suk.cc

uint norm_val(int val) {
    if (val > 255) return 255;
    else if (val < 0) return 0;
    else
        return val;
}

Image unsharp(Image src_image) {
    class KernelMatrix {

    public:
        const int radius = 1;
        const Matrix<double> coef = {{-1./6, -2./3, -1./6},
                                     {-2./3, 4./3, -2./3},
                                     {-1./6, -2./3, -1./6}};
        std::tuple<uint, uint, uint> operator()(const Image &img) const {
            double r, g, b;
            r = g = b = 0;
            for (uint i = 0; i < img.n_rows; i++) {
                for (uint j = 0; j < img.n_cols; j++) {
                    r += std::get<0>(img(i, j)) * coef(i, j);
                    g += std::get<1>(img(i, j)) * coef(i, j);
                    b += std::get<2>(img(i, j)) * coef(i, j);
                }
            }
            norm_val(r);
            norm_val(g);
            norm_val(b);
            return std::make_tuple(r, g, b);
            //return norm_pixel(std::make_tuple(r, g, b));
        }
    };

    return src_image.unary_map(KernelMatrix());
}