Merge pull request #1861 from tkf/dvipng

Use dvipng to format sympy.Matrix, enabling display of matrices in the Qt console with the sympy printing extension.

Two changes are introduced:

    new dvipng backend is added to latex_to_png
    PNG formatter for sympy.Matrix uses the dvipng backend

IPython/extensions/sympyprinting.py

@@ -11,7 +11,7 pretty-printed.
 
 """
 #-----------------------------------------------------------------------------
-#  Copyright (C) 2008-2011  The IPython Development Team
+#  Copyright (C) 2008  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
@@ -45,7 +45,9 def print_basic_unicode(o, p, cycle):
 
 
 def print_png(o):
-    """A function to display sympy expression using LaTex -> PNG."""
+    """
+    A function to display sympy expression using inline style LaTeX in PNG.
+    """
     s = latex(o, mode='inline')
     # mathtext does not understand certain latex flags, so we try to replace
     # them with suitable subs.
@@ -54,6 +56,19 def print_png(o):
     png = latex_to_png(s)
     return png
 
+
+def print_display_png(o):
+    """
+    A function to display sympy expression using display style LaTeX in PNG.
+    """
+    s = latex(o, mode='plain')
+    s = s.strip('$')
+    # As matplotlib does not support display style, dvipng backend is
+    # used here.
+    png = latex_to_png('$$%s$$' % s, backend='dvipng')
+    return png
+
+
 def can_print_latex(o):
     """
     Return True if type o can be printed with LaTeX.
@@ -115,6 +130,9 def load_ipython_extension(ip):
         png_formatter.for_type_by_name(
             'sympy.core.basic', 'Basic', print_png
         )
+        png_formatter.for_type_by_name(
+            'sympy.matrices.matrices', 'Matrix', print_display_png
+        )
         for cls in [dict, int, long, float] + printable_containers:
             png_formatter.for_type(cls, print_png)
 

IPython/lib/latextools.py

@@ -6,7 +6,7 Authors:
 * Brian Granger
 """
 #-----------------------------------------------------------------------------
-# Copyright (C) 2010-2011, IPython Development Team.
+# Copyright (C) 2010 IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
@@ -19,14 +19,20 Authors:
 
 from StringIO import StringIO
 from base64 import encodestring
+import os
+import tempfile
+import shutil
+import subprocess
+
+from IPython.utils.process import find_cmd, FindCmdError
 
 #-----------------------------------------------------------------------------
 # Tools
 #-----------------------------------------------------------------------------
 
 
-def latex_to_png(s, encode=False):
-    """Render a LaTeX string to PNG using matplotlib.mathtext.
+def latex_to_png(s, encode=False, backend='mpl'):
+    """Render a LaTeX string to PNG.
 
     Parameters
     ----------
@@ -34,18 +40,82 def latex_to_png(s, encode=False):
         The raw string containing valid inline LaTeX.
     encode : bool, optional
         Should the PNG data bebase64 encoded to make it JSON'able.
+    backend : {mpl, dvipng}
+        Backend for producing PNG data.
+
+    None is returned when the backend cannot be used.
+
     """
+    if backend == 'mpl':
+        f = latex_to_png_mpl
+    elif backend == 'dvipng':
+        f = latex_to_png_dvipng
+    else:
+        raise ValueError('No such backend {0}'.format(backend))
+    bin_data = f(s)
+    if encode and bin_data:
+        bin_data = encodestring(bin_data)
+    return bin_data
+
+
+def latex_to_png_mpl(s):
+    try:
     from matplotlib import mathtext
+    except ImportError:
+        return None
     
     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 f.getvalue()
+
+
+def latex_to_png_dvipng(s):
+    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") as f:
+            f.write(_latex_header)
+            f.write(s)
+            f.write(_latex_footer)
+
+        subprocess.check_call(
+            ["latex", "-halt-on-errror", tmpfile], cwd=workdir,
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+
+        subprocess.check_call(
+            ["dvipng", "-T", "tight", "-x", "1500", "-z", "9",
+             "-bg", "transparent", "-o", outfile, dvifile], cwd=workdir,
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+
+        with open(outfile) as f:
+            bin_data = f.read()
+    finally:
+        shutil.rmtree(workdir)
     return bin_data
 
 
+_latex_header = r'''
+\documentclass{article}
+\usepackage{amsmath}
+\usepackage{amsthm}
+\usepackage{amssymb}
+\usepackage{bm}
+\pagestyle{empty}
+\begin{document}
+'''
+
+_latex_footer = r'\end{document}'
+
+
 _data_uri_template_png = """<img src="data:image/png;base64,%s" alt=%s />"""
 
 def latex_to_html(s, alt='image'):
@@ -59,6 +129,7 def latex_to_html(s, alt='image'):
         The alt text to use for the HTML.
     """
     base64_data = latex_to_png(s, encode=True)
+    if base64_data:
     return _data_uri_template_png  % (base64_data, alt)