shift_monochrome_levels.py

import numpy
import sys

from PIL import Image

from _common import exit_with_prompt, print_error, process_folder_images, select_parent_folder

SCAN_AREA = 0.8
BLACK_THRESHOLD = 51
WHITE_THRESHOLD = 204

def main():
  if len(sys.argv) > 1:
    process_parent_folder(sys.argv[1])
  else:
    select_parent_folder('Enter the path to the parent folder containing the folders or images you want to level shift:\n', process_parent_folder)

def process_parent_folder(folder_path):
  process_folder_images(folder_path, process_image)

def process_image(file_path):
  img = Image.open(file_path)
  if not is_grayscale(img):
    return

  arr = numpy.array(img.convert('L'), dtype = numpy.float32)

  arr_min, arr_max = get_min_max(arr, SCAN_AREA)

  if arr_max != arr_min:
    scaled = (arr - arr_min) * (255 / (arr_max - arr_min))
  else:
    scaled = arr.copy()

  scaled = numpy.clip(scaled, BLACK_THRESHOLD, WHITE_THRESHOLD)
  scaled = (scaled - BLACK_THRESHOLD) * (255 / (WHITE_THRESHOLD - BLACK_THRESHOLD))
  scaled = numpy.clip(scaled, 0, 255).astype(numpy.uint8)

  out_img = Image.fromarray(scaled)
  out_img.save(file_path, quality=80)

def is_grayscale(img, tolerance = 5):
  if img.mode == 'L':
    return True
  if img.mode in ['RGB', 'RGBA']:
    arr = numpy.array(img)
    if img.mode == 'RGBA':
      arr = arr[:, :, :3]
    diff = arr.max(axis = 2) - arr.min(axis = 2)
    return numpy.all(diff <= tolerance)
  return False

def get_min_max(array, scan_area = 1):
  if scan_area <= 0 or scan_area >= 1:
    return array.min(), array.max()

  h, w = array.shape
  h_crop = int(h * (1 - scan_area) / 2)
  w_crop = int(w * (1 - scan_area) / 2)
  cropped_arr = array[h_crop:h - h_crop, w_crop:w - w_crop]
  return cropped_arr.min(), cropped_arr.max()

if __name__ == '__main__':
  try:
    main()
  except Exception as ex:
    print_error(ex)
    exit_with_prompt()