To increase saturation on an image which has a fair amount of saturation already in certain areas might be difficult since the already colorful areas will be pushed even further.
Adobes Lightroom introduced a feature called “Vibrancy”. The algorithm behind this is not entirely open to the public. But several forums mentioned it might be some masked saturation boost, in which the mask is the already existing saturation.

To mimic this behaviour as well as diving into c++ and plug-in development i thought i might be a good idea to tackle this very task.