html+js实现图片上传前预先预览 

<html>
<head>
<script type="text/javascript">  
function setImagePreview() {  
    var docObj=document.getElementById("doc");  
    var imgObjPreview=document.getElementById("<%=preview.ClientID%>");  
    if(docObj.files && docObj.files[0]){  
        //火狐下，直接设img属性  
        imgObjPreview.style.display = 'block';  
        imgObjPreview.style.width = '90px';  
        imgObjPreview.style.height = '120px';                      
        //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[0]);  
    }else{  
        //IE下，使用滤镜  
        docObj.select();  
        var imgSrc = document.selection.createRange().text;  
        var localImagId = document.getElementById("localImag");  
        //必须设置初始大小  
        localImagId.style.width = "90px";  
        localImagId.style.height = "120px";  
        //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 id="localImag" style="width:130px;text-align:center; margin-left:auto; margin-right:auto;"><img id="preview" style="width:90px; height:120px;" runat="server" /></div>
                                        <p><input type=file name="doc" id="doc" onchange="javascript:setImagePreview();"></p>
</body>

posted @ 2015-08-06 15:54  燕儿归  阅读(199)  评论(0)    收藏  举报