apostrophe/uberwriter/latex_to_PNG.py

# -*- Mode: Python; coding: utf-8; indent-tabs-mode: nil; tab-width: 4 -*-
"""
Based on latex2png.py from Stuart Rackham

AUTHOR
    Written by Stuart Rackham, <srackham@gmail.com>
    The code was inspired by Kjell Magne Fauske"s code:
    http://fauskes.net/nb/htmleqII/

    See also:
    http://www.amk.ca/python/code/mt-math
    http://code.google.com/p/latexmath2png/

COPYING
    Copyright (C) 2010 Stuart Rackham. Free use of this software is
    granted under the terms of the MIT License.
"""

import os
import subprocess
import tempfile


class LatexToPNG:
    TEX_HEADER = r"""\documentclass{article}
    \usepackage{amsmath}
    \usepackage{amsthm}
    \usepackage{amssymb}
    \usepackage{bm}
    \newcommand{\mx}[1]{\mathbf{\bm{#1}}} % Matrix command
    \newcommand{\vc}[1]{\mathbf{\bm{#1}}} % Vector command
    \newcommand{\T}{\text{T}}			 % Transpose
    \pagestyle{empty}
    \begin{document}"""

    TEX_FOOTER = r"""\end{document}"""

    def __init__(self):
        self.temp_result = tempfile.NamedTemporaryFile(suffix=".png")

    def latex2png(self, tex, outfile, dpi, modified):
        """Convert LaTeX input file infile to PNG file named outfile."""
        outfile = os.path.abspath(outfile)
        outdir = os.path.dirname(outfile)
        texfile = tempfile.mktemp(suffix=".tex", dir=os.path.dirname(outfile))
        basefile = os.path.splitext(texfile)[0]
        dvifile = basefile + ".dvi"
        temps = [basefile + ext for ext in (".tex", ".dvi", ".aux", ".log")]
        skip = False

        tex = "{}\n{}\n{}\n".format(self.TEX_HEADER, tex.strip(), self.TEX_FOOTER)

        open(texfile, "w").write(tex)
        saved_pwd = os.getcwd()

        os.chdir(outdir)

        args = ["latex", "-halt-on-error", texfile]
        p = subprocess.Popen(args,
                             stderr=subprocess.STDOUT,
                             stdout=subprocess.PIPE)

        output = p.stdout
        output_lines = output.readlines()
        if os.path.isfile(dvifile):  # DVI File exists
            # Convert DVI file to PNG.
            args = ["dvipng",
                    "-D", str(dpi),
                    "-T", "tight",
                    "-x", "1000",
                    "-z", "9",
                    "-bg", "Transparent",
                    "-o", outfile,
                    dvifile]

            p = subprocess.Popen(args)
            p.communicate()

        else:
            self.clean_up(temps)
            """
            Errors in Latex output start with "! "
            Stripping exclamation marks and superflous newlines
            and telling the user what he"s done wrong.
            """
            i = []
            error = ""
            for line in output_lines:
                line = line.decode("utf-8")
                if line.startswith("!"):
                    error += line[2:]  # removing "! "
            if error.endswith("\n"):
                error = error[:-1]
            raise Exception(error)

    def generatepng(self, formula):
        try:
            self.temp_result = tempfile.NamedTemporaryFile(suffix=".png")
            formula = "$" + formula + "$"
            self.latex2png(formula, self.temp_result.name, 300, False)
            return True, self.temp_result.name

        except Exception as e:
            self.temp_result.close()
            return False, e.args[0]

    def clean_up(self, files):
        for f in files:
            if os.path.isfile(f):
                os.remove(f)