如何在OpenCV中进行逆DFT [英] How to do inverse DFT in OpenCV
本文介绍了如何在OpenCV中进行逆DFT的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试使用C ++中的OpenCV实现逆DFT 我在docs.opencv.org中下载了完整的dft示例,只是将几行调整为相反.
I'm trying to implement inverse DFT using OpenCV in C++ I downloaded complete dft example in docs.opencv.org and just adjust couple of lines to inverse.
我的DFT代码是这样的
my DFT code is like this
Mat DFT(const char* filename)
{
Mat I = imread(filename, CV_LOAD_IMAGE_GRAYSCALE);
if (I.empty())
{
Mat emty(7, 7, CV_32FC2, Scalar(1, 3));
return emty;
}
Mat padded; //expand input image to optimal size
int m = getOptimalDFTSize(I.rows);
int n = getOptimalDFTSize(I.cols); // on the border add zero values
copyMakeBorder(I, padded, 0, m - I.rows, 0, n - I.cols, BORDER_CONSTANT, Scalar::all(0));
Mat planes[] = { Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F) };
Mat complexI;
merge(planes, 2, complexI); // Add to the expanded another plane with zeros
dft(complexI, complexI); // this way the result may fit in the source matrix
// compute the magnitude and switch to logarithmic scale
// => log(1 + sqrt(Re(DFT(I))^2 + Im(DFT(I))^2))
split(complexI, planes); // planes[0] = Re(DFT(I), planes[1] = Im(DFT(I))
magnitude(planes[0], planes[1], planes[0]);// planes[0] = magnitude
Mat magI = planes[0];
magI += Scalar::all(1); // switch to logarithmic scale
log(magI, magI);
normalize(magI, magI, 0, 1, CV_MINMAX); // Transform the matrix with float values into a
// viewable image form (float between values 0 and 1).
imshow("Input Image", I); // Show the result
imshow(filename, magI);
// waitKey();
return magI;
}
,并进行IDFT.通过仅将dft修复为idft.但是输出看起来就像是噪音.我做错什么了?我以为dft和idft一样....
and did IDFT. By just fix dft to idft. But the output was just look like noise. What did I do wrong? I thought the dft and idft is just same....
Mat IDFT(Mat src)
{
Mat I = src;
Mat padded; //expand input image to optimal size
int m = getOptimalDFTSize(I.rows);
int n = getOptimalDFTSize(I.cols); // on the border add zero values
copyMakeBorder(I, padded, 0, m - I.rows, 0, n - I.cols, BORDER_CONSTANT, Scalar::all(0));
Mat planes[] = { Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F) };
Mat complexI;
merge(planes, 2, complexI); // Add to the expanded another plane with zeros
dft(complexI, complexI, DFT_INVERSE); // this way the result may fit in the source matrix
// compute the magnitude and switch to logarithmic scale
// => log(1 + sqrt(Re(IDFT(I))^2 + Im(IDFT(I))^2))
split(complexI, planes); // planes[0] = Re(IDFT(I), planes[1] = Im(IDFT(I))
magnitude(planes[0], planes[1], planes[0]);// planes[0] = magnitude
Mat magI = planes[0];
magI += Scalar::all(1); // switch to logarithmic scale
log(magI, magI);
normalize(magI, magI, 0, 1, CV_MINMAX);
imshow("forged map", magI);
return magI;
}
推荐答案
您必须像这样重写代码,以获取逆DFT,它是读取的原始图像:
you have to rewrite your code like this to get the inverse DFT which is the original image read :
#include "stdafx.h"
#include <opencv2/core/core.hpp>
#include <opencv2\highgui\highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
using namespace std;
using namespace cv;
int main()
{
Mat I = imread("test.tif", CV_LOAD_IMAGE_GRAYSCALE);
if( I.empty())
return -1;
Mat padded; //expand input image to optimal size
int m = getOptimalDFTSize( I.rows );
int n = getOptimalDFTSize( I.cols ); // on the border add zero values
copyMakeBorder(I, padded, 0, m - I.rows, 0, n - I.cols, BORDER_CONSTANT, Scalar::all(0));
Mat planes[] = {Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F)};
Mat complexI;
merge(planes, 2, complexI); // Add to the expanded another plane with zeros
dft(complexI, complexI); // this way the result may fit in the source matrix
// compute the magnitude and switch to logarithmic scale
// => log(1 + sqrt(Re(DFT(I))^2 + Im(DFT(I))^2))
split(complexI, planes); // planes[0] = Re(DFT(I), planes[1] = Im(DFT(I))
magnitude(planes[0], planes[1], planes[0]);// planes[0] = magnitude
Mat magI = planes[0];
magI += Scalar::all(1); // switch to logarithmic scale
log(magI, magI);
// crop the spectrum, if it has an odd number of rows or columns
magI = magI(Rect(0, 0, magI.cols & -2, magI.rows & -2));
// rearrange the quadrants of Fourier image so that the origin is at the image center
int cx = magI.cols/2;
int cy = magI.rows/2;
Mat q0(magI, Rect(0, 0, cx, cy)); // Top-Left - Create a ROI per quadrant
Mat q1(magI, Rect(cx, 0, cx, cy)); // Top-Right
Mat q2(magI, Rect(0, cy, cx, cy)); // Bottom-Left
Mat q3(magI, Rect(cx, cy, cx, cy)); // Bottom-Right
Mat tmp; // swap quadrants (Top-Left with Bottom-Right)
q0.copyTo(tmp);
q3.copyTo(q0);
tmp.copyTo(q3);
q1.copyTo(tmp); // swap quadrant (Top-Right with Bottom-Left)
q2.copyTo(q1);
tmp.copyTo(q2);
normalize(magI, magI, 0, 1, CV_MINMAX); // Transform the matrix with float values into a
normalize(phaseVals, phaseVals, 0, 1, CV_MINMAX);
// viewable image form (float between values 0 and 1).
imshow("Input Image" , I ); // Show the result
imshow("Spectrum Magnitude", magI);
waitKey();
//calculating the idft
cv::Mat inverseTransform;
cv::dft(complexI, inverseTransform, cv::DFT_INVERSE|cv::DFT_REAL_OUTPUT);
normalize(inverseTransform, inverseTransform, 0, 1, CV_MINMAX);
imshow("Reconstructed", inverseTransform);
waitKey();
return 0;
}
我刚刚将这部分添加到您的代码中:
I just added this part to your code :
//calculating the idft
cv::Mat inverseTransform;
cv::dft(complexI, inverseTransform, cv::DFT_INVERSE|cv::DFT_REAL_OUTPUT);
normalize(inverseTransform, inverseTransform, 0, 1, CV_MINMAX);
imshow("Reconstructed", inverseTransform);
waitKey();
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