to ease the reading of code related to an upcoming patch to convert
transparency to alpha, since there is already a GetAlpha in Color.
Change-Id: I1af0f8f6dd94acfe4673c8556c7aff6c20da3f7a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/145209
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
