braille.py

import numpy as np
from sys import byteorder


_utf32 = 'utf-32-le' if byteorder == 'little' else 'utf-32-be'

_braille_char_base = 0x2800  # U+2800 BRAILLE PATTERN BLANK

_braille_matrix = np.array([
    [0x01, 0x08],
    [0x02, 0x10],
    [0x04, 0x20],
    [0x40, 0x80],
], dtype=np.uint32)


def to_braille(bitmap: np.ndarray, threshold: float=128) -> list[str]:
    """
    Converts a bitmap into Braille characters. Returns a list of lines.
    `bitmap` should be a 2D Numpy array of bools or numbers.
    `True` values or numeric values >= `threshold` are shown as dots.
    """
    if bitmap.dtype != np.bool_:
        bitmap = bitmap >= threshold
    h, w = bitmap.shape
    if h % 4 != 0 or w % 2 != 0:
        bitmap = np.pad(bitmap, ((0, (4 - h) % 4), (0, w % 2)))
        h, w = bitmap.shape
    
    # split the bitmap into 4-row chunks and each row into 2-pixel chunks:
    chunks = np.reshape(bitmap, (h // 4, 4, w // 2, 2))
    # multiply every 4×2 chunk by `_braille_matrix` using scalar multiplication:
    braille_char_numbers = np.tensordot(chunks, _braille_matrix, axes=((1, 3), (0, 1)))
    
    utf32_codepoints = (_braille_char_base + braille_char_numbers).astype(np.uint32)
    return [line.tobytes().decode(_utf32) for line in utf32_codepoints]


_format_normal = '\033[0m'
_format_bold = '\033[1m'


def print_braille(bitmap: np.ndarray, threshold: float=128, bold: bool=True) -> None:
    joined_lines = '\n'.join(to_braille(bitmap, threshold))
    if bold:
        print(_format_bold + joined_lines + _format_normal)
    else:
        print(joined_lines)


if __name__ == '__main__':
    r = 25
    def f(x: float, y: float) -> float:
        return ((x - r)**2 + (y - r)**2) % 200

    bitmap = np.fromfunction(f, (2 * r, 2 * r))
    
    print_braille(bitmap, threshold=100, bold=False)
    print()
    print_braille(bitmap, threshold=100, bold=True)