void smooth(int dim, pixel *src, pixel *dst)
{
    register int i;
    register int j;

    register int d = dim;

    for(j = 0; j < d; ++j)
    {
        register int rdx = j;

        for(i = 0; i < d; ++i)
        {
            register int red = 0;
            register int green = 0;
            register int blue = 0;
            register int num = 0;

            register int min_i = min(i+1,d-1);
            register int min_j = min(j+1,d-1);
            register int max_i = max(i-1,0);

            register int jj = max(j-1,0);

            for(; jj <= min_j; ++jj)
            {
                register int rdx2 = jj + max_i * d;
                register int ii = max_i;
                for(; ii <= min_i; ++ii) 
                {
                    red += src[rdx2].red;
                    green += src[rdx2].green;
                    blue += src[rdx2].blue;
                    ++num;
                    rdx2 += d;
                }
            }

            dst[rdx].red = (red / num);
            dst[rdx].green = (green / num);
            dst[rdx].blue = (blue / num);

            rdx += d;
        }
    }
}