js实现上传图片及时预览

本文实例为大家分享了javascript图片预览功能实现的具体代码，供大家参考，具体内容如下

先为大家分享一段关于js图片预览的代码，兼容火狐和谷歌浏览器

 /* 案例展示图片预览 */
$(function(){
  $("#file0").bind("change",function(){

    clickupLoad();
  });
});
function clickupLoad(){

  var imgObject = document.getElementById('file0');
  var getImageSrc = getFullPath(imgObject); // 本地路径
  var srcs = window.URL.createObjectURL(imgObject.files[0]);
  var pos = getImageSrc.lastIndexOf(".");
  var lastname = getImageSrc.substring(pos, getImageSrc.length) // 图片后缀]

  if(srcs!=""){
    $("#yulan2").attr("src",srcs);
  }else{
    alert("请选择一张图片");
  }

}
function getFullPath(obj) {  //得到图片的完整路径
  if (obj)
  {
    if (window.navigator.userAgent.indexOf("MSIE") >= 1){
      obj.select();
      return document.selection.createRange().text;

    }else if(window.navigator.userAgent.indexOf("Firefox") >= 1) {
      if (obj.files) {
        return window.URL.createObjectURL(obj.files[0]);
      }
      return obj.value;
    }
    return obj.value;
  }
}

实例代码实现js上传图片及时预览：

<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，希望对大家学习javascript程序设计有所帮助。