本文實例介紹了基于JQUERY擴展，圖片上傳預覽插件，目前兼容瀏覽器(IE 谷歌 火狐) 不支持safari，分享給大家供大家參考，具體內容如下
HTML代碼：
<html><head><title>圖片上傳預覽演示</title><script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script><script src="16/uploadPreview.js" type="text/javascript"></script><script>$(function () {$("#up").uploadPreview({ Img: "ImgPr", Width: 120, Height: 120 });});</script></head><body><div style="width:500px;margin:0px auto;"><h2>圖片上傳預覽演示</h2><a href="# target="_blank">原文</a><div><img id="ImgPr" width="120" height="120" /></div><input type="file" id="up" /></div></body></html> js代碼：
*參數說明: Img:圖片ID;Width:預覽寬度;Height:預覽高度;ImgType:支持文件類型;Callback:選擇文件顯示圖片后回調方法;*使用方法: <div><img id="ImgPr" width="120" height="120" /></div><input type="file" id="up" />把需要進行預覽的IMG標簽外 套一個DIV 然后給上傳控件ID給予uploadPreview事件$("#up").uploadPreview({ Img: "ImgPr", Width: 120, Height: 120, ImgType: ["gif", "jpeg", "jpg", "bmp", "png"], Callback: function () { }});*/jQuery.fn.extend({uploadPreview: function (opts) {var _self = this,_this = $(this);opts = jQuery.extend({Img: "ImgPr",Width: 100,Height: 100,ImgType: ["gif", "jpeg", "jpg", "bmp", "png"],Callback: function () {}}, opts || {});_self.getObjectURL = function (file) {var url = null;if (window.createObjectURL != undefined) {url = window.createObjectURL(file)} else if (window.URL != undefined) {url = window.URL.createObjectURL(file)} else if (window.webkitURL != undefined) {url = window.webkitURL.createObjectURL(file)}return url};_this.change(function () {if (this.value) {if (!RegExp("/.(" + opts.ImgType.join("|") + ")$", "i").test(this.value.toLowerCase())) {alert("選擇文件錯誤,圖片類型必須是" + opts.ImgType.join("，") + "中的一種");this.value = "";return false}if ($.browser.msie) {try {$("#" + opts.Img).attr('src', _self.getObjectURL(this.files[0]))} catch (e) {var src = "";var obj = $("#" + opts.Img);var div = obj.parent("div")[0];_self.select();if (top != self) {window.parent.document.body.focus()} else {_self.blur()}src = document.selection.createRange().text;document.selection.empty();obj.hide();obj.parent("div").css({'filter': 'progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)','width': opts.Width + 'px','height': opts.Height + 'px'});div.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = src}} else {$("#" + opts.Img).attr('src', _self.getObjectURL(this.files[0]))}opts.Callback()}})}}); 直接上第二段代碼，jquery js實現上傳圖片之前預覽本地圖片
<style type="text/css">#preview_wrapper{ display:inline-block; width:300px; height:300px; background-color:#CCC;} #preview_fake{ filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale); } #preview_size_fake{ filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image); visibility:hidden; } #preview{ width:300px; height:300px; } </style><script type="text/javascript">function onUploadImgChange(sender){ if( !sender.value.match( /.jpg|.gif|.png|.bmp/i ) ){ alert('圖片格式無效！'); return false; } var objPreview = document.getElementByIdx_x('preview'); var objPreviewFake = document.getElementByIdx_x('preview_fake'); var objPreviewSizeFake = document.getElementByIdx_x('preview_size_fake'); if( sender.files && sender.files[0] ){ objPreview.style.display = 'block'; objPreview.style.width = 'auto'; objPreview.style.height = 'auto'; // Firefox 因安全性問題已無法直接通過 input[file].value 獲取完整的文件路徑 objPreview.src = sender.files[0].getAsDataURL(); }else if( objPreviewFake.filters ){ // IE7,IE8 在設置本地圖片地址為 img.src 時出現莫名其妙的后果 //（相同環境有時能顯示，有時不顯示），因此只能用濾鏡來解決 // IE7, IE8因安全性問題已無法直接通過 input[file].value 獲取完整的文件路徑 sender.select(); var imgSrc = document.selection.createRange().text; objPreviewFake.filters.item( 'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc; objPreviewSizeFake.filters.item( 'DXImageTransform.Microsoft.AlphaImageLoader').src = imgSrc; autoSizePreview( objPreviewFake, objPreviewSizeFake.offsetWidth, objPreviewSizeFake.offsetHeight ); objPreview.style.display = 'none'; } } function onPreviewLoad(sender){ autoSizePreview( sender, sender.offsetWidth, sender.offsetHeight ); } function autoSizePreview( objPre, originalWidth, originalHeight ){ var zoomParam = clacImgZoomParam( 300, 300, originalWidth, originalHeight ); objPre.style.width = zoomParam.width + 'px'; objPre.style.height = zoomParam.height + 'px'; objPre.style.marginTop = zoomParam.top + 'px'; objPre.style.marginLeft = zoomParam.left + 'px'; } function clacImgZoomParam( maxWidth, maxHeight, width, height ){ var param = { width:width, height:height, top:0, left:0 }; if( width>maxWidth || height>maxHeight ){ rateWidth = width / maxWidth; rateHeight = height / maxHeight; if( rateWidth > rateHeight ){ param.width = maxWidth; param.height = height / rateWidth; }else{ param.width = width / rateHeight; param.height = maxHeight; } } param.left = (maxWidth - param.width) / 2; param.top = (maxHeight - param.height) / 2; return param; }</script> <input name="localfile" type="file" id="localfile" size="28" onchange="onUploadImgChange(this)"/> <!--以下是預覽圖片用的--><div id="preview_wrapper"><div id="preview_fake"><img id="preview" src="" onload="onPreviewLoad(this)"/></div></div><br/><img id="preview_size_fake" /> 以上就是本文的全部內容，希望對大家的學習有所幫助。
