[chronojump] Better ColorIsDark formula

[Xavier de Blas <xaviblas src gnome org>]

commit 740e528a3a8fac4d1b6e89f43d5b6c6ff3116007
Author: Xavier de Blas <xaviblas gmail com>
Date:   Tue Apr 14 12:21:20 2020 +0200

    Better ColorIsDark formula

 src/utilGtk.cs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/utilGtk.cs b/src/utilGtk.cs
index a7a3b1fd..5de9f4d7 100644
--- a/src/utilGtk.cs
+++ b/src/utilGtk.cs
@@ -498,7 +498,10 @@ public class UtilGtk
        {
                //LogB.Information(string.Format("color red: {0}, green: {1}, blue: {2}", color.Red, 
color.Green, color.Blue));
                //3 components come in ushort (0-65535)
-               return (color.Red + color.Green + color.Blue < 3 * 65535 / 2.0);
+               //return (color.Red + color.Green + color.Blue < 3 * 65535 / 2.0);
+
+               
//https://stackoverflow.com/questions/3942878/how-to-decide-font-color-in-white-or-black-depending-on-background-color
+               return (color.Red * 0.299 + color.Green * 0.587 + color.Blue * 0.114 < 186 * 256);
        }
        public static bool ColorIsDark(string colorString)
        {