ENH: add XKCD colorname -> hex mapping

doc/users/beginner.rst

@@ -20,8 +20,6 @@ Beginner's Guide
     legend_guide.rst
     annotations_guide.rst
     screenshots.rst
+    colors.rst
     colormaps.rst
     colormapnorms.rst
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-
-

doc/users/colors.rst

@@ -0,0 +1,71 @@
+.. _colors:
+
+*****************
+Specifying Colors
+*****************
+
+In almost all places in matplotlib where a color can be specified by the user it can be provided as:
+
+* ``(r, g, b)`` tuples
+* ``(r, g, b, a)`` tuples
+* hex string, ex ``#OFOFOF``
+* float value between [0, 1] for gray level
+* One of ``{'b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'}``
+* valid css4/X11 color names
+* valid name from the `XKCD color survey
+  <http://blog.xkcd.com/2010/05/03/color-survey-results/>`__ These
+  names are available both with and with out spaces.  In the case of name clashes
+  the css/X11 names have priority.  To ensure colors
+  from the XKCD mapping are used prefix the space-less name with
+  ``'XKCD'``.
+
+All string specifications of color are case-insensitive.
+
+Internally, mpl is moving to storing all colors as RGBA float quadruples.
+
+Name clash between CSS4/X11 and XKCD
+------------------------------------
+
+The color names in the XKCD survey include spaces (unlike css4/X11
+names).  Matplotlib exposes all of the XKCD colors both with and
+without spaces.
+
+There are 95 (out of 148 colors in the css color list) conflicts
+between the css4/X11 names and the XKCD names.  Given that these are
+the standard color names of the web, matplotlib should follow these
+conventions.  To accesses the XKCD colors which are shadowed by css4,
+prefix the colorname with ``'XKCD'``, for example ``'blue'`` maps to
+``'#0000FF'`` where as ``'XKCDblue'`` maps to ``'#0343DF'``.
+
+.. plot::
+
+   import matplotlib.pyplot as plt
+   import matplotlib._color_data as mcd
+
+   import matplotlib.patches as mpatch
+   overlap = (set(mcd.CSS4_COLORS) & set(mcd.XKCD_COLORS))
+
+   fig = plt.figure(figsize=[4.8, 16])
+   ax = fig.add_axes([0, 0, 1, 1])
+
+   j = 0
+
+   for n in sorted(overlap, reverse=True):
+       cn = mcd.CSS4_COLORS[n]
+       xkcd = mcd.XKCD_COLORS[n].upper()
+       if cn != xkcd:
+           print (n, cn, xkcd)
+
+       r1 = mpatch.Rectangle((0, j), 1, 1, color=cn)
+       r2 = mpatch.Rectangle((1, j), 1, 1, color=xkcd)
+       txt = ax.text(2, j+.5, '  ' + n, va='center', fontsize=10)
+       ax.add_patch(r1)
+       ax.add_patch(r2)
+       ax.axhline(j, color='k')
+       j += 1
+
+   ax.text(.5, j+.1, 'X11', ha='center')
+   ax.text(1.5, j+.1, 'XKCD', ha='center')
+   ax.set_xlim(0, 3)
+   ax.set_ylim(0, j + 1)
+   ax.axis('off')

doc/users/index.rst

@@ -16,11 +16,8 @@ User's Guide
     configuration.rst
     beginner.rst
     developer.rst
+    colors.rst
     whats_new.rst
     github_stats.rst
     license.rst
     credits.rst
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