tdf#161833 treat semi-transparent pixels as opaque

Limiting the contour wrapping polygon to only opaque pixels
causes clipping of any shadows or other semi-transaprent
areas in the image. So, instead of testing for fully opaque
pixels, treat pixels that are not fully transparent as opaque.

Also, tdf#161833 would cause semi-transparent pixels to be
treated as fully transparent pixels when calculating the wrap
contour for an image. To force the correct contour when loading
a document, force the contour to be recalculated by ignoring
the saved polygon if the contour is set to "recreate on edit".

Change-Id: Ibe256f54e1c82de30c2b7d5b92a69344b4a7ba10
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/169745
Reviewed-by: Patrick Luby <guibomacdev@gmail.com>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins

2 files changed, 26 insertions, 16 deletions

diff --git a/vcl/source/bitmap/BitmapEx.cxx b/vcl/source/bitmap/BitmapEx.cxx
index ebcb7aa1cb9a..c541579744b0 100644
--- a/vcl/source/bitmap/BitmapEx.cxx
+++ b/vcl/source/bitmap/BitmapEx.cxx
@@ -1286,11 +1286,12 @@ tools::Polygon  BitmapEx::GetContour( bool bContourEdgeDetect,
             std::unique_ptr<Point[]> pPoints2;
             tools::Long                nX, nY;
             sal_uInt16              nPolyPos = 0;
-            // tdf#161498 use COL_ALPHA_OPAQUE for finding opaque pixels
-            // Starting with commit 81994cb2b8b32453a92bcb011830fcb884f22ff3,
-            // pixels now contain an alpha value instead of a transparency
-            // value.
-            const BitmapColor   aTransparencyOpaque = pAcc->GetBestMatchingColor( COL_ALPHA_OPAQUE );
+            // tdf#161833 treat semi-transparent pixels as opaque
+            // Limiting the contour wrapping polygon to only opaque pixels
+            // causes clipping of any shadows or other semi-transaprent
+            // areas in the image. So, instead of testing for fully opaque
+            // pixels, treat pixels that are not fully transparent as opaque.
+            const BitmapColor   aTransparent = pAcc->GetBestMatchingColor( COL_ALPHA_TRANSPARENT );
 
             pPoints1.reset(new Point[ nHeight ]);
             pPoints2.reset(new Point[ nHeight ]);
@@ -1303,7 +1304,7 @@ tools::Polygon  BitmapEx::GetContour( bool bContourEdgeDetect,
                 // scan row from left to right
                 while( nX < nEndX1 )
                 {
-                    if( aTransparencyOpaque == pAcc->GetPixelFromData( pScanline, nX ) )
+                    if( aTransparent != pAcc->GetPixelFromData( pScanline, nX ) )
                     {
                         pPoints1[ nPolyPos ] = Point( nX, nY );
                         nX = nStartX2;
@@ -1311,7 +1312,7 @@ tools::Polygon  BitmapEx::GetContour( bool bContourEdgeDetect,
                         // this loop always breaks eventually as there is at least one pixel
                         while( true )
                         {
-                            if( aTransparencyOpaque == pAcc->GetPixelFromData( pScanline, nX ) )
+                            if( aTransparent != pAcc->GetPixelFromData( pScanline, nX ) )
                             {
                                 pPoints2[ nPolyPos ] = Point( nX, nY );
                                 break;
diff --git a/xmloff/source/text/XMLTextFrameContext.cxx b/xmloff/source/text/XMLTextFrameContext.cxx
index 87752f73b199..5c293c7670c2 100644
--- a/xmloff/source/text/XMLTextFrameContext.cxx
+++ b/xmloff/source/text/XMLTextFrameContext.cxx
@@ -271,17 +271,26 @@ XMLTextFrameContourContext_Impl::XMLTextFrameContourContext_Impl(
     const SdXMLImExViewBox aViewBox( sViewBox, GetImport().GetMM100UnitConverter());
     basegfx::B2DPolyPolygon aPolyPolygon;
 
-    if( bPath )
+    // Related tdf#161833: ignore saved polygon for "recreate on edit" contours
+    // tdf#161833 would cause semi-transparent pixels to be treated as fully
+    // transparent pixels when calculating the wrap contour for an image. To
+    // force the correct contour when loading a document, force the contour
+    // to be recalculated by ignoring the saved polygon if the contour is set
+    // to "recreate on edit".
+    if( !bAuto )
     {
-        basegfx::utils::importFromSvgD(aPolyPolygon, sD, GetImport().needFixPositionAfterZ(), nullptr);
-    }
-    else
-    {
-        basegfx::B2DPolygon aPolygon;
-
-        if(basegfx::utils::importFromSvgPoints(aPolygon, sPoints))
+        if( bPath )
         {
-            aPolyPolygon = basegfx::B2DPolyPolygon(aPolygon);
+            basegfx::utils::importFromSvgD(aPolyPolygon, sD, GetImport().needFixPositionAfterZ(), nullptr);
+        }
+        else
+        {
+            basegfx::B2DPolygon aPolygon;
+
+            if(basegfx::utils::importFromSvgPoints(aPolygon, sPoints))
+            {
+                aPolyPolygon = basegfx::B2DPolyPolygon(aPolygon);
+            }
         }
     }