truchet.py

# !/usr/bin/env python3
# Nicolas Seriot
# 2022-06-09
# Reproducing Roni Kaufman's art
# https://twitter.com/KaufmanRoni/status/1520372880156073984
# Sample output: https://seriot.ch/visualization/truchet.png

import cairo
import math
import random

NB_COLS = 16
NB_ROWS = 16

MARGIN = 128

W = 128

GRID = False

M_PI_2 = math.pi/2.0

P = ((1/255., 26/255., 92/255.), # background, default color
     (255/255.,212/255.,0/255.), # yellow
     (220/255.,6/255.,14/255.),  # red
     (0/255.,100/255.,177/255.), # blue
     (1,1,1))

FILLED = set()

class Tile:

    # color indices in global palette P
    bg = 0
    nw = 0
    ne = 0
    sw = 0
    se = 0

    def colors_used(self):
        
        colors = [self.bg, self.nw, self.ne, self.sw, self.se]
        s = set(colors)
        #s.remove(None)
        return s
    
    def fill(self, pos, color):

        p = getattr(self, pos)
        
        if p == 0:
            setattr(self, pos, color)
        elif p == None:
            self.bg = color
    
def draw_arc(c, x, y, start_angle, fill_color):
    
    c.save()
    
    c.move_to(x, y)
    c.set_source_rgb(*P[fill_color])
    c.arc(x, y, W/2.0, start_angle, start_angle + math.pi/2.0)
    c.fill()
    
    c.set_source_rgb(*P[0])
    c.set_line_width(12)
    c.arc(x, y, W/2.0, start_angle, start_angle + math.pi/2.0)
    c.stroke()

    c.restore()

def draw_tile(c, t):
    
    c.save()
    
    if GRID:
        c.save()
        c.set_line_width(5)
        c.rectangle(0, 0, W, W)
        c.set_source_rgb(1,1,1)
        c.stroke()
        c.restore()
    
    if t.bg != None:
        c.set_source_rgb(*P[t.bg])
        c.rectangle(0, 0, W, W)
        c.fill()
        
    if t.nw != None:
        draw_arc(c, 0, 0, M_PI_2 * 0, t.nw)

    if t.ne != None:
        draw_arc(c, W, 0, M_PI_2 * 1, t.ne)
    
    if t.se != None:
        draw_arc(c, W, W, M_PI_2 * 2, t.se)

    if t.sw != None:
        draw_arc(c, 0, W, M_PI_2 * 3, t.sw)

    c.restore()

def generate_tiles():
    
    m = [[Tile() for c in range(NB_COLS)] for r in range(NB_ROWS)]
    
    for c in range(NB_COLS):

        # first row
        t = m[0][c]
        t.nw = None
        t.ne = None

        # last row
        t = m[-1][c]
        t.sw = None
        t.se = None
    
    for r in range(NB_ROWS):
    
        # first col
        t = m[r][0]
        t.nw = None
        t.sw = None        

        # last col
        t = m[r][-1]
        t.ne = None
        t.se = None        

    # inner tiles
    for c in range(1, NB_COLS-1):
        for r in range(1, NB_ROWS-1):
        
            t = m[r][c]
            
            if random.choice([0, 1]) == 0:                     
                t.nw = None
                t.se = None
            else:
                t.ne = None
                t.sw = None
    
    return m

def fill(m, c, r, pos, color):
    
    key = "%d-%d-%s-%d" % (c, r, pos, color)
    if key in FILLED:
        return
    
    FILLED.add(key)
    
    t = m[r][c]

    t.fill(pos, color)
    
    if pos == "ne":
    
        fill(m, c+1, r,   "nw", color)
        fill(m, c,   r-1, "se", color)
        fill(m, c+1, r-1, "sw", color)

        if t.ne == None:
            fill(m, c, r, "sw", color)

    elif pos == "se":
    
        fill(m, c+1, r,   "sw", color)
        fill(m, c,   r+1, "ne", color)
        fill(m, c+1, r+1, "nw", color)

        if t.se == None:
            fill(m, c, r, "nw", color)

    elif pos == "nw":

        fill(m, c-1, r,   "ne", color)
        fill(m, c,   r-1, "sw", color)
        fill(m, c-1, r-1, "se", color)

        if t.nw == None:
            fill(m, c, r, "se", color)

    elif pos == "sw":

        fill(m, c-1, r,   "se", color)
        fill(m, c,   r+1, "nw", color)
        fill(m, c-1, r+1, "ne", color)

        if t.sw == None:
            fill(m, c, r, "ne", color)
        
def do_color_tiles(m):

    for r in range(NB_ROWS):
        for c in range(NB_COLS):
            
            t = m[r][c]
            
            colors_in_tile = t.colors_used()
            candidates = list(set([1,2,3,4]) - colors_in_tile)
            
            if t.nw == 0:
                fill(m, c, r, "nw", random.choice(candidates))

            if t.ne == 0:
                fill(m, c, r, "ne", random.choice(candidates))

            if t.se == 0:
                fill(m, c, r, "se", random.choice(candidates))

            if t.sw == 0:
                fill(m, c, r, "sw", random.choice(candidates))
    
    return None

def draw_png(filename):

    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32,
                                 W*NB_COLS + 2*MARGIN,
                                 W*NB_ROWS + 2*MARGIN)
    c = cairo.Context(surface)
    
    c.set_source_rgb(*P[0])
    c.paint()
    
    c.translate(MARGIN, MARGIN)
    
    m = generate_tiles()
    
    do_color_tiles(m)
        
    for row in range(NB_ROWS):
        
        tiles_row = m[row]
        
        for col in range(NB_COLS):

            t = tiles_row[col]

            c.save()

            c.translate(col*W, row*W)
            
            draw_tile(c, t)
            
            c.restore()
        
    surface.write_to_png(filename)
    
draw_png("truchet.png")