I have been using Photoshop for years and would like to migrate over to Gimp but find one huge stumbling block.

With Photoshop CS
I use ctl-alt-tilde (~) to select highlights - called Load composite as selection.
Then I can use ctl-I to alternate from low to high values (lowlight to highlights) - called invert.
I use ctl-H to hide the marching ants - called toggle extra's
ctl-D to deselect and go back to whole image manipulation.

Benefits
Very simple, easy to use and allows me to use any number of filters to manipulate either value.  For instance, increase or decrease contrast and/or brightness within each value, or blur, or saturation, or put a very subtle canvas affect, or use a plug in that only affects that one value, the choices are almost unlimited.  It gives me far more control and like I said, it is very, very easy to use.

With Gimp 2.6.7 used with Ubuntu 9.10
From what I can see I need to produce layers, and it is a many step process.  

Solution
I have been looking everywhere for hours for an easy way to do this with Gimp, but so far have come up empty. A plug in?  Or something even simpler?

About me
I'm one of those types that like things simple, the many step process leaves to much room for errors.

Conclusion
Am I missing something, or am I stuck with layers and thus laying out big bucks (or stealing it) for Photoshop CS and Windows when I really want to use Ubuntu?

Thanks for your help.
Jim
.

 

Not entirely sure what you're trying to do here. I'm not able to load up PS right now to reproduce your process...

But have you tried Gimpshop? Gimp is extremely maleable, so some bright soul decided to take a Gimp install, move everything around, and change the keyboard shortcuts to mimic photoshop as closely as possible.

I have to say it isn't half bad. It's not exact, but if you want to feel more comfortable, this may be the way to go.

I may recommend though, that you tryout normal gimp JUST FOR A WHILE. Then switch to gimpshop. This should give you a much better grasp of where the missing things are ;)

Although from the content of your message, I don't see much that couldn't be handled with quickmasks. (again, can't pull up PS at the moment.)

If you bring up the channel window, (Windows->Dockable Dialogs->Channels) you can load any channel into selection, then switch over to quickmask (Shift+q). You can treat the quickmask exactly as you would in Photoshop. It is essentially a grayscale layer (it doesn't look grayscale, it's actually red by default, but you can change that.) you can invert, apply levels/curves, filters, etc. Once you exit quickmask (shift+q again) your grayscale image is loaded as a selection.
If you were already aware of this and it doesn't help in any way, I apologize!