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# -*- coding: utf-8 -*-
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"""Tools for handling LaTeX."""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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from io import BytesIO, open
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import os
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import tempfile
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import shutil
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import subprocess
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from base64 import encodebytes
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import textwrap
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from IPython.utils.process import find_cmd, FindCmdError
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from traitlets.config import get_config
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from traitlets.config.configurable import SingletonConfigurable
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from traitlets import List, Bool, Unicode
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from IPython.utils.py3compat import cast_unicode
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class LaTeXTool(SingletonConfigurable):
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"""An object to store configuration of the LaTeX tool."""
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def _config_default(self):
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return get_config()
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backends = List(
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Unicode(), ["matplotlib", "dvipng"],
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help="Preferred backend to draw LaTeX math equations. "
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"Backends in the list are checked one by one and the first "
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"usable one is used. Note that `matplotlib` backend "
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"is usable only for inline style equations. To draw "
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"display style equations, `dvipng` backend must be specified. ",
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# It is a List instead of Enum, to make configuration more
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# flexible. For example, to use matplotlib mainly but dvipng
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# for display style, the default ["matplotlib", "dvipng"] can
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# be used. To NOT use dvipng so that other repr such as
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# unicode pretty printing is used, you can use ["matplotlib"].
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).tag(config=True)
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use_breqn = Bool(
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True,
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help="Use breqn.sty to automatically break long equations. "
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"This configuration takes effect only for dvipng backend.",
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).tag(config=True)
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packages = List(
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['amsmath', 'amsthm', 'amssymb', 'bm'],
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help="A list of packages to use for dvipng backend. "
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"'breqn' will be automatically appended when use_breqn=True.",
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).tag(config=True)
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preamble = Unicode(
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help="Additional preamble to use when generating LaTeX source "
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"for dvipng backend.",
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).tag(config=True)
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def latex_to_png(s, encode=False, backend=None, wrap=False, color='Black',
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scale=1.0):
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"""Render a LaTeX string to PNG.
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Parameters
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----------
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s : str
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The raw string containing valid inline LaTeX.
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encode : bool, optional
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Should the PNG data base64 encoded to make it JSON'able.
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backend : {matplotlib, dvipng}
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Backend for producing PNG data.
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wrap : bool
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If true, Automatically wrap `s` as a LaTeX equation.
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color : string
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Foreground color name among dvipsnames, e.g. 'Maroon' or on hex RGB
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format, e.g. '#AA20FA'.
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scale : float
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Scale factor for the resulting PNG.
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None is returned when the backend cannot be used.
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"""
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s = cast_unicode(s)
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allowed_backends = LaTeXTool.instance().backends
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if backend is None:
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backend = allowed_backends[0]
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if backend not in allowed_backends:
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return None
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if backend == 'matplotlib':
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f = latex_to_png_mpl
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elif backend == 'dvipng':
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f = latex_to_png_dvipng
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if color.startswith('#'):
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# Convert hex RGB color to LaTeX RGB color.
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if len(color) == 7:
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try:
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color = "RGB {}".format(" ".join([str(int(x, 16)) for x in
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textwrap.wrap(color[1:], 2)]))
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except ValueError as e:
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raise ValueError('Invalid color specification {}.'.format(color)) from e
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else:
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raise ValueError('Invalid color specification {}.'.format(color))
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else:
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raise ValueError('No such backend {0}'.format(backend))
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bin_data = f(s, wrap, color, scale)
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if encode and bin_data:
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bin_data = encodebytes(bin_data)
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return bin_data
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def latex_to_png_mpl(s, wrap, color='Black', scale=1.0):
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try:
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from matplotlib import mathtext
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from pyparsing import ParseFatalException
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except ImportError:
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return None
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# mpl mathtext doesn't support display math, force inline
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s = s.replace('$$', '$')
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if wrap:
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s = u'${0}$'.format(s)
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try:
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mt = mathtext.MathTextParser('bitmap')
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f = BytesIO()
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dpi = 120*scale
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mt.to_png(f, s, fontsize=12, dpi=dpi, color=color)
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return f.getvalue()
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except (ValueError, RuntimeError, ParseFatalException):
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return None
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def latex_to_png_dvipng(s, wrap, color='Black', scale=1.0):
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try:
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find_cmd('latex')
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find_cmd('dvipng')
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except FindCmdError:
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return None
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try:
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workdir = tempfile.mkdtemp()
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tmpfile = os.path.join(workdir, "tmp.tex")
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dvifile = os.path.join(workdir, "tmp.dvi")
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outfile = os.path.join(workdir, "tmp.png")
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with open(tmpfile, "w", encoding='utf8') as f:
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f.writelines(genelatex(s, wrap))
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with open(os.devnull, 'wb') as devnull:
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subprocess.check_call(
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["latex", "-halt-on-error", "-interaction", "batchmode", tmpfile],
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cwd=workdir, stdout=devnull, stderr=devnull)
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resolution = round(150*scale)
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subprocess.check_call(
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["dvipng", "-T", "tight", "-D", str(resolution), "-z", "9",
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"-bg", "transparent", "-o", outfile, dvifile, "-fg", color],
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cwd=workdir, stdout=devnull, stderr=devnull)
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with open(outfile, "rb") as f:
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return f.read()
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except subprocess.CalledProcessError:
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return None
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finally:
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shutil.rmtree(workdir)
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def kpsewhich(filename):
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"""Invoke kpsewhich command with an argument `filename`."""
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try:
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find_cmd("kpsewhich")
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proc = subprocess.Popen(
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["kpsewhich", filename],
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stdout=subprocess.PIPE, stderr=subprocess.PIPE)
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(stdout, stderr) = proc.communicate()
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return stdout.strip().decode('utf8', 'replace')
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except FindCmdError:
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pass
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def genelatex(body, wrap):
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"""Generate LaTeX document for dvipng backend."""
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lt = LaTeXTool.instance()
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breqn = wrap and lt.use_breqn and kpsewhich("breqn.sty")
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yield r'\documentclass{article}'
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packages = lt.packages
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if breqn:
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packages = packages + ['breqn']
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for pack in packages:
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yield r'\usepackage{{{0}}}'.format(pack)
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yield r'\pagestyle{empty}'
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if lt.preamble:
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yield lt.preamble
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yield r'\begin{document}'
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if breqn:
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yield r'\begin{dmath*}'
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yield body
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yield r'\end{dmath*}'
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elif wrap:
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yield u'$${0}$$'.format(body)
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else:
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yield body
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yield u'\\end{document}'
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_data_uri_template_png = u"""<img src="data:image/png;base64,%s" alt=%s />"""
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def latex_to_html(s, alt='image'):
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"""Render LaTeX to HTML with embedded PNG data using data URIs.
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Parameters
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----------
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s : str
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The raw string containing valid inline LateX.
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alt : str
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The alt text to use for the HTML.
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"""
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base64_data = latex_to_png(s, encode=True).decode('ascii')
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if base64_data:
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return _data_uri_template_png % (base64_data, alt)
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