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上传图片前预览(兼容Firefox3,IE6,IE7,IE8)

2010-07-22 18:58 721 查看

<!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">

</style>

<script type="text/javascript">
function onUploadImgChange(sender){
if( !sender.value.match( /.jpg|.gif|.png|.bmp/i ) ){
alert('图片格式无效！');
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();
}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';
}
}

function onPreviewLoad(sender){
autoSizePreview( sender, sender.offsetWidth, sender.offsetHeight );
}

function autoSizePreview( objPre, originalWidth, originalHeight ){
var zoomParam = clacImgZoomParam( 100, 120, 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 class="pr">
<div id="preview_wrapper">
<div id="preview_fake">
<img id="preview" onload="onPreviewLoad(this)"/>
</div>
</div>
</div>
<br/>
<input id="upload_img" type="file" onchange="onUploadImgChange(this)"/>
<br/>
<img id="preview_size_fake"/>
</body>
</html>

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