.net web实现选择本地图片（上传）后预览图

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.net web实现选择本地图片（上传）后预览图

html：

 <asp:FileUpload ID="fuPic" runat="server" onchange="onFileChange(this);"/><asp:Image CssClass="cropper" ID="fuPiccropper" runat="server"/>

js：

function onFileChange(sender) {document.getElementById("fuPiccropper").src = window.URL.createObjectURL(sender.files[0]);        };

效果图：

更新于2016年2月17 ---------- 实现该功能的第二种办法（纯js，IE用滤镜实现），实现兼容所有浏览器：

css：

<style type="text/css">    #preview {        width: 260px;        height: 190px;        border: 1px solid #000;        overflow: hidden;    }    #imghead {        filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);    }</style>

html：

<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>

实现功能核心js代码：

<script type="text/javascript">    //图片上传预览  IE用滤镜。    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>

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