用户上传本地磁盘中的一个图片文件作为头像

<script type="text/javascript">

//图片上传预览 IE是用了滤镜。

function previewImage(file)

{

var MAXWIDTH = 180;

var MAXHEIGHT = 180;

var div = document.getElementById('preview');

if (file.files && file.files[0])

{

div.innerHTML ='<img id=imghead>';

var img = document.getElementById('imghead');

img.onload = function(){

var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);

img.width = rect.width;

img.height = rect.height;

// img.style.marginLeft = rect.left+'px';

img.style.marginTop = rect.top+'px';

}

var reader = new FileReader();

reader.onload = function(evt){img.src = evt.target.result;}

reader.readAsDataURL(file.files[0]);

}

else //兼容IE

{

var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="';

file.select();

var src = document.selection.createRange().text;

div.innerHTML = '<img id=imghead>';

var img = document.getElementById('imghead');

img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src;

var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);

status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height);

div.innerHTML = "<div id=divhead style='width:"+rect.width+"px;height:"+rect.height+"px;margin-top:"+rect.top+"px;"+sFilter+src+"\"'></div>";

}

}

function clacImgZoomParam( maxWidth, maxHeight, width, height ){

var param = {top:0, left:0, width:width, height:height};

if( width>maxWidth || height>maxHeight )

{

rateWidth = width / maxWidth;

rateHeight = height / maxHeight;

if( rateWidth > rateHeight )

{

param.width = maxWidth;

param.height = Math.round(height / rateWidth);

}else

{

param.width = Math.round(width / rateHeight);

param.height = maxHeight;

}

}

param.left = Math.round((maxWidth - param.width) / 2);

param.top = Math.round((maxHeight - param.height) / 2);

return param;

}

</script>