A LaTeX filter for blogofile

latex.py

"""
Render TeX blocks to png

This is a Blogofile filter. Place it in your _filters directory.
"""
import tempfile
import subprocess
import shutil
import shlex
import os
import re
import hashlib
import blogofile_bf as bf

html_escape_table = {"&": "&amp;",'"': "&quot;","'": "&apos;",">": "&gt;","<": "&lt;"}

html_escape = lambda text: "".join(html_escape_table.get(c,c) for c in text)

tex_template = r"""
\documentclass[12pt]{article}
\usepackage{ucs}
\usepackage[utf8x]{inputenc}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amssymb}
\pagestyle{empty}
\begin{document}
$%s$
\end{document}
"""

latex_block_re = re.compile(r"\s\$\$latex\s(.*?)\s\$", re.DOTALL)

def render_tex_to_png(latex_block, png_location):
    """Render a TeX formatted string to an image file

    Depends on 'latex' and 'dvipng' binaries on the system path
    """

    #Create a temporary directory and go into it
    tmp_dir = tempfile.mkdtemp()
    previous_dir = os.getcwd()
    os.chdir(tmp_dir)

    tex_f = open(os.path.join(tmp_dir,"source.tex"),"w")
    tex_f.write((tex_template % latex_block))
    tex_f.close()

    try:
        #Generate the .dvi
        p = subprocess.Popen(shlex.split(
                'latex -interaction=nonstopmode source.tex'),
                             stdout=subprocess.PIPE)
        p.wait()
        #Generate the .ps

        try:
            p = subprocess.Popen(shlex.split(
                    'dvipng -bg Transparent -gamma 1.5 -D 120 -T tight'
                    ' --strict source.dvi -o rendered.png'),
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE)
            p.wait()
        except:
            p = subprocess.Popen(shlex.split('dvips source.dvi'),
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE)
            p.wait()
            #Generate the .png
            p = subprocess.Popen(shlex.split(
                    'convert -density 120 -trim -transparent'
                    ' "#FFFFFF" source.ps rendered.png'),stdout=subprocess.PIPE)
            p.wait()

        #Copy the .png to the png_location
        os.chdir(previous_dir)
        shutil.copyfile(os.path.join(tmp_dir,"rendered.png"),png_location)
    finally:
        #Go back to the original directory and clean up the temp files
        os.chdir(previous_dir)
        shutil.rmtree(tmp_dir)
        
def render_latex_blocks(src, cache_dir="_tmp", site_images_dir="images"):
    """Render a document with LaTeX blocks

    1) Extract all the $$latex blocks
    2) Render each TeX block to an image to the cache
    3) Copy the (pre)rendered image from the cache to the _site dir
    4) Replace the $$latex blocks with <img> tags
    """
    img_substitutions = {}
    for m in latex_block_re.finditer(src):
        tex_expr = m.groups()[0]
        fn = hashlib.md5(tex_expr).hexdigest()+".png"
        png_cached = os.path.join(cache_dir,fn)
        site_png_dir = bf.util.path_join("_site",bf.util.fs_site_path_helper(
                site_images_dir))
        site_png = bf.util.path_join(site_png_dir,fn)
        #only render the image if the image is not already cached
        if(not os.path.isfile(png_cached)):
            bf.util.mkdir(cache_dir)
            bf.filter.logger.info("Rendering LaTeX: "+tex_expr)
            render_tex_to_png(tex_expr,png_cached)
        #copy the rendered image to the site dir
        bf.util.mkdir(site_png_dir)
        shutil.copyfile(png_cached,site_png)
        #record the $$latex block and it's replacement <img> tag
        img_substitutions[m.group()] = "<img alt=\"%s\" src=\"%s%s\">" % \
            (html_escape(tex_expr), bf.config.site.url,
             bf.util.site_path_helper(site_images_dir,fn))
    #Make the <img> tag replacements in a single pass
    p = re.compile('|'.join(map(re.escape, img_substitutions)))
    return p.sub(lambda x: img_substitutions[x.group(0)], src)
    
def run(src):
    return render_latex_blocks(src)

sample_post

---
categories: Category 1, Category 2
date: 2009/07/24 16:20:00
title: Sample LaTeX post
filter: latex, markdown
tags: test, blogofile, cool-stuff
author: Ryan
---
This is a sample post with TeX blocks.

This is a TeX block:
$$latex
y = \int_0^\infty \gamma^2 \cos(x) dx $ this is after the block.

This is an inline Tex block: $$latex \cos(x) $ and this is after.

This is two seperate inline Tex blocks: $$latex \sin(x) $ and then $$latex \tan(x) $ and this is after.

This is a mistyped TeX block because I didn't terminate it properly. $$latex \tan(x)$ and this text is rendered too because I didn't put a space before the dollar sign $

This is a broken TeX block because I didn't put a space before it$$latex \tan(x) $