基于javascript代码实现通过点击图片显示原图片

前端技术 2023/09/02 JavaScript

废话不多说了，直接给大家贴js实现点击图片显示原图片的代码，具体代码如下所示：

function DrawImage(ImgD){
  var image = new Image();
  image.src=ImgD.src;
  var width = $(ImgD).attr(\"width\");
  var height = $(ImgD).attr(\"height\");
  if(width >100 && height>80){
    ImgD.width=100; 
    ImgD.height=80;
    ImgD.alt=image.width+\"×\"+image.height;
  }else{
    if(image.width>0 && image.height>0){
      flag=true;
      if(image.width>300 || image.height>200){
        ImgD.width=image.width/2; 
        ImgD.height=image.height/2;
        ImgD.alt=image.width+\"×\"+image.height;
      }else{
        ImgD.width=image.width;  
        ImgD.height=image.height;
        ImgD.alt=image.width+\"×\"+image.height;
      }
    }
  }
}

下面分享一段关于js实现上传图片及时预览

<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">
<html xmlns=\"http://www.w3.org/1999/xhtml\" >
<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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