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


def fft(imgs):
    img = cv2.imread(imgs,0)

    dft = cv2.dft(np.float32(img),flags = cv2.DFT_COMPLEX_OUTPUT)
    dft_shift = np.fft.fftshift(dft)

    magnitude_spectrum = 10*np.log(cv2.magnitude(dft_shift[:,:,0],dft_shift[:,:,1]))


    rows, cols = img.shape
    crow,ccol = rows/2 , cols/2

    mask = np.zeros((rows,cols,2),np.uint8)
    mask[200:300, 200:300] = 1

    fshift = dft_shift*mask
    f_ishift = np.fft.ifftshift(fshift)
    img_back = cv2.idft(f_ishift)
    img_back = cv2.magnitude(img_back[:,:,0],img_back[:,:,1])

    plt.subplot(121),plt.imshow(magnitude_spectrum, cmap = 'gray')
    plt.title('Magnitude spectrum'), plt.xticks([]), plt.yticks([])
    plt.subplot(122),plt.imshow(img_back, cmap = 'gray')
    plt.title('Magnitude Spectrum inverse'), plt.xticks([]), plt.yticks([])
    plt.show()
