js上传图片预览的实现方法
程序员文章站
2022-10-31 13:23:04
本文实例为大家分享了js上传图片预览的方法，供大家参考，具体内容如下
本文实例为大家分享了js上传图片预览的方法，供大家参考，具体内容如下
<html >
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>图片上传本地预览</title>
<style type="text/css">
#preview{width:260px;height:190px;border:1px solid #000;overflow:hidden;}
#imghead {filter:progid:dximagetransform.microsoft.alphaimageloader(sizingmethod=image);}
</style>
<script type="text/javascript">
//图片上传预览 ie是用了滤镜。
function previewimage(file)
{
var maxwidth = 260;
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>
</head>
<body>
<div id="preview">
<img id="imghead" width=100 height=100 border=0 src='<%=request.getcontextpath()%>/images/defaul.jpg'>
</div>
<input type="file" onchange="previewimage(this)" />
</body>
</html>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。