用JavaScript限制图片上传长宽
类别: JavaScript教程 
<html>
<head>
<title>Upload Image</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<form name="IUpload" action="upfile.asp" method="post">
<p><input type="file" name="picsrc" size="40" onchange="picshow.src=document.IUpload.picsrc.value">
<input type="button" value="上载" onclick="detect()"></p></form>
<p><img name="picshow" src="http://www.webjx.com/img/photo09291-7.jpg" title="图像预览"></p>
</body>
</html>
<SCRIPT LANGUAGE="JavaScript">
<!--
function imgExceedSize(w,h){
if(!document.IUpload.picsrc.value==""){
if(picshow.width>w||picshow.height>h){
alert("图像尺寸："+picshow.width+"X"+picshow.height+"。\\图像尺寸过大！你只能上传尺寸为 "+w+"×"+h+"的图像，请重新浏览图片！");
return true;
}else{
return false;
}
}else{
return true;
}
}
function detect(){
var ok=imgExceedSize(50,50);
if(ok){
document.IUpload.reset();
}else{
document.IUpload.submit();
}
}
//-->
</SCRIPT>
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