python用opencv 影象傅立葉變換
阿新 • • 發佈:2021-01-06
傅立葉變換
dft = cv.dft(np.float32(img),flags = cv.DFT_COMPLEX_OUTPUT)
傅立葉逆變換
img_back = cv.idft(f_ishift)
實驗:將影象轉換到頻率域,低通濾波,將頻率域轉回到時域,顯示影象
import numpy as np import cv2 as cv from matplotlib import pyplot as plt img = cv.imread('d:/paojie_g.jpg',0) rows,cols = img.shape crow,ccol = rows//2,cols//2 dft = cv.dft(np.float32(img),flags = cv.DFT_COMPLEX_OUTPUT) dft_shift = np.fft.fftshift(dft) # create a mask first,center square is 1,remaining all zeros mask = np.zeros((rows,cols,2),np.uint8) mask[crow-30:crow+31,ccol-30:ccol+31,:] = 1 # apply mask and inverse DFT fshift = dft_shift*mask f_ishift = np.fft.ifftshift(fshift) img_back = cv.idft(f_ishift) img_back = cv.magnitude(img_back[:,:,0],img_back[:,1]) plt.subplot(121),plt.imshow(img,cmap = 'gray') plt.title('Input Image'),plt.xticks([]),plt.yticks([]) plt.subplot(122),plt.imshow(img_back,cmap = 'gray') plt.title('Low Pass Filter'),plt.yticks([]) plt.show()