Recursive SVG generator.

recur.py

#!/usr/bin/env python3

from argparse import ArgumentParser
from datetime import datetime
from os import stat
from time import sleep
from xml.dom.minidom import Element, parse


def get_viewbox_dimensions(view_box_string):
    _, _, width, height = view_box_string.split()
    return float(width), float(height)


def process_doc(doc, iters=2, keep_rects=True):
    svg_elem = doc.getElementsByTagName('svg')[0]

    svg_width, svg_height = get_viewbox_dimensions(
        svg_elem.getAttribute('viewBox'))

    g_clone = doc.createElement('g')
    g_clone.childNodes = [c.cloneNode(True)
                          for c in svg_elem.childNodes
                          if isinstance(c, Element)
                          and c.tagName != 'defs']

    for _ in range(iters):
        for rect in svg_elem.getElementsByTagName('rect'):
            if rect.getAttribute('class') == 'recur':
                x = rect.getAttribute('x')
                y = rect.getAttribute('y')
                width = float(rect.getAttribute('width'))
                height = float(rect.getAttribute('height'))
                x_scale = width / svg_width
                y_scale = height / svg_height

                new_g = g_clone.cloneNode(True)
                new_g.setAttribute('transform',
                                   rect.getAttribute('transform') +
                                   f'translate({x} {y}) '
                                   f'scale({x_scale} {y_scale}) '
                                   )
                rect.parentNode.replaceChild(new_g, rect)

    if not keep_rects:
        for rect in svg_elem.getElementsByTagName('rect'):
            if rect.getAttribute('class') == 'recur':
                rect.parentNode.removeChild(rect)

    return svg_elem


def process_file(input_filename, output_filename, iters, keep_rects):
    with open(input_filename) as fh:
        doc = parse(fh)
    out_doc = process_doc(doc, iters, keep_rects)
    with open(output_filename, 'w') as fh:
        out_doc.writexml(fh)


def watch_loop(input_filename, output_filename, iters, keep_rects):
    last_updated = 0
    while True:
        last_modified = stat(input_filename).st_mtime
        if last_modified == last_updated:
            sleep(0.1)
            continue
        print(f'Change detected {datetime.now()}...', end='', flush=True)
        process_file(input_filename, output_filename, iters, keep_rects)
        print('Saved.')
        last_updated = last_modified


def main():
    parser = ArgumentParser(description='''Recursive SVG generator.
        Every <rect> element with the class name "recur" will be replaced with
        a copy of the whole drawing. The drawing’s viewport will be scaled to
        the size of the rect. This process is repeated iters times.''')
    parser.add_argument('input_svg', help='input SVG file')
    parser.add_argument('output_svg', help='desired output file')
    parser.add_argument('--iters', '-i', default=4, type=int,
                        help='number of recursive iterations')
    parser.add_argument('--keep-rects', '-k', action='store_true',
                        help='don’t delete recur rectangles (for debugging)')
    parser.add_argument('--watch', '-w', action='store_true',
                        help='watch input file for modifications')

    args = parser.parse_args()

    if args.watch:
        watch_loop(args.input_svg, args.output_svg,
                   args.iters, args.keep_rects)
    else:
        process_file(args.input_svg, args.output_svg,
                     args.iters, args.keep_rects)


if __name__ == '__main__':
    main()