前段時(shí)間做了一個(gè)會(huì)員頭像上傳，能自動(dòng)生成多尺寸預(yù)覽效果，當(dāng)然如果你并不需要那么多尺寸的預(yù)覽效果就用一個(gè)預(yù)覽區(qū)即可。剛開始考慮采用ajax調(diào)用，但前臺(tái)數(shù)據(jù)需要點(diǎn)擊提交才能調(diào)用數(shù)據(jù)庫內(nèi)容，并不是同步預(yù)覽，這條路并不通，因此還是采用JS的方法。

JS部分

       先引用公共JS庫，下面增加

<script type="text/javascript">
<!--
//下面用于圖片上傳預(yù)覽功能
function setImagePreview(avalue){
 var docObj=document.getElementById("face");//上傳元素ID
 var imgObjPreview=document.getElementById("preview");
 var imgObjPreview=document.getElementById("preview2");
 var imgObjPreview=document.getElementById("preview3");
 if(docObj.files &&docObj.files[0])
 {
 //火狐下，直接設(shè)img屬性
 imgObjPreview.style.display = 'block';
 imgObjPreview.style.width = '150px';
 imgObjPreview.style.height = '150px';
 imgObjPreview2.style.display = 'block';
 imgObjPreview2.style.width = '110px';
 imgObjPreview2.style.height = '110px';
 imgObjPreview3.style.display = 'block';
 imgObjPreview3.style.width = '40px';
 imgObjPreview3.style.height = '40px';
 //imgObjPreview.src = docObj.files[0].getAsDataURL();
 //火狐7以上版本不能用上面的getAsDataURL()方式獲取，需要以下方式
 imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
 imgObjPreview2.src = window.URL.createObjectURL(docObj.files[0]);
 imgObjPreview3.src = window.URL.createObjectURL(docObj.files[0]);
 }
 else
 {
 //IE下，使用濾鏡
 docObj.select();
 var imgSrc = document.selection.createRange().text;
 var localImagId = document.getElementById("localImag");
 var localImagId2 = document.getElementById("localImag2");
 var localImagId3 = document.getElementById("localImag3");
 //必須設(shè)置初始大小
 localImagId.style.width = "150px";
 localImagId.style.height = "150px";
 localImagId2.style.width = "110px";
 localImagId2.style.height = "110px";
 localImagId3.style.width = "40px";
 localImagId3.style.height = "40px";
 //圖片異常的捕捉，防止用戶修改后綴來偽造圖片
 try{
 localImagId.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
 localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
 localImagId2.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
 localImagId2.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
 localImagId3.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
 localImagId3.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
 }
 catch(e){  
 alert("您上傳的圖片格式不正確，請(qǐng)重新選擇!");
 return false;
 }
 imgObjPreview.style.display = 'none'; document.selection.empty(); 
 imgObjPreview2.style.display = 'none'; document.selection.empty(); 
 imgObjPreview3.style.display = 'none'; document.selection.empty(); 
 } 
 return true;
}
-->
</script>

HTML部分

<p class="fieldbtn">
 <input name="face" type="file" id="face" size="45" onchange="javascript:setImagePreview();"/>
</p>
<p id="localImag" >
 <img id="preview" src="images/view.png" width="150" height="150"/>
 <img id="preview2" src="images/view.png" width="110" height="110"/>
 <img id="preview3" src="images/view.png" width="40" height="40"/>
</p>

上傳按鈕CSS樣式

       系統(tǒng)默認(rèn)的上傳按鈕比較難看，分享案例的上傳按鈕樣式

<style type="text/css">
.fieldbtn{width:84px;height:28px;text-align:center;border:1px solid #ccc;position:relative;overflow:hidden;display:inline-block;cursor:pointer;}
.fieldbtn input{font-size:100px;right:0;top:0;position:absolute;opacity:0;filter:alpha(opacity=0);cursor:pointer;z-index:999;}
</style>