python+opencv FFT 快速傅里葉變換代碼

import cv2
import numpy as np
import math
from matplotlib import pyplot as plt

def magnitude(x, y):
    x_m = x * x
    y_m = y * y
    z_m = x_m + y_m
    return np.sqrt(z_m)

img = cv2.imread("lena.jpg", 0)
dft = cv2.dft(np.float32(img), flags=cv2.DFT_COMPLEX_OUTPUT)
dft_shift = np.fft.fftshift(dft)
magnitude_spectrum2 = 20 * np.log10(magnitude(dft_shift[:, :, 0], dft_shift[:, :, 1]))

plt.subplot(121), plt.imshow(img, "gray")
plt.title("Input image"), plt.xticks([]), plt.yticks([])
plt.subplot(122), plt.imshow(magnitude_spectrum2, cmap="gray")
plt.title("DFT image"), plt.xticks([]), plt.yticks([])
plt.show()