mirror_closure.py

import math
import numpy as np

def original_mirror(x, direction=0, reverse=False):
  """Mirrors left to right or top to bottom as per the direction."""
  x_ = np.copy(x)
  height, width = x.shape
  if direction == 0:
    half_break = math.ceil(height/2)
    shift = height % 2
    if reverse:
      x_[:half_break, :] = np.flipud(x_[half_break - shift:, :])
    else:
      x_[half_break - shift:, :] = np.flipud(x_[:half_break, :])
  elif direction == 1:
    half_break = math.ceil(width/2)
    shift = width % 2
    if reverse:
      x_[:, :half_break] = np.fliplr(x_[:, half_break -shift:])
    else:
      x_[:, half_break - shift:] = np.fliplr(x_[:, :half_break])
  else:
      raise ValueError(f'Mirror direction {direction} unsupported')
  return x_


def mirror(x):
  "Horizontal mirror"
  height = x.shape[0]
  half_break = math.ceil(height/2)
  shift = height % 2
  x_ = np.copy(x)
  x_[half_break - shift:, :] = np.flipud(x_[:half_break, :])
  return x_


x = np.array([[1,2,3], [4,5,6], [7,8,9]])

assert np.all(original_mirror(x, 0, False) == mirror(x))
assert np.all(original_mirror(x, 1, False) == mirror(x.T).T)
assert np.all(original_mirror(x, 0, True) == mirror(np.flipud(x)))
assert np.all(original_mirror(x, 1, True) == mirror(np.flipud(x.T)).T)