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解析svg:path d属性

pythonsvg
5

我需要解密SVG文档中的路径元素，以便使CNC机沿着该路径移动。 我想知道是否有任何Python库可以解析SVG并为d属性提供一些类似于Python列表的内容，例如：

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

解析成

[["M", 20, 30],
 ["L", 20, 20],
 ["L", 20, 40],
 ["L", 40, 40]]
事实证明，对于我的需求，dvg:polyline/已经足够了，而且比svg:path/更容易解析。我现在正在使用它。 - iter
2个回答
3

使用svgpathtools可以轻松地获取d字符串，其余部分可使用正则表达式完成。

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

paths是一组svgpathtools Path对象（仅包含曲线信息，没有颜色、样式等）。

attributes是属性字典对象的列表。

假设您感兴趣的路径是在SVG中列出的第一个（0），则可以使用以下代码提取d字符串：

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

我这里没有将数字转换为字符串，因为如何转换取决于它们是否始终为整数以及您是否关心它们保持原样。对于大多数情况，可以在“nums = ...”行下方使用以下类似的代码完成此操作。

for k, n in enumerate(nums):
    try:
        nums[k] = int(n)
    except ValueError:
        nums[k] = float(n)
在svgpathtools中，是否也可以从path-d字符串生成Path对象？ - Student
1
@学生 是的，你可以使用parse_path函数。请参阅自述文件以获取示例。https://github.com/mathandy/svgpathtools - mathandy
3

这是一个由我用Python 2.7.2编写的起始代码。如果您想要，请删除测试和打印语句。

   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
很好，用def __iter__(self): return iter(self.elements)替换next()方法并移除EOI，这个类就可以作为一个合适的Python迭代器使用了，所以你可以使用for char in PathIterator(path)而不必再处理EOI。当然，如果字母代码前没有空格（这是有效的），需要进行额外的预处理步骤。但总体来说，对我来说效果还不错 - 谢谢。 - Ian
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