My guess is that the source image, "my_rgba_image.tif", is uint8 or uint16. So
when you do the colorconvert into an uninitialized ImageBuf, it makes the
transformed data have the same data format as the input. It doesn't know at
that point that you wish to eventually write it out as an EXR that can handle
floating point.
Assuming my hypothesis is right, here's how to fix:
ImageBuf* workingImage = new ImageBuf("my_rgba_image.tif");
ImageSpec newspec = workingimage->spec(); // Copy spec of input...
newspec.set_format (OIIO::TypeDesc::FLOAT); // ...but change data type to float
ImageBuf labSpaceBuffer (newspec); // ...and use that to initialize
the buffer
ColorProcessor* unsharpSpaceProcessor = config.createColorProcessor("linear",
"CIE Lab D65");
bool result = ImageBufAlgo::colorconvert(labSpaceBuffer, *workingImage,
unsharpSpaceProcessor, true);
labSpaceBuffer.write("test_out.exr");
Extra note: don't forget to delete workingimage at the end! (Since you
allocated a new ImageBuf, instead of just making one directly on the stack as
you did with labSpaceBuffer.)
> On Feb 17, 2017, at 9:50 AM, Andrew Wood <[email protected]> wrote:
>
> Hey there!
>
> I'm playing around with OCIO to do a transform from linear to CIELAB space to
> do an unsharpen. I've got a config.ocio that gives me the expected results
> in Nuke just fine, however using oiio and ocio, I'm getting a very different
> result.
>
> CIELAB does use negative numbers, so I'm wondering if there is some issue
> with those in oiio? I convert to lab, and then write out an exr, and there
> aren't any negative values in there...
>
> My code looks something like this:
>
> ImageBuf* workingImage = new ImageBuf("my_rgba_image.tif");
> ColorProcessor* unsharpSpaceProcessor = config.createColorProcessor("linear",
> "CIE Lab D65");
>
> ImageBuf labSpaceBuffer;
> bool result = ImageBufAlgo::colorconvert(labSpaceBuffer,
> *workingImage, unsharpSpaceProcessor, true);
> labSpaceBuffer.write("test_out.exr")
>
> Using Nuke on the source image, I expect to see negative values in the green
> and blue channels, but looking at test_out.exr they seem to be clamped at 0.
>
> config.ocio looks something like this (based on linear), but since it looks
> correct in Nuke, and not in my code, I must be doing something wrong!
> https://gist.github.com/andrewhwood/badb691a5c940af670fe3b9f8cfb189f
> <https://gist.github.com/andrewhwood/badb691a5c940af670fe3b9f8cfb189f>
>
> any ideas?
> thanks!
> Andrew
>
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> Oiio-dev mailing list
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--
Larry Gritz
[email protected]
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