How about this (presuming it's a 4 channel RGBA):
oiiotool in.exr -dup -mulc 10000 -clamp:min=0:max=1 -ch R=A,G=A,B=A,A
-mul -autorim -o out.exr
This reads in.exr, duplicates it on the stack, multiplies pixel values 10000
then clamps to [0,1] (that has the effect of turning all nonzero alpha into
1.0), replicates the thresholded alpha value into all 4 channels, multiplies
that mask by the original image (still below it on the stack!) -- now we've
squashed all color to 0 in pixels that were original alpha 0 -- and finally
write it out with autotrim!
I haven't tested this, so take with a grain of salt that I've spelled
everything correctly and whatnot. But I think the overall methodology is sound.
If you are using master (so you have expression substitution), another clever
trick might be:
oiiotool in.exr --ch A -autotrim -o alphatrim.exr
oiiotool alphatrim.exr in.exr -crop {IMG[1].geom} -o out.exr
This extracts just the alpha channel and saves to a temporary file with
auto-trimming. Then it uses the size of the saved auto-trimmed alpha to
explicitly crop the original. I would prefer to do it in one step, but it looks
like --autotrim only works upon the saved output of "-o", and I neglected to
implement a --trim (trim the outer black "in place" so you can then use the
trimmed image).
On Mar 25, 2015, at 10:42 PM, Jason Iversen <[email protected]> wrote:
> Perhaps you can premultiply (--premult) before autotrimming?
>
> On Wed, Mar 25, 2015 at 8:48 PM, Sebastian Kral <[email protected]> wrote:
> Hi,
>
> I was wondering if it's possible to create a DataWindow in an EXR with the
> --autotrim flag which is based purely on the Alpha instead of black pixels.
> We have some rather large mattepaintings which I am trying to trim but since
> the background isn't black the autotrim doesn't seem to work.
>
> Perhaps I am missing something and someone can help me out.
>
> The command I am running:
> oiiotool in.exr --scanline --compress zips --autotrim -o out.exr
>
> Thank you.
>
> Cheers,
> Sebastian
>
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>
>
>
> --
> jason iversen
> http://www.odforce.net
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Larry Gritz
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