filter.py

from PIL import Image
import numpy as np
img = Image.open(input("Enter image you want to change: "))
result_img = input("Enter image to write your result onto: ")
arr = np.array(img)
height = len(arr)
width = len(arr[1])
size = int(input("Enter size: "))
gradation = int(input("Enter gradation: "))
step = int(255 / gradation)


def return_average(i, j, arr, size):
  color_sum = np.sum((arr[i: i + size, j: j + size]) / 3)
  average = int(color_sum // (size * size))
  return average


class Grey:
  def __init__(self, step, height, width, size, arr):
    self.step = step
    self.height = height
    self.width = width
    self.size = size
    self.arr = arr

  def getGrey(self):
    for i in range(0, self.height, self.size):
      for j in range(0, self.width, self.size):
        average = return_average(i, j, arr, size)
        self.arr[i: i + self.size, j: j + self.size] = int(average // self.step) * self.step
    return self.arr

newPicture = Grey(step, height, width, size, arr)
res = Image.fromarray(newPicture.getGrey())
res.save(result_img)