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>

7 files changed, 39 insertions, 11 deletions

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 )