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