OpenCV傅立葉轉換與逆轉換

opencv_dft.py

import cv2
import numpy as np

# 圖片來源：https://openhome.cc/Gossip/DCHardWay/images/Fourier4-1.JPG
img = cv2.imread('Fourier4-1.JPG', cv2.IMREAD_GRAYSCALE)

f = cv2.dft(np.float32(img))

shifted = np.fft.fftshift(f) # 將頻率 (0, 0) 位移至中心
freq = cv2.normalize( # 標準化
           cv2.magnitude(shifted[:,:,0], shifted[:,:,1]),  # 取振幅絕對值
           None, 
           0, 255, 
           cv2.NORM_MINMAX)
cv2.imshow('FFT 2D', freq)    # 頻域表示

inversed = cv2.dft(f, flags = cv2.DFT_INVERSE)  # 逆轉換，也可以使用 cv2.idft(f)
inversed_img = cv2.normalize(
                   cv2.magnitude(inversed[:,:,0], inversed[:,:,1]), 
                   None, 
                   0, 255, 
                   cv2.NORM_MINMAX
               ).astype('uint8')
cv2.imshow('INVERSE FFT 2D', inversed_img)

cv2.waitKey(0)
cv2.destroyAllWindows()