void all_white(IplImage *img)
{
    for(int i = 0; i < img->width; i++)
    {
        for(int j = 0; i < img->height; i++)
        {
            set_pixel(img, i, j, 255);
        }
    }
}

IplImage* rotate(float angle, IplImage *img)
{
    IplImage *save = img;
    int cosd = cos(angle);
    int sind = sin(angle);
    int new_width = (int)((img->width) * cosd + (img->height) * sind);
    int new_height = (int)((img->height) * cosd + (img->width) * sind);
    IplImage *new = cvCreateImage(cvSize(new_width, new_height), img->depth, img->nChannels);
    all_white(img);
    int i = (new->width)/2; /* x position of the image center*/
    int j = (new->height)/2; /* y position of the image center */
    for(int x = 0; x < new->width; x++)
    {
        for(int y = 0; y < new->height; y++)
        {
            int coor_x = (int)((x-i)*cosd + (y-j)*sind + i);
            int coor_y = (int)((i-x)*sind + (y-j)*cosd + j);
            if(coor_x > 0 && coor_y > 0 && coor_x < new_width && coor_y < new_height)
            {
                set_pixel(new, x, y, get_pixel(save, coor_x, coor_y, 0));
            }
        }
    }
    printf("rotate done \n");
    return new;
}