Hi Larry et al,
I’ve just subscribed to the olio-dev list so apologies if this question has
been asked and answered before.
I’m using python (3.7 and OIIO 2.0.5) and trying to assemble a multichannel
ImageBuf which will contain RGB from one EXR source in float16 format and some
arbitrary uint8 channels read from some numpy.ndarray’s. All these channels
will be written out to one EXR. I could switch to C++ but I have most of my
code already in python so I thought I’d give the python bindings a shot.
I’m most of the way of there, the exr gets written to disk with the correct
channel names and so on, but all the channels whose format I expect to be
written as uint8 are written as float16.
From what I could gather from the python and C++ docs, my ImageBuf’s
ImageSpec.format would be used as the format for all channels unless
ImageSpec.channelformats is defined (and is a tuple of TypeDesc objects).
My code for assembling these channels and setting up the channel formats looks
something like the below. The most relevant part is probably at the end, I'm
including my methodology for assembling the ImageBuf with the various channels
if that makes a difference. Any pointers on what I might be doing incorrectly
would be much appreciated
Cheers
Jonathan
import OpenImageIO as oiio
exr_buf_input = olio.ImageBuf(“/path/to/my.exr”)
exr_spec = exr_buf_input.spec()
# Setup output buffer for RGB + some arbitrary channels
output_buf_spec =
oiio.ImageSpec(exr_spec.full_width,exr_spec.full_height,3,'half')
channelnames = ['R', 'G', 'B'] + list_of_arb_channelnames
output_buf_spec.channelnames = channelnames
output_buf = oiio.ImageBuf(output_buf_spec)
# Copy just RGB channels out of my exr to my output buffer
output_buf = oiio.ImageBufAlgo.channels(exr_buf_input,('R','G','B'))
# Create a buffer out of each numpy array[y][x], appending it to the output
arb_buf_spec =
oiio.ImageSpec(exr_spec.full_width,exr_spec.full_height,1,oiio.TypeUInt8)
channeltypes = [oiio.TypeHalf, oiio.TypeHalf, oiio.TypeHalf]
for channel_array in arbitrary_channel_arrays:
temp_buf = oiio.ImageBuf(arb_buf_spec,False)
# assume channel_array's values are already normalized 0-255
temp_buf.set_pixels(oiio.ROI.All, channel_array.astype(np.uint8))
output_buf = oiio.ImageBufAlgo.channel_append(output_buf, temp_buf)
channeltypes.append(oiio.TypeUInt8)
# Set the ImageSpec's channelformats to the tuple of TypeDescs
output_buf.specmod().channelformats = tuple(channeltypes)
# The output buf's ImageSpec's channelformats are all the values I'd expect
print(output_buf.spec().channelformats)
# All the channels in the EXR float16
output_buf.write('/tmp/output.exr')
# All the channels in the EXR are still float16
output_buf.write('/tmp/output.exr','uint8')_______________________________________________
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