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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 base64 import encodebytes
import textwrap
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
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, color='Black',
scale=1.0):
"""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.
color : string
Foreground color name among dvipsnames, e.g. 'Maroon' or on hex RGB
format, e.g. '#AA20FA'.
scale : float
Scale factor for the resulting PNG.
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
if color.startswith('#'):
# Convert hex RGB color to LaTeX RGB color.
if len(color) == 7:
try:
color = "RGB {}".format(" ".join([str(int(x, 16)) for x in
textwrap.wrap(color[1:], 2)]))
except ValueError:
raise ValueError('Invalid color specification {}.'.format(color))
else:
raise ValueError('Invalid color specification {}.'.format(color))
else:
raise ValueError('No such backend {0}'.format(backend))
bin_data = f(s, wrap, color, scale)
if encode and bin_data:
bin_data = encodebytes(bin_data)
return bin_data
def latex_to_png_mpl(s, wrap, color='Black', scale=1.0):
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('$$', '$')
if wrap:
s = u'${0}$'.format(s)
try:
mt = mathtext.MathTextParser('bitmap')
f = BytesIO()
dpi = 120*scale
mt.to_png(f, s, fontsize=12, dpi=dpi, color=color)
return f.getvalue()
except (ValueError, RuntimeError, ParseFatalException):
return None
def latex_to_png_dvipng(s, wrap, color='Black', scale=1.0):
try:
find_cmd('latex')
find_cmd('dvipng')
except FindCmdError:
return None
try:
workdir = tempfile.mkdtemp()
tmpfile = os.path.join(workdir, "tmp.tex")
dvifile = os.path.join(workdir, "tmp.dvi")
outfile = os.path.join(workdir, "tmp.png")
with open(tmpfile, "w", encoding='utf8') as f:
f.writelines(genelatex(s, wrap))
with open(os.devnull, 'wb') as devnull:
subprocess.check_call(
["latex", "-halt-on-error", "-interaction", "batchmode", tmpfile],
cwd=workdir, stdout=devnull, stderr=devnull)
resolution = round(150*scale)
subprocess.check_call(
[
"dvipng",
"-T",
"tight",
"-D",
str(resolution),
"-z",
"9",
"-bg",
"Transparent",
"-o",
outfile,
dvifile,
"-fg",
color,
],
cwd=workdir,
stdout=devnull,
stderr=devnull,
)
with open(outfile, "rb") as f:
return f.read()
except subprocess.CalledProcessError:
return None
finally:
shutil.rmtree(workdir)
def kpsewhich(filename):
"""Invoke kpsewhich command with an argument `filename`."""
try:
find_cmd("kpsewhich")
proc = subprocess.Popen(
["kpsewhich", filename],
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(stdout, stderr) = proc.communicate()
return stdout.strip().decode('utf8', 'replace')
except FindCmdError:
pass
def genelatex(body, wrap):
"""Generate LaTeX document for dvipng backend."""
lt = LaTeXTool.instance()
breqn = wrap and lt.use_breqn and kpsewhich("breqn.sty")
yield r'\documentclass{article}'
packages = lt.packages
if breqn:
packages = packages + ['breqn']
for pack in packages:
yield r'\usepackage{{{0}}}'.format(pack)
yield r'\pagestyle{empty}'
if lt.preamble:
yield lt.preamble
yield r'\begin{document}'
if breqn:
yield r'\begin{dmath*}'
yield body
yield r'\end{dmath*}'
elif wrap:
yield u'$${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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