type="file" 选择图片后预览

function setImagePreview(avalue) {
    var docObj = document.getElementById("doc");
    
    var imgObjPreview = document.getElementById("preview");
    if(docObj.files &&docObj.files[0]){
    /*//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[0]);*/
    
        $("#localImag").html('<img id="preview" src='+window.URL.createObjectURL(docObj.files[0])+' style="display: block; width: 192px; height: 144px;" />');
    }
    else
    {
    //IE下，使用滤镜
    docObj.select();
    docObj.blur();
    var imgSrc = document.selection.createRange().text;
    var localImagId = document.getElementById("localImag");
    //必须设置初始大小
    localImagId.style.width = "192px";
    localImagId.style.height = "144px";
    //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;
}