void ljb_cv_rotate_buf_size(IplImage *imgSrc, double degree, int *w_dst, int *h_dst)

{

    double angle, a, b;

    int    w_src, h_src;

    angle = degree  * CV_PI / 180.;

    a = sin(angle), b = cos(angle); 

    w_src = imgSrc->width;

    h_src = imgSrc->height;

    *w_dst = (int)(h_src * fabs(a) + w_src * fabs(b));

    *h_dst = (int)(w_src * fabs(a) + h_src * fabs(b));

}

void ljb_cv_rotate(IplImage *imgSrc, IplImage *imgDst, double degree)

{

    double angle, a, b;

    int    w_src, h_src, w_dst, h_dst;

    double map[6];

    CvMat  map_matrix = cvMat(2, 3, CV_64FC1, map);

    CvPoint2D32f pt = {0};

    angle = degree  * CV_PI / 180.;

    a = sin(angle), b = cos(angle); 

    w_src = imgSrc->width;

    h_src = imgSrc->height;

    w_dst = imgDst->width;

    h_dst = imgDst->height;

    pt = cvPoint2D32f(w_src / 2, h_src / 2);

    cv2DRotationMatrix(pt, degree, 1.0, &map_matrix);//旋转中心，角度，尺度，生成2*3旋转矩阵

    // Adjust rotation center to dst's center,

    // otherwise you will get only part of the result

    map[2] += (w_dst - w_src) / 2;

    map[5] += (h_dst - h_src) / 2;

    cvWarpAffine(

        imgSrc,

        imgDst,

        &map_matrix,

        CV_INTER_LINEAR | CV_WARP_FILL_OUTLIERS,

        cvScalarAll(0)

        );

}

    IplImage* img = cvLoadImage("E:\\bgtest.bmp", CV_LOAD_IMAGE_GRAYSCALE);

    IplImage* dst = NULL;

    int dstWidth, dstHeight = 0;

    IplImage* imgRotate = NULL;

    CvSize cvsize = {0};

    ljb_cv_rotate_buf_size(img, 45, &dstWidth, &dstHeight);

    cvsize.width = dstWidth;

    cvsize.height = dstHeight;

    imgRotate = cvCreateImage(cvsize, IPL_DEPTH_8U, 1);

    cvZero(imgRotate);

    ljb_cv_rotate(img, imgRotate, 45);

     cvSaveImage("E:\\saltsingle3000.bmp",imgRotate);