You all are my heros. I had gotten so caught up in the XYZ to LAB calculation that I didn't notice it could be reduced to a 1d LUT and simple matrix. Troy, I was looking through your (amazing)

Doesn't really answer your question (sorry) but.... On Transformers the director wanted sharper cg robots! so we had a sharpen shootout. The joint winners were either LAB or Log, unshapen masks.i.e.

Whilst stranded in an airport... https://gist.github.com/sobotka/97707cf481049fd3267d85510f30db1e No assurances expressed or implied. Seems the values are darn close to Lindbloom's, which may account

The conversion from XYZ to CIELab can be done with matrices and 1d-LUTs, so you should be able to do the forward and reverse quite exactly with the existing machinery and without resorting to

The shaper here would be a purely technological solution, simply helping out interpolation given that your input happens to be imagery. In your CTL, you would assume that you are being fed Log2 values

L* is inherently logarithmic, so perhaps you could use L* it's self as the shaper here. But I think the inherently negative a*b* values will make this effort futile, unless there is an alternative all

Looking at my values closer, looks like you are probably right. My input image is 0 to 1 linear, so I wasn't using a shaper. However, when I get to LAB space, there are negative values, which would

That screams bad shaper to me. What are you using for a shaper here? With respect, TJS

Ha. Yeah, that pull request is exactly what I'd want. I'll add my +1 to the PR :) And thanks for the response Sean and Troy --that's pretty much what I'd tried already, CMSTestPattern -> ColorSpace

FWIW there is an old pull request for a simple expression transform which would have been perfect for this, https://github.com/imageworks/OpenColorIO/pull/366 Sent from my phone

Tacking onto Sean's comments, roughly: Use ociolutimage --generate --maxwidth 4225 --cubesize 65 --output all-in-one.exr to generate an all-in-one RGB EXR. Roll that through your L*a*b* CTL functions

OCIO is just a LUT and simple math processor(+,-,*,**,log, etc.), so its not really intended to implement algorithms like L*a*b*. Some equations are more LUT friendly than others something RGB-like to

Can you expand on that? Looking into CTL now, does look like I could define L*a*b* there, but how would that tie in to a config.ocio? I haven't used it before, got some reading to do

Would be more optimal to define L*a*b* according to the proper formulas in a CTL and generate the to and froms from there on an EXR, using a suitable shaper to the 3D LUT. With respect, TJS

hmm, I tried that but it didn't line up. I'll poke around with other lut formats maybe. I used nuke to generate two .cube files

You can use a 3D LUT but still have a reversible colorspace transform by defining both the to-reference and from-reference transforms (I.e to reference would use lab_to_xyz.lut and from-ref would use

Hey all! So I'm trying to get my team off of doing so much in photoshop, and have written some tools using oiio to replace a lot of the workflow. Right now, they like to do an unsharpen mask in

Jack Holm had identified a number of issues with the ICC profiles and was willing to help correct them. Alex

Lars is certainly the right person to receive that suggestion... HP

We always bake to sRGB and have the computers use that as their display profile. Nuke doesn't respect the actual display properties, so we don't want Photoshop to either. In the past few years