imagesFs.read(reinterpret_cast<char*>(q.vec().data()), sizeof(double) * 3);

[ronaldpan]

q has 4 members, why read 3 doubles?
In rgbdreg-colmap.cpp lines 162-163:
imagesFs.read(reinterpret_cast<char*>(q.vec().data()),
sizeof(double) * 3);

[ronaldpan]

Sorry. I did not see readBin(imagesFs, q.w());