mGifFile = DGifOpen(this, onRead, &mError);
if (mError) {
    throw System::InvalidOperation(GifErrorString(mError));
}

mError = DGifSlurp(mGifFile);
if (mError == 0) {
    throw System::InvalidOperation(GifErrorString(mGifFile->Error));
}
...

mImageNumber = (mImageNumber + 1) % (mGifFile->ImageCount);
auto& img = mGifFile->SavedImages[mImageNumber];

assert(img.ImageDesc.Width == mGifFile->SWidth && img.ImageDesc.Height == mGifFile->SHeight);

std::vector<uint32> colorData(img.ImageDesc.Width * img.ImageDesc.Height);
auto colorMap = img.ImageDesc.ColorMap ? img.ImageDesc.ColorMap : mGifFile->SColorMap;

memset(&mGcb, 0, sizeof(mGcb));
int ret = DGifSavedExtensionToGCB(mGifFile, mImageNumber, &mGcb);
if (ret == GIF_OK) {
    mHasGcb = true;
    mLastFrame = sTime->getGameTime();
} else {
    mHasGcb = false;
}

for (uint32 i = 0; i < colorData.size(); ++i) {
    auto& clrObj = colorMap->Colors[img.RasterBits[i]];
    auto r = clrObj.Red;
    auto g = clrObj.Green;
    auto b = clrObj.Blue;
    auto alpha = 0xFF;
    colorData[i] = (alpha << 24) | (b << 16) | (g << 8) | r;
}

mTexture->fromMemory(mGifFile->SWidth, mGifFile->SHeight, colorData);