[Libreoffice-commits] core.git: canvas/source vcl/source

[Thorsten Behrens (via logerrit)]

 canvas/source/vcl/spritehelper.cxx |    6 ++++--
 vcl/source/bitmap/alpha.cxx        |    4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

New commits:
commit ad1f69d28d31725a22e7e1cbb4d950aa9ad3bea7
Author:     Thorsten Behrens <thorsten.behr...@allotropia.de>
AuthorDate: Sun Aug 6 01:19:17 2023 +0200
Commit:     Noel Grandin <noel.gran...@collabora.co.uk>
CommitDate: Sun Aug 6 12:23:07 2023 +0200

    tdf#156540 invert alpha mask when drawing sprites
    
    Due to the switch from transparency to alpha in commit
    81994cb2b8b32453a92bcb011830fcb884f22ff3, a sprite's
    alpha mask needs to be inverted.
    
    Additionally, fixes an oversight in vcl's alpha.cxx, where manual
    blend math got mangled, also in
    81994cb2b8b32453a92bcb011830fcb884f22ff3.
    
    Change-Id: I8ebbbc7fe624d8dfc8121d8814d30875c498870d
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155378
    Reviewed-by: Patrick Luby <plub...@neooffice.org>
    Tested-by: Jenkins
    Reviewed-by: Noel Grandin <noel.gran...@collabora.co.uk>

diff --git a/canvas/source/vcl/spritehelper.cxx 
b/canvas/source/vcl/spritehelper.cxx
index 3494a5fbda8f..f188526930a0 100644
--- a/canvas/source/vcl/spritehelper.cxx
+++ b/canvas/source/vcl/spritehelper.cxx
@@ -134,12 +134,14 @@ namespace vclcanvas
                 // sprite content might contain alpha, create
                 // BmpEx, then.
                 BitmapEx aMask( mpBackBufferMask->getOutDev().GetBitmapEx( 
aEmptyPoint,
-                                                                       
aOutputSize ) );
+                                                                           
aOutputSize ) );
+                AlphaMask aAlpha( aMask.GetBitmap() );
+                aAlpha.Invert();
 
                 // Note: since we retrieved aBmp and aMask
                 // directly from an OutDev, it's already a
                 // 'display bitmap' on windows.
-                maContent = BitmapEx( aBmp.GetBitmap(), AlphaMask( 
aMask.GetBitmap()) );
+                maContent = BitmapEx( aBmp.GetBitmap(), aAlpha );
             }
         }
 
diff --git a/vcl/source/bitmap/alpha.cxx b/vcl/source/bitmap/alpha.cxx
index 8e082c695137..ff0d035d52d1 100644
--- a/vcl/source/bitmap/alpha.cxx
+++ b/vcl/source/bitmap/alpha.cxx
@@ -118,8 +118,8 @@ void AlphaMask::BlendWith(const AlphaMask& rOther)
             // Awkward calculation because the original used transparency, and 
to replicate
             // the logic we need to translate into transparency, perform the 
original logic,
             // then translate back to alpha.
-            auto tmp = 255 - ((255 - nGrey1) + (255 - nGrey2) - (255 - nGrey1) 
* (255 - nGrey2));
-            *scanline = static_cast<sal_uInt8>(tmp / 255);
+            auto tmp = 255 - ((255 - nGrey1) + (255 - nGrey2) - (255 - nGrey1) 
* (255 - nGrey2) / 255);
+            *scanline = static_cast<sal_uInt8>(tmp);
             ++scanline;
             ++otherScanline;
         }