Opencv cvDrawContours not working

我尝试用CvPoint矢量绘制轮廓，同时使用cvDrawContours，它不会在图像上绘制轮廓，但cvDrawRect工作完美。请说明以下代码是否有错误

 IplImage *iplMaskKeyPoints = cvCreateImage(cvGetSize(iplObjGrey),iplObjGrey->depth,1);
 CvMemStorage *msObjImgStorage = cvCreateMemStorage(0);
 CvSeq* sqObjImgPoly = cvCreateSeq(CV_32SC2, sizeof(CvSeq), sizeof(CvPoint), msObjImgStorage );
 cvZero(iplMaskKeyPoints);
 for(int i = 0; i < (int)vecObjPoly.size(); i++ )
 {
    CvPoint pt = vecObjPoly[i];
    cvSeqPush(sqObjImgPoly, &pt );
 }
cvDrawContours(iplMaskKeyPoints,sqObjImgPoly,cvScalar(255,255,255),cvScalar(255,255,255),1,CV_FILLED);
cvShowImage("output",iplMaskKeyPoints);
cvWaitKey(0);
if(sqObjImgPoly != NULL)
        {
            cvClearSeq(sqObjImgPoly);
            sqObjImgPoly = NULL;
        }
        if(msObjImgStorage != NULL)
        {
            cvClearMemStorage(msObjImgStorage);
            cvReleaseMemStorage(&msObjImgStorage);
        }
vecObjPoly.clear();
cvReleaseImage(&iplMaskKeyPoints);