optimize AlphaMask::BlendWith()

It shows up in profiling in some cases (e.g. tdf#134160).
- If it's 8-bit, simply work on scanlines instead of pixel by pixel.
- The extra precision from using floats doesn't matter and the round()
  costs something (at least with MSVC).

Change-Id: I37bbe31fae03d61946a7382de1fb79cfe2d2ec30
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97010
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>
(cherry picked from commit a3ef92cfb512ce70c7dc48f7957b40f9f78f5628)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97005
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>

0 files changed, 0 insertions, 0 deletions