[wellylug] compositing frames

[E.Chalaron]

Hello Pete

> When you say 'composite' - I presume your images have an alpha channel -
> or are you expecting that each image will be 'automagically' assigned a
> 'global' alpha value - e.g. a solid red square composited over a black
> image will show a 'dark red' colour?

Yes I did assume that...

> If the latter (magic global alpha value) you might be better off
> scripting the GIMP to do this - load 1 pnm file, load the next into a
> new layer, set alpha of new layer to 0.5, save resulting image or similar.

Ok, I have some scripts I can modify here, BTW, do you need to decrease alpha 
value by the amount of frames 
1, 0.5,0.5 or 1, 0.5, 0.25 etc ... or if you have 3 frames : 1,0.3,0.3 etc..

> ImageMagick etc. can probably do this on the command line, but by
> default it will likely assume your images come pre-alpha-channeled and
> you won't get what you expected - e.g. layering a solid red image over a
> solid black image just gives you a solid red image.

I have been reading that results from IM are not terribly good .. I make no 
assumtpion against image magick, just reporting.

> IF you can be more specific about what you want to do, that might help.

Well When I reshoot each movie reel I end up wit the  3600 * 4Mb of pnm for 
one reel of 50 ft (the classic little Kodak one in yellow pocket).
Ideally I'd like to reshoot with various levels of exposure to open up scenes 
with strong backlight while recompositing, moreover the ratio signal/ noise 
should improve as well...

Either I trigger once get x Frames_n, composite x in Frame_final_n
or I trigger once get one frame, reshoot the all reel n times in other 
folders.
Advantage of the first method is image stability, adv. of second method : get 
several levels of exposure, but image may not be so stable (which if happens 
just crap the all idea down)

Alternative would be to overlay DVs, Cinelerra may do that, but the GUI is 
just a nightmare...
Let's say that I am just exploring before I move to windows........

Na .. just kidding..
E