The order of parameters for vcl::bitmap::premultiply and vcl::bitmap::unpremultiply was wrong because when doing that I just used the same order that the indexing that was to be replaced used it. Corrected that. Change-Id: I59473acca8afdc58105b3381d1fdcedd6c0fd83b Reviewed-on: https://gerrit.libreoffice.org/c/core/+/173683 Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com> Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com> Tested-by: Jenkins