Merge pull request #11840 from oscargus/enablelatexfontcolor

Enable changing the font color for LaTeX rendering

IPython/lib/latextools.py

@@ -10,6 +10,7 b' import tempfile'
 import shutil
 import subprocess
 from base64 import encodebytes
+import textwrap
 
 from IPython.utils.process import find_cmd, FindCmdError
 from traitlets.config import get_config
@@ -55,7 +56,8 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',
+                 scale=1.0):
     """Render a LaTeX string to PNG.
 
     Parameters
@@ -68,6 +70,11 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, e.g. 'Maroon' or on hex RGB
+        format, e.g. '#AA20FA'.
+    scale : float
+        Scale factor for the resulting PNG.
 
     None is returned when the backend cannot be used.
 
@@ -82,15 +89,25 b' def latex_to_png(s, encode=False, backend=None, wrap=False):'
         f = latex_to_png_mpl
     elif backend == 'dvipng':
         f = latex_to_png_dvipng
+        if color.startswith('#'):
+            # Convert hex RGB color to LaTeX RGB color.
+            if len(color) == 7:
+                try:
+                    color = "RGB {}".format(" ".join([str(int(x, 16)) for x in
+                                                      textwrap.wrap(color[1:], 2)]))
+                except ValueError:
+                    raise ValueError('Invalid color specification {}.'.format(color))
+            else:
+                raise ValueError('Invalid color specification {}.'.format(color))
     else:
         raise ValueError('No such backend {0}'.format(backend))
-    bin_data = f(s, wrap)
+    bin_data = f(s, wrap, color, scale)
     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', scale=1.0):
     try:
         from matplotlib import mathtext
         from pyparsing import ParseFatalException
@@ -105,13 +122,14 b' def latex_to_png_mpl(s, wrap):'
     try:
         mt = mathtext.MathTextParser('bitmap')
         f = BytesIO()
-        mt.to_png(f, s, fontsize=12)
+        dpi = 120*scale
+        mt.to_png(f, s, fontsize=12, dpi=dpi, 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', scale=1.0):
     try:
         find_cmd('latex')
         find_cmd('dvipng')
@@ -131,10 +149,11 b' def latex_to_png_dvipng(s, wrap):'
                 ["latex", "-halt-on-error", "-interaction", "batchmode", tmpfile],
                 cwd=workdir, stdout=devnull, stderr=devnull)
 
+            resolution = round(150*scale)
             subprocess.check_call(
-                ["dvipng", "-T", "tight", "-x", "1500", "-z", "9",
-                 "-bg", "transparent", "-o", outfile, dvifile], cwd=workdir,
-                stdout=devnull, stderr=devnull)
+                ["dvipng", "-T", "tight", "-D", str(resolution), "-z", "9",
+                 "-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 +132,50 b' def test_genelatex_wrap_without_breqn():'
 \begin{document}
 $$x^2$$
 \end{document}''')
+
+
+@skipif_not_matplotlib
+@onlyif_cmds_exist('latex', 'dvipng')
+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)
+    default_hexblack = latextools.latex_to_png(latex_string, wrap=False,
+                                               color='#000000')
+    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])
+    nt.assert_in(default_hexblack, [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)
+    mpl_white = latextools.latex_to_png_mpl(latex_string, False, 'White')
+    mpl_hexwhite = latextools.latex_to_png_mpl(latex_string, False, '#FFFFFF')
+    nt.assert_equal(mpl_white, mpl_hexwhite)
+
+    mpl_white_scale = latextools.latex_to_png_mpl(latex_string, False,
+                                                  'White', 1.2)
+    nt.assert_not_equal(mpl_white, mpl_white_scale)
+
+
+def test_latex_to_png_invalid_hex_colors():
+    """
+    Test that invalid hex colors provided to dvipng gives an exception.
+    """
+    latex_string = "$x^2$"
+    nt.assert_raises(ValueError, lambda: latextools.latex_to_png(latex_string,
+                                        backend='dvipng', color="#f00bar"))
+    nt.assert_raises(ValueError, lambda: latextools.latex_to_png(latex_string,
+                                        backend='dvipng', color="#f00"))