Hi Hugh,
Perhaps you can share how you achieved the speedup from a tip on SO? I'm
doing something similar to you for a project, and hitting similar
performance issues.
> I was initially doing the concatenating by hand in Python, which was
> horrendously slow (10s for a UHD image), but was pointed in the right
> direction by SO on that, which reduced it to <1% of the time.
>
On Mon, Aug 15, 2022 at 12:54 PM Hugh Macdonald <
hugh.macdon...@scanlinevfx.com> wrote:
> Thanks Larry,
>
> It's good to know that I wasn't missing anything OIIO-specific in there. I
> was initially doing the concatenating by hand in Python, which was
> horrendously slow (10s for a UHD image), but was pointed in the right
> direction by SO on that, which reduced it to <1% of the time.
>
> That's helpful to see how I'd do it with ImageBuf. I think I'll probably
> stick with what I've got for now, though, if there's nothing majorly wrong
> with it, as it certainly works.
>
> Thanks
> Hugh
>
> On 15/08/2022 19:36, Larry Gritz wrote:
>
> Yeah, that looks like it should work.
>
> If you really needed it done with ImageBuf specifically for some reason, I
> think it might look like
>
> # read old images
> src_img = ImageBuf(src_image_file)
> dst_img = ImageBuf(dst_image_file)
>
> # make spec to describe the new image and allocate it
> spec = src_img.spec.copy()
> spec.nchannels = spec.nchannels + 1
> spec.channel_names.append("new_layer.new_channel")
> new_img = ImageBuf(spec)
>
> # copy the right parts to the right places
> # ... the first three channels get pasted from dst
> ImageBufAlgo.paste(new_img, 0, 0, 0, 0, dst_img)
> # ... the last channel gets pasted from src.G
> roi = src.roi.copy()
> roi.chbegin = 1
> roi.chend = 2
> ImageBufAlgo.paste(new_img, 0, 0, 0, spec.nchannels - 1, src_img, roi)
>
> # write results
> new_img.write(dest_image_file)
>
>
> (I haven't tried this, it's off the top of my head, but it's probably
> close to correct.)
>
> I don't necessarily think this is any better or more efficient than what
> you did, I just thought it might be helpful to compare how it would be done
> with ImageBuf alone, no ImageInput/ImageOutput.
>
> -- lg
>
>
> On Aug 15, 2022, at 9:14 AM, Hugh Macdonald <
> hugh.macdon...@scanlinevfx.com> wrote:
>
> Hi Larry,
>
> (b) is the closest to what I'm trying to do.
>
> Since sending my initial email, I'm now doing this. This keeps RGB in
> dest_img, and copies G from src_img into new_layer.new_channel
>
> src_img = oiio.ImageInput.open(src_image_file)
> dest_img = oiio.ImageInput.open(dest_image_file)
>
> src_data = src_img.read_image()
> dest_data = dest_img.read_image()
>
> src_spec = src_img.spec()
> dest_spec = dest_img.spec()
>
> src_img.close()
> dest_img.close()
>
> width = dest_spec.width
> height = dest_spec.height
>
> new_channels = list(dest_spec.channelnames)
> new_channels.append("new_layer.new_channel")
> copy_channel_indices = [1]
>
> out_data = np.concatenate((dest_data, src_data[:, :, copy_channel_indices]),
> axis=2)
>
> out_img = oiio.ImageOutput.create(dest_image_file)
> out_spec = oiio.ImageSpec(width, height, len(new_channels), "float32")
> out_spec.channelnames = tuple(new_channels)
> out_img.open(dest_image_file, out_spec)
>
> out_img.write_image(out_data)
> out_img.close()
>
>
> Thanks
> Hugh
>
> On 14/08/2022 23:02, Larry Gritz wrote:
>
> Hi, Hugh. Can you clarify whether you want to
>
> (a) make a new RGB image R from B but G and B from A?
> (b) make a new image with an additional channel, yielding {R, G, B, and
> New}, where R,G,B came from A and New is the R channel from B?
>
> ?
>
>
> On Aug 8, 2022, at 8:14 AM, Hugh Macdonald <hugh.macdon...@scanlinevfx.com>
> wrote:
>
> Hey all,
>
>
> I'm not overly familiar with the OIIO python API, so apologies if this is
> quite a simple question! I can't find any information online on how to do
> this with the Python API...
>
> I've got 2 EXRs, both with RGB channels, and I'd like to take the R
> channel from one of them and put it into another channel in the other.
>
> I've been looking at doing a 2-step process. The first step being to
> rename the channels in one ImageBuf, and to remove the unneeded channels,
> and the second being to use ImageBufAlgo.channel_append() to combine the
> two images together.
>
>
> This feels like it is unnecessarily 2 steps. Could someone point me at
> some examples for how to do this in a single step?
>
>
> I'm sure that this is pretty simple, but all the examples that I can find
> are for how to do this kind of thing using oiiotool, rather than doing it
> directly using the API.
>
>
> Thanks
>
> --
> Hugh
>
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>
>
> --
> Larry Gritz
> l...@larrygritz.com
>
>
>
>
>
>
> _______________________________________________
> Oiio-dev mailing
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>
>
> --
> Hugh Macdonald
> Product Owner, Volumetric Capture
> Eyeline Studios
> Ext: 4165www.scanlinevfx.com
>
> _______________________________________________
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> Oiio-dev@lists.openimageio.org
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>
>
> --
> Larry Gritz
> l...@larrygritz.com
>
>
>
>
>
>
> _______________________________________________
> Oiio-dev mailing
> listOiio-dev@lists.openimageio.orghttp://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>
>
> --
> Hugh Macdonald
> Product Owner, Volumetric Capture
> Eyeline Studios
> Ext: 4165www.scanlinevfx.com
>
> _______________________________________________
> Oiio-dev mailing list
> Oiio-dev@lists.openimageio.org
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
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