void screenshot()
{
    SDL_Surface *image;
    SDL_Surface *temp;
    int idx;
    if((image = SDL_CreateRGBSurface(SDL_SWSURFACE, scr_w, scr_h, 24, 0x0000FF, 0x00FF00, 0xFF0000, 0)))
    {
        if((temp = SDL_CreateRGBSurface(SDL_SWSURFACE, scr_w, scr_h, 24, 0x0000FF, 0x00FF00, 0xFF0000, 0)))
        {
            glReadPixels(0, 0, scr_w, scr_h, GL_RGB, GL_UNSIGNED_BYTE, image->pixels);
            for (idx = 0; idx<scr_h; idx++)
            {
                char *dest = (char *)temp->pixels+temp->pitch*idx;
                memcpy(dest, (char *)image->pixels+image->pitch*(scr_h-1-idx), 3*scr_w);
                endianswap(dest, 3, scr_w);
            }
            s_sprintfd(buf)("screenshot_%d.bmp", lastmillis);
            SDL_SaveBMP(temp, buf);
            SDL_FreeSurface(temp);
        }
        SDL_FreeSurface(image);
    }
}