Enable changing the font color for LaTeX rendering

IPython/lib/latextools.py

@@ -55,7 +55,7 b' class LaTeXTool(SingletonConfigurable):'
         ).tag(config=True)
 
 
-def latex_to_png(s, encode=False, backend=None, wrap=False):
+def latex_to_png(s, encode=False, backend=None, wrap=False, color='Black'):
     """Render a LaTeX string to PNG.
 
     Parameters
@@ -68,6 +68,8 b' def latex_to_png(s, encode=False, backend=None, wrap=False):'
         Backend for producing PNG data.
     wrap : bool
         If true, Automatically wrap `s` as a LaTeX equation.
+    color : string
+        Foreground color name among dvipsnames.
 
     None is returned when the backend cannot be used.
 
@@ -84,13 +86,13 b' def latex_to_png(s, encode=False, backend=None, wrap=False):'
         f = latex_to_png_dvipng
     else:
         raise ValueError('No such backend {0}'.format(backend))
-    bin_data = f(s, wrap)
+    bin_data = f(s, wrap, color)
     if encode and bin_data:
         bin_data = encodebytes(bin_data)
     return bin_data
 
 
-def latex_to_png_mpl(s, wrap):
+def latex_to_png_mpl(s, wrap, color='Black'):
     try:
         from matplotlib import mathtext
         from pyparsing import ParseFatalException
@@ -105,13 +107,13 b' def latex_to_png_mpl(s, wrap):'
     try:
         mt = mathtext.MathTextParser('bitmap')
         f = BytesIO()
-        mt.to_png(f, s, fontsize=12)
+        mt.to_png(f, s, fontsize=12, color=color)
         return f.getvalue()
     except (ValueError, RuntimeError, ParseFatalException):
         return None
 
 
-def latex_to_png_dvipng(s, wrap):
+def latex_to_png_dvipng(s, wrap, color='Black'):
     try:
         find_cmd('latex')
         find_cmd('dvipng')
@@ -133,8 +135,8 b' def latex_to_png_dvipng(s, wrap):'
 
             subprocess.check_call(
                 ["dvipng", "-T", "tight", "-x", "1500", "-z", "9",
-                 "-bg", "transparent", "-o", outfile, dvifile], cwd=workdir,
-                stdout=devnull, stderr=devnull)
+                 "-bg", "transparent", "-o", outfile, dvifile, "-fg", color],
+                 cwd=workdir, stdout=devnull, stderr=devnull)
 
         with open(outfile, "rb") as f:
             return f.read()

IPython/lib/tests/test_latextools.py

@@ -132,3 +132,26 b' def test_genelatex_wrap_without_breqn():'
 \begin{document}
 $$x^2$$
 \end{document}''')
+
+
+def test_latex_to_png_color():
+    """
+    Test color settings for latex_to_png.
+    """
+    latex_string = "$x^2$"
+    default_value = latextools.latex_to_png(latex_string, wrap=False)
+    dvipng_default = latextools.latex_to_png_dvipng(latex_string, False)
+    dvipng_black = latextools.latex_to_png_dvipng(latex_string, False, 'Black')
+    nt.assert_equal(dvipng_default, dvipng_black)
+    mpl_default = latextools.latex_to_png_mpl(latex_string, False)
+    mpl_black = latextools.latex_to_png_mpl(latex_string, False, 'Black')
+    nt.assert_equal(mpl_default, mpl_black)
+    nt.assert_in(default_value, [dvipng_black, mpl_black])
+
+    # Test that dvips name colors can be used without error
+    dvipng_maroon = latextools.latex_to_png_dvipng(latex_string, False, 'Maroon')
+    # And that it doesn't return the black one
+    nt.assert_not_equal(dvipng_black, dvipng_maroon)
+
+    mpl_maroon = latextools.latex_to_png_mpl(latex_string, False, 'Maroon')
+    nt.assert_not_equal(mpl_black, mpl_maroon)