diff --git a/src/experiments/algorithms/fft.py b/src/experiments/algorithms/fft.py new file mode 100644 index 0000000..6b05f3b --- /dev/null +++ b/src/experiments/algorithms/fft.py @@ -0,0 +1,68 @@ +from __future__ import print_function +import sys +import cv2 as cv +import matplotlib.pyplot as plt +import numpy as np +def print_help(): + print(''' + This program demonstrated the use of the discrete Fourier transform (DFT). + The dft of an image is taken and it's power spectrum is displayed. + Usage: + discrete_fourier_transform.py [image_name -- default lena.jpg]''') + +def main(argv): + print_help() + filename = argv[0] if len(argv) > 0 else 'lena.jpg' + I = cv.imread(cv.samples.findFile(filename), cv.IMREAD_GRAYSCALE) + if I is None: + print('Error opening image') + return -1 + I = cv.resize(I, (0,0), None, fx=1, fy=1) + + rows, cols = I.shape + m = cv.getOptimalDFTSize( rows ) + n = cv.getOptimalDFTSize( cols ) + padded = cv.copyMakeBorder(I, 0, m - rows, 0, n - cols, cv.BORDER_CONSTANT, value=[0, 0, 0]) + + planes = [np.float32(padded), np.zeros(padded.shape, np.float32)] + complexI = cv.merge(planes) # Add to the expanded another plane with zeros + + cv.dft(complexI, complexI) # this way the result may fit in the source matrix + + cv.split(complexI, planes) # planes[0] = Re(DFT(I), planes[1] = Im(DFT(I)) + cv.magnitude(planes[0], planes[1], planes[0])# planes[0] = magnitude + magI = planes[0] + + matOfOnes = np.ones(magI.shape, dtype=magI.dtype) + cv.add(matOfOnes, magI, magI) # switch to logarithmic scale + cv.log(magI, magI) + + magI_rows, magI_cols = magI.shape + # crop the spectrum, if it has an odd number of rows or columns + magI = magI[0:(magI_rows & -2), 0:(magI_cols & -2)] + cx = int(magI_rows/2) + cy = int(magI_cols/2) + q0 = magI[0:cx, 0:cy] # Top-Left - Create a ROI per quadrant + q1 = magI[cx:cx+cx, 0:cy] # Top-Right + q2 = magI[0:cx, cy:cy+cy] # Bottom-Left + q3 = magI[cx:cx+cx, cy:cy+cy] # Bottom-Right + tmp = np.copy(q0) # swap quadrants (Top-Left with Bottom-Right) + magI[0:cx, 0:cy] = q3 + magI[cx:cx + cx, cy:cy + cy] = tmp + tmp = np.copy(q1) # swap quadrant (Top-Right with Bottom-Left) + magI[cx:cx + cx, 0:cy] = q2 + magI[0:cx, cy:cy + cy] = tmp + + cv.normalize(magI, magI, 0, 1, cv.NORM_MINMAX) # Transform the matrix with float values into a + + cv.imshow("Input Image" , I ) # Show the result + cv.imshow("spectrum magnitude", magI) + cv.imwrite("src\\experiments\\algorithms\\image\\fft.jpg", magI) + cv.waitKey() + + x = cv.calcHist([I], [0], None, [256], [0, 256]) + plt.plot(x) + plt.show() + +if __name__ == "__main__": + main(sys.argv[1:])