1 files changed, 20 insertions, 0 deletions
diff --git a/colors.py b/colors.py
index af75e1a..161c0e6 100644
--- a/colors.py
+++ b/colors.py
@@ -1,3 +1,5 @@
+import logging
+
 CREDIT_COLOR = '#009900'
 
 DEBIT_COLOR = '#ff4040'
@@ -41,3 +43,21 @@ def get_category_color_str(catname):
     color = get_category_color(catname)
     return "#%02x%02x%02x" % \
         (int(color[0] * 255), int(color[1] * 255), int(color[2] * 255))
+
+
+def is_too_light(color):
+    return _luminance(color) > 96
+
+
+def _luminance(color):
+    ''' Calculate luminance value '''
+    return int(color[1:3], 16) * 0.3 + int(color[3:5], 16) * 0.6 + \
+        int(color[5:7], 16) * 0.1
+
+
+def test_luminances():
+    for cat_color in CATEGORY_COLORS:
+        color = "#%02x%02x%02x" % \
+            (int(cat_color[0] * 255), int(cat_color[1] * 255),
+             int(cat_color[2] * 255))
+        logging.error('color %s luminance %s', color, _luminance(color))