schotter_color.py

#!/usr/bin/env python

# Nicolas Seriot, 2018-11-04
# According to "Schotter" by Georg Nees
# https://collections.vam.ac.uk/item/O221321/schotter-print-nees-georg/
# Idea: randomness for x, y, rotation and alpta does increase at each row
# Sample output: ...

import cairo
import random
import math

def rainbow_color(pct = 0.0, offset = 0.0):

    p = 2 * math.pi * (offset + pct)

    r = math.sin(p + 0) * 0.5 + 0.5
    g = math.sin(p + 2) * 0.5 + 0.5
    b = math.sin(p + 4) * 0.5 + 0.5

    return (r,g,b)

if __name__ == "__main__":

    COLS = 12
    ROWS = 24
    MARGIN = 80
    WIDTH = 60
    
    CANVAS_WIDTH = COLS * WIDTH + MARGIN * 2
    CANVAS_HEIGHT = ROWS * WIDTH + MARGIN * 2 + 20
    
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, CANVAS_WIDTH, CANVAS_HEIGHT)
    c = cairo.Context(surface)
    
    c.set_line_width(2)

    c.save()
    c.set_source_rgb(1,1,1)
    c.paint()
    c.restore()
    
    for col in xrange(COLS):
        for row in xrange(ROWS):
            origin_x = MARGIN + col * WIDTH
            origin_y = MARGIN + row * WIDTH
            translate_x = origin_x + random.uniform(-0.5, 0.5) * row * 5
            translate_y = origin_y + random.uniform(-0.5, 0.5) * row * 5
            radians = random.uniform(-0.5, 0.5) * row / 10.0
            
            r,g,b = rainbow_color(pct = 1.0 * row / ROWS)
            alpha = 1.0 - (1.0 * row / ROWS)
            c.set_source_rgba(r,g,b,alpha)
            
            c.save()
            c.translate(translate_x, translate_y)
            c.rotate(radians)
            c.rectangle(0, 0, WIDTH, WIDTH)
            c.fill_preserve()
            c.set_source_rgb(0,0,0)
            c.stroke()
            c.restore()
    
    surface.write_to_png("schotter_color.png")