When C is decomposed it is diffrent from the color picker

[Ofnuts]

(02-20-2024, 11:35 PM)jarj Wrote:

(02-20-2024, 10:30 PM)Ofnuts Wrote: You are assuming that the maximum C is 100% but this is not true.  If you create the color #0B03FF you will see that its chroma is 130.4, so the maximum theoretical chroma value is higher that 100 and the mapping is between (0..100%) and (0..255) but between (0..max) and (0..255). And max could be 200 since the 130.4 is decomposed to 65.3% (and in the color selector you can push the C slider to 200 even if you are told that there is no corresponding RGB color).

Another clue for the (0..200) range of the chroma is given by the two animation on the Wikipedia page of the CIELab color model:

Thanks for the reply Ofnuts.  I'm not questioning Gimps C* calculations - it is the inconsistency between the C* in the color picker Vs the decomposed C* 

Are you saying I just have to double the decomposed value?

Yes, you double the value. 

It's not an "inconsistency".  It is just that the C range isn't the 0..100 you assumed it was. Otherwise the Hue layer that maps 0..360 to 0..255 would also be an inconsistency, right?