Well that sure is weird! Usually, both the python bindings and the oiiotool
operation are pretty thin wrappers around the corresponding ImageBufAlgo
function which is doing almost all the work. A big perf difference is not
expected.
Can I assume that this is reproducible by any 70 channel image? Like I can just
use oiiotool to generate a black image and see a big speed disparity like this?
Or is it in any way specific to the particular image?
Wednesdays are pretty packed, but I'l try to take a look at this today if I can.
> On Nov 10, 2021, at 4:08 AM, Daniel Flehner Heen <flehnerhee...@gmail.com>
> wrote:
>
> Hi!
>
> I'm attempting to extract only the RGBA channels of an EXR with 70+ channels.
>
> Using:
> oiiotool -i:ch=R,G,B,A /path/to/gigantic.exr -o manageable.exr
> takes about 8 seconds.
>
> In python (2.7 !caugh..):
> buf = oiio.ImageBuf('/path/to/gigantic.exr')
> obuf = oiio.ImageBufAlgo.channels(buf, ('R', 'G', 'B', 'A'))
> obuf.write('manageable.exr')
> takes 4+ minutes
>
> I tried only extracting one channel and it took the exact amount of time. I
> expect a performance hit using python but this seems a bit off. I suspect the
> python bindings are reading all the channels even though I'm asking for a
> specific few.
> I might of course be going about this completely wrong, in which case a
> pointer in the right direction would be highly appreciated :)
>
> Straight read and write of the same file is done quickly.
>
> Thanks!
>
> --
> -Daniel
> _______________________________________________
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> Oiio-dev@lists.openimageio.org
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
--
Larry Gritz
l...@larrygritz.com
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