opencv 低通滤波器

#include "stdafx.h"
#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

using namespace cv;
using namespace std;

void shiftDFT(cv::Mat& fImage);
void create_lowpass_filter(cv::Mat &dft_Filter, float fc, int type);
void lowpass_dft(const cv::Mat& image, cv::Mat& dft_filter_img, float fc);

int main()
{
float scale = 1.0;
cv::Mat image = cv::imread("FileName.tif", cv::IMREAD_GRAYSCALE);

if (image.empty())
{
return 0;
}

cv::Mat src;
cv::resize(image, src, cv::Size(), scale, scale);

imwrite("src.tif", src);
float fc = 0.3;
cv::Mat dft_filter_img;
lowpass_dft(src, dft_filter_img, fc);
imwrite("dft_filter_img.bmp", dft_filter_img);

return 0;
}

void create_lowpass_filter(cv::Mat &dft_Filter, float fc, int type)
{
cv::Point centre = cv::Point(dft_Filter.rows / 2, dft_Filter.cols / 2);
double radius;

float x, y;
int state = -1;
x = dft_Filter.cols * 0.5;
y = dft_Filter.rows * 0.5;
double tempD;
double D0 = fc * min(dft_Filter.rows, dft_Filter.cols) / 2.0;
for (int i = 0; i < dft_Filter.rows; i++)
{
float* ptr = dft_Filter.ptr<float>(i);
for (int j = 0; j < dft_Filter.cols; j++)
{
if (i > y && j > x)
{
state = 3;
}
else if (i > y)
{
state = 1;
}
else if (j > x)
{
state = 2;
}
else
{
state = 0;
}

switch (state)
{

case 0:
tempD = pow(i, (double)2.0) + pow(j, (double)2.0); tempD = sqrt(tempD); break;
case 1:
tempD = pow((dft_Filter.rows - i), (double)2.0) + pow(j, (double)2.0); tempD = sqrt(tempD); break;
case 2:
tempD = pow(i, (double)2.0) + pow((dft_Filter.cols - j), (double)2.0); tempD = sqrt(tempD); break;
case 3:
tempD = pow((dft_Filter.rows - i), (double)2.0) + pow((dft_Filter.cols - j), (double)2.0); tempD = sqrt(tempD); break;
default:
break;
}

switch (type)
{
case 0://理想滤波器
if(tempD <= D0)
{
ptr[j * 2] = 1.0;
ptr[j * 2 + 1] = 1.0;
}
else
{
ptr[j * 2] = 0.0;
ptr[j * 2 + 1] = 0.0;
}
break;
case 1://2阶巴特沃思低通滤波器传递函数
tempD = 1 / (1 + pow(tempD / D0, 2 * 2));
ptr[j * 2] = tempD;
ptr[j * 2 + 1] = tempD;
break;
case 2://二维高斯低通滤波器传递函数
tempD = exp(-0.5 * pow(tempD / D0, 2));
ptr[j * 2] = tempD;
ptr[j * 2 + 1] = tempD;
break;
case 3://衰减系数为2的二维指数低通滤波器传递函数
tempD = exp(-pow(tempD / D0, 2));
ptr[j * 2] = tempD;
ptr[j * 2 + 1] = tempD;
break;

}
}
}

}

void lowpass_dft(const cv::Mat& image, cv::Mat& dft_filter_img, float fc)
{
int M = getOptimalDFTSize(image.rows);
int N = getOptimalDFTSize(image.cols);
cv::Mat padded;
copyMakeBorder(image, padded, 0, M - image.rows, 0, N - image.cols, BORDER_CONSTANT, Scalar::all(0));

cv::Mat planes[] = { cv::Mat_<float>(padded), cv::Mat::zeros(padded.size(), CV_32F) };
cv::Mat complexImg(planes[0].size(), planes[0].type(), CV_32FC2);
merge(planes, 2, complexImg);
///傅里叶正变换
dft(complexImg, complexImg);

//显示频域图
split(complexImg, planes);
magnitude(planes[0], planes[1], planes[0]);
Mat mag = planes[0].clone();
mag += Scalar::all(1);
log(mag, mag);
shiftDFT(mag);
normalize(mag, mag, 0, 1, NORM_MINMAX);

///创建滤波器
cv::Mat filterImg = cv::Mat(complexImg.size(), complexImg.type());
create_lowpass_filter(filterImg, fc, 2);

////显示滤波器图
split(filterImg, planes);
magnitude(planes[0], planes[1], planes[0]);
Mat magFilter = planes[0].clone();
magFilter += Scalar::all(1);
log(magFilter, magFilter);
shiftDFT(magFilter);
normalize(magFilter, magFilter, 0, 1, NORM_MINMAX);

//同时显示频域图和滤波器图
cv::Mat dftDebug = mag + magFilter;

//频域滤波
mulSpectrums(complexImg, filterImg, complexImg, 0);
///傅里叶逆变换
idft(complexImg, complexImg, cv::DFT_SCALE);

split(complexImg, planes);
dft_filter_img.create(complexImg.size(), CV_8UC1);
planes[0].convertTo(dft_filter_img, CV_8UC1);
dft_filter_img = dft_filter_img(cv::Rect(0, 0, image.cols, image.rows));
}

void shiftDFT(cv::Mat& fImage)
{
Mat tmp, q0, q1, q2, q3;
//first crop the image, if it has an odd number of rows or columns
int cx = fImage.cols / 2;
int cy = fImage.rows / 2;

// rearrange the quadrants of Fourier image
// so that the origin is at the image center

q0 = fImage(Rect(0, 0, cx, cy));
q1 = fImage(Rect(cx, 0, cx, cy));
q2 = fImage(Rect(0, cy, cx, cy));
q3 = fImage(Rect(cx, cy, cx, cy));

q0.copyTo(tmp);
q3.copyTo(q0);
tmp.copyTo(q3);

q1.copyTo(tmp);
q2.copyTo(q1);
tmp.copyTo(q2);
}