Svg files from python

cell.py

from collections import defaultdict
import sys

from svg import *

def log(*a, **k):
    print(*a, **k, file=sys.stderr)

ROWS = 64
COLS = ROWS*2-1
BOXSIZE = 10

IMG_HEIGHT = 2000
IMG_WIDTH = IMG_HEIGHT / (ROWS * BOXSIZE + 1) * (COLS * BOXSIZE + 1)

# Basic header
svg_header()
svg_open(width=IMG_WIDTH, height=IMG_HEIGHT,
         x_bias=-BOXSIZE*COLS/2, y_bias=-1,
         xw=COLS*BOXSIZE+2, yh=ROWS*BOXSIZE+2)

def draw_cell(row, col, value=None):
    fill = "grey" if value else "white"
    svg_rect((BOXSIZE*(col-0.5), BOXSIZE*row), BOXSIZE, BOXSIZE,
             fill=fill, stroke="black")

if len(sys.argv) > 1:
    rule = int(sys.argv[1])
else:
    rule = 30

cells = defaultdict(lambda: False)
cells[(0,0)] = True
draw_cell(0, 0, cells[(0,0)])

for j in range(1, ROWS):
    for i in range(-j, j+1):
        prev =  4 * cells[(j-1, i-1)]
        prev += 2 * cells[(j-1, i  )]
        prev += 1 * cells[(j-1, i+1)]
        cells[(j,i)] = rule & (1 << prev) != 0
        draw_cell(j, i, cells[(j,i)])

# Footer
svg_close()

Makefile

n = 24

$(n).mp4: stringart.py
	$(MAKE) -j 4 $$(for i in $$(seq -w 1 $n); do echo -n "$n-$$i.png "; done)
	ffmpeg -r 2 -f image2 -s 800x800 -i $(n)-%02d.png -vcodec libx264 -crf 25  -pix_fmt yuv420p $@

%.png: %.svg
	convert $^ $@

$(n)-%.svg: stringart.py
	python3 $^ $(n) $* > $@

$(n).svg: stringart.py
	python3 $^ > $@

.PHONY: clean
clean:
	rm -f *.png *.svg *.mp4

stringart.py

import math
import sys

from svg import *

def log(*a, **k):
    print(*a, **k, file=sys.stderr)

def point_to_tick(point, s):
    p1 = (point[0] * (1+s), point[1] * (1+s))
    p2 = (point[0] * (1-s), point[1] * (1-s))
    return p1, p2

def circle(n, s=1, r=1):
    for i in range(0, n+1):
        t = 2 * math.pi * i * s / n
        yield r*math.sin(-t), -r*math.cos(t)

if len(sys.argv) >= 2:
    ticks = int(sys.argv[1])
else:
    ticks = 24

# Basic header
svg_header()
svg_open(width=800, height=800, x_bias=-110, y_bias=-110, xw=220, yh=220)

# Outer circle
svg_circle((0, 0), 100, fill='none', stroke='black')

# Tick marks
for point in circle(ticks, r=100):
    print(svg_line(*point_to_tick(point, 0.03), stroke='black'))

if len(sys.argv) >= 3:
    circ = tuple(circle(ticks, int(sys.argv[2]), 100))
    svg_poly(*circ[1:], stroke='red', fill='none')
    svg_line(*circ[:2], stroke='blue')
else:
    # Draw all non-generating cycles
    for k in range(2, ticks, 2):
        for j in range(2, k+1):
            if (ticks % j) == (k % j) == 0:
                svg_poly(*circle(ticks, k, 100), stroke='red', fill='none')
                log(k)
                break

# Footer
svg_close()

svg.py

def xml(tag, _xml_tag_is_a_singleton=True, **options):
    s = f'<{tag}'
    kw_attrib = lambda x: x.replace('_', '-')
    if options:
        s += ' '
        s += ' '.join(f'{kw_attrib(k)}="{str(v)}"' for k, v in options.items())
    if _xml_tag_is_a_singleton:
        s += ' />'
    else:
        s += '>'
    print(s)

def xml_open(*args, **kwargs):
    xml(*args, **kwargs, _xml_tag_is_a_singleton=False)

def xml_close(tag):
    print(f'</{tag}>')

def svg_header():
    '<?xml version="1.0" encoding="UTF-8" standalone="no"?>'

def svg_open(width, height, x_bias, y_bias, xw, yh):
    vb = f'{x_bias} {y_bias} {xw} {yh}'
    ns = 'http://www.w3.org/2000/svg'
    xml_open('svg', width=width, height=height, viewBox=vb, xmlns=ns)

def svg_close():
    xml_close('svg')

def svg_poly(*points, **opts):
    point_str = ' '.join(f'{x},{y}' for x, y in points)
    xml('polyline', points=point_str, **opts)

def svg_circle(point, radius, **opts):
    xml('circle', cx=point[0], cy=point[1], r=radius, **opts)

def svg_line(p1, p2, **opts):
    xml('line', x1=p1[0], y1=p1[1], x2=p2[0], y2=p2[1], **opts)

def svg_rect(p, width, height, x_radius=0, y_radius=0, **opts):
    xml('rect', x=p[0], y=p[1], width=width, height=height,
              rx=x_radius, ry=y_radius, **opts)