js前端实现多图图片上传预览的两个方法

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>

最后再给大家推荐一个源码网站，原创源码库，我感觉很不错，可以找到很多大部分的网站程序，很值得收藏

js前端实现多图图片上传预览的两个方法

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