Creating shapers using basic operators

[nick (Nick Shaw)]

@doug_walker

Finally, the Camera Log style transforms would be written as follows:

<Log inBitDepth="32f" outBitDepth="10i" style="cameraLinToLog">
    <LogParams linSideSlope="1.0" linSideOffset="0.0" logSideSlope="1.0" logSideOffset="0.0" linSideBreak="0.0" linearGain="1.0" base="10.0"  />
</Log>
<Log inBitDepth="10i" outBitDepth="32f" style="cameraLogToLin">
    <LogParams linSideSlope="1.0" linSideOffset="0.0" logSideSlope="1.0" logSideOffset="0.0" linSideBreak="0.0" linearGain="1.0" base="10.0"  />
</Log>

The implied lin-to-log equation is:

if (x <= linSideBreak)
  y = x * linearGain + k;
else
  y = logSideSlope * log( linSideSlope * x + linSideOffset, base ) + logSideOffset;

One camera log which wouldn’t be fully covered by this form is Canon Log 3, due to the three part nature of the curve, mirroring about linear zero.

How often it would actually be problematic to treat the curve as if the linear segment continued for ever into negative values, rather than changing back to an inverted log curve, I am not sure.