사용한 라이브러리

Q.35. 푸리에 변환 밴드 패스 필터

int main()
{
    PPM ppm("imori.pnm");
    int width = ppm.Get_width();
    int height = ppm.Get_height();

    std::vector<std::vector<std::complex<double>>> f(width, std::vector<std::complex<double>>(height));
    for (int j = 0; j < height; j++)
        for (int i = 0; i < width; i++)
        {
            int r = ppm(i, j, 'r');
            int g = ppm(i, j, 'g');
            int b = ppm(i, j, 'b');
            int y = (std::round)(0.2126 * r + 0.7152 * g + 0.0722 * b);
            f[i][j] = y;
        }
    DFT2D dft2d(width, height);
    auto F = dft2d.forward(f);
    F = dft2d.shift(F);
    double r = width / 2;
    for (int j = 0; j < height; j++)
        for (int i = 0; i < width; i++)
        {
            double R2 = (i - width / 2) * (i - width / 2) + (j - height / 2) * (j - height / 2);
            if ( R2 < 0.01 * r * r || R2 > 0.25*r*r) F[i][j] = 0;
        }
    F = dft2d.ishift(F);
    f = dft2d.backward(F);

    PPM ppm2(width, height);
    for (int j = 0; j < height; j++)
        for (int i = 0; i < width; i++)
        {
            int val = f[i][j].real();
            if (val >= 256) val = 255;
            if (val < 0)val = 0;
            ppm2(i, j, 'r') = val;
            ppm2(i, j, 'g') = val;
            ppm2(i, j, 'b') = val;
        }
    ppm2.Flush("out.ppm");

    return 0;
}