Ofnuts is a better answer, My answer FWIW
@akgimp
You are not comparing like-with-like. The scales are different 0-100 v -100 <> +100
Trying your image HSV 215,20,45 Looks like this: http://i.imgur.com/RZzlAFg.jpg
Decompose that: Colors -> Components -> Decompose (into layers): http://i.imgur.com/6IYMobf.jpg
Fill the saturation and value layers with white (RGB 255,255,255 = 100%) : http://i.imgur.com/an7WejM.jpg
Recompose that: Colors -> Components > Recompose gives this: http://i.imgur.com/4CunaLQ.jpg
Do you have a specific purpose for this? Someone might come up with better advice.
edit: If you are using specific images and you need to set 100% saturation and value have a look at the gmic plugin http://www.gmic.eu which has interactive color curves, you can drag a curve up to give 100% and have a real time display of the effect.
@akgimp
You are not comparing like-with-like. The scales are different 0-100 v -100 <> +100
Trying your image HSV 215,20,45 Looks like this: http://i.imgur.com/RZzlAFg.jpg
Decompose that: Colors -> Components -> Decompose (into layers): http://i.imgur.com/6IYMobf.jpg
Fill the saturation and value layers with white (RGB 255,255,255 = 100%) : http://i.imgur.com/an7WejM.jpg
Recompose that: Colors -> Components > Recompose gives this: http://i.imgur.com/4CunaLQ.jpg
Do you have a specific purpose for this? Someone might come up with better advice.
edit: If you are using specific images and you need to set 100% saturation and value have a look at the gmic plugin http://www.gmic.eu which has interactive color curves, you can drag a curve up to give 100% and have a real time display of the effect.