svg_cleaner.py

#!/usr/bin/env python3
# Copyright 2015 Google, Inc. All Rights Reserved.
#
# 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.
#
# Google Author(s): Doug Felt

"""Clean SVG.

svgo could do this, but we're fussy.  Also, emacs doesn't understand
that 'style' defaults to 'text/css' and svgo strips this out by
default.

The files we're getting that are exported from AI contain lots of extra
data so that it can reimport the svg, and we don't need it."""


import argparse
import codecs
import logging
import os
from os import path
import re
import sys

from nototools import tool_utils

from xml.parsers import expat
from xml.sax import saxutils

# Expat doesn't allow me to identify empty tags (in particular, with an
# empty tag the parse location for the start and end is not the same) so I
# have to take a dom-like approach if I want to identify them. There are a
# lot of empty tags in svg.  This way I can do some other kinds of cleanup
# as well (remove unnecessary 'g' elements, for instance).

# Use nodes instead of tuples and strings because it's easier to mutate
# a tree of these, and cleaner will want to do this.

class _Elem_Node(object):
  def __init__(self, name, attrs, contents):
    self.name = name
    self.attrs = attrs
    self.contents = contents

  def __repr__(self):
    line = ["elem(name: '%s'" % self.name]
    if self.attrs:
      line.append(" attrs: '%s'" % self.attrs)
    if self.contents:
      line.append(" contents[%s]: '%s'" % (len(self.contents), self.contents))
    line.append(')')
    return ''.join(line)

class _Text_Node(object):
  def __init__(self, text):
    self.text = text

  def __repr__(self):
    return "text('%s')" % self.text

class SvgCleaner(object):
  """Strip out unwanted parts of an svg file, primarily the xml declaration and
  doctype lines, comments, and some attributes of the outermost <svg> element.
  The id will be replaced when it is inserted into the font. (viewBox causes
  unwanted scaling when used in a font and its effect is difficult to
  predict, but for outside a font we need to keep it sometimes so we keep it).
  version is unneeded, xml:space is ignored (we're processing spaces
  so a request to maintain them has no effect).  enable-background appears to
  have no effect.  x and y on the outermost svg element have no effect.  We
  keep width and height, and will elsewhere assume these are the dimensions
  used for the character box."""

  def __init__(self, strip=False):
    self.reader = SvgCleaner._Reader()
    self.cleaner = SvgCleaner._Cleaner()
    self.writer = SvgCleaner._Writer(strip)

  class _Reader(object):
    """Loosely based on fonttools's XMLReader.  This generates a tree of nodes,
    either element nodes or text nodes.  Successive text content is merged
    into one node, so contents will never contain more than one _Text_Node in
    a row.  This drops comments, xml declarations, and doctypes."""

    def _reset(self, parser):
      self._stack = []
      self._textbuf = []

    def _start_element(self, name, attrs):
      self._flush_textbuf()
      node = _Elem_Node(name, attrs, [])
      if len(self._stack):
        self._stack[-1].contents.append(node)
      self._stack.append(node)

    def _end_element(self, name):
      self._flush_textbuf()
      if len(self._stack) > 1:
        self._stack = self._stack[:-1]

    def _character_data(self, data):
      if len(self._stack):
        self._textbuf.append(data)

    def _flush_textbuf(self):
      if self._textbuf:
        node = _Text_Node(''.join(self._textbuf))
        self._stack[-1].contents.append(node)
        self._textbuf = []

    def from_text(self, data):
      """Return the root node of a tree representing the svg data."""

      parser = expat.ParserCreate()
      parser.StartElementHandler = self._start_element
      parser.EndElementHandler = self._end_element
      parser.CharacterDataHandler = self._character_data
      self._reset(parser)
      parser.Parse(data)
      return self._stack[0]

  class _Cleaner(object):
    def _clean_elem(self, node):
      viewBox, x, y, width, height = None, None, None, None, None
      nattrs = {}
      for k, v in node.attrs.items():
        if node.name == 'svg' and k in [
            'x', 'y', 'id', 'version', 'viewBox', 'width', 'height',
            'enable-background', 'xml:space', 'xmlns:graph', 'xmlns:i',
            'xmlns:x']:
          if k == 'viewBox':
            viewBox = v
          elif k == 'width':
            width = v
          elif k == 'height':
            height = v
          elif k.startswith('xmlns:') and 'ns.adobe.com' not in v:
            # keep if not an adobe namespace
            logging.debug('keep "%s" = "%s"' % (k, v))
            nattrs[k] = v
          logging.debug('removing %s=%s' % (k, v))
          continue
        v = re.sub('\s+', ' ', v)
        nattrs[k] = v

      if node.name == 'svg':
        if viewBox:
          x, y, width, height = viewBox.split()
        if not width or not height:
          if not viewBox:
            raise ValueError('no viewBox, width, or height')
        nattrs['width'] = width
        nattrs['height'] = height
        # keep for svg use outside of font
        if viewBox and (int(x) != 0 or int(y) != 0):
          logging.warn('viewbox "%s" x: %s y: %s' % (viewBox, x, y));
          nattrs['viewBox'] = viewBox
      node.attrs = nattrs

      # if display:none, skip this and its children
      style = node.attrs.get('style')
      if (style and 'display:none' in style) or node.attrs.get('display') == 'none':
          node.contents = []
          return

      # scan contents. remove any empty text nodes, or empty 'g' element nodes.
      # if a 'g' element has no attrs and only one subnode, replace it with the
      # subnode.
      wpos = 0
      for n in node.contents:
        if isinstance(n, _Text_Node):
          if not n.text:
            continue
        elif n.name == 'g':
          if not n.contents:
            continue
          if 'i:extraneous' in n.attrs:
            del n.attrs['i:extraneous']
          if not n.attrs and len(n.contents) == 1:
            n = n.contents[0]
        elif n.name == 'i:pgf' or n.name == 'foreignObject':
          continue
        elif n.name =='switch' and len(n.contents) == 1:
          n = n.contents[0]
        elif n.name == 'style':
          # some emacsen don't default 'style' properly, so leave this in.
          if False and n.attrs.get('type') == 'text/css':
            del n.attrs['type']

        node.contents[wpos] = n
        wpos += 1
      if wpos < len(node.contents):
        node.contents = node.contents[:wpos]

    def _clean_text(self, node):
      text = node.text.strip()
      # common case is text is empty (line endings between elements)
      if text:
        # main goal here is to leave linefeeds in for style elements
        text = re.sub(r'[ \t]*\n+[ \t]*', '\n', text)
        text = re.sub(r'[ \t]+', ' ', text)
      node.text = text

    def clean(self, node):
      if isinstance(node, _Text_Node):
        self._clean_text(node)
      else:
        # do contents first, so we can check for empty subnodes after
        for n in node.contents:
          self.clean(n)
        self._clean_elem(node)

  class _Writer(object):
    """For text nodes, replaces sequences of whitespace with a single space.
    For elements, replaces sequences of whitespace in attributes, and
    removes unwanted attributes from <svg> elements."""
    def __init__(self, strip):
      logging.warning('writer strip: %s' % strip);
      self._strip = strip

    def _write_node(self, node, lines, indent):
      """Node is a node generated by _Reader, either a TextNode or an
      ElementNode. Lines is a list to collect the lines of output.  Indent is
      the indentation level for this node."""

      if isinstance(node, _Text_Node):
        if node.text:
          lines.append(node.text)
      else:
        margin = '' if self._strip else '  ' * indent
        line = [margin]
        line.append('<%s' % node.name)
        # custom sort attributes of svg, yes this is a hack
        if node.name == 'svg':
          def svgsort(k):
            if k == 'width': return (0, None)
            elif k == 'height': return (1, None)
            else: return (2, k)
          ks = sorted(node.attrs.keys(), key=svgsort)
        else:
          def defsort(k):
            if k == 'id': return (0, None)
            elif k == 'class': return (1, None)
            else: return (2, k)
          ks = sorted(node.attrs.keys(), key=defsort)
        for k in ks:
          v = node.attrs[k]
          line.append(' %s=%s' % (k, saxutils.quoteattr(v)))
        if node.contents:
          line.append('>')
          lines.append(''.join(line))
          for elem in node.contents:
            self._write_node(elem, lines, indent + 1)
          line = [margin]
          line.append('</%s>' % node.name)
          lines.append(''.join(line))
        else:
          line.append('/>')
          lines.append(''.join(line))

    def to_text(self, root):
      # set up lines for recursive calls, let them append lines, then return
      # the result.
      lines = []
      self._write_node(root, lines, 0)
      return ''.join(lines) if self._strip else '\n'.join(lines)

  def tree_from_text(self, svg_text):
    return self.reader.from_text(svg_text)

  def clean_tree(self, svg_tree):
    self.cleaner.clean(svg_tree)

  def tree_to_text(self, svg_tree):
    return self.writer.to_text(svg_tree)

  def clean_svg(self, svg_text):
    """Return the cleaned svg_text."""
    tree = self.tree_from_text(svg_text)
    self.clean_tree(tree)
    return self.tree_to_text(tree)


def clean_svg_files(in_dir, out_dir, match_pat=None, clean=False, strip=False):
  regex = re.compile(match_pat) if match_pat else None
  count = 0

  if clean and path.samefile(in_dir, out_dir):
    logging.error('Cannot clean %s (same as in_dir)', out_dir)
    return

  out_dir = tool_utils.ensure_dir_exists(out_dir, clean=clean)

  cleaner = SvgCleaner(strip)
  for file_name in os.listdir(in_dir):
    if regex and not regex.match(file_name):
      continue
    in_path = os.path.join(in_dir, file_name)
    logging.debug('read: %s', in_path)
    with open(in_path) as in_fp:
      result = cleaner.clean_svg(in_fp.read())
    out_path = os.path.join(out_dir, file_name)
    with codecs.open(out_path, 'w', 'utf-8') as out_fp:
      logging.debug('write: %s', out_path)
      out_fp.write(result)
      count += 1
  if not count:
    logging.warning('Failed to match any files')
  else:
    logging.info('Wrote %s files to %s', count, out_dir)


def main():
  parser = argparse.ArgumentParser(
      description="Generate 'cleaned' svg files.")
  parser.add_argument(
      'in_dir', help='Input directory.', metavar='dir')
  parser.add_argument(
      '-o', '--out_dir', help='Output directory, defaults to sibling of in_dir',
      metavar='dir')
  parser.add_argument(
      '-c', '--clean', help='Clean output directory', action='store_true')
  parser.add_argument(
      '-r', '--regex', help='Regex to select files, default matches all files.',
      metavar='regex', default=None)
  parser.add_argument(
      '-l', '--loglevel', help='log level name/value', default='warning')
  parser.add_argument(
      '-w', '--strip_whitespace', help='remove newlines and indentation',
      action='store_true')
  args = parser.parse_args()

  tool_utils.setup_logging(args.loglevel)

  if not args.out_dir:
    if args.in_dir.endswith('/'):
      args.in_dir = args.in_dir[:-1]
    args.out_dir = args.in_dir + '_clean'
    logging.info('Writing output to %s', args.out_dir)

  clean_svg_files(
      args.in_dir, args.out_dir, match_pat=args.regex, clean=args.clean,
      strip=args.strip_whitespace)


if __name__ == '__main__':
  main()