Function HatDescSearch

jni/stasm/hatdesc.cpp:143–177

// this function and its callees do not modify any data that is not on the stack.

void HatDescSearch(      // search in a grid around the current landmark
    double&      x,      // io: (in: old position of landmark, out: new position)
    double&      y,      // io:
    const HatFit hatfit) // in: func to estimate descriptor match
{
    // If HAT_SEARCH_RESOL is 2, force x,y positions to be divisible
    // by 2 to increase cache hit rate. This increases the mean hit rate
    // from about 67% to 88% and barely affects landmark accuracy.
    int ix = HAT_SEARCH_RESOL == 2? round2(x): cvRound(x);
    int iy = HAT_SEARCH_RESOL == 2? round2(y): cvRound(y);

    double fit_best = -FLT_MAX;

    int xoffset_best = 0, yoffset_best = 0; // in pixels

    for (int yoffset = -HAT_MAX_OFFSET;
             yoffset <= HAT_MAX_OFFSET;
             yoffset += HAT_SEARCH_RESOL)
    {
        for (int xoffset = -HAT_MAX_OFFSET;
                 xoffset <= HAT_MAX_OFFSET;
                 xoffset += HAT_SEARCH_RESOL)
        {
            const double fit = GetHatFit(ix + xoffset, iy + yoffset, hatfit);
            if (fit > fit_best)
            {
                fit_best = fit;
                xoffset_best = xoffset;
                yoffset_best = yoffset;
            }
        }
    }
    x += xoffset_best;
    y += yoffset_best;
}

} // namespace stasm