differentiate between 8bit and any-bit grey palette (tdf#121120)

Only the grey palette with 256 colors means that pixel values map
directly to color values. Tdf#121120 has an image with 2-bit
palette where color index 1 is (255,255,255), but that means
the pixel value 1 cannot be just treated as color.

Change-Id: Ifbd953af7f291e4fb8032ea0f4c33c0514770856
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97283
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

14 files changed, 64 insertions, 24 deletions

diff --git a/include/vcl/BitmapPalette.hxx b/include/vcl/BitmapPalette.hxx
index ba6ef09af9f4..9a2d08d4dccb 100644
--- a/include/vcl/BitmapPalette.hxx
+++ b/include/vcl/BitmapPalette.hxx
@@ -128,7 +128,10 @@ public:
         return nRetIndex;
     }
 
-    bool IsGreyPalette() const;
+    /// Returns true if the palette is 8-bit grey palette.
+    bool IsGreyPalette8Bit() const;
+    /// Returns true if the paleete is a grey palette (may not be 8-bit).
+    bool IsGreyPaletteAny() const;
 };
 
 #endif // INCLUDED_VCL_BITMAPPALETTE_HXX
diff --git a/include/vcl/bitmap.hxx b/include/vcl/bitmap.hxx
index 742e7a3a56f8..9ed602942322 100644
--- a/include/vcl/bitmap.hxx
+++ b/include/vcl/bitmap.hxx
@@ -133,7 +133,8 @@ public:
     sal_uInt16              GetBitCount() const;
     inline sal_Int64        GetColorCount() const;
     inline sal_uLong        GetSizeBytes() const;
-    bool                    HasGreyPalette() const;
+    bool                    HasGreyPalette8Bit() const;
+    bool                    HasGreyPaletteAny() const;
     /** get system dependent bitmap data
 
         @param rData
diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index cd3a56a7ae00..e9b1bca73665 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -356,6 +356,13 @@ GLuint OpenGLSalBitmap::CreateTexture()
 
             determineTextureFormat(mnBits, nFormat, nType);
         }
+        else if( mnBits == 8 && maPalette.IsGreyPalette8Bit() )
+        {
+            // no conversion needed for 8bit grayscale
+            pData = mpUserBuffer.get();
+            nFormat = GL_LUMINANCE;
+            nType = GL_UNSIGNED_BYTE;
+        }
         else
         {
             VCL_GL_INFO( "::CreateTexture - convert from " << mnBits << " to 24 bits" );
@@ -401,7 +408,7 @@ bool OpenGLSalBitmap::ReadTexture()
     xContext->state().scissor().disable();
     xContext->state().stencil().disable();
 
-    if ((mnBits == 8 && maPalette.IsGreyPalette()) || mnBits == 24 || mnBits == 32)
+    if ((mnBits == 8 && maPalette.IsGreyPalette8Bit()) || mnBits == 24 || mnBits == 32)
     {
         determineTextureFormat(mnBits, nFormat, nType);
 
@@ -730,7 +737,7 @@ bool OpenGLSalBitmap::ConvertToGreyscale()
     VCL_GL_INFO("::ConvertToGreyscale");
 
     // avoid re-converting to 8bits.
-    if ( mnBits == 8 && maPalette == Bitmap::GetGreyPalette(256) )
+    if ( mnBits == 8 && maPalette.IsGreyPalette8Bit())
         return true;
 
     OpenGLZone aZone;
diff --git a/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx b/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
index 71bfc40265b5..73e3baab91a3 100644
--- a/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
+++ b/vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx
@@ -248,7 +248,7 @@ void BitmapRenderTest::testTdf116888()
     CPPUNIT_ASSERT(pAccess);
     const ScanlineFormat eFormat = pAccess->GetScanlineFormat();
     CPPUNIT_ASSERT_EQUAL(ScanlineFormat::N8BitPal, eFormat);
-    CPPUNIT_ASSERT(!aBitmap.HasGreyPalette());
+    CPPUNIT_ASSERT(!aBitmap.HasGreyPaletteAny());
     // HACK: Some rendering backends change white to #FEFEFE while scaling for some reason.
     // That is pretty much white too in practice, so adjust for that.
     BitmapColor white(COL_WHITE);
diff --git a/vcl/qa/cppunit/jpeg/JpegWriterTest.cxx b/vcl/qa/cppunit/jpeg/JpegWriterTest.cxx
index fc06256c5f86..b4d9d24603eb 100644
--- a/vcl/qa/cppunit/jpeg/JpegWriterTest.cxx
+++ b/vcl/qa/cppunit/jpeg/JpegWriterTest.cxx
@@ -71,7 +71,7 @@ void JpegWriterTest::testWrite8BitGrayscale()
     const ScanlineFormat format = access->GetScanlineFormat();
     // Check that it's still 8bit grayscale.
     CPPUNIT_ASSERT_EQUAL(ScanlineFormat::N8BitPal, format);
-    CPPUNIT_ASSERT(bitmap.HasGreyPalette());
+    CPPUNIT_ASSERT(bitmap.HasGreyPalette8Bit());
     // Check that the content is valid.
     CPPUNIT_ASSERT_EQUAL(BitmapColor(COL_WHITE), access->GetColor(0, 0));
     CPPUNIT_ASSERT_EQUAL(BitmapColor(COL_WHITE), access->GetColor(0, access->Width() - 1));
@@ -87,10 +87,11 @@ void JpegWriterTest::testWrite8BitNonGrayscale()
     const ScanlineFormat format = access->GetScanlineFormat();
     // Check that it's still 8bit grayscale.
     CPPUNIT_ASSERT_EQUAL(ScanlineFormat::N8BitPal, format);
-    // The original image has grayscale palette, just with entries in a different order,
-    // so do not check for non-grayscale, the roundtrip apparently fixes that. What's important
+    // The original image has grayscale palette, just with entries in a different order.
+    // Do not check for grayscale 8bit, the roundtrip apparently fixes that. What's important
     // is the content.
-    // CPPUNIT_ASSERT(!bitmap.HasGreyPalette());
+    CPPUNIT_ASSERT(bitmap.HasGreyPaletteAny());
+    // CPPUNIT_ASSERT(bitmap.HasGreyPalette8Bit());
     // Check that the content is valid.
     CPPUNIT_ASSERT_EQUAL(BitmapColor(COL_WHITE), access->GetColor(0, 0));
     CPPUNIT_ASSERT_EQUAL(BitmapColor(COL_WHITE), access->GetColor(0, access->Width() - 1));
diff --git a/vcl/quartz/salbmp.cxx b/vcl/quartz/salbmp.cxx
index 524fad183b8e..43c39e66ca23 100644
--- a/vcl/quartz/salbmp.cxx
+++ b/vcl/quartz/salbmp.cxx
@@ -219,7 +219,7 @@ bool QuartzSalBitmap::CreateContext()
         // no conversion needed for truecolor
         m_pContextBuffer = m_pUserBuffer;
     }
-    else if( mnBits == 8 && maPalette.IsGreyPalette() )
+    else if( mnBits == 8 && maPalette.IsGreyPalette8Bit() )
     {
         // no conversion needed for grayscale
         m_pContextBuffer = m_pUserBuffer;
diff --git a/vcl/skia/salbmp.cxx b/vcl/skia/salbmp.cxx
index 2ac221fdba19..5a426fa6e404 100644
--- a/vcl/skia/salbmp.cxx
+++ b/vcl/skia/salbmp.cxx
@@ -348,7 +348,7 @@ bool SkiaSalBitmap::ConvertToGreyscale()
     // Avoid the costly SkImage->buffer->SkImage conversion.
     if (!mBuffer && mImage)
     {
-        if (mBitCount == 8 && mPalette == Bitmap::GetGreyPalette(256))
+        if (mBitCount == 8 && mPalette.IsGreyPalette8Bit())
             return true;
         sk_sp<SkSurface> surface = SkiaHelper::createSkSurface(mPixelsSize);
         SkPaint paint;
@@ -377,7 +377,7 @@ bool SkiaSalBitmap::InterpretAs8Bit()
 #ifdef DBG_UTIL
     assert(mWriteAccessCount == 0);
 #endif
-    if (mBitCount == 8 && mPalette == Bitmap::GetGreyPalette(256))
+    if (mBitCount == 8 && mPalette.IsGreyPalette8Bit())
         return true;
     // This is usually used by AlphaMask, the point is just to treat
     // the content as an alpha channel. This is often used
@@ -692,7 +692,7 @@ void SkiaSalBitmap::EnsureBitmapData()
             }
         }
     }
-    else if (mBitCount == 8 && mPalette.IsGreyPalette())
+    else if (mBitCount == 8 && mPalette.IsGreyPalette8Bit())
     {
         for (long y = 0; y < mSize.Height(); ++y)
         {
diff --git a/vcl/source/bitmap/bitmap.cxx b/vcl/source/bitmap/bitmap.cxx
index fd37da07e9ef..0dae9d5ace4f 100644
--- a/vcl/source/bitmap/bitmap.cxx
+++ b/vcl/source/bitmap/bitmap.cxx
@@ -208,7 +208,7 @@ const BitmapPalette& Bitmap::GetGreyPalette( int nEntries )
     return GetGreyPalette(2);
 }
 
-bool BitmapPalette::IsGreyPalette() const
+bool BitmapPalette::IsGreyPaletteAny() const
 {
     const int nEntryCount = GetEntryCount();
     if( !nEntryCount ) // NOTE: an empty palette means 1:1 mapping
@@ -233,6 +233,21 @@ bool BitmapPalette::IsGreyPalette() const
     return bRet;
 }
 
+bool BitmapPalette::IsGreyPalette8Bit() const
+{
+    const int nEntryCount = GetEntryCount();
+    if( !nEntryCount ) // NOTE: an empty palette means 1:1 mapping
+        return true;
+    if( nEntryCount != 256 )
+        return false;
+    for (sal_uInt16 i = 0; i < 256; ++i)
+    {
+        if( maBitmapColor[i] != BitmapColor(i, i, i))
+            return false;
+    }
+    return true;
+}
+
 Bitmap& Bitmap::operator=( const Bitmap& rBitmap )
 {
     if (this == &rBitmap)
@@ -303,7 +318,7 @@ sal_uInt16 Bitmap::GetBitCount() const
     return 0;
 }
 
-bool Bitmap::HasGreyPalette() const
+bool Bitmap::HasGreyPaletteAny() const
 {
     const sal_uInt16    nBitCount = GetBitCount();
     bool            bRet = nBitCount == 1;
@@ -312,7 +327,20 @@ bool Bitmap::HasGreyPalette() const
 
     if( pIAcc )
     {
-        bRet = pIAcc->HasPalette() && pIAcc->GetPalette().IsGreyPalette();
+        bRet = pIAcc->HasPalette() && pIAcc->GetPalette().IsGreyPaletteAny();
+    }
+
+    return bRet;
+}
+
+bool Bitmap::HasGreyPalette8Bit() const
+{
+    bool            bRet = false;
+    ScopedInfoAccess pIAcc(const_cast<Bitmap&>(*this));
+
+    if( pIAcc )
+    {
+        bRet = pIAcc->HasPalette() && pIAcc->GetPalette().IsGreyPalette8Bit();
     }
 
     return bRet;
diff --git a/vcl/source/bitmap/salbmp.cxx b/vcl/source/bitmap/salbmp.cxx
index 7e1b9a347140..f731a5690948 100644
--- a/vcl/source/bitmap/salbmp.cxx
+++ b/vcl/source/bitmap/salbmp.cxx
@@ -150,7 +150,7 @@ std::unique_ptr< sal_uInt8[] > SalBitmap::convertDataBitCount( const sal_uInt8*
     static const int bpp[] = { 1, 3, 3, 4, 4 };
     std::unique_ptr< sal_uInt8[] > data( new sal_uInt8[width * height * bpp[ static_cast<int>(type) ]] );
 
-    if(type == BitConvert::A8 && bitCount == 8 && palette.IsGreyPalette())
+    if(type == BitConvert::A8 && bitCount == 8 && palette.IsGreyPalette8Bit())
     { // no actual data conversion
         for( int y = 0; y < height; ++y )
             memcpy( data.get() + y * width, src + y * bytesPerRow, width );
diff --git a/vcl/source/filter/jpeg/JpegWriter.cxx b/vcl/source/filter/jpeg/JpegWriter.cxx
index 82ed4bf98ad9..bc41530047ed 100644
--- a/vcl/source/filter/jpeg/JpegWriter.cxx
+++ b/vcl/source/filter/jpeg/JpegWriter.cxx
@@ -231,7 +231,7 @@ bool JPEGWriter::Write( const Graphic& rGraphic )
             *mpExpWasGrey = mbGreys;
 
         if ( mbGreys )
-            mbNative = ( mpReadAccess->GetScanlineFormat() == ScanlineFormat::N8BitPal && aGraphicBmp.HasGreyPalette());
+            mbNative = ( mpReadAccess->GetScanlineFormat() == ScanlineFormat::N8BitPal && aGraphicBmp.HasGreyPalette8Bit());
         else
             mbNative = ( mpReadAccess->GetScanlineFormat() == ScanlineFormat::N24BitTcRgb );
 
diff --git a/vcl/source/gdi/alpha.cxx b/vcl/source/gdi/alpha.cxx
index bc1d54f36c22..3fa43c8eaa6a 100644
--- a/vcl/source/gdi/alpha.cxx
+++ b/vcl/source/gdi/alpha.cxx
@@ -63,7 +63,7 @@ const Bitmap& AlphaMask::ImplGetBitmap() const
 void AlphaMask::ImplSetBitmap( const Bitmap& rBitmap )
 {
     SAL_WARN_IF( 8 != rBitmap.GetBitCount(), "vcl.gdi", "Bitmap should be 8bpp, not " << rBitmap.GetBitCount() << "bpp" );
-    SAL_WARN_IF( !rBitmap.HasGreyPalette(), "vcl.gdi", "Bitmap isn't greyscale" );
+    SAL_WARN_IF( !rBitmap.HasGreyPalette8Bit(), "vcl.gdi", "Bitmap isn't greyscale" );
     *static_cast<Bitmap*>(this) = rBitmap;
 }
 
diff --git a/vcl/source/gdi/bitmap3.cxx b/vcl/source/gdi/bitmap3.cxx
index c9942fc04f76..ec80b03c6008 100644
--- a/vcl/source/gdi/bitmap3.cxx
+++ b/vcl/source/gdi/bitmap3.cxx
@@ -805,7 +805,7 @@ void Bitmap::AdaptBitCount(Bitmap& rNew) const
             }
             case 4:
             {
-                if(HasGreyPalette())
+                if(HasGreyPaletteAny())
                 {
                     rNew.Convert(BmpConversion::N4BitGreys);
                 }
@@ -817,7 +817,7 @@ void Bitmap::AdaptBitCount(Bitmap& rNew) const
             }
             case 8:
             {
-                if(HasGreyPalette())
+                if(HasGreyPaletteAny())
                 {
                     rNew.Convert(BmpConversion::N8BitGreys);
                 }
diff --git a/vcl/source/gdi/dibtools.cxx b/vcl/source/gdi/dibtools.cxx
index 54d17c83d47c..f2164b94d129 100644
--- a/vcl/source/gdi/dibtools.cxx
+++ b/vcl/source/gdi/dibtools.cxx
@@ -1001,7 +1001,7 @@ bool ImplReadDIBBody(SvStream& rIStm, Bitmap& rBmp, AlphaMask* pBmpAlpha, sal_uL
     const BitmapPalette* pPal = &aPalette;
     //ofz#948 match the surrounding logic of case TransparentType::Bitmap of
     //ReadDIBBitmapEx but do it while reading for performance
-    const bool bIsAlpha = (nBitCount == 8 && !!aPalette && aPalette.IsGreyPalette());
+    const bool bIsAlpha = (nBitCount == 8 && !!aPalette && aPalette.IsGreyPalette8Bit());
     const bool bForceToMonoWhileReading = (bIsMask && !bIsAlpha && nBitCount != 1);
     if (bForceToMonoWhileReading)
     {
@@ -1782,7 +1782,7 @@ bool ReadDIBBitmapEx(
                             if(!!aMask)
                             {
                                 // do we have an alpha mask?
-                                if((8 == aMask.GetBitCount()) && aMask.HasGreyPalette())
+                                if((8 == aMask.GetBitCount()) && aMask.HasGreyPalette8Bit())
                                 {
                                     AlphaMask aAlpha;
 
diff --git a/vcl/source/gdi/pdfwriter_impl.cxx b/vcl/source/gdi/pdfwriter_impl.cxx
index de1cea050f04..e68642aa5100 100644
--- a/vcl/source/gdi/pdfwriter_impl.cxx
+++ b/vcl/source/gdi/pdfwriter_impl.cxx
@@ -8788,7 +8788,7 @@ bool PDFWriterImpl::writeBitmapObject( BitmapEmit& rObject, bool bMask )
         aLine.append( "/ColorSpace" );
         if( bTrueColor )
             aLine.append( "/DeviceRGB\n" );
-        else if( aBitmap.HasGreyPalette() )
+        else if( aBitmap.HasGreyPaletteAny() )
         {
             aLine.append( "/DeviceGray\n" );
             if( aBitmap.GetBitCount() == 1 )