now that Bitmap can handle transparency Also add a utility method Bitmap::GetPixelColor, to use in unit test code. One of the unit tests needed tweaking because we are converting back and forth a few times which adds some inaccuracy. Change-Id: I760c7da8845488e547b16ed243819fe3288b0985 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/188537 Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk> Tested-by: Jenkins