Aligning region bounding boz to one of the projected coordinate system axes

[lenamat]

Hello,

I have a georeferenced project where the processing region is not aligned with the horizontal plane. I have tried running the script that aligns the region to all of the three axes of the coordinate system and it works fine. What I want to do is to keep the original X and Y directions, which if I'm not mistaken means that I want to keep the original rotation angle around the Z-axis.

I have done multiple tests but I can't seem to get it right!... Could you please explain what are the components of the transform and rotation matrices, and how can I retrieve the x, y, z rotation angles of the local coordinate system ?

Many thanks.