Parse svg: path d attribute

Question

Necesito descifrar un elemento de ruta en un documento SVG para conducir una máquina CNC a lo largo de esa ruta. Me pregunto si hay algunas bibliotecas de Python que analizan SVG y dan algún tipo de lista de Pythonic para el atributo d, por ejemplo:

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

analiza sintácticamente en

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

Answer 1

Aquí es un comienzo que está escrito por mí y en Python 2.7.2. Simplemente elimine las pruebas e imprima declaraciones si lo desea.

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.-^A-z]' 
    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

Conseguir el d-secuencia puede estar abajo en un par de líneas utilizando svgpathtools, el resto se puede hacer uso de expresiones regulares.

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

caminos es una lista de objetos svgpathtools Path (que contienen sólo la información curva, no hay colores, estilos, etc.). atributos es una lista de objetos de diccionario de los atributos.

Supongamos que el camino le interesa es la primera (del 0 ª) que aparece en su SVG, a continuación, para extraer sólo el d-cadena que puede utilizar:

d = attributes[0]['d'] # d-string from first path in SVG 

# Now for some regular expressions magic 
import re 
split_by_letters = re.findall('[A-Z|a-z][^A-Z|a-z]*', 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 

que no convirtió la los números en cadenas aquí, como quiera hacer eso, depende de si siempre son enteros y si le importa que sigan así. Para la mayoría de los propósitos, esto se puede hacer con algo como lo siguiente debajo de la línea "nums = ...".

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