js上传图片预览的实现方法

2019-11-19 16:37:45

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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>

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