laplace_of_gaussian_1D.cpp

cv::Mat createLOGKernel1D(int ksize, float sigma)
{
    using namespace cv;

    float std2 = sigma * sigma;
    std::vector<float> seq(ksize);
    std::iota(begin(seq), end(seq), -(ksize-1)/2);
    Mat_<float> kSeq(1, ksize, seq.data());

    Mat XX;
    multiply(kSeq, kSeq, XX);

    Mat H = -(XX / (2.*std2));
    exp(H, H);

    double minVal, maxVal;
    minMaxIdx(H, &minVal, &maxVal);
    Mat mask = H < std::numeric_limits<float>::epsilon()*maxVal;
    H.setTo(0, mask);

    float sumh = sum(H)[0];
    if (sumh != 0) H /= sumh;

    Mat H1;
    multiply(H, (XX - 2.*std2)/(std2 * std2), H1);
    H = H1 - sum(H1)[0] / ksize;
    return H;
}