JezK
Edit File: svg_regex.py
# This software is OSI Certified Open Source Software. # OSI Certified is a certification mark of the Open Source Initiative. # # Copyright (c) 2006, Enthought, Inc. # All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are met: # # * Redistributions of source code must retain the above copyright notice, this # list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above copyright notice, # this list of conditions and the following disclaimer in the documentation # and/or other materials provided with the distribution. # * Neither the name of Enthought, Inc. nor the names of its contributors may # be used to endorse or promote products derived from this software without # specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR # ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES # (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. """ 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)])] """ from __future__ import absolute_import import re from decimal import Decimal, getcontext from functools import partial # 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']) self.number_tokens = list(['int', 'float']) def parse(self, text): """ Parse a string of SVG <path> data. """ gen = self.lexer.lex(text) next_val_fn = partial(next, *(gen,)) token = next_val_fn() return self.rule_svg_path(next_val_fn, token) def rule_svg_path(self, next_val_fn, 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_val_fn, token) commands.append(command_group) return commands def rule_closepath(self, next_val_fn, token): command = token[1] token = next_val_fn() return (command, []), token def rule_moveto_or_lineto(self, next_val_fn, token): command = token[1] token = next_val_fn() coordinates = [] while token[0] in self.number_tokens: pair, token = self.rule_coordinate_pair(next_val_fn, token) coordinates.extend(pair) return (command, coordinates), token def rule_orthogonal_lineto(self, next_val_fn, token): command = token[1] token = next_val_fn() coordinates = [] while token[0] in self.number_tokens: coord, token = self.rule_coordinate(next_val_fn, token) coordinates.append(coord) return (command, coordinates), token def rule_curveto3(self, next_val_fn, token): command = token[1] token = next_val_fn() coordinates = [] while token[0] in self.number_tokens: pair1, token = self.rule_coordinate_pair(next_val_fn, token) pair2, token = self.rule_coordinate_pair(next_val_fn, token) pair3, token = self.rule_coordinate_pair(next_val_fn, token) coordinates.extend(pair1) coordinates.extend(pair2) coordinates.extend(pair3) return (command, coordinates), token def rule_curveto2(self, next_val_fn, token): command = token[1] token = next_val_fn() coordinates = [] while token[0] in self.number_tokens: pair1, token = self.rule_coordinate_pair(next_val_fn, token) pair2, token = self.rule_coordinate_pair(next_val_fn, token) coordinates.extend(pair1) coordinates.extend(pair2) return (command, coordinates), token def rule_curveto1(self, next_val_fn, token): command = token[1] token = next_val_fn() coordinates = [] while token[0] in self.number_tokens: pair1, token = self.rule_coordinate_pair(next_val_fn, token) coordinates.extend(pair1) return (command, coordinates), token def rule_elliptical_arc(self, next_val_fn, token): command = token[1] token = next_val_fn() arguments = [] while token[0] in self.number_tokens: rx = Decimal(token[1]) * 1 if rx < Decimal("0.0"): raise SyntaxError("expecting a nonnegative number; got %r" % (token,)) token = next_val_fn() if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) ry = Decimal(token[1]) * 1 if ry < Decimal("0.0"): raise SyntaxError("expecting a nonnegative number; got %r" % (token,)) token = next_val_fn() if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) axis_rotation = Decimal(token[1]) * 1 token = next_val_fn() if token[1][0] not in ('0', '1'): raise SyntaxError("expecting a boolean flag; got %r" % (token,)) large_arc_flag = Decimal(token[1][0]) * 1 if len(token[1]) > 1: token = list(token) token[1] = token[1][1:] else: token = next_val_fn() if token[1][0] not in ('0', '1'): raise SyntaxError("expecting a boolean flag; got %r" % (token,)) sweep_flag = Decimal(token[1][0]) * 1 if len(token[1]) > 1: token = list(token) token[1] = token[1][1:] else: token = next_val_fn() if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) x = Decimal(token[1]) * 1 token = next_val_fn() if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) y = Decimal(token[1]) * 1 token = next_val_fn() arguments.extend([rx, ry, axis_rotation, large_arc_flag, sweep_flag, x, y]) return (command, arguments), token def rule_coordinate(self, next_val_fn, token): if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) x = getcontext().create_decimal(token[1]) token = next_val_fn() return x, token def rule_coordinate_pair(self, next_val_fn, 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 = getcontext().create_decimal(token[1]) token = next_val_fn() if token[0] not in self.number_tokens: raise SyntaxError("expecting a number; got %r" % (token,)) y = getcontext().create_decimal(token[1]) token = next_val_fn() return [x, y], token svg_parser = SVGPathParser()