Non-inlined call to rgb_to_yuv was costing a lot of perf, do the
calculations inline with a note.
Also tweak the look to scale U,V non-uniformly, similar to previous
scope behavior. Uses the horizontal texture resolution better.
Byte is showing inverted (white-color) overlay, whereas float was
showing overlay as black stripes. Goes back to 16 years ago when VSE
code was added. Looks like an accident, made both show inverted colors.
- RGB -> YUV conversion uses BT709 (just like image vectorscope),
instead of "something similar but not quite".
- It now has square aspect ratio.
- Shows skin tone line, just like image vectorscope.
- Shows full saturation and "safe" saturation range as filled area,
drawing that on the GPU instead of poking in the full saturation
ring on the CPU into the texture.
Aras Pranckevicius