[wellylug] compositing frames

[Pete Black]

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?

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.

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.

There are also a variety of blending modes that will give different 
results with the same source images to consider - and you can acheive 
these using the layer compositing operators in the GIMP as well.

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

-Pete


>Hi all
>Among the GIs gourous here, is there anybody who knows how to composite 
>several pnm or ppm files together ?
>
>Thanks a lot 
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