Re: [Gimp-user] GIMP Gif Export

[Steve Kinney <admin pilobilus net>]

On 12/21/2015 11:41 AM, pickupthestix16 wrote:
> Hello All! 
>
> This is my first post and I'm a bit familiar with GIMP but am still kind of a
> newbie to the program. I particularly got it so that I could create my own
> signature for a forum that I participate on regularly.
>
> I recently hit a road block that I can't seem to get around and I'm not sure if
> it's possible at all. I wanted to make an animated Gif image and I wanted the
> original gif to be transparent. I didn't know any other way to do this, so I
> simply separated all 54 frames and edited each photo myself, and then
> re-formatted them back into a gif. I then opened as layers each of the frames.

So far so good.  However, see below...

> I used the "Lighten Only" effect on the rest of the images on the signature, so
> I wanted to keep the gif that way too. This required me to go through each of
> the 54 frames and select "Lighten Only". At first, I ran into this problem
> http://imgur.com/l5fiKq7. Even though each frame said "replace", it didn't seem
> to actually replace the previous frame.

The GIF file format does not have any provision for layer modes.  It
doesn't even have 'real' transparency - each pixel can be either
completely opaque or completely transparent, but nothing in between.

So, although the file you are editing in the GIMP displays the
results you intend when setting layers to Lighten Only mode, every
frame / layer of an exported GIF file will be saved in 'normal' mode
and effects created by stacking layers in Lighten Only mode will be
lost.

> Then I downloaded an animation script called "Animastack". I put [bg] on the
> background frame and [fg] on the foreground frame and then "processed animastack
> tags" and it grouped together all frames with the foreground and background so I
> had 54 separate groups. When I did the "playback" though, it worked! IT FINALLY
> WORKED! i was so happy; I had spent so long trying to get it to work.
>
> Then I tried to export the file as a gif and ran into the "indexed or grayscale"
> issue. Is there ANY WAY to export this without changing the colors? Anything
> other than "gif" that I could export to that would have a similar effect?

I don't think indexed vs. grayscale is the problem.  All GIF images
are indexed; that's way the GIF file format works.  Every color that
appears in a GIF image is specified in a palette stored in the image
file, with an "index" that enables programs that display GIF images
to fetch the right color from the palette to every pixel.  A
grayscale image exported as a GIF will be an indexed file, where
every color in the index is a shade of gray.

Whatever effect you are getting by using a Lighten Only mode can be
exported to a GIF, but you will need to use a stack of "normal mode"
layers to make that happen.

First get one frame of the animation to show up in your main image
window (the canvas), looking like you want it to, by using layer
modes or any other tool or technique.  Then in the Layers dialogue
do "New from visible."  This will give you a new layer that is a
'normal' mode snapshot, duplicating what you see on the canvas.
Layers made this way can then be stacked up and saved as an animation.

Making the first frame of your animation transparent will 'just
work'.  Replacing one layer rather then adding layers as the
animation plays is an option you can select while saving your image
as an animated GIF.

You can also adjust the delay between frame changes in your
animation any way you want, by hand - for instance to briefly stop
it on one frame before continuing with the others.  Just re-open the
animated GIF in the GIMP and look at the names of the layers:  The
duration of the frame is part of the layer name.  Editing this, then
saving the file as an animated GIF, results in an animation with
whatever frame change delays (or speed-ups) you specified.

:o)