Pre-Review: Op Collapsing

Jeremy Selan <jeremy...@...>

I have some development under progress, not yet ready for review, but I thought it may interest people:

During processor creation, this branch adds an internal optimization pass that makes for more efficient color processing.

But the most interesting consequence is that this allows for transforms which were not previously possible:

Say you have 2 colorspaces: A and B.  Both of these these colorspaces apply the same 3D lut, but B then also applies an additional matrix.

Previously, it would not have been possible to compute the processor to go directly from A to B because an inverse 3d lut is needed.
old op chain:   LUT3D (inv) -> LUT3D (forward) -> matrix

However, the new optimizer will detect that the same 3dlut is being applied in a row in both an inverse and forward direction, and they will cancel out! (This works even if the nesting is deep.)

new op chain: matrix

Remaining tasks:
- substantially more unit tests
- matrix concatenation.

-- Jeremy

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