /* 該對象用戶在FF下顯示預覽圖片 */
width:300px;
height:300px;
}
</style>
<script type="text/javascript">
function onUploadImgChange(sender){
if( !sender.value.match( /.jpg|.gif|.png|.bmp/i ) ){
alert('圖片格式無效！');
return false;
}
var objPreview = document.getElementById( 'preview' );
var objPreviewFake = document.getElementById( 'preview_fake' );
var objPreviewSizeFake = document.getElementById( 'preview_size_fake' );
if( sender.files && sender.files[0] ){
objPreview.style.display = 'block';
objPreview.style.width = 'auto';
objPreview.style.height = 'auto';
// Firefox 因安全性問題已無法直接通過 input[file].value 獲取完整的文件路徑
objPreview.src = sender.files[0].getAsDataURL();
}else if( objPreviewFake.filters ){
// IE7,IE8 在設置本地圖片地址為 img.src 時出現(xiàn)莫名其妙的后果
//（相同環(huán)境有時能顯示，有時不顯示），因此只能用濾鏡來解決
// IE7, IE8因安全性問題已無法直接通過 input[file].value 獲取完整的文件路徑
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';
}
}
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;
}
</script>
</head>
<body>
<div id="preview_wrapper">
<div id="preview_fake">
<img id="preview" onload="onPreviewLoad(this)"/>
</div>
</div>
<br/>
<input id="upload_img" type="file" onchange="onUploadImgChange(this)"/>
<br/>
<img id="preview_size_fake"/>
</body>
</html>
