fast fourier transform

Day4/fast_fourier.py

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+''' Do fast fourier transform on an image '''
+
+import cv2
+import numpy as np 
+
+img = cv2.imread('lenna.jpg', 0)
+rows, cols = img.shape
+
+#convert to frequency domain
+f = np.fft.fft2(img)
+#bring the dc component( 0 freq) to the center by 
+#shifting by n/2 in both directions
+fshift = np.fft.fftshift(f)
+magnitude_spectrum = 20 * np.log( np.abs(fshift) )
+
+cv2.imwrite('fft.jpg', magnitude_spectrum)
+
+''' ## inverse fft
+crow = rows / 2
+ccol = cols / 2
+fshift[crow - 30:crow + 30, ccol - 30:ccol + 30] = 0
+f_ishift = np.fft.ifftshift(fshift)
+img_back = np.fft.ifft2(f_ishift)
+img_back = np.abs(img_back)
+cv2.imwrite('orignal_fft.jpg', img_back)
+ '''