vcl: add "color channel bitcount" for an bitmap buffer (Linux)

In addition to "bitcount" on bitmap buffer, which represents the
number of bits one pixel takes, we also need the bitcount that the
color channels take of one pixel take.

For example RGB can be contined in 32 bits (because that the
underlaying buffer supports) In this case GetBitCount returns
32bit so we can traverse the buffer correctly. However, we also
need to know the bitcount of the actual color channels - in this
case this would be 24 bits.

Change-Id: I0a64928336540dc66d60659c46d64f369e786c3a

9 files changed, 43 insertions, 12 deletions

diff --git a/include/vcl/salbtype.hxx b/include/vcl/salbtype.hxx
index 04baf9095b9b..25f4159ad41e 100644
--- a/include/vcl/salbtype.hxx
+++ b/include/vcl/salbtype.hxx
@@ -267,7 +267,18 @@ struct VCL_DLLPUBLIC BitmapBuffer
     long            mnWidth;
     long            mnHeight;
     long            mnScanlineSize;
+
+    /**
+     * Bitcount of one pixel in the buffer.
+     * color + alpha channels with padding (for example in an RGBX format)
+     */
     sal_uInt16      mnBitCount;
+
+    /**
+     * Bitcount color channels of one pixel.
+     * color + alpha channels only (i.e. 8, 16, 24, 32)
+     */
+    sal_uInt16      mnColorChannelBitCount;
     ColorMask       maColorMask;
     BitmapPalette   maPalette;
     sal_uInt8*      mpBits;
diff --git a/vcl/headless/svpbmp.cxx b/vcl/headless/svpbmp.cxx
index 202d63c0a84e..1dc6c19827a4 100644
--- a/vcl/headless/svpbmp.cxx
+++ b/vcl/headless/svpbmp.cxx
@@ -70,6 +70,7 @@ BitmapBuffer* ImplCreateDIB(
         {
             const sal_uInt16 nColors = ( nBitCount <= 8 ) ? ( 1 << nBitCount ) : 0;
 
+            pDIB->mnColorChannelBitCount = nBitCount;
             switch (nBitCount)
             {
                 case 1:
@@ -229,16 +230,14 @@ Size SvpSalBitmap::GetSize() const
     return aSize;
 }
 
-sal_uInt16 SvpSalBitmap::GetBitCount() const
+sal_uInt16 SvpSalBitmap::GetColorChannelBitCount() const
 {
-    sal_uInt16 nBitCount;
-
-    if (mpDIB)
-        nBitCount = mpDIB->mnBitCount;
-    else
-        nBitCount = 0;
+    return (mpDIB) ? mpDIB->mnColorChannelBitCount : 0;
+}
 
-    return nBitCount;
+sal_uInt16 SvpSalBitmap::GetBitCount() const
+{
+    return (mpDIB) ? mpDIB->mnBitCount : 0;
 }
 
 BitmapBuffer* SvpSalBitmap::AcquireBuffer(BitmapAccessMode)
diff --git a/vcl/inc/headless/svpbmp.hxx b/vcl/inc/headless/svpbmp.hxx
index af50ecff6cf5..8e90399fe4ea 100644
--- a/vcl/inc/headless/svpbmp.hxx
+++ b/vcl/inc/headless/svpbmp.hxx
@@ -52,6 +52,7 @@ public:
     virtual void            Destroy() final override;
     virtual Size            GetSize() const override;
     virtual sal_uInt16      GetBitCount() const override;
+    virtual sal_uInt16      GetColorChannelBitCount() const override;
 
     virtual BitmapBuffer*   AcquireBuffer( BitmapAccessMode nMode ) override;
     virtual void            ReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMode ) override;
diff --git a/vcl/inc/opengl/salbmp.hxx b/vcl/inc/opengl/salbmp.hxx
index d10129ce8d0c..4579e34c06c6 100644
--- a/vcl/inc/opengl/salbmp.hxx
+++ b/vcl/inc/opengl/salbmp.hxx
@@ -68,6 +68,7 @@ public:
 
     Size            GetSize() const override;
     sal_uInt16      GetBitCount() const override;
+    sal_uInt16      GetColorChannelBitCount() const override;
 
     BitmapBuffer*   AcquireBuffer( BitmapAccessMode nMode ) override;
     void            ReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMode ) override;
diff --git a/vcl/inc/salbmp.hxx b/vcl/inc/salbmp.hxx
index 69d25392a448..91e4e5c1031e 100644
--- a/vcl/inc/salbmp.hxx
+++ b/vcl/inc/salbmp.hxx
@@ -61,6 +61,7 @@ public:
     virtual void            Destroy() = 0;
     virtual Size            GetSize() const = 0;
     virtual sal_uInt16      GetBitCount() const = 0;
+    virtual sal_uInt16      GetColorChannelBitCount() const = 0;
 
     virtual BitmapBuffer*   AcquireBuffer( BitmapAccessMode nMode ) = 0;
     virtual void            ReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMode ) = 0;
diff --git a/vcl/inc/unx/salbmp.h b/vcl/inc/unx/salbmp.h
index 81998ba35bea..a1cc20c45a35 100644
--- a/vcl/inc/unx/salbmp.h
+++ b/vcl/inc/unx/salbmp.h
@@ -139,6 +139,7 @@ public:
 
     virtual Size                GetSize() const override;
     virtual sal_uInt16          GetBitCount() const override;
+    virtual sal_uInt16          GetColorChannelBitCount() const override;
 
     virtual BitmapBuffer*       AcquireBuffer( BitmapAccessMode nMode ) override;
     virtual void                ReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMode ) override;
diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index 9fb8c474818b..d2eb8f23828d 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -627,6 +627,11 @@ sal_uInt16 OpenGLSalBitmap::GetBitCount() const
     return mnBits;
 }
 
+sal_uInt16 OpenGLSalBitmap::GetColorChannelBitCount() const
+{
+    return mnBits;
+}
+
 bool OpenGLSalBitmap::calcChecksumGL(OpenGLTexture& rInputTexture, ChecksumType& rChecksum) const
 {
     OUString FragShader("areaHashCRC64TFragmentShader");
diff --git a/vcl/source/gdi/impbmp.cxx b/vcl/source/gdi/impbmp.cxx
index ab06a712d0e1..e232b5046d1f 100644
--- a/vcl/source/gdi/impbmp.cxx
+++ b/vcl/source/gdi/impbmp.cxx
@@ -73,9 +73,15 @@ Size ImpBitmap::ImplGetSize() const
 
 sal_uInt16 ImpBitmap::ImplGetBitCount() const
 {
-    sal_uInt16 nBitCount = mpSalBitmap->GetBitCount();
-    return ( nBitCount <= 4 ) ? ( ( nBitCount <= 1 ) ? 1 : 4 ):
-                                ( ( nBitCount <= 8 ) ? 8 : 24);
+    sal_uInt16 nBitCount = mpSalBitmap->GetColorChannelBitCount();
+    if (nBitCount <= 1)
+        return 1;
+    else if (nBitCount <= 4)
+        return 4;
+    else if (nBitCount <= 8)
+        return 8;
+    else
+        return 24;
 }
 
 BitmapBuffer* ImpBitmap::ImplAcquireBuffer( BitmapAccessMode nMode )
diff --git a/vcl/unx/generic/gdi/salbmp.cxx b/vcl/unx/generic/gdi/salbmp.cxx
index 158a2f52d0fc..844c9c749b4c 100644
--- a/vcl/unx/generic/gdi/salbmp.cxx
+++ b/vcl/unx/generic/gdi/salbmp.cxx
@@ -148,7 +148,7 @@ BitmapBuffer* X11SalBitmap::ImplCreateDIB(
         if( pDIB )
         {
             const sal_uInt16 nColors = ( nBitCount <= 8 ) ? ( 1 << nBitCount ) : 0;
-
+            pDIB->mnColorChannelBitCount = nBitCount;
             pDIB->mnFormat = ScanlineFormat::NONE;
 
             switch( nBitCount )
@@ -259,6 +259,7 @@ BitmapBuffer* X11SalBitmap::ImplCreateDIB(
             aSrcBuf.mnWidth = nWidth;
             aSrcBuf.mnHeight = nHeight;
             aSrcBuf.mnBitCount = pImage->bits_per_pixel;
+            aSrcBuf.mnColorChannelBitCount = aSrcBuf.mnBitCount;
             aSrcBuf.mnScanlineSize = pImage->bytes_per_line;
             aSrcBuf.mpBits = reinterpret_cast<sal_uInt8*>(pImage->data);
 
@@ -847,6 +848,11 @@ sal_uInt16 X11SalBitmap::GetBitCount() const
     return nBitCount;
 }
 
+sal_uInt16 X11SalBitmap::GetColorChannelBitCount() const
+{
+    return GetBitCount();
+}
+
 BitmapBuffer* X11SalBitmap::AcquireBuffer( BitmapAccessMode /*nMode*/ )
 {
     if( !mpDIB && mpDDB )