Alpha channel in BitmapColor - change bIndex to alpha

We want to store the alpha channel in BitmapColor. To achieve this
we can repurpose bIndex attribute for alpha. Generally we don't
need bIndex at all as we can infer if we use index colors or not
from the context (using palette or not)

Change-Id: I18fe748beeca59e2869368a1c3c2ee9d2062b41e
Reviewed-on: https://gerrit.libreoffice.org/61057
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

6 files changed, 76 insertions, 66 deletions

diff --git a/include/vcl/alpha.hxx b/include/vcl/alpha.hxx
index b1133b967957..b4ec04de031a 100644
--- a/include/vcl/alpha.hxx
+++ b/include/vcl/alpha.hxx
@@ -69,6 +69,8 @@ public:
     typedef vcl::ScopedBitmapAccess< BitmapReadAccess, AlphaMask, &AlphaMask::AcquireReadAccess >
         ScopedReadAccess;
 
+    using Bitmap::IsEmpty;
+
 private:
     friend class BitmapEx;
     friend class ::OutputDevice;
diff --git a/include/vcl/salbtype.hxx b/include/vcl/salbtype.hxx
index b965fa333c08..ac2f283e7172 100644
--- a/include/vcl/salbtype.hxx
+++ b/include/vcl/salbtype.hxx
@@ -94,20 +94,19 @@ private:
     sal_uInt8               mcBlueOrIndex;
     sal_uInt8               mcGreen;
     sal_uInt8               mcRed;
-    bool                    mbIndex;
+    sal_uInt8               mcAlpha;
 
 public:
 
     inline              BitmapColor();
-    constexpr           BitmapColor( sal_uInt8 cRed, sal_uInt8 cGreen, sal_uInt8 cBlue );
+    constexpr           BitmapColor( sal_uInt8 cRed, sal_uInt8 cGreen, sal_uInt8 cBlue, sal_uInt8 cAlpha = 0 );
+
     inline              BitmapColor( const Color& rColor );
     explicit inline     BitmapColor( sal_uInt8 cIndex );
 
     inline bool         operator==( const BitmapColor& rBitmapColor ) const;
     inline bool         operator!=( const BitmapColor& rBitmapColor ) const;
 
-    inline bool         IsIndex() const;
-
     inline sal_uInt8    GetRed() const;
     inline void         SetRed( sal_uInt8 cRed );
 
@@ -122,6 +121,9 @@ public:
 
     Color               GetColor() const;
 
+    inline sal_uInt8    GetAlpha() const;
+    inline void         SetAlpha( sal_uInt8 cAlpha );
+
     inline sal_uInt8    GetBlueOrIndex() const;
 
     inline BitmapColor& Invert();
@@ -137,7 +139,7 @@ template<typename charT, typename traits>
 inline std::basic_ostream<charT, traits>& operator <<(std::basic_ostream<charT, traits>& rStream, const BitmapColor& rColor)
 {
     return rStream << "mcBlueOrIndex: " << static_cast<int>(rColor.GetBlueOrIndex()) << ", mcGreen: "
-        << static_cast<int>(rColor.GetGreen()) << ", mcRed: " << static_cast<int>(rColor.GetRed()) << ", mbIndex: " << static_cast<int>(rColor.IsIndex());
+        << static_cast<int>(rColor.GetGreen()) << ", mcRed: " << static_cast<int>(rColor.GetRed()) << ", mcAlpha: " << static_cast<int>(rColor.GetAlpha());
 }
 
 class Palette;
@@ -350,18 +352,18 @@ VCL_DLLPUBLIC std::unique_ptr<BitmapBuffer> StretchAndConvert(
     ScanlineFormat nDstBitmapFormat, const BitmapPalette* pDstPal = nullptr, const ColorMask* pDstMask = nullptr );
 
 inline BitmapColor::BitmapColor() :
-            mcBlueOrIndex   ( 0 ),
-            mcGreen         ( 0 ),
-            mcRed           ( 0 ),
-            mbIndex         (false)
+            mcBlueOrIndex   (0),
+            mcGreen         (0),
+            mcRed           (0),
+            mcAlpha         (0)
 {
 }
 
-constexpr BitmapColor::BitmapColor( sal_uInt8 cRed, sal_uInt8 cGreen, sal_uInt8 cBlue ) :
+constexpr BitmapColor::BitmapColor(sal_uInt8 cRed, sal_uInt8 cGreen, sal_uInt8 cBlue, sal_uInt8 cAlpha) :
             mcBlueOrIndex   ( cBlue ),
             mcGreen         ( cGreen ),
             mcRed           ( cRed ),
-            mbIndex         (false)
+            mcAlpha         ( cAlpha )
 {
 }
 
@@ -369,7 +371,7 @@ inline BitmapColor::BitmapColor( const Color& rColor ) :
             mcBlueOrIndex   ( rColor.GetBlue() ),
             mcGreen         ( rColor.GetGreen() ),
             mcRed           ( rColor.GetRed() ),
-            mbIndex         (false)
+            mcAlpha         ( rColor.GetTransparency() )
 {
 }
 
@@ -377,15 +379,16 @@ inline BitmapColor::BitmapColor( sal_uInt8 cIndex ) :
             mcBlueOrIndex   ( cIndex ),
             mcGreen         ( 0 ),
             mcRed           ( 0 ),
-            mbIndex         (true)
+            mcAlpha         ( 0 )
 {
 }
 
 inline bool BitmapColor::operator==( const BitmapColor& rBitmapColor ) const
 {
-    return( ( mcBlueOrIndex == rBitmapColor.mcBlueOrIndex ) &&
-            ( mbIndex ? rBitmapColor.mbIndex :
-            ( mcGreen == rBitmapColor.mcGreen && mcRed == rBitmapColor.mcRed ) ) );
+    return mcBlueOrIndex == rBitmapColor.mcBlueOrIndex &&
+           mcGreen == rBitmapColor.mcGreen &&
+           mcRed == rBitmapColor.mcRed &&
+           mcAlpha == rBitmapColor.mcAlpha;
 }
 
 inline bool BitmapColor::operator!=( const BitmapColor& rBitmapColor ) const
@@ -393,63 +396,59 @@ inline bool BitmapColor::operator!=( const BitmapColor& rBitmapColor ) const
     return !( *this == rBitmapColor );
 }
 
-inline bool BitmapColor::IsIndex() const
-{
-    return mbIndex;
-}
-
 inline sal_uInt8 BitmapColor::GetRed() const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     return mcRed;
 }
 
 inline void BitmapColor::SetRed( sal_uInt8 cRed )
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     mcRed = cRed;
 }
 
 inline sal_uInt8 BitmapColor::GetGreen() const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     return mcGreen;
 }
 
 inline void BitmapColor::SetGreen( sal_uInt8 cGreen )
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     mcGreen = cGreen;
 }
 
 inline sal_uInt8 BitmapColor::GetBlue() const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     return mcBlueOrIndex;
 }
 
 inline void BitmapColor::SetBlue( sal_uInt8 cBlue )
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     mcBlueOrIndex = cBlue;
 }
 
 inline sal_uInt8 BitmapColor::GetIndex() const
 {
-    assert( mbIndex && "Pixel represents color values" );
     return mcBlueOrIndex;
 }
 
 inline void BitmapColor::SetIndex( sal_uInt8 cIndex )
 {
-    assert( mbIndex && "Pixel represents color values" );
     mcBlueOrIndex = cIndex;
 }
 
 inline Color BitmapColor::GetColor() const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
-    return Color(mcRed, mcGreen, mcBlueOrIndex);
+    return Color(mcAlpha, mcRed, mcGreen, mcBlueOrIndex);
+}
+
+inline sal_uInt8 BitmapColor::GetAlpha() const
+{
+    return mcAlpha;
+}
+
+inline void BitmapColor::SetAlpha( sal_uInt8 cAlpha )
+{
+    mcAlpha = cAlpha;
 }
 
 inline sal_uInt8 BitmapColor::GetBlueOrIndex() const
@@ -460,7 +459,6 @@ inline sal_uInt8 BitmapColor::GetBlueOrIndex() const
 
 inline BitmapColor& BitmapColor::Invert()
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     mcBlueOrIndex = ~mcBlueOrIndex;
     mcGreen = ~mcGreen;
     mcRed = ~mcRed;
@@ -470,7 +468,6 @@ inline BitmapColor& BitmapColor::Invert()
 
 inline sal_uInt8 BitmapColor::GetLuminance() const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
     return (static_cast<sal_uInt32>(mcBlueOrIndex) * 28
             + static_cast<sal_uInt32>(mcGreen) * 151
             + static_cast<sal_uInt32>(mcRed) * 77) >> 8;
@@ -479,8 +476,6 @@ inline sal_uInt8 BitmapColor::GetLuminance() const
 
 inline BitmapColor& BitmapColor::Merge( const BitmapColor& rBitmapColor, sal_uInt8 cTransparency )
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
-    assert( !rBitmapColor.mbIndex && "Pixel represents index into colortable" );
     mcBlueOrIndex = ColorChannelMerge( mcBlueOrIndex, rBitmapColor.mcBlueOrIndex, cTransparency );
     mcGreen = ColorChannelMerge( mcGreen, rBitmapColor.mcGreen, cTransparency );
     mcRed = ColorChannelMerge( mcRed, rBitmapColor.mcRed, cTransparency );
@@ -491,8 +486,6 @@ inline BitmapColor& BitmapColor::Merge( const BitmapColor& rBitmapColor, sal_uIn
 
 inline sal_uInt16 BitmapColor::GetColorError( const BitmapColor& rBitmapColor ) const
 {
-    assert( !mbIndex && "Pixel represents index into colortable" );
-    assert( !rBitmapColor.mbIndex && "Pixel represents index into colortable" );
     return static_cast<sal_uInt16>(
         abs( static_cast<int>(mcBlueOrIndex) - static_cast<int>(rBitmapColor.mcBlueOrIndex) ) +
         abs( static_cast<int>(mcGreen) - static_cast<int>(rBitmapColor.mcGreen) ) +
diff --git a/vcl/qa/cppunit/bitmapcolor.cxx b/vcl/qa/cppunit/bitmapcolor.cxx
index 2953c0d0eab8..c8cae6aef973 100644
--- a/vcl/qa/cppunit/bitmapcolor.cxx
+++ b/vcl/qa/cppunit/bitmapcolor.cxx
@@ -35,9 +35,8 @@ public:
     void defaultConstructor();
     void colorValueConstructor();
     void colorClassConstructor();
-
+    void getColor();
     void setValue();
-
     void invert();
     void getLuminance();
 
@@ -45,6 +44,7 @@ public:
     CPPUNIT_TEST(defaultConstructor);
     CPPUNIT_TEST(colorValueConstructor);
     CPPUNIT_TEST(colorClassConstructor);
+    CPPUNIT_TEST(getColor);
     CPPUNIT_TEST(setValue);
     CPPUNIT_TEST(invert);
     CPPUNIT_TEST(getLuminance);
@@ -58,7 +58,7 @@ void BitmapColorTest::defaultConstructor()
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Red wrong", static_cast<sal_uInt8>(0), aBmpColor.GetRed());
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Green wrong", static_cast<sal_uInt8>(0), aBmpColor.GetGreen());
     CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(0), aBmpColor.GetBlue());
-    CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0), aBmpColor.GetAlpha());
 }
 
 void BitmapColorTest::colorValueConstructor()
@@ -70,7 +70,8 @@ void BitmapColorTest::colorValueConstructor()
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Green wrong", static_cast<sal_uInt8>(0),
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(0), aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
     }
 
     {
@@ -81,7 +82,8 @@ void BitmapColorTest::colorValueConstructor()
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(128),
                                      aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
     }
 
     {
@@ -92,7 +94,8 @@ void BitmapColorTest::colorValueConstructor()
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(255),
                                      aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
     }
 }
 
@@ -106,7 +109,8 @@ void BitmapColorTest::colorClassConstructor()
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Green wrong", static_cast<sal_uInt8>(0),
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(0), aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
     }
 
     {
@@ -118,7 +122,8 @@ void BitmapColorTest::colorClassConstructor()
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(127),
                                      aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
     }
 
     {
@@ -130,10 +135,35 @@ void BitmapColorTest::colorClassConstructor()
                                      aBmpColor.GetGreen());
         CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(255),
                                      aBmpColor.GetBlue());
-        CPPUNIT_ASSERT_EQUAL_MESSAGE("Index wrong", false, aBmpColor.IsIndex());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(0),
+                                     aBmpColor.GetAlpha());
+    }
+
+    // Transparency / Alpha
+    {
+        Color aColor(255, 128, 64, 0);
+        BitmapColor aBmpColor(aColor);
+
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Red wrong", static_cast<sal_uInt8>(128), aBmpColor.GetRed());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Green wrong", static_cast<sal_uInt8>(64),
+                                     aBmpColor.GetGreen());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", static_cast<sal_uInt8>(0), aBmpColor.GetBlue());
+        CPPUNIT_ASSERT_EQUAL_MESSAGE("Alpha wrong", static_cast<sal_uInt8>(255),
+                                     aBmpColor.GetAlpha());
     }
 }
 
+void BitmapColorTest::getColor()
+{
+    BitmapColor aBitmapColor(255, 128, 64, 32);
+    Color aColor = aBitmapColor.GetColor();
+
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Red wrong", sal_uInt8(255), aColor.GetRed());
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Green wrong", sal_uInt8(128), aColor.GetGreen());
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Blue wrong", sal_uInt8(64), aColor.GetBlue());
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("Transparecy wrong", sal_uInt8(32), aColor.GetTransparency());
+}
+
 void BitmapColorTest::setValue()
 {
     BitmapColor aBmpColor;
diff --git a/vcl/source/bitmap/BitmapTools.cxx b/vcl/source/bitmap/BitmapTools.cxx
index aaa678b888dd..13a133295b06 100644
--- a/vcl/source/bitmap/BitmapTools.cxx
+++ b/vcl/source/bitmap/BitmapTools.cxx
@@ -652,18 +652,7 @@ css::uno::Sequence< sal_Int8 > GetMaskDIB(BitmapEx const & aBmpEx)
 
 static sal_uInt8 lcl_GetColor(BitmapColor const& rColor)
 {
-    sal_uInt8 nTemp(0);
-    if (rColor.IsIndex())
-    {
-        nTemp = rColor.GetIndex();
-    }
-    else
-    {
-        nTemp = rColor.GetBlue();
-        // greyscale expected here, or what would non-grey colors mean?
-        assert(rColor.GetRed() == nTemp && rColor.GetGreen() == nTemp);
-    }
-    return nTemp;
+    return rColor.GetBlueOrIndex();
 }
 
 
diff --git a/vcl/source/gdi/bmpacc2.cxx b/vcl/source/gdi/bmpacc2.cxx
index 1d7cec5f4c79..25606c09509e 100644
--- a/vcl/source/gdi/bmpacc2.cxx
+++ b/vcl/source/gdi/bmpacc2.cxx
@@ -79,11 +79,7 @@ BitmapColor BitmapReadAccess::GetPixelForN8BitPal(ConstScanline pScanline, long
 
 void BitmapReadAccess::SetPixelForN8BitPal(Scanline pScanline, long nX, const BitmapColor& rBitmapColor, const ColorMask&)
 {
-    if (rBitmapColor.IsIndex())
-        pScanline[ nX ] = rBitmapColor.GetIndex();
-    else
-        // Let's hope that the RGB color values equal, so it doesn't matter what do we pick
-        pScanline[ nX ] = rBitmapColor.GetBlueOrIndex();
+    pScanline[ nX ] = rBitmapColor.GetBlueOrIndex();
 }
 
 BitmapColor BitmapReadAccess::GetPixelForN8BitTcMask(ConstScanline pScanline, long nX, const ColorMask& rMask)
diff --git a/vcl/unx/generic/print/genpspgraphics.cxx b/vcl/unx/generic/print/genpspgraphics.cxx
index f74ecffdb990..88e7fcdf901a 100644
--- a/vcl/unx/generic/print/genpspgraphics.cxx
+++ b/vcl/unx/generic/print/genpspgraphics.cxx
@@ -192,7 +192,7 @@ SalPrinterBmp::GetPixelRGB (sal_uInt32 nRow, sal_uInt32 nColumn) const
     Scanline pScan = mpScanAccess + nRow * mnScanOffset;
     BitmapColor aColor = mpFncGetPixel (pScan, nColumn, mpBmpBuffer->maColorMask);
 
-    if (aColor.IsIndex())
+    if (!!mpBmpBuffer->maPalette)
         GetPaletteColor(aColor.GetIndex());
 
     return ((aColor.GetBlue())        & 0x000000ff)
@@ -206,7 +206,7 @@ SalPrinterBmp::GetPixelGray (sal_uInt32 nRow, sal_uInt32 nColumn) const
     Scanline pScan = mpScanAccess + nRow * mnScanOffset;
     BitmapColor aColor = mpFncGetPixel (pScan, nColumn, mpBmpBuffer->maColorMask);
 
-    if (aColor.IsIndex())
+    if (!!mpBmpBuffer->maPalette)
         aColor = mpBmpBuffer->maPalette[aColor.GetIndex()];
 
     return (  aColor.GetBlue()  *  28UL
@@ -221,7 +221,7 @@ SalPrinterBmp::GetPixelIdx (sal_uInt32 nRow, sal_uInt32 nColumn) const
     Scanline pScan = mpScanAccess + nRow * mnScanOffset;
     BitmapColor aColor = mpFncGetPixel (pScan, nColumn, mpBmpBuffer->maColorMask);
 
-    if (aColor.IsIndex())
+    if (!!mpBmpBuffer->maPalette)
         return aColor.GetIndex();
     else
         return 0;