makesvg.py

makesvg.py

#! /usr/bin/env python3
'''
Making SVGs by hand is a pain.  This is a better way:
It's functional, rather than using the XML "markup language" directly.
No closing tags, just balanced parentheses!

#xml #svg #python #python3 #graphicsprogramming
https://twitter.com/halcanary/status/1458802118136111107

Updated to use `xml.dom.minidom` instead of `lxml`.
'''

import copy
import math
import os
import subprocess
import shutil
import sys
import tempfile
import numbers
import xml.dom.minidom

################################################################################

def create_svg(width, height):
    def stringy(v):
        return '%g' % v if isinstance(v,numbers.Number) else str(v)
    class ElementFactory:
        def __init__(self, doc):
            self.doc = doc
        def make(self, name, *children, **kws):
            e = self.doc.createElement(name)
            for k, v in kws.items():
                e.setAttribute(k, stringy(v))
            for c in children:
                e.appendChild(copy.copy(c))
            return e
        def defs(self, **kws):
            d = self.doc.createElement('def')
            for k, v in kws.items():
                v.setAttribute('id', k)
                d.appendChild(v)
            return d
        def use(self, href, **kws):
            use = self.doc.createElement('use')
            use.setAttribute('xlink:href', href)
            for k, v in kws.items():
                use.setAttribute(k, stringy(v))
            return use
        def __getattr__(self, name):
            def fn(*children, **kws):
                return self.make(name, *children, **kws)
            return fn
        def append(self, *children):
            for c in children:
                self.doc.documentElement.appendChild(c)
        def write(self, o):
            self.doc.writexml(o, addindent='    ', newl='\n', encoding='UTF-8')

    dom_impl = xml.dom.minidom.getDOMImplementation()
    doc = dom_impl.createDocument('http://www.w3.org/2000/svg', 'svg',
         dom_impl.createDocumentType('svg', "-//W3C//DTD SVG 1.1//EN",
         "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"))
    doc.documentElement.setAttribute('xmlns', 'http://www.w3.org/2000/svg')
    doc.documentElement.setAttribute('xmlns:xlink',
        'http://www.w3.org/1999/xlink')
    doc.documentElement.setAttribute('width', '%d'%width)
    doc.documentElement.setAttribute('height', '%d'%height)
    return ElementFactory(doc)

def closed_path(pts):
    return open_path(pts) + 'Z'

def open_path(pts):
    return ''.join(('%s%g,%g' % ('L' if i else 'M', x, y) for i, (x, y) in enumerate(pts)))

def cartesian(radius, theta, x=0, y=0):
    rad = math.radians(theta)
    return (radius * math.cos(rad) + x, radius * math.sin(rad) + y)

################################################################################

def example(height, output):
    E = create_svg(height * 1.9, height)
    E.append(
        E.defs(
            star=E.path(fill="#FFF", d=closed_path(
                      (cartesian(120, 180 * (0.8 * i - 0.5)) for i in range(5)))),
            stripe=E.rect(id='stripe', fill='#B22234', width=7410, height=300)),
         E.g(E.rect(width=7410, height=3900, fill='#FFF'),
             *[E.use('#stripe', y=(i * 300)) for i in range(0, 13, 2)],
             E.rect(width=2964, height=2100, fill='#3C3B6E'),
             *[E.use('#star', x=(x * 247), y=(y * 210)) 
               for x in range(1, 12) for y in range(1, 10) if (x + y) % 2 == 0],
             transform=('scale(%g)' % (height / 3900))))
    E.write(output)

if __name__ == '__main__':
    example(1024, sys.stdout)