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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>js特效实现图片上传前的预览效果（支持IE，FF火狐等浏览器）</title>
<script>
function setImagePreview() {
var docObj=document.getElementById("doc");
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 = '300px';
imgObjPreview.style.height = '120px';
//imgObjPreview.src = docObj.files[0].getAsDataURL();
//火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式
imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
}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 = "250px";
localImagId.style.height = "200px";
//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>
</head>
<body>
<input type=file name="doc" id="doc" onchange="javascript:setImagePreview();">
<p><div id="localImag"><img id="preview" width=-1 height=-1 style="diplay:none" /></div></p>
</body>
</html>
