1 #include "opencv2/core.hpp"
2 #include "opencv2/core/utility.hpp"
3 #include "opencv2/imgproc.hpp"
4 #include "opencv2/imgcodecs.hpp"
5 #include "opencv2/highgui.hpp"
6
7 #include <stdio.h>
8
9 using namespace cv;
10 using namespace std;
11
help()12 static void help()
13 {
14 printf("\nThis program demonstrated the use of the discrete Fourier transform (dft)\n"
15 "The dft of an image is taken and it's power spectrum is displayed.\n"
16 "Usage:\n"
17 "./dft [image_name -- default ../data/lena.jpg]\n");
18 }
19
20 const char* keys =
21 {
22 "{@image|../data/lena.jpg|input image file}"
23 };
24
main(int argc,const char ** argv)25 int main(int argc, const char ** argv)
26 {
27 help();
28 CommandLineParser parser(argc, argv, keys);
29 string filename = parser.get<string>(0);
30
31 Mat img = imread(filename.c_str(), IMREAD_GRAYSCALE);
32 if( img.empty() )
33 {
34 help();
35 printf("Cannot read image file: %s\n", filename.c_str());
36 return -1;
37 }
38 int M = getOptimalDFTSize( img.rows );
39 int N = getOptimalDFTSize( img.cols );
40 Mat padded;
41 copyMakeBorder(img, padded, 0, M - img.rows, 0, N - img.cols, BORDER_CONSTANT, Scalar::all(0));
42
43 Mat planes[] = {Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F)};
44 Mat complexImg;
45 merge(planes, 2, complexImg);
46
47 dft(complexImg, complexImg);
48
49 // compute log(1 + sqrt(Re(DFT(img))**2 + Im(DFT(img))**2))
50 split(complexImg, planes);
51 magnitude(planes[0], planes[1], planes[0]);
52 Mat mag = planes[0];
53 mag += Scalar::all(1);
54 log(mag, mag);
55
56 // crop the spectrum, if it has an odd number of rows or columns
57 mag = mag(Rect(0, 0, mag.cols & -2, mag.rows & -2));
58
59 int cx = mag.cols/2;
60 int cy = mag.rows/2;
61
62 // rearrange the quadrants of Fourier image
63 // so that the origin is at the image center
64 Mat tmp;
65 Mat q0(mag, Rect(0, 0, cx, cy));
66 Mat q1(mag, Rect(cx, 0, cx, cy));
67 Mat q2(mag, Rect(0, cy, cx, cy));
68 Mat q3(mag, Rect(cx, cy, cx, cy));
69
70 q0.copyTo(tmp);
71 q3.copyTo(q0);
72 tmp.copyTo(q3);
73
74 q1.copyTo(tmp);
75 q2.copyTo(q1);
76 tmp.copyTo(q2);
77
78 normalize(mag, mag, 0, 1, NORM_MINMAX);
79
80 imshow("spectrum magnitude", mag);
81 waitKey();
82 return 0;
83 }
84
