[NTLUG:Discuss] Anybody good with GIMP?

[steve]

Leroy Tennison wrote:
> My question involves animated GIFs in GIMP: How can I get a given layer 
> to appear by itself in the Image Window (or Main Interface if that's 
> what it's called) so that it can be viewed/edited?
> 
> I have discovered the Layers/Channels/Paths dialog and have been able to 
> successfully manipulate frame order and delete a frame but haven't found 
> any way to view/edit one.  Can anybody help me out or point me to a 
> tutorial specifically on this subject?
> 
> Thanks for your help,

I'm using GIMP 2.0 here - but I'm pretty sure it's much
the same in all versions.

Load the GIF file in the usual way.

Open the Layers dialog (which was Layers/Channels/Paths in pre-2.0).

The one layer that's highlighted is the layer you are editing - BUT
what you're seeing on the screen is a combination of all the layers
with eyeball icons next to them.

So to cleanly edit one layer, click on the eyeballs on all the *other*
layers to get rid of them, then make sure the layer you want to edit
is both highlighted (so you can change it) *and* has an eyeball next
to it (so you can see it).

However, with many animated GIF's, some or all layers are just
modifications of the background layer - that optimises the
animation to make the file size smaller.  In that case, you'd need
to toggle on the eyeball on the bottom layer (named 'Background')
in order to be able to see what you are doing...but this is hopelessly
confusing/difficult to do in practice.

Hence, in the menu under 'Filters/Animation' you'll find a button
marked 'Unoptimise'.  Click that and you'll get a set of layers
where every layer carries the complete image for one moment in time.

You can use the 'Filters/Animation/Playback...' dialog to view your
animation at any time in the painting process.

This is really easy to edit - but if you save it back out again,
you'll get a much larger GIF file.

So when you've finished editing, go back into the 'Filters/Animation'
menu and hit 'Optimise (for GIF)' and it'll rip out everything that
didn't change from one frame to the next.  The resulting file should
be much smaller/simpler.

The other ikky thing about GIF's (animated or not) is that they use
a small color palette of (IIRC) just 256 colours.  This results in
some GIMP operations like smoothing and blurring and airbrushing to
not work very well.  You may need to go into the menu and pick
'Image/Mode/RGB' to get a full RGB image for painting - but note that
when you save it out as a GIF again, it's going to knock you back
to 256 colors again - and your final result may not look as nice as
the thing you painted.