add single color generating function

test/test_wordcloud.py

-from wordcloud import WordCloud
+from wordcloud import WordCloud, get_single_color_func
 import numpy as np
+from random import Random
 from nose.tools import assert_equal, assert_greater, assert_true, assert_raises
 from numpy.testing import assert_array_equal
 from PIL import Image
@@ -131,6 +132,35 @@ def test_mask():
     assert_greater(wc_array[mask == 0].sum(), 10000)
 
 
+def test_single_color_func():
+    # test single color function for different color formats
+    random = Random(42)
+
+    red_function = get_single_color_func('red')
+    assert_equal(red_function(random_state=random), 'rgb(181, 0, 0)')
+
+    hex_function = get_single_color_func('#00b4d2')
+    assert_equal(hex_function(random_state=random), 'rgb(0, 48, 56)')
+
+    rgb_function = get_single_color_func('rgb(0,255,0)')
+    assert_equal(rgb_function(random_state=random), 'rgb(0, 107, 0)')
+
+    rgb_perc_fun = get_single_color_func('rgb(80%,60%,40%)')
+    assert_equal(rgb_perc_fun(random_state=random), 'rgb(97, 72, 48)')
+
+    hsl_function = get_single_color_func('hsl(0,100%,50%)')
+    assert_equal(hsl_function(random_state=random), 'rgb(201, 0, 0)')
+
+
+def test_single_color_func_grey():
+    # grey is special as it's a corner case
+    random = Random(42)
+
+    red_function = get_single_color_func('darkgrey')
+    assert_equal(red_function(random_state=random), 'rgb(181, 181, 181)')
+    assert_equal(red_function(random_state=random), 'rgb(56, 56, 56)')
+
+
 def check_parameters():
     # check that parameters are actually used
     pass

wordcloud/__init__.py

-from .wordcloud import WordCloud, STOPWORDS, random_color_func
+from .wordcloud import WordCloud, STOPWORDS, random_color_func, get_single_color_func
 from .color_from_image import ImageColorGenerator
 
-__all__ = ['WordCloud', 'STOPWORDS', 'random_color_func', 'ImageColorGenerator']
+__all__ = ['WordCloud', 'STOPWORDS', 'random_color_func', 'get_single_color_func', 'ImageColorGenerator']

wordcloud/wordcloud.py

@@ -10,10 +10,12 @@ from random import Random
 import os
 import re
 import sys
+import colorsys
 import numpy as np
 from operator import itemgetter
 
 from PIL import Image
+from PIL import ImageColor
 from PIL import ImageDraw
 from PIL import ImageFont
 
@@ -77,6 +79,37 @@ def random_color_func(word=None, font_size=None, position=None,
         random_state = Random()
     return "hsl(%d, 80%%, 50%%)" % random_state.randint(0, 255)
 
+def get_single_color_func(color):
+    """Create a color function which returns a single hue and saturation with.
+    different values (HSV). Accepted values are color strings as usable by PIL/Pillow.
+
+    >>> color_func1 = get_single_color_func('deepskyblue')
+    >>> color_func2 = get_single_color_func('#00b4d2')
+    """
+    old_r, old_g, old_b = ImageColor.getrgb(color)
+    rgb_max = 255.
+    h, s, v = colorsys.rgb_to_hsv(old_r/rgb_max, old_g/rgb_max, old_b/rgb_max)
+    def single_color_func(word=None, font_size=None, position=None,
+                          orientation=None, font_path=None, random_state=None):
+        """Random color generation.
+
+        Additional coloring method. It picks a random value with hue and
+        saturation based on the color given to the generating function.
+
+        Parameters
+        ----------
+        word, font_size, position, orientation  : ignored.
+
+        random_state : random.Random object or None, (default=None)
+          If a random object is given, this is used for generating random numbers.
+
+        """
+        if random_state is None:
+            random_state = Random()
+        r, g, b = colorsys.hsv_to_rgb(h, s, random_state.uniform(0.2, 1))
+        return 'rgb({:.0f}, {:.0f}, {:.0f})'.format(r * rgb_max, g * rgb_max, b * rgb_max)
+    return single_color_func
+
 
 class WordCloud(object):
     """Word cloud object for generating and drawing.