82 lines
2.1 KiB
C++
82 lines
2.1 KiB
C++
#include "opencv2/core/core.hpp"
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#include "opencv2/imgproc/imgproc.hpp"
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#include "opencv2/highgui/highgui.hpp"
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#include <stdio.h>
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using namespace cv;
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using namespace std;
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static void help()
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{
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printf("\nThis program demonstrated the use of the discrete Fourier transform (dft)\n"
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"The dft of an image is taken and it's power spectrum is displayed.\n"
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"Usage:\n"
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"./dft [image_name -- default lena.jpg]\n");
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}
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const char* keys =
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{
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"{1| |lena.jpg|input image file}"
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};
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int main(int argc, const char ** argv)
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{
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help();
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CommandLineParser parser(argc, argv, keys);
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string filename = parser.get<string>("1");
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Mat img = imread(filename.c_str(), CV_LOAD_IMAGE_GRAYSCALE);
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if( img.empty() )
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{
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help();
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printf("Cannot read image file: %s\n", filename.c_str());
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return -1;
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}
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int M = getOptimalDFTSize( img.rows );
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int N = getOptimalDFTSize( img.cols );
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Mat padded;
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copyMakeBorder(img, padded, 0, M - img.rows, 0, N - img.cols, BORDER_CONSTANT, Scalar::all(0));
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Mat planes[] = {Mat_<float>(padded), Mat::zeros(padded.size(), CV_32F)};
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Mat complexImg;
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merge(planes, 2, complexImg);
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dft(complexImg, complexImg);
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// compute log(1 + sqrt(Re(DFT(img))**2 + Im(DFT(img))**2))
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split(complexImg, planes);
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magnitude(planes[0], planes[1], planes[0]);
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Mat mag = planes[0];
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mag += Scalar::all(1);
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log(mag, mag);
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// crop the spectrum, if it has an odd number of rows or columns
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mag = mag(Rect(0, 0, mag.cols & -2, mag.rows & -2));
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int cx = mag.cols/2;
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int cy = mag.rows/2;
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// rearrange the quadrants of Fourier image
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// so that the origin is at the image center
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Mat tmp;
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Mat q0(mag, Rect(0, 0, cx, cy));
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Mat q1(mag, Rect(cx, 0, cx, cy));
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Mat q2(mag, Rect(0, cy, cx, cy));
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Mat q3(mag, Rect(cx, cy, cx, cy));
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q0.copyTo(tmp);
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q3.copyTo(q0);
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tmp.copyTo(q3);
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q1.copyTo(tmp);
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q2.copyTo(q1);
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tmp.copyTo(q2);
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normalize(mag, mag, 0, 1, CV_MINMAX);
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imshow("spectrum magnitude", mag);
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waitKey();
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return 0;
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}
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