triplet_to_brightness(): New function

diff --git a/Tools/pynche/ColorDB.py b/Tools/pynche/ColorDB.py
index fae0a3bed7d805af5853e47ca9993f94f05a9d39..a4c834227a01d7fa14b8f2323c4530a6cac7d9e3 100644 (file)
--- a/Tools/pynche/ColorDB.py
+++ b/Tools/pynche/ColorDB.py
@@ -174,6 +174,15 @@ def triplet_to_fractional_rgb(rgbtuple):
     return map(operator.__div__, rgbtuple, _maxtuple)
 
 
+def triplet_to_brightness(rgbtuple):
+    # return the brightness (grey level) along the scale 0.0==black to
+    # 1.0==white
+    r = 0.299
+    g = 0.587
+    b = 0.114
+    return r*rgbtuple[0] + g*rgbtuple[1] + b*rgbtuple[2]
+
+
 \f
 if __name__ == '__main__':
     import string