move pixel color extracting from canvas to BitmapEx

part of making GetAlpha/GetMask an internal detail of vcl

Change-Id: I874a68f340cd3074cfbeb6303f52adeeb13e56a5
Reviewed-on: https://gerrit.libreoffice.org/51435
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

3 files changed, 35 insertions, 16 deletions

diff --git a/canvas/source/vcl/canvasbitmaphelper.cxx b/canvas/source/vcl/canvasbitmaphelper.cxx
index c2003f6a67cf..eef6258dded3 100644
--- a/canvas/source/vcl/canvasbitmaphelper.cxx
+++ b/canvas/source/vcl/canvasbitmaphelper.cxx
@@ -194,28 +194,14 @@ namespace vclcanvas
         ENSURE_ARG_OR_THROW( pos.Y >= 0 && pos.Y < aBmpSize.Height(),
                          "Y coordinate out of bounds" );
 
-        Bitmap aBitmap( mpBackBuffer->getBitmapReference().GetBitmap() );
-        Bitmap aAlpha( mpBackBuffer->getBitmapReference().GetAlpha().GetBitmap() );
-
-        Bitmap::ScopedReadAccess pReadAccess( aBitmap );
-        Bitmap::ScopedReadAccess pAlphaReadAccess( aAlpha.IsEmpty() ?
-                                                 nullptr : aAlpha.AcquireReadAccess(),
-                                                 aAlpha );
-        ENSURE_OR_THROW( pReadAccess.get() != nullptr,
-                         "Could not acquire read access to bitmap" );
+        ::Color aColor = mpBackBuffer->getBitmapReference().GetPixelColor(pos.X, pos.Y);
 
         uno::Sequence< sal_Int8 > aRes( 4 );
         sal_Int8* pRes = aRes.getArray();
-
-        const BitmapColor aColor( pReadAccess->GetColor( pos.Y, pos.X ) );
         pRes[ 0 ] = aColor.GetRed();
         pRes[ 1 ] = aColor.GetGreen();
         pRes[ 2 ] = aColor.GetBlue();
-
-        if( pAlphaReadAccess.get() != nullptr )
-            pRes[ 3 ] = pAlphaReadAccess->GetPixel( pos.Y, pos.X ).GetIndex();
-        else
-            pRes[ 3 ] = sal_uInt8(255);
+        pRes[ 3 ] = aColor.GetTransparency();
 
         return aRes;
     }
diff --git a/include/vcl/bitmapex.hxx b/include/vcl/bitmapex.hxx
index d78f273b21ad..c61969869b33 100644
--- a/include/vcl/bitmapex.hxx
+++ b/include/vcl/bitmapex.hxx
@@ -378,6 +378,18 @@ public:
                             sal_Int32 nX,
                             sal_Int32 nY) const;
 
+    /** Get pixel color (including alpha) at given position
+
+        @param nX
+        integer X-Position in Bitmap
+
+        @param nY
+        integer Y-Position in Bitmap
+     */
+    ::Color             GetPixelColor(
+                            sal_Int32 nX,
+                            sal_Int32 nY) const;
+
     /** Create transformed Bitmap
 
         @param fWidth
diff --git a/vcl/source/gdi/bitmapex.cxx b/vcl/source/gdi/bitmapex.cxx
index 14b3fa17efd6..dba603347679 100644
--- a/vcl/source/gdi/bitmapex.cxx
+++ b/vcl/source/gdi/bitmapex.cxx
@@ -769,6 +769,27 @@ sal_uInt8 BitmapEx::GetTransparency(sal_Int32 nX, sal_Int32 nY) const
     return nTransparency;
 }
 
+
+Color BitmapEx::GetPixelColor(sal_Int32 nX, sal_Int32 nY) const
+{
+        Bitmap aAlpha( GetAlpha().GetBitmap() );
+
+        Bitmap aTestBitmap(maBitmap);
+        Bitmap::ScopedReadAccess pReadAccess( aTestBitmap );
+        assert( pReadAccess );
+
+        Color aColor = pReadAccess->GetColor( nY, nX ).GetColor();
+
+        if (!aAlpha.IsEmpty())
+        {
+            Bitmap::ScopedReadAccess pAlphaReadAccess( aAlpha.AcquireReadAccess(), aAlpha );
+            aColor.SetTransparency( pAlphaReadAccess->GetPixel( nY, nX ).GetIndex() );
+        }
+        else
+            aColor.SetTransparency(255);
+        return aColor;
+}
+
 // Shift alpha transparent pixels between cppcanvas/ implementations
 // and vcl in a generally grotesque and under-performing fashion
 bool BitmapEx::Create( const css::uno::Reference< css::rendering::XBitmapCanvas > &xBitmapCanvas,