Implement support for Sony S-Log2.

[KelSolaar]

There have been user requests for Sony S-Log 2 support on Slack:

References

• #87

[doug-walker]

Here are the parameters to use with an OCIO CameraLogTransform to implement the SLog2 function. These values are generated by starting with the CTL implementation and rearranging terms. All numeric constants used here come from the CTL, which I'm assuming is the definitive reference.

    b = 64. / 1023.
    w = 940. / 1023.
    ab = 90. / 1023.
    linSideSlope = 155. / (0.9 * 219.)
    linSideOffset = 0.037584
    logSideSlope = 0.432699 * (w - b)
    logSideOffset = (0.616596 + 0.03) * (w - b) + b
    linearSlope = 3.53881278538813 * (w - b) / 0.9
    base = 10.0
    logSideBreak = ab
    linSideBreak = ( np.power( base, (logSideBreak - logSideOffset) / logSideSlope ) - linSideOffset ) / linSideSlope

[KelSolaar]

Thank you!

[doug-walker]

One of the challenges with adding an S-Log2 color space is that there are actually three S-Log2 color spaces in the OCIO v1 ACES configs. The working group has decided to postpone adding this until we get a more specific proposal/request for what flavor of S-Log2 to add.