Hỏi về code khôi phục ảnh nhiễu định kỳ sử dụng bộ lọc notch reject filter

[Vinh_JK (Nguyễn Phú Vinh)]

Chào mọi người. E có bài tập đi tham khảo code nhưng không rõ họ làm ntn. Mọi người có thể giải thích giúp e được không ạ.

#include <iostream>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/imgproc.hpp>
using namespace cv;
using namespace std;
void fftshift(const Mat& inputImg, Mat& outputImg);
void filter2DFreq(const Mat& inputImg, Mat& outputImg, const Mat& H);
void synthesizeFilterH(Mat& inputOutput_H, Point center, int radius);
void calcPSD(const Mat& inputImg, Mat& outputImg, int flag = 0);
int main()
{
Mat imgIn = imread("input.jpg", IMREAD_GRAYSCALE);
if (imgIn.empty()) //check whether the image is loaded or not
{
cout << "ERROR : Image cannot be loaded..!!" << endl;
return -1;
}
imgIn.convertTo(imgIn, CV_32F);

Rect roi = Rect(0, 0, imgIn.cols & -2, imgIn.rows & -2);
imgIn = imgIn(roi);
// PSD calculation (start)
Mat imgPSD;
calcPSD(imgIn, imgPSD);
fftshift(imgPSD, imgPSD);
normalize(imgPSD, imgPSD, 0, 255, NORM_MINMAX);
// PSD calculation (stop)
//H calculation (start)
Mat H = Mat(roi.size(), CV_32F, Scalar(1));
const int r = 21;
synthesizeFilterH(H, Point(705, 458), r);
synthesizeFilterH(H, Point(850, 391), r);
synthesizeFilterH(H, Point(993, 325), r);

Mat imgOut;
fftshift(H, H);
filter2DFreq(imgIn, imgOut, H);


imgOut.convertTo(imgOut, CV_8U);
normalize(imgOut, imgOut, 0, 255, NORM_MINMAX);
imwrite("result.jpg", imgOut);
imwrite("PSD.jpg", imgPSD);
fftshift(H, H);
normalize(H, H, 0, 255, NORM_MINMAX);
imwrite("filter.jpg", H);
return 0;
}
void fftshift(const Mat& inputImg, Mat& outputImg)
{
outputImg = inputImg.clone();
int cx = outputImg.cols / 2;
int cy = outputImg.rows / 2;
Mat q0(outputImg, Rect(0, 0, cx, cy));
Mat q1(outputImg, Rect(cx, 0, cx, cy));
Mat q2(outputImg, Rect(0, cy, cx, cy));
Mat q3(outputImg, Rect(cx, cy, cx, cy));
Mat tmp;
q0.copyTo(tmp);
q3.copyTo(q0);
tmp.copyTo(q3);
q1.copyTo(tmp);
q2.copyTo(q1);
tmp.copyTo(q2);
}
void filter2DFreq(const Mat& inputImg, Mat& outputImg, const Mat& H)
{
Mat planes2] = { [Mat_<float>(inputImg.clone()), Mat::zeros(inputImg.size(), CV_32F) };
Mat complexI;
merge(planes, 2, complexI);
dft(complexI, complexI, DFT_SCALE);
Mat planesH2] = { [Mat_<float>(H.clone()), Mat::zeros(H.size(), CV_32F) };
Mat complexH;
merge(planesH, 2, complexH);
Mat complexIH;
mulSpectrums(complexI, complexH, complexIH, 0);
idft(complexIH, complexIH);
split(complexIH, planes);
outputImg = planes[0];
}
void synthesizeFilterH(Mat& inputOutput_H, Point center, int radius)
{
Point c2 = center, c3 = center, c4 = center;
c2.y = inputOutput_H.rows - center.y;
c3.x = inputOutput_H.cols - center.x;
c4 = Point(c3.x,c2.y);
circle(inputOutput_H, center, radius, 0, -1, 8);
circle(inputOutput_H, c2, radius, 0, -1, 8);
circle(inputOutput_H, c3, radius, 0, -1, 8);
circle(inputOutput_H, c4, radius, 0, -1, 8);
}


void calcPSD(const Mat& inputImg, Mat& outputImg, int flag)
{
Mat planes2] = { [Mat_<float>(inputImg.clone()), Mat::zeros(inputImg.size(), CV_32F) };
Mat complexI;
merge(planes, 2, complexI);
dft(complexI, complexI);
split(complexI, planes); // planes[0] = Re(DFT(I)), planes[1] = Im(DFT(I))
planes0].[at<float>(0) = 0;
planes1].[at<float>(0) = 0;
// compute the PSD = sqrt(Re(DFT(I))^2 + Im(DFT(I))^2)^2
Mat imgPSD;
magnitude(planes[0], planes[1], imgPSD); //imgPSD = sqrt(Power spectrum density)
pow(imgPSD, 2, imgPSD); //it needs ^2 in order to get PSD
outputImg = imgPSD;
// logPSD = log(1 + PSD)
if (flag)
{
Mat imglogPSD;
imglogPSD = imgPSD + Scalar::all(1);
log(imglogPSD, imglogPSD);
outputImg = imglogPSD;
}
}