No result given --> impossible so not serious

[mfaure]

Observed behaviour

• foreground = white
• background = rgb(105, 209, 0);
• ratio = 4.5
• algo = close to initial color
• result = no result (!)

Expected behaviour

I would like to have a result. No result implies that not any green in the world could be used with white text, which is wrong.

Suggestion: if the first algorithm (close to initial color) fails, then switch back to the other one (range of color), event if it take 5ms more !

[dzc34]

added to #161 and closed