Fix darken/lighten

pygal/style.py

@@ -20,8 +20,7 @@
 Charts styling
 """
 from __future__ import division
-from pygal.util import cycle_fill
+from pygal.util import cycle_fill, rgb_to_hsl, hsl_to_rgb
-from colorsys import rgb_to_hls, hls_to_rgb
 
 
 def darken(color, percent):
@@ -30,15 +29,10 @@ def darken(color, percent):
     assert len(color) in (3, 6), '#rrggbb and #rgb format are supported'
     if len(color) == 3:
         color = [a for b in zip(color, color) for a in b]
-
+    return '#%02x%02x%02x' % hsl_to_rgb(
-    return '#%02x%02x%02x' % tuple(
+        *(lambda h, s, l: (h, s, max(0, min(100, l - percent))))(
-        map(lambda x: 255 * x,
+            *rgb_to_hsl(*map(lambda x: int(''.join(x), 16),
-            hls_to_rgb(*(
+                             zip(color[::2], color[1::2])))))
-                lambda h, l, s: (h, max(0, min(1, l - percent / 100)), s))(
-                    *rgb_to_hls(*map(
-                        lambda x: int(''.join(x), 16) / 255,
-                        zip(color[::2], color[1::2])))
-                ))))
 
 
 def lighten(color, percent):

pygal/test/test_util.py

@@ -19,7 +19,7 @@
 from pygal._compat import u
 from pygal.util import (
     round_to_int, round_to_float, _swap_curly, template, humanize,
-    is_major, truncate, minify_css)
+    is_major, truncate, minify_css, rgb_to_hsl, hsl_to_rgb)
 from pytest import raises
 
 

pygal/util.py

@@ -382,3 +382,54 @@ def split_title(title, width, title_fs):
         title = title[i:].strip()
     titles.append(title)
     return titles
+
+
+def rgb_to_hsl(r, g, b):
+    r /= 255
+    g /= 255
+    b /= 255
+    max_ = max((r, g, b))
+    min_ = min((r, g, b))
+    d = max_ - min_
+
+    if not d:
+        h = 0
+    elif r is max_:
+        h = 60 * (g - b) / d
+    elif g is max_:
+        h = 60 * (b - r) / d + 120
+    else:
+        h = 60 * (r - g) / d + 240
+
+    l = .5 * (max_ + min_)
+    if not d:
+        s = 0
+    elif l < 0.5:
+        s = .5 * d / l
+    else:
+        s = .5 * d / (1 - l)
+
+    return h % 360, s * 100, l * 100
+
+
+def hsl_to_rgb(h, s, l):
+    h /= 360
+    s /= 100
+    l /= 100
+
+    m2 = l * (s + 1) if l <= .5 else l + s - l * s
+    m1 = 2 * l - m2
+
+    def h_to_rgb(h):
+        h = h % 1
+        if 6 * h < 1:
+            return m1 + 6 * h * (m2 - m1)
+        if 2 * h < 1:
+            return m2
+        if 3 * h < 2:
+            return m1 + 6 * (2 / 3 - h) * (m2 - m1)
+        return m1
+    r, g, b = map(lambda x: round(x * 255),
+                  map(h_to_rgb, (h + 1 / 3, h, h - 1 / 3)))
+
+    return r, g, b