An image filter based on the Fourier transform

img_filter.py

import pathlib

import numpy as np

from PIL import Image
from scipy import signal

def filterLowPass():
    return signal.butter(4, 50, 'lp', fs = 1000000, output = 'sos')

def main():
    img = Image.open(pathlib.Path("Img.jpeg")).convert("RGB")

    imgArray = np.array(img)
    imgCpy = imgArray.copy()

    filter = filterLowPass()

    filteredRSignal = signal.sosfilt(filter, imgArray[..., 0].flatten())
    filteredGSignal = signal.sosfilt(filter, imgArray[..., 1].flatten())
    filteredBSignal = signal.sosfilt(filter, imgArray[..., 2].flatten())

    imgCpy[..., 0] = filteredRSignal.reshape(imgArray.shape[0], imgArray.shape[1])
    imgCpy[..., 1] = filteredGSignal.reshape(imgArray.shape[0], imgArray.shape[1])
    imgCpy[..., 2] = filteredBSignal.reshape(imgArray.shape[0], imgArray.shape[1])
    
    Image.fromarray(imgArray[..., 1].flatten()).save(pathlib.Path("ImgGreen.jpeg"))

    Image.fromarray(imgCpy).save(pathlib.Path("ImgFiltered.jpeg"))

if __name__ == "__main__":
    main()