normalize_svg.py

#!/usr/bin/env python3

'''
Application for "normalizing" SVGs

These problems are addressed:

* Inkscape notoriously copies class styles into the object definitions.
https://bugs.launchpad.net/inkscape/+bug/167937

* Inkscape uses labels on layers. Layers are basically named groups.
  Inkscape does not sync the group id with the layer label.

Usage Example:
python3 inkscape_svg_fixup.py vector_source.svg
'''

import lxml.etree as etree
import sys
import re

color_classes = {
	'skin', 'head', 'torso', 'boob', 'penis', 'scrotum', 'belly',
	'areola', 'bellybutton', 'labia', 'hair', 'pubic_hair', 'underarm_hair',
	'eyebrow_hair', 'shoe', 'shoe_shadow', 'smart_piercing', 'steel_piercing',
	'steel_chastity', 'outfit_base', 'gag', 'shadow', 'glasses', 'eye', 'sclera'
}


def fix(tree):
	# know namespaces
	ns = {
		'svg': 'http://www.w3.org/2000/svg',
		'inkscape': 'http://www.inkscape.org/namespaces/inkscape'
	}

	# find document global style definition
	# mangle it and interpret as python dictionary
	style_element = tree.find('./svg:style', namespaces=ns)
	style_definitions = style_element.text
	pythonic_style_definitions = '{'+style_definitions.\
		replace('\t.', '"').replace('{', '":"').replace('}', '",').\
		replace('/*', '#')+'}'
	styles = eval(pythonic_style_definitions)

	# go through all SVG elements
	for elem in tree.iter():
		if (elem.tag == etree.QName(ns['svg'], 'g')):
			# compare inkscape label with group element ID
			lbl = elem.get(etree.QName(ns['inkscape'], 'label'))
			if lbl:
				i = elem.get('id')
				if (i != lbl):
					print("Overwriting ID %s with Label %s..." % (i, lbl))
					elem.set('id', lbl)

		# clean styles (for easier manual merging)
		style_string = elem.get('style')
		if style_string:
			split_styles = style_string.strip('; ').split(';')
			styles_pairs = [s.strip('; ').split(':') for s in split_styles]
			filtered_pairs = [(k, v) for k, v in styles_pairs if not (
				k.startswith('font-') or
				k.startswith('text-') or
				k.endswith('-spacing') or
				k in ["line-height", " direction", " writing", " baseline-shift", " white-space", " writing-mode"]
			)]
			split_styles = [':'.join(p) for p in filtered_pairs]
			style_string = ';'.join(sorted(split_styles))
			elem.attrib["style"] = style_string

		# remove all style attributes offending class styles
		s = elem.get('style')
		c = elem.get('class')
		if (c and s):
			s = s.lower()
			c = c.split(' ')[0]  # regard main style only
			classes = c.split(' ')
			hasColorClass = any(x in color_classes for x in classes)
			if hasColorClass:
				s_new = re.sub('fill:#[0-9a-f]+;?', '', s)
				if s != s_new:
					print("Explicit fill was removed from style string ({0}) for element with ID {1} "
											"because its class ({2}) controls the fill color".format(s, i, c))
				s = s_new
			if s == 'style=""':  # the style is empty now
				del elem.attrib["style"]
				continue
			cs = ''
			if c in styles:
				cs = styles[c].strip('; ').lower()
			if (c not in styles):
				print("Object id %s references unknown style class %s." % (i, c))
			else:
				if (cs != s.strip('; ')):
					print("Style %s removed from object id %s differed from class %s style %s." % (s, i, c, cs))
					del elem.attrib["style"]

		# remove explicit fill color if element class is one of the color_classes



if __name__ == "__main__":
	input_file = sys.argv[1]
	tree = etree.parse(input_file)
	fix(tree)
	# store SVG into file (input file is overwritten)
	svg = etree.tostring(tree, pretty_print=True)
	with open(input_file, 'wb') as f:
		f.write('<?xml version="1.0" encoding="UTF-8" standalone="no"?>\n'.encode("utf-8"))
		f.write(svg)