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# -*- coding: utf-8 -*-
"""Tools for handling LaTeX."""
# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.
from io import BytesIO, open
import os
import tempfile
import shutil
import subprocess
from IPython.utils.process import find_cmd, FindCmdError
from traitlets.config import get_config
from traitlets.config.configurable import SingletonConfigurable
from traitlets import List, Bool, Unicode
from IPython.utils.py3compat import cast_unicode, cast_unicode_py2 as u, PY3
try: # Py3
from base64 import encodebytes
except ImportError: # Py2
from base64 import encodestring as encodebytes
class LaTeXTool(SingletonConfigurable):
"""An object to store configuration of the LaTeX tool."""
def _config_default(self):
return get_config()
backends = List(
Unicode(), ["matplotlib", "dvipng"],
help="Preferred backend to draw LaTeX math equations. "
"Backends in the list are checked one by one and the first "
"usable one is used. Note that `matplotlib` backend "
"is usable only for inline style equations. To draw "
"display style equations, `dvipng` backend must be specified. ",
# It is a List instead of Enum, to make configuration more
# flexible. For example, to use matplotlib mainly but dvipng
# for display style, the default ["matplotlib", "dvipng"] can
# be used. To NOT use dvipng so that other repr such as
# unicode pretty printing is used, you can use ["matplotlib"].
).tag(config=True)
use_breqn = Bool(
True,
help="Use breqn.sty to automatically break long equations. "
"This configuration takes effect only for dvipng backend.",
).tag(config=True)
packages = List(
['amsmath', 'amsthm', 'amssymb', 'bm'],
help="A list of packages to use for dvipng backend. "
"'breqn' will be automatically appended when use_breqn=True.",
).tag(config=True)
preamble = Unicode(
help="Additional preamble to use when generating LaTeX source "
"for dvipng backend.",
).tag(config=True)
def latex_to_png(s, encode=False, backend=None, wrap=False):
"""Render a LaTeX string to PNG.
Parameters
----------
s : str
The raw string containing valid inline LaTeX.
encode : bool, optional
Should the PNG data base64 encoded to make it JSON'able.
backend : {matplotlib, dvipng}
Backend for producing PNG data.
wrap : bool
If true, Automatically wrap `s` as a LaTeX equation.
None is returned when the backend cannot be used.
"""
s = cast_unicode(s)
allowed_backends = LaTeXTool.instance().backends
if backend is None:
backend = allowed_backends[0]
if backend not in allowed_backends:
return None
if backend == 'matplotlib':
f = latex_to_png_mpl
elif backend == 'dvipng':
f = latex_to_png_dvipng
else:
raise ValueError('No such backend {0}'.format(backend))
bin_data = f(s, wrap)
if encode and bin_data:
bin_data = encodebytes(bin_data)
return bin_data
def latex_to_png_mpl(s, wrap):
try:
from matplotlib import mathtext
from pyparsing import ParseFatalException
except ImportError:
return None
# mpl mathtext doesn't support display math, force inline
s = s.replace('$$', '$')
if wrap:
s = u'${0}$'.format(s)
try:
mt = mathtext.MathTextParser('bitmap')
f = BytesIO()
mt.to_png(f, s, fontsize=12)
return f.getvalue()
except (ValueError, RuntimeError, ParseFatalException):
return None
def latex_to_png_dvipng(s, wrap):
try:
find_cmd('latex')
find_cmd('dvipng')
except FindCmdError:
return None
try:
workdir = tempfile.mkdtemp()
tmpfile = os.path.join(workdir, "tmp.tex")
dvifile = os.path.join(workdir, "tmp.dvi")
outfile = os.path.join(workdir, "tmp.png")
with open(tmpfile, "w", encoding='utf8') as f:
f.writelines(genelatex(s, wrap))
with open(os.devnull, 'wb') as devnull:
subprocess.check_call(
["latex", "-halt-on-error", "-interaction", "batchmode", tmpfile],
cwd=workdir, stdout=devnull, stderr=devnull)
subprocess.check_call(
["dvipng", "-T", "tight", "-x", "1500", "-z", "9",
"-bg", "transparent", "-o", outfile, dvifile], cwd=workdir,
stdout=devnull, stderr=devnull)
with open(outfile, "rb") as f:
return f.read()
except subprocess.CalledProcessError:
return None
finally:
shutil.rmtree(workdir)
def kpsewhich(filename):
"""Invoke kpsewhich command with an argument `filename`."""
try:
find_cmd("kpsewhich")
proc = subprocess.Popen(
["kpsewhich", filename],
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(stdout, stderr) = proc.communicate()
return stdout.strip().decode('utf8', 'replace')
except FindCmdError:
pass
def genelatex(body, wrap):
"""Generate LaTeX document for dvipng backend."""
lt = LaTeXTool.instance()
breqn = wrap and lt.use_breqn and kpsewhich("breqn.sty")
yield u(r'\documentclass{article}')
packages = lt.packages
if breqn:
packages = packages + ['breqn']
for pack in packages:
yield u(r'\usepackage{{{0}}}'.format(pack))
yield u(r'\pagestyle{empty}')
if lt.preamble:
yield lt.preamble
yield u(r'\begin{document}')
if breqn:
yield u(r'\begin{dmath*}')
yield body
yield u(r'\end{dmath*}')
elif wrap:
yield u'$${0}$$'.format(body)
else:
yield body
yield u'\end{document}'
_data_uri_template_png = u"""<img src="data:image/png;base64,%s" alt=%s />"""
def latex_to_html(s, alt='image'):
"""Render LaTeX to HTML with embedded PNG data using data URIs.
Parameters
----------
s : str
The raw string containing valid inline LateX.
alt : str
The alt text to use for the HTML.
"""
base64_data = latex_to_png(s, encode=True).decode('ascii')
if base64_data:
return _data_uri_template_png % (base64_data, alt)
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