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JavaScript实现图片上传预览功能

来源：互联网发布：linux 入门基础教程编辑：程序博客网时间：2024/04/29 19:33

JavaScript实现图片上传预览功能

HTML部门

<html>

<head>

</head>

<body>

<div class="control-group">
<label class="control-label">头像</label>
<div class="controls">
<div class="fileupload fileupload-new" data-provides="fileupload">
<div id="preview" class="fileupload-preview thumbnail" style="width: 180px;height:180px;margin-bottom:5px"></div>
<div>
<input name="portrait" id="por" type="file" onchange="previewImage(this)"/>
</div>
</div>
</div>

</body>

</html>

JavaScript部分:

<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 = '3px';
}
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>

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