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
>>> <mailto: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
>>>
>>> _______________________________________________
>>> Oiio-dev mailing list
>>> Oiio-dev@lists.openimageio.org <mailto:Oiio-dev@lists.openimageio.org>
>>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org>
>>>
>>
>> --
>> Larry Gritz
>> l...@larrygritz.com <mailto:l...@larrygritz.com>
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Oiio-dev mailing list
>> Oiio-dev@lists.openimageio.org <mailto:Oiio-dev@lists.openimageio.org>
>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
>> <http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org>
>
> --
> Hugh Macdonald
> Product Owner, Volumetric Capture
> Eyeline Studios
> Ext: 4165
> www.scanlinevfx.com
> <http://www.scanlinevfx.com/>_______________________________________________
> Oiio-dev mailing list
> Oiio-dev@lists.openimageio.org
> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org
--
Larry Gritz
l...@larrygritz.com
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