Reland "add getAlphaf() to pixmap/bitmap"
This is a reland of f3ebd312f21325f9afc4479fd7a4e90a32ffb920
PS 2: use faster half->float routine
PS 3: relax tolerance to 2^-10 for half, keeping others 2^-12
Original change's description:
> add getAlphaf() to pixmap/bitmap
>
> Convenient for just extracting alpha (and more efficient than getColor()) and
> works for super-normal formats w/o loss of precision.
>
> Somewhat inspired by examining multiple chrome call-sites for getColor(), where
> chrome only really cared about the alpha. This new method runs about twice
> as fast as getColor() for the simple cases (i.e. no colorspace xforms), and
> even faster in the complex cases (since retrieving alpha doesn't care about
> colorspaces).
>
> Bug: skia:
> Change-Id: I7cd5a2c7f78de781aaa69dd1aa0dba3c532fcb73
> Reviewed-on: https://skia-review.googlesource.com/155606
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>
Cq-Include-Trybots: skia.primary:Test-Android-Clang-Nexus7-CPU-Tegra3-arm-Debug-All-Android,Test-Debian9-Clang-GCE-CPU-AVX2-x86_64-Release-All-SK_CPU_LIMIT_SSE2,Test-Debian9-GCC-GCE-CPU-AVX2-x86_64-Release-All,Test-Win2016-MSVC-GCE-CPU-AVX2-x86_64-Release-All,Test-Win8-Clang-Golo-CPU-AVX-x86_64-Debug-All
Bug: skia:
Change-Id: Ie94e5c89e185fde12cbd6c56ed4026c4dc5a1623
Reviewed-on: https://skia-review.googlesource.com/156242
Commit-Queue: Ravi Mistry <rmistry@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
5 files changed