commit a98000c028a3c68329fdb2047f51f8d271b2290c
author Patrick Luby <plubius@neooffice.org> Thu Oct 19 20:01:16 2023 -0400
committer Patrick Luby <plubius@neooffice.org> Fri Oct 20 14:41:04 2023 +0200
tree e7d3d95ba3ca34febe2f6f0deb4abd41560802d3
parent 5e7f7917fd589f661982d481a45bf84337e4c03c

tdf#157793 limit tdf#157635 fix to only larger palettes

I don't know why, but the fix for tdf#157635 causes
images with a palette of 16 entries to be inverted.
Is this the only condition for masking out black
pixels in non-transparent animation frames?

Change-Id: I9550baab4dc4d9b75a21c8af2f6c0b5eb8e46c12
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/158214
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Reviewed-by: Patrick Luby <plubius@neooffice.org>

vcl/source/filter/igif/gifread.cxx

diff --git a/vcl/source/filter/igif/gifread.cxx b/vcl/source/filter/igif/gifread.cxx
index afbf084..78d3190 100644
--- a/vcl/source/filter/igif/gifread.cxx
+++ b/vcl/source/filter/igif/gifread.cxx
@@ -99,6 +99,7 @@ class GIFReader : public GraphicReader
    sal_uInt8           nGCDisposalMethod;      // 'Disposal Method' (see GIF docs)
    sal_uInt8           cTransIndex1;
    sal_uInt8           cNonTransIndex1;
    bool                bEnhance;

    void                ReadPaletteEntries( BitmapPalette* pPal, sal_uLong nCount );
    void                ClearImageExtensions();
@@ -156,6 +157,7 @@ GIFReader::GIFReader( SvStream& rStm )
    , nGCTransparentIndex ( 0 )
    , cTransIndex1 ( 0 )
    , cNonTransIndex1 ( 0 )
    , bEnhance( false )
{
    maUpperName = "SVIGIF";
    aSrcBuf.resize(256);    // Memory buffer for ReadNextBlock
@@ -317,6 +319,8 @@ void GIFReader::ReadPaletteEntries( BitmapPalette* pPal, sal_uLong nCount )
        rColor.SetBlue( *pTmp++ );
    }

    bEnhance = false;

    // if possible accommodate some standard colours
    if( nCount < 256 )
    {
@@ -325,6 +329,15 @@ void GIFReader::ReadPaletteEntries( BitmapPalette* pPal, sal_uLong nCount )
        if( nCount < 255 )
            (*pPal)[ 254UL ] = COL_BLACK;
    }
    else
    {
        // tdf#157793 limit tdf#157635 fix to only larger palettes
        // I don't know why, but the fix for tdf#157635 causes
        // images with a palette of 16 entries to be inverted.
        // Is this the only condition for masking out black
        // pixels in non-transparent animation frames?
        bEnhance = true;
    }
}

bool GIFReader::ReadExtension()
@@ -671,7 +684,10 @@ void GIFReader::CreateNewBitmaps()
        // Due to the switch from transparency to alpha in commit
        // 81994cb2b8b32453a92bcb011830fcb884f22ff3, mask out black
        // pixels in bitmap.
        aAnimationFrame.maBitmapEx = BitmapEx( aBmp8, aBmp8 );
        if (bEnhance)
            aAnimationFrame.maBitmapEx = BitmapEx( aBmp8, aBmp8 );
        else
            aAnimationFrame.maBitmapEx = BitmapEx( aBmp8 );
    }

    aAnimationFrame.maPositionPixel = Point( nImagePosX, nImagePosY );