integral-image

void integral2(int h, int w, uchar *src, uint *sum)
{
    uchar *pg;
    uint *ps;
    uint *psu;
    uint s; // line sum

    for (int c = 0; c < n_bins; c++) {
        pg = src + c * w * h;
        ps = sum + n_bins * (w + 2) + c;
        psu = sum + n_bins + c;

        for (int y = 1; y < h + 1; y++, ps += n_bins, psu += n_bins) {
            s = 0;

            for (int x = 1; x < w + 1; x++, pg++, ps += n_bins, psu += n_bins) {
                s += *pg;
                *ps = *psu + s;
            }
        }
    }
}