js前端实现多图图片上传预览的两个方法(推荐)

一、将图片转成icon码的实现方式

html代码：

<div class="yanzRight">
	<input style="margin-top:5px;float: left;" id="st18" name="evidence" onchange="previewImage(this,5)" type="file"/>
	<span class="dui" id="imgOrder_dui" style="display: none;"></span>
</div>
	<div id="preview5" style="margin-left:150px;clear:both; padding-top:15px;">
	<img src="" alt="" id="imghead5" height="200" width="200" style="display:none;"/>
</div>

js代码

//图片预览功能
function previewImage(file,imgNum)
{
 var MAXWIDTH = 200;
 var MAXHEIGHT = 200;
 var div = document.getElementById('preview'+imgNum);
 if (file.files && file.files[0])
 {
  div.innerHTML ='<img id=imghead'+imgNum+'>';
  var img = document.getElementById('imghead'+imgNum+'');
  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 //
 {
 var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="';
 file.select();
 var src = document.selection.createRange().text;
 div.innerHTML = '<img id=imghead'+imgNum+'>';
 var img = document.getElementById('imghead2');
 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"+imgNum+" 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;
}

二、使用js的另一种方法一次选中多个图片预览展示

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>测试页面</title>
<script type="text/javascript">
 //下面用于多图片上传预览功能
 function setImagePreviews(avalue) {
  var docObj = document.getElementById("doc");
  var dd = document.getElementById("dd");
  dd.innerHTML = "";
  var fileList = docObj.files;
  for (var i = 0; i < fileList.length; i++) {   

   dd.innerHTML += "<div style='float:left' > <img id='img" + i + "' /> </div>";
   var imgObjPreview = document.getElementById("img"+i);
   if (docObj.files && docObj.files[i]) {
    //火狐下，直接设img属性
    imgObjPreview.style.display = 'block';
    imgObjPreview.style.width = '150px';
    imgObjPreview.style.height = '180px';
    //imgObjPreview.src = docObj.files[0].getAsDataURL();
    //火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式
    imgObjPreview.src = window.URL.createObjectURL(docObj.files[i]);
   }
   else {
    //IE下，使用滤镜
    docObj.select();
    var imgSrc = document.selection.createRange().text;
    alert(imgSrc)
    var localImagId = document.getElementById("img" + i);
    //必须设置初始大小
    localImagId.style.width = "150px";
    localImagId.style.height = "180px";
    //图片异常的捕捉，防止用户修改后缀来伪造图片
    try {
     localImagId.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
     localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
    }
    catch (e) {
     alert("您上传的图片格式不正确，请重新选择!");
     return false;
    }
    imgObjPreview.style.display = 'none';
    document.selection.empty();
   }
  } 

  return true;
 }

</script>
</head>

<body>
<div style="margin :0px auto; width:990px;">
<input type="file" name="file" id="doc" multiple="multiple" style="width:150px;" onchange="javascript:setImagePreviews();" accept="image/*" />
<div id="dd" style=" width:990px;"></div>
</div>
</body>
</html>

以上这篇js前端实现多图图片上传预览的两个方法(推荐)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持我们。