Parse svg: path d attribute

Question

I need to decrypt a path element in an SVG document to control the CNC machine along that path. I wonder if there are any Python libraries that parse SVG and give some kind of pythonic list for the d attribute, for example:

<path d="M 20 30 L 20 20 20 40 40 40"/> 

analyzes on

 [["M", 20, 30], ["L", 20, 20], ["L", 20, 40], ["L", 40, 40]] 

Answer 1

Run it here, written by me and in python 2.7.2. Just remove the tests and print instructions if you want.

  Copyright 2012 Christopher L. Ramsey Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. from collections import OrderedDict from re import match from re import split from re import sub class PathIterator(object): EOI = 'End of Iteration' PATH_IDENTIFIERS = r'[MLHVCSQTAmlhvcsqa]' NUMBERS = r'[0-9.-^Az]' SEPERATORS = r'\s|\,' PATH_END = r'[Zz]' def __init__(self, path): self.parseable = path.translate(None, '\t\f') self.parseable = self.parseable.replace('\n', ' ') print 'strip_newlines: {}'.format(self.parseable) self.parseable = sub(r'([A-Za-z])([0-9]|\-)', self.insert, self.parseable) print 'add_space: {}'.format(self.parseable) self.parseable = self.parseable.replace(',', ' ') print 'replace_commas: {}'.format(self.parseable) self.parseable = sub(r'\s+', ' ', self.parseable) # replace any double space with a single space print 'strip_extra_space: {}'.format(self.parseable) self.tokens = split(' ', self.parseable) self.map = self.produce_map(self.tokens) print self.map self.elements = self.process(self.map) def produce_map(self, tkns): self.m = OrderedDict() self.i = 0 while self.i < len(tkns): if match(self.PATH_IDENTIFIERS, tkns[self.i]): self.m[self.i] = tkns[self.i] elif match(self.PATH_END, tkns[self.i]): self.m[self.i] = tkns[self.i] else: pass self.i += 1 return self.m.items() def process(self, map): self.mm = [] self.l = len(map) for e in range(self.l): try: self.element = map[e] self.future = map[e + 1] self.ident = self.element[1] self.start = self.element[0] + 1 self.end = self.future[0] self.nbrs = self.tokens[self.start:self.end] except: self.element = map[e] self.ident = self.element[1] self.start = self.element[0] + 1 self.end = len(self.tokens) self.nbrs = self.tokens[self.start:self.end] print 'start: {} end {}'.format(self.start, self.end) finally: self.numbers = [] for number in self.nbrs: self.numbers.append(float(number)) self.mm.append((self.ident, self.numbers)) return iter(self.mm) def next(self): try: return self.elements.next() except: return self.EOI def insert(self, match_obj): self.group = match_obj.group() return '{} {}'.format(self.group[0], self.group[1]) if __name__ == '__main__': inkscape_path = "M 12,90 C 8.676,90 6,87.324 6,84 L 6,82 6,14 6,12 c 0,-0.334721 0.04135,-0.6507 0.09375,-0.96875 0.0487,-0.295596 0.09704,-0.596915 0.1875,-0.875 C 6.29113,10.12587 6.302142,10.09265 6.3125,10.0625 6.411365,9.774729 6.5473802,9.515048 6.6875,9.25 6.8320918,8.976493 7.0031161,8.714385 7.1875,8.46875 7.3718839,8.223115 7.5612765,7.995278 7.78125,7.78125 8.221197,7.353194 8.72416,6.966724 9.28125,6.6875 9.559795,6.547888 9.8547231,6.440553 10.15625,6.34375 9.9000482,6.443972 9.6695391,6.580022 9.4375,6.71875 c -0.00741,0.0044 -0.023866,-0.0045 -0.03125,0 -0.031933,0.0193 -0.062293,0.04251 -0.09375,0.0625 -0.120395,0.0767 -0.2310226,0.163513 -0.34375,0.25 -0.1061728,0.0808 -0.2132809,0.161112 -0.3125,0.25 C 8.4783201,7.442683 8.3087904,7.626638 8.15625,7.8125 8.0486711,7.942755 7.9378561,8.077785 7.84375,8.21875 7.818661,8.25713 7.805304,8.30462 7.78125,8.34375 7.716487,8.446782 7.6510225,8.548267 7.59375,8.65625 7.4927417,8.850956 7.3880752,9.071951 7.3125,9.28125 7.30454,9.30306 7.288911,9.3218 7.28125,9.34375 7.2494249,9.4357 7.2454455,9.530581 7.21875,9.625 7.1884177,9.731618 7.1483606,9.828031 7.125,9.9375 7.0521214,10.279012 7,10.635705 7,11 l 0,2 0,68 0,2 c 0,2.781848 2.2181517,5 5,5 l 2,0 68,0 2,0 c 2.781848,0 5,-2.218152 5,-5 l 0,-2 0,-68 0,-2 C 89,10.635705 88.94788,10.279012 88.875,9.9375 88.83085,9.730607 88.78662,9.539842 88.71875,9.34375 88.71105,9.3218 88.69545,9.30306 88.6875,9.28125 88.62476,9.107511 88.549117,8.913801 88.46875,8.75 88.42717,8.6672 88.38971,8.580046 88.34375,8.5 88.28915,8.40279 88.216976,8.31165 88.15625,8.21875 88.06214,8.077785 87.951329,7.942755 87.84375,7.8125 87.700576,7.63805 87.540609,7.465502 87.375,7.3125 87.36383,7.3023 87.35502,7.29135 87.34375,7.28125 87.205364,7.155694 87.058659,7.046814 86.90625,6.9375 86.803679,6.86435 86.701932,6.784136 86.59375,6.71875 c -0.0074,-0.0045 -0.02384,0.0044 -0.03125,0 -0.232039,-0.138728 -0.462548,-0.274778 -0.71875,-0.375 0.301527,0.0968 0.596455,0.204138 0.875,0.34375 0.55709,0.279224 1.060053,0.665694 1.5,1.09375 0.219973,0.214028 0.409366,0.441865 0.59375,0.6875 0.184384,0.245635 0.355408,0.507743 0.5,0.78125 0.14012,0.265048 0.276135,0.524729 0.375,0.8125 0.01041,0.03078 0.02133,0.06274 0.03125,0.09375 0.09046,0.278085 0.1388,0.579404 0.1875,0.875 C 89.95865,11.3493 90,11.665279 90,12 l 0,2 0,68 0,2 c 0,3.324 -2.676,6 -6,6 l -72,0 z" mdn_path = "M10 80 Q 52.5 10, 95 80 T 180 80" w3c_path = "M100,200 C100,100 250,100 250,200 S400,300 400,200" w3c_path_neg = "M-100,200 C100,100 250,100 250,200 S-400,300 400,200" w3c_path_nl = ''' M600,350 l 50,-25 a25,25 -30 0,1 50,-25 l 50,-25 a25,50 -30 0,1 50,-25 l 50,-25 a25,75 -30 0,1 50,-25 l 50,-25 a25,100 -30 0,1 50,-25 l 50,-25 ''' paths = [inkscape_path, mdn_path, w3c_path, str.strip(w3c_path_nl), w3c_path_neg] for path in paths: p = PathIterator(path) char = '' while char != PathIterator.EOI: char = p.next() print char 

Answer 2

Getting d-lines can be reduced to a couple of lines using svgpathtools , the rest can be done using regular expressions.

 from svgpathtools import svg2paths paths, attributes = svg2paths('some_svg_file.svg') 

paths is a list of svgpathtools Path path objects (containing only curve information, without colors, styles, etc.). attributes - a list of attributes dictionary objects.

Suppose the path you are interested in is the first (0th) specified in your SVG, and then extract only the d-string that you can use:

 d = attributes[0]['d'] # d-string from first path in SVG # Now for some regular expressions magic import re split_by_letters = re.findall('[AZ|az][^AZ|az]*', d) split_as_you_want = [] for x in split_by_letters: nums = x[1:].replace(',',' ').split() # list of numbers after letter for k in range(len(nums) // 2): split_as_you_want.append([x[0]] + [nums[k]] + [nums[k+1]]) print split_as_you_want 

I have not converted the numbers to strings here, since how you want to do this depends on whether they are always integers and whether you care to keep them that way. For most purposes, this can be done as follows: "nums = ...".

 for k, n in enumerate(nums): try: nums[k] = int(n) except ValueError: nums[k] = float(n)