无效的过程调用和参数

<script>
<!-- fnSetRotation function --> 
var deg2radians = Math.PI * 2 / 360;
var nowDeg=0
function fnSetRotation(oObj, deg)
{   nowDeg=nowDeg+deg
    rad = nowDeg * deg2radians ;
    costheta = Math.cos(rad);
    sintheta = Math.sin(rad);
    oObj.filters.item(0).M11 = costheta;
    oObj.filters.item(0).M12 = -sintheta;
    oObj.filters.item(0).M21 = sintheta;
    oObj.filters.item(0).M22 = costheta;
}

</script><table>
    <tr>
        <td style="width: 31px" bordercolor="lightblue">
            <img id="ImageLeft" onmouseover="swapImage(this)" title="逆时针旋转90度" onclick="fnSetRotation( oDiv,-90)"
                onmouseout="unswapImage(this)" height="31" src="../images/showimgtools/turnLeft.jpg"
                width="31" runat="server">
        </td>
        <td> </td>
    </tr>
    <tr>
        <td>
            <div id="oDiv" style="z-index: 101; filter: progid:DXImageTransform.Microsoft.Matrix(sizingMethod='auto expand');
                position: absolute; top: 0px">
                <div id="oDiv1" style="padding-right: 5px; padding-left: 5px; padding-bottom: 5px;
                    padding-top: 5px; background-color: lightblue">
                    <img id="Image_pvis" src="" align="middle" runat="server" />
                </div>
            </div>
        </td>
    </tr>
</table>