commit 110eb4f6f8ed43faf7d2a4e74bfdcb93934f6439
author Attila Szűcs <attila.szucs@collabora.com> Mon Mar 25 01:04:14 2024 +0100
committer Caolán McNamara <caolan.mcnamara@collabora.com> Thu Mar 28 10:19:23 2024 +0100
tree 12ad2f9953f6bbd8038afde8b844979827a23293
parent 147063f58c6b7898e659321f581ea9551305a574

tdf#153162 Gif load transparency optimization

Converting a bitmap from transparency to alpha can be very slow.
fortunately it can be avoided.
Inverted the transparency colors (cTransIndex1, cNonTransIndex1)
that are used to create aBmp1 in GIFReader::FillImages.
It create the transparency bitmap inverted, so no need to invert it.

Change-Id: I14714fe4b8bbcd7849db57b2824a7077dda40f81
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165261
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

vcl/source/filter/igif/gifread.cxx

diff --git a/vcl/source/filter/igif/gifread.cxx b/vcl/source/filter/igif/gifread.cxx
index 8f56eda..cfb4e84 100644
--- a/vcl/source/filter/igif/gifread.cxx
+++ b/vcl/source/filter/igif/gifread.cxx
@@ -220,18 +220,22 @@ void GIFReader::CreateBitmaps(tools::Long nWidth, tools::Long nHeight, BitmapPal
    if (bGCTransparent)
    {
        const Color aWhite(COL_WHITE);
        const Color aBlack(COL_BLACK);

        aBmp1 = Bitmap(aSize, vcl::PixelFormat::N8_BPP, &Bitmap::GetGreyPalette(256));

        if (!aAnimation.Count())
            aBmp1.Erase(aWhite);
            aBmp1.Erase(aBlack);

        pAcc1 = aBmp1;

        if (pAcc1)
        {
            cTransIndex1 = static_cast<sal_uInt8>(pAcc1->GetBestPaletteIndex(aWhite));
            cNonTransIndex1 = cTransIndex1 ? 0 : 1;
            // We have to make an AlphaMask from it, that needs to be inverted from transparency.
            // It is faster to invert it here.
            // So Non-Transparent color should be 0xff , and Transparent should be 0.
            cNonTransIndex1 = static_cast<sal_uInt8>(pAcc1->GetBestPaletteIndex(aWhite));
            cTransIndex1 = static_cast<sal_uInt8>(pAcc1->GetBestPaletteIndex(aBlack));
        }
        else
        {
@@ -671,7 +675,8 @@ void GIFReader::CreateNewBitmaps()
    {
        pAcc1.reset();
        AlphaMask aAlphaMask(aBmp1);
        aAlphaMask.Invert(); // convert from transparency to alpha
        // No need to convert from transparency to alpha
        // aBmp1 is already inverted
        aAnimationFrame.maBitmapEx = BitmapEx( aBmp8, aAlphaMask );
    }
    else