I created the recompose filter and am reasonably familiar with the others, although it's
been a couple of years since I have worked with the code. I'll be happy to try to answer
questions; I'm not up to writing a lengthy description right now though.

Regard, -- Bill Skaggs

The "registration color" is a feature that has recently been added, I believe,
and I don't know anything about it.

Concerning Recompose, its function is to reverse Decompose. If you decompose a layer and then want to reassemble the original layer using Compose, you have to do a lot of work -- you have to set up all the component layers properly using menus. Recompose does all of this silently, and replaces the original layer (the one that was decomposed) with the result. If you don't alter any of the decomposed layers, Recompose will give you exactly the result you started with (except for numerical errors),
so you won't see anything change. If you alter one of the decomposed layers and then choose Recompose, you should see the original layer change.

The reason for setting this up was to make it easier to edit individual color channels of a layer. For example, if you want to edit the luminosity of a layer without affecting hues, you can decompose it as LAB, do whatever you want to the L channel, then do recompose, and your original layer will automatically show the result.

-- Bill

Den 25.10.2010 22:11, skreiv Bill Skaggs:

The "registration color" is a feature that has recently been added, I believe,
and I don't know anything about it.

Someone other knows?

Concerning Recompose, its function is to reverse Decompose. If you decompose a layer and then want to reassemble the original layer using Compose, you have to do a lot of work -- you have to set up all the component layers properly using menus. Recompose does all of this silently, and replaces the original layer (the one that was decomposed) with the result. If you don't alter any of the decomposed layers, Recompose
will give you exactly the result you started with (except for numerical errors),
so you won't see anything change. If you alter one of the decomposed layers
and then choose Recompose, you should see the original layer change.

The reason for setting this up was to make it easier to edit individual color channels of a layer. For example, if you want to edit the luminosity
of a layer without affecting hues, you can decompose it as LAB, do whatever you want to the L channel, then do recompose, and your original layer will automatically show the result.

-- Bill

Thank you, Bill! This explained a lot. I'll try it out and perhaps incorporate this in some way in the GIMP manual. I am using this plugin, together with others, very often at the moment checking out images before printing.

Kolbjoern