#!python
# -*- mode: python; Encoding: utf-8; coding: utf-8 -*-
# Last updated: <2022/06/19 23:18:39 +0900>
"""
Ordered dithering

Windows10 x64 21H2 + Python 3.9.13 64bit + Pillow 9.1.1
"""

from PIL import Image


odtbl2x2 = [
    [1, 3],
    [4, 2]
]

odtbl3x3 = [
    [3, 7, 4],
    [6, 1, 9],
    [2, 8, 5]
]

# odtbl3x3 = [
#     [7, 9, 5],
#     [2, 1, 4],
#     [6, 3, 8]
# ]

odtbl4x4 = [
    [1, 9, 3, 11],
    [13, 5, 15, 7],
    [4, 12, 2, 10],
    [16, 8, 14, 6]
]

odtbl8x8 = [
    [1, 33, 9, 41, 3, 35, 11, 43],
    [49, 17, 57, 25, 51, 19, 59, 27],
    [13, 45, 5, 37, 15, 47, 7, 39],
    [61, 29, 53, 21, 63, 31, 55, 23],
    [4, 36, 12, 44, 2, 34, 10, 42],
    [52, 20, 60, 28, 50, 18, 58, 26],
    [16, 48, 8, 40, 14, 46, 6, 38],
    [64, 32, 56, 24, 62, 30, 54, 22]
]

odtbls = {
    "2x2": [5, odtbl2x2],
    "3x3": [10, odtbl3x3],
    "4x4": [17, odtbl4x4],
    "8x8": [65, odtbl8x8]
}


def get_dither_table(odtype):
    d, tbl = odtbls[odtype]
    w = len(tbl[0])
    h = len(tbl)
    odtbl = [[0 for i in range(w)] for j in range(h)]

    for y in range(h):
        for x in range(w):
            odtbl[y][x] = tbl[y][x] * 256 / d

    return w, h, odtbl


def get_dither_image(odtype, im):
    width, height = im.size
    oim = Image.new("L", im.size)

    tw, th, od = get_dither_table(odtype)

    src_pixel = im.load()
    dst_pixel = oim.load()

    for y in range(height):
        dy = y % th
        for x in range(width):
            dx = x % tw
            if src_pixel[x, y] < od[dy][dx]:
                dst_pixel[x, y] = 0
            else:
                dst_pixel[x, y] = 255

    return oim


def main():
    # im = Image.open("mandrill.png").convert("L")
    im = Image.open("gradation.png")

    for odtype in ["2x2", "3x3", "4x4", "8x8"]:
        oim = get_dither_image(odtype, im)
        oim.save("output_dither_%s.png" % odtype)


if __name__ == '__main__':
    main()