269 lines
8.5 KiB
Text
269 lines
8.5 KiB
Text
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#!/usr/bin/env python3
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"""latex2svg
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Read LaTeX code from stdin and render a SVG using LaTeX, dvisvgm and svgo.
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Returns a minified SVG with `width`, `height` and `style="vertical-align:"`
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attribues whose values are in `em` units. The SVG will have (pseudo-)unique
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IDs in case more than one is used on the same HTML page.
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Based on [original work](https://github.com/tuxu/latex2svg) by Tino Wagner.
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"""
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__version__ = '0.2.1'
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__author__ = 'Matthias C. Hormann'
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__email__ = 'mhormann@gmx.de'
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__license__ = 'MIT'
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__copyright__ = 'Copyright (c) 2022, Matthias C. Hormann'
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import os
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import sys
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import subprocess
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import shlex
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import re
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from tempfile import TemporaryDirectory
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from ctypes.util import find_library
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default_template = r"""
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\documentclass[{{ fontsize }}pt,preview]{standalone}
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{{ preamble }}
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\begin{document}
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\begin{preview}
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{{ code }}
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\end{preview}
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\end{document}
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"""
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default_preamble = r"""
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\usepackage[utf8x]{inputenc}
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\usepackage{amsmath}
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\usepackage{amsfonts}
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\usepackage{amssymb}
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\usepackage{amstext}
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\usepackage{newtxtext}
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\usepackage[libertine]{newtxmath}
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% prevent errors from old font commands
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\DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm}
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\DeclareOldFontCommand{\sf}{\normalfont\sffamily}{\mathsf}
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\DeclareOldFontCommand{\tt}{\normalfont\ttfamily}{\mathtt}
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\DeclareOldFontCommand{\bf}{\normalfont\bfseries}{\mathbf}
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\DeclareOldFontCommand{\it}{\normalfont\itshape}{\mathit}
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\DeclareOldFontCommand{\sl}{\normalfont\slshape}{\@nomath\sl}
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\DeclareOldFontCommand{\sc}{\normalfont\scshape}{\@nomath\sc}
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% prevent errors from undefined shortcuts
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\newcommand{\N}{\mathbb{N}}
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\newcommand{\R}{\mathbb{R}}
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\newcommand{\Z}{\mathbb{Z}}
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"""
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default_svgo_config = r"""
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module.exports = {
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plugins: [
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{
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// use default preset (almost)
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name: 'preset-default',
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params: {
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overrides: {
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// viewbox required to resize SVGs with CSS, disable removal
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removeViewBox: false,
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},
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},
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// enable prefixIds
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name: 'prefixIds',
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params: {
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prefix: '{{ prefix }}',
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delim: '_',
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},
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},
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],
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};
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"""
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latex_cmd = 'latex -interaction nonstopmode -halt-on-error'
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dvisvgm_cmd = 'dvisvgm --no-fonts'
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svgo_cmd = 'svgo'
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default_params = {
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'fontsize': 12, # TeX pt
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'template': default_template,
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'preamble': default_preamble,
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'latex_cmd': latex_cmd,
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'dvisvgm_cmd': dvisvgm_cmd,
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'svgo_cmd': svgo_cmd,
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'svgo_config': default_svgo_config,
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'libgs': None,
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}
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if not hasattr(os.environ, 'LIBGS') and not find_library('gs'):
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if sys.platform == 'darwin':
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# Fallback to homebrew Ghostscript on macOS
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homebrew_libgs = '/usr/local/opt/ghostscript/lib/libgs.dylib'
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if os.path.exists(homebrew_libgs):
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default_params['libgs'] = homebrew_libgs
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if not default_params['libgs']:
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print('Warning: libgs not found', file=sys.stderr)
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def latex2svg(code, params=default_params, working_directory=None):
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"""Convert LaTeX to SVG using dvisvgm and svgo.
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Parameters
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----------
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code : str
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LaTeX code to render.
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params : dict
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Conversion parameters.
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working_directory : str or None
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Working directory for external commands and place for temporary files.
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Returns
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-------
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dict
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Dictionary of SVG output and output information:
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* `svg`: SVG data
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* `width`: image width in *em*
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* `height`: image height in *em*
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* `valign`: baseline offset in *em*
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"""
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if working_directory is None:
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with TemporaryDirectory() as tmpdir:
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return latex2svg(code, params, working_directory=tmpdir)
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# Caution: TeX & dvisvgm work with TeX pt (1/72.27"), but we need DTP pt (1/72")
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# so we need a scaling factor for correct output sizes
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scaling = 1.00375 # (1/72)/(1/72.27)
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fontsize = params['fontsize']
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document = code
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with open(os.path.join(working_directory, 'code.tex'), 'w') as f:
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f.write(document)
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# Run LaTeX and create DVI file
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try:
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ret = subprocess.run(shlex.split(params['latex_cmd']+' code.tex'),
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stdout=subprocess.PIPE, stderr=subprocess.PIPE,
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cwd=working_directory)
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ret.check_returncode()
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except FileNotFoundError:
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raise RuntimeError('latex not found')
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# Add LIBGS to environment if supplied
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env = os.environ.copy()
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if params['libgs']:
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env['LIBGS'] = params['libgs']
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# Convert DVI to SVG
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try:
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ret = subprocess.run(shlex.split(params['dvisvgm_cmd']+' code.dvi'),
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stdout=subprocess.PIPE, stderr=subprocess.PIPE,
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cwd=working_directory, env=env)
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ret.check_returncode()
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except FileNotFoundError:
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raise RuntimeError('dvisvgm not found')
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# Parse dvisvgm output for size and alignment
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def get_size(output):
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regex = r'\b([0-9.]+)pt x ([0-9.]+)pt'
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match = re.search(regex, output)
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if match:
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return (float(match.group(1)) / fontsize * scaling,
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float(match.group(2)) / fontsize * scaling)
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else:
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return None, None
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def get_measure(output, name):
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regex = r'\b%s=([0-9.e-]+)pt' % name
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match = re.search(regex, output)
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if match:
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return float(match.group(1)) / fontsize * scaling
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else:
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return None
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output = ret.stderr.decode('utf-8')
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width, height = get_size(output)
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depth = get_measure(output, 'depth')
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# Modify SVG attributes, to a get a self-contained, scaling SVG
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from lxml import etree
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# read SVG, discarding all comments ("<-- Generated by… -->")
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parser = etree.XMLParser(remove_comments=True)
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xml = etree.parse(os.path.join(working_directory, 'code.svg'), parser)
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svg = xml.getroot()
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svg.set('width', f'{width:.6f}em')
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svg.set('height', f'{height:.6f}em')
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svg.set('style', f'vertical-align:{-depth:.6f}em')
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xml.write(os.path.join(working_directory, 'code.svg'))
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# Run svgo to get a minified oneliner with (pseudo-)unique Ids
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# generate random prefix using ASCII letters (ID may not start with a digit)
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import random, string
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prefix = ''.join(random.choice(string.ascii_letters) for n in range(4))
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svgo_config = (params['svgo_config']
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.replace('{{ prefix }}', prefix))
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# write svgo params file
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with open(os.path.join(working_directory, 'svgo.config.js'), 'w') as f:
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f.write(svgo_config)
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try:
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ret = subprocess.run(shlex.split(params['svgo_cmd']+' code.svg'),
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stdout=subprocess.PIPE, stderr=subprocess.PIPE,
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cwd=working_directory, env=env)
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ret.check_returncode()
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except FileNotFoundError:
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raise RuntimeError('svgo not found')
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with open(os.path.join(working_directory, 'code.svg'), 'r') as f:
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svg = f.read()
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return {'svg': svg, 'valign': round(-depth,6),
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'width': round(width,6), 'height': round(height,6)}
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def main():
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"""Simple command line interface to latex2svg.
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- Read from `stdin`.
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- Write SVG to `stdout`.
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- On error: write error messages to `stderr` and return with error code.
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"""
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import json
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import argparse
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parser = argparse.ArgumentParser(description="""
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Render LaTeX code from stdin as SVG to stdout. Writes metadata (baseline
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offset, width, height in em units) into the SVG attributes.
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""")
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parser.add_argument('--version', action='version',
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version='%(prog)s {version}'.format(version=__version__))
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parser.add_argument('--preamble',
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help="LaTeX preamble code to read from file")
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parser.add_argument('--fontsize',
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help="LaTeX fontsize in pt")
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args = parser.parse_args()
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preamble = default_preamble
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if args.preamble is not None:
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with open(args.preamble) as f:
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preamble = f.read()
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fontsize = 12
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if args.fontsize is not None:
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fontsize = int(args.fontsize)
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latex = sys.stdin.read()
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try:
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params = default_params.copy()
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params['preamble'] = preamble
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params['fontsize'] = fontsize
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out = latex2svg(latex, params)
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sys.stdout.write(out['svg'])
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except subprocess.CalledProcessError as exc:
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# LaTeX prints errors on stdout instead of stderr (stderr is empty),
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# dvisvgm to stderr, so print both (to stderr)
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print(exc.output.decode('utf-8'), file=sys.stderr)
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print(exc.stderr.decode('utf-8'), file=sys.stderr)
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sys.exit(exc.returncode)
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if __name__ == '__main__':
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main()
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