1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
|
""" Small hand-written recursive descent parser for SVG <path> data.
In [1]: from svg_regex import svg_parser
In [3]: svg_parser.parse('M 10,20 30,40V50 60 70')
Out[3]: [('M', [(10.0, 20.0), (30.0, 40.0)]), ('V', [50.0, 60.0, 70.0])]
In [4]: svg_parser.parse('M 0.6051.5') # An edge case
Out[4]: [('M', [(0.60509999999999997, 0.5)])]
In [5]: svg_parser.parse('M 100-200') # Another edge case
Out[5]: [('M', [(100.0, -200.0)])]
"""
import re
# Sentinel.
class _EOF(object):
def __repr__(self):
return 'EOF'
EOF = _EOF()
lexicon = [
('float', r'[-\+]?(?:(?:[0-9]*\.[0-9]+)|(?:[0-9]+\.?))(?:[Ee][-\+]?[0-9]+)?'),
('int', r'[-\+]?[0-9]+'),
('command', r'[AaCcHhLlMmQqSsTtVvZz]'),
]
class Lexer(object):
""" Break SVG path data into tokens.
The SVG spec requires that tokens are greedy. This lexer relies on Python's
regexes defaulting to greediness.
This style of implementation was inspired by this article:
http://www.gooli.org/blog/a-simple-lexer-in-python/
"""
def __init__(self, lexicon):
self.lexicon = lexicon
parts = []
for name, regex in lexicon:
parts.append('(?P<%s>%s)' % (name, regex))
self.regex_string = '|'.join(parts)
self.regex = re.compile(self.regex_string)
def lex(self, text):
""" Yield (token_type, str_data) tokens.
The last token will be (EOF, None) where EOF is the singleton object
defined in this module.
"""
for match in self.regex.finditer(text):
for name, _ in self.lexicon:
m = match.group(name)
if m is not None:
yield (name, m)
break
yield (EOF, None)
svg_lexer = Lexer(lexicon)
class SVGPathParser(object):
""" Parse SVG <path> data into a list of commands.
Each distinct command will take the form of a tuple (command, data). The
`command` is just the character string that starts the command group in the
<path> data, so 'M' for absolute moveto, 'm' for relative moveto, 'Z' for
closepath, etc. The kind of data it carries with it depends on the command.
For 'Z' (closepath), it's just None. The others are lists of individual
argument groups. Multiple elements in these lists usually mean to repeat the
command. The notable exception is 'M' (moveto) where only the first element
is truly a moveto. The remainder are implicit linetos.
See the SVG documentation for the interpretation of the individual elements
for each command.
The main method is `parse(text)`. It can only consume actual strings, not
filelike objects or iterators.
"""
def __init__(self, lexer=svg_lexer):
self.lexer = lexer
self.command_dispatch = {
'Z': self.rule_closepath,
'z': self.rule_closepath,
'M': self.rule_moveto_or_lineto,
'm': self.rule_moveto_or_lineto,
'L': self.rule_moveto_or_lineto,
'l': self.rule_moveto_or_lineto,
'H': self.rule_orthogonal_lineto,
'h': self.rule_orthogonal_lineto,
'V': self.rule_orthogonal_lineto,
'v': self.rule_orthogonal_lineto,
'C': self.rule_curveto3,
'c': self.rule_curveto3,
'S': self.rule_curveto2,
's': self.rule_curveto2,
'Q': self.rule_curveto2,
'q': self.rule_curveto2,
'T': self.rule_curveto1,
't': self.rule_curveto1,
'A': self.rule_elliptical_arc,
'a': self.rule_elliptical_arc,
}
self.number_tokens = set(['int', 'float'])
def parse(self, text):
""" Parse a string of SVG <path> data.
"""
next = self.lexer.lex(text).next
token = next()
return self.rule_svg_path(next, token)
def rule_svg_path(self, next, token):
commands = []
while token[0] is not EOF:
if token[0] != 'command':
raise SyntaxError("expecting a command; got %r" % (token,))
rule = self.command_dispatch[token[1]]
command_group, token = rule(next, token)
commands.append(command_group)
return commands
def rule_closepath(self, next, token):
command = token[1]
token = next()
return (command, None), token
def rule_moveto_or_lineto(self, next, token):
command = token[1]
token = next()
coordinates = []
while token[0] in self.number_tokens:
pair, token = self.rule_coordinate_pair(next, token)
coordinates.append(pair)
return (command, coordinates), token
def rule_orthogonal_lineto(self, next, token):
command = token[1]
token = next()
coordinates = []
while token[0] in self.number_tokens:
coord, token = self.rule_coordinate(next, token)
coordinates.append(coord)
return (command, coordinates), token
def rule_curveto3(self, next, token):
command = token[1]
token = next()
coordinates = []
while token[0] in self.number_tokens:
pair1, token = self.rule_coordinate_pair(next, token)
pair2, token = self.rule_coordinate_pair(next, token)
pair3, token = self.rule_coordinate_pair(next, token)
coordinates.append((pair1, pair2, pair3))
return (command, coordinates), token
def rule_curveto2(self, next, token):
command = token[1]
token = next()
coordinates = []
while token[0] in self.number_tokens:
pair1, token = self.rule_coordinate_pair(next, token)
pair2, token = self.rule_coordinate_pair(next, token)
coordinates.append((pair1, pair2))
return (command, coordinates), token
def rule_curveto1(self, next, token):
command = token[1]
token = next()
coordinates = []
while token[0] in self.number_tokens:
pair1, token = self.rule_coordinate_pair(next, token)
coordinates.append(pair1)
return (command, coordinates), token
def rule_elliptical_arc(self, next, token):
command = token[1]
token = next()
arguments = []
while token[0] in self.number_tokens:
rx = float(token[1])
if rx < 0.0:
raise SyntaxError("expecting a nonnegative number; got %r" % (token,))
token = next()
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
ry = float(token[1])
if ry < 0.0:
raise SyntaxError("expecting a nonnegative number; got %r" % (token,))
token = next()
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
axis_rotation = float(token[1])
token = next()
if token[1] not in ('0', '1'):
raise SyntaxError("expecting a boolean flag; got %r" % (token,))
large_arc_flag = bool(int(token[1]))
token = next()
if token[1] not in ('0', '1'):
raise SyntaxError("expecting a boolean flag; got %r" % (token,))
sweep_flag = bool(int(token[1]))
token = next()
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
x = float(token[1])
token = next()
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
y = float(token[1])
token = next()
arguments.append(((rx,ry), axis_rotation, large_arc_flag, sweep_flag, (x,y)))
return (command, arguments), token
def rule_coordinate(self, next, token):
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
x = float(token[1])
token = next()
return x, token
def rule_coordinate_pair(self, next, token):
# Inline these since this rule is so common.
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
x = float(token[1])
token = next()
if token[0] not in self.number_tokens:
raise SyntaxError("expecting a number; got %r" % (token,))
y = float(token[1])
token = next()
return (x,y), token
svg_parser = SVGPathParser()
|
