經測試IE仍有安全性問題須設定，但一般USER並不會設定，故最佳建議還是把檔案直接透過AJ上傳後再來處理ㄅ
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<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{ /* 該物件用戶在IE下顯示預覽圖片 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
#preview_size_fake{ /* 該物件只用來在IE下獲得圖片的原始尺寸，無其他用途 */
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);
visibility:hidden;
}
#preview{ /* 該物件用戶在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 獲取完整的檔路徑
objPreview.src = sender.files[0].getAsDataURL();
}else if( objPreviewFake.filters ){
// IE7,IE8 在設置本地圖片位址為 img.src 時出現莫名其妙的後果
//（相同環境有時能顯示，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 獲取完整的檔路徑
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>
