IPython/lib/latextools.py

# -*- coding: utf-8 -*-
"""Tools for handling LaTeX.

Authors:

* Brian Granger
"""
#-----------------------------------------------------------------------------
# Copyright (c) 2010, IPython Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------

from StringIO import StringIO
from base64 import encodestring

#-----------------------------------------------------------------------------
# Tools
#-----------------------------------------------------------------------------


def latex_to_png(s, encode=False):
    """Render a LaTeX string to PNG using matplotlib.mathtext.

    Parameters
    ----------
    s : str
        The raw string containing valid inline LaTeX.
    encode : bool, optional
        Should the PNG data bebase64 encoded to make it JSON'able.
    """
    from matplotlib import mathtext
    
    mt = mathtext.MathTextParser('bitmap')
    f = StringIO()
    mt.to_png(f, s, fontsize=12)
    bin_data = f.getvalue()
    if encode:
        bin_data = encodestring(bin_data)
    return bin_data


_data_uri_template_png = """<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)
    return _data_uri_template_png  % (base64_data, alt)


# From matplotlib, thanks to mdboom. Once this is in matplotlib releases, we
# will remove.
def math_to_image(s, filename_or_obj, prop=None, dpi=None, format=None):
    """
    Given a math expression, renders it in a closely-clipped bounding
    box to an image file.

    *s*
       A math expression.  The math portion should be enclosed in
       dollar signs.

    *filename_or_obj*
       A filepath or writable file-like object to write the image data
       to.

    *prop*
       If provided, a FontProperties() object describing the size and
       style of the text.

    *dpi*
       Override the output dpi, otherwise use the default associated
       with the output format.

    *format*
       The output format, eg. 'svg', 'pdf', 'ps' or 'png'.  If not
       provided, will be deduced from the filename.
    """
    from matplotlib import figure
    # backend_agg supports all of the core output formats
    from matplotlib.backends import backend_agg
    from matplotlib.font_manager import FontProperties
    from matplotlib.mathtext import MathTextParser

    if prop is None:
        prop = FontProperties()

    parser = MathTextParser('path')
    width, height, depth, _, _ = parser.parse(s, dpi=72, prop=prop)

    fig = figure.Figure(figsize=(width / 72.0, height / 72.0))
    fig.text(0, depth/height, s, fontproperties=prop)
    backend_agg.FigureCanvasAgg(fig)
    fig.savefig(filename_or_obj, dpi=dpi, format=format)

    return depth