rename to bt709_luminance_or_luma_to_alpha
We conflate luminance (dot of linear r,g,b) and luma (dot of
gamma-encoded r',g',b') all over the place in Skia. This one is
possibly the most confusing of any of them, in that the dot-product
coefficients for BT.709 luma were somewhat arbitrarily chosen to be the
same as the coefficients for luminance.
So, big old ridiculously new long name to make it clear it works
for both luma and luminance, but that it's hardcoded to BT.709.
My quick reference when I forget things:
https://en.wikipedia.org/wiki/Luma_(video)
Change-Id: I5a6567de296795f558acc5dd3c39974b8035234e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226762
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed