sobelk · April 7, 2010 20:03 · Apr 8, 2010 · Apr 7, 2010
diff --git a/latex.py b/latex.py
@@ -56,7 +56,6 @@ def render(self, context):
         if not os.path.exists(os.path.join(workingdir, filebase + '.png')):
             latexpath = r'%s%s.tex' % (workingdir, filebase)
 
-            # TODO: if file exists:
             latexfile = open(latexpath, 'w')
             latexfile.write('\n'.join(('% generated at: ' + str(datetime.now()),
                                        self.LATEX_HEADER,

diff --git a/latex.py b/latex.py
@@ -0,0 +1,108 @@
+"""
+Django LaTeX custom template tag for equations (using amsmath).
+
+Creates a .png in the project media directory and returns an img tag that references it. 
+
+Usage: 
+    {% latex %}
+    x=\frac{-b \pm \sqrt {b^2-4ac}}{2a}
+    {% endlatex %}
+
+Requirements:
+    LaTeX (http://www.latex-project.org/ftp.html)
+    dvipng (http://savannah.nongnu.org/projects/dvipng/)
+
+Thanks to Kjell Magne Fauske (http://www.fauskes.net/nb/htmleqII/) for outlining the method.
+"""
+
+from django import template
+register = template.Library()
+
+class LaTeXNode(template.Node):
+    # directory to append to MEDIA_ROOT and MEDIA_URL, terminate with /
+    OUTPUT_DIR = 'image/latex/'
+
+    # class name to assign to generated <img> tag
+    IMG_CLASS_NAME = 'latex'
+
+    LATEX_HEADER = '''
+    \\documentclass{article}
+    \\usepackage{amsmath}
+    \\usepackage{amsthm}
+    \\usepackage{amssymb}
+    \\usepackage{bm}
+    \\pagestyle{empty}
+    \\begin{document}
+    '''
+    LATEX_FOOTER = '''
+    \\end{document}
+    '''
+
+    def __init__(self, nodelist, label=None):
+        self.nodelist = nodelist
+        self.label = label
+
+    def render(self, context):
+        import subprocess
+        import os
+        from datetime import datetime
+        from hashlib import md5
+        from django.conf import settings
+
+        latex = self.nodelist.render(context)
+        filebase = md5(latex).hexdigest()
+        workingdir = os.path.join(settings.MEDIA_ROOT, self.OUTPUT_DIR)
+
+        if not os.path.exists(os.path.join(workingdir, filebase + '.png')):
+            latexpath = r'%s%s.tex' % (workingdir, filebase)
+
+            # TODO: if file exists:
+            latexfile = open(latexpath, 'w')
+            latexfile.write('\n'.join(('% generated at: ' + str(datetime.now()),
+                                       self.LATEX_HEADER,
+                                       '$%s$' % latex,  # delimit equation with $
+                                       self.LATEX_FOOTER)))
+            latexfile.close()
+
+            old_workingdir = os.getcwd()
+            os.chdir(workingdir)
+            latex_exitcode = subprocess.call((r'latex',
+                                              filebase + '.tex'))
+            dvipng_exitcode = subprocess.call((r'dvipng',
+                                               '-o', filebase + '.png',
+                                               '-pp', '1',  # only page one
+                                               '-T', 'tight',
+                                               '-x', '1600',  # scale
+                                               filebase + '.dvi'))
+            if latex_exitcode or dvipng_exitcode:
+                # TODO: There is room for better error reporting here,
+                # but I'm happy to fail silently and leave the temp
+                # files behind for debugging.
+                return latex
+            else:
+                os.unlink(filebase + '.tex')
+                os.unlink(filebase + '.log')
+                os.unlink(filebase + '.aux')
+                os.unlink(filebase + '.dvi')
+                os.chdir(old_workingdir) 
+
+        return '<img src="%s" alt="%s" %s/>' % (
+            settings.MEDIA_URL + self.OUTPUT_DIR + filebase + '.png',
+            latex,
+            self.IMG_CLASS_NAME and 'class="%s" ' % self.IMG_CLASS_NAME or '')
+
+def latex(parser, token):
+    nodelist = parser.parse(('endlatex',))
+    parser.delete_first_token()
+
+    parts = token.contents.split()
+    if len(parts) == 1:
+        return LaTeXNode(nodelist)
+    else:
+        raise template.TemplateSyntaxError(
+            "latex tag does not accept parameters, got '%s'" % (
+                ' '.join(parts[1:])))
+
+register.tag('latex', latex)
+
+