怎麼辦逆DFT在OpenCV中

Question

我試圖實現使用OpenCV的在C++ 我docs.opencv.org下載完整的DFT例子，只是調整幾行逆逆DFT。

我DFT代碼是這樣的

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; 
} 

，做IDFT。通過將dft修復爲idft。但輸出看起來像噪音。我做錯了什麼？我認爲，DFT和IDFT只是相同....

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; 
} 

Answer 1

你必須重寫代碼像這樣得到的逆DFT這是原始圖像閱讀：

#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; 
} 

我只是說這部分代碼：

//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(); 

Answer 2

使用給定IDFT塊正規化功能並不完全得到所需的原始圖像（對比度明智的）某種原因。而是使用convertTo。準確地說，用下面的行替換normalize函數。

inverseTransform.convertTo（inverseTransform，CV_8U）;