commit f62846d54ef9d4eb447cf405b74b6f47599d6d69
author Luboš Luňák <l.lunak@collabora.com> Thu Oct 08 15:58:21 2020 +0200
committer Luboš Luňák <l.lunak@collabora.com> Fri Oct 09 11:08:14 2020 +0200
tree f24289bd596711d1654a7b4eded4eefda3fd79cb
parent b69ea390ff475f58b8f0da3abf0c158021aba4d2

32bpp SKIA_USE_BITMAP32 bitmaps always need kPremul_SkAlphaType

I'm not sure if kOpaque_SkAlphaType would guarantee 255 in the alpha,
so better be safe. This should be a rare case anyway.

Change-Id: Iadec97a83621403a56f62ac07e238d8e98a3a905
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/104090
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

vcl/skia/salbmp.cxx

diff --git a/vcl/skia/salbmp.cxx b/vcl/skia/salbmp.cxx
index 531c966..d1cd76b 100644
--- a/vcl/skia/salbmp.cxx
+++ b/vcl/skia/salbmp.cxx
@@ -995,18 +995,18 @@ void SkiaSalBitmap::EnsureBitmapData()
    // Try to fill mBuffer from mImage.
    assert(mImage->colorType() == kN32_SkColorType);
    SkiaZone zone;
    // Use kUnpremul_SkAlphaType to make Skia convert from premultiplied alpha when reading
    // from the SkImage, in case there is any alpha involved. If converting to bpp<32 formats,
    // we will ignore the alpha when converting to mBuffer. Unless bpp==32 and SKIA_USE_BITMAP32,
    // in which case keep the format, since SKIA_USE_BITMAP32 implies premultiplied alpha.
    // If the source image has no alpha, then use no alpha (faster to convert), otherwise
    // use kUnpremul_SkAlphaType to make Skia convert from premultiplied alpha when reading
    // from the SkImage (the alpha will be ignored if converting to bpp<32 formats, but
    // the color channels must be unpremultiplied. Unless bpp==32 and SKIA_USE_BITMAP32,
    // in which case use kPremul_SkAlphaType, since SKIA_USE_BITMAP32 implies premultiplied alpha.
    SkAlphaType alphaType = kUnpremul_SkAlphaType;
    if (mImage->imageInfo().alphaType() == kOpaque_SkAlphaType)
        alphaType = kOpaque_SkAlphaType;
#if SKIA_USE_BITMAP32
    if (mBitCount == 32)
        alphaType = kPremul_SkAlphaType;
#endif
    // But if the source image has no alpha, then use no alpha (faster to convert).
    if (mImage->imageInfo().alphaType() == kOpaque_SkAlphaType)
        alphaType = kOpaque_SkAlphaType;
    SkBitmap bitmap;
    if (!bitmap.tryAllocPixels(SkImageInfo::MakeS32(mSize.Width(), mSize.Height(), alphaType)))
        abort();