tkregister-style registration matrix (Also known as register.dat)

This is the format that various freesurfer programs (eg, tkregister2, bbregister, spmregister, mri_vol2surf, mri_vol2vol, etc) use to store and access a 4x4 matrix transformation matrix. It consists of four lines of header and a 4x4 matrix followed by a "footer" line.

The header lines are: 1. Subject - name of subject as found in $SUBJECTS_DIR/subject (not always necessary) 2. In-plane voxel resolution in mm -- ignored 3. Between-plane voxel resolution in mm -- ignored 4. Intensity - used by tkregister2

The footer line should always be "round".

The registration matrix maps from the tkRAS of the subject anatomical target volume to the tkRAS of the input/movable volume and can code up to 12 DOF (ie, an affine transform).

Example:

mgh-02407836-v2 3.437500 5.000000 0.150000 9.999921e-01 1.462518e-04 -3.969864e-03 7.764969e-01 3.899203e-03 -2.272341e-01 9.738325e-01 -3.873044e+01 7.596778e-04 9.738404e-01 2.272329e-01 -1.456367e+00 0.000000e+00 0.000000e+00 0.000000e+00 1.000000e+00 round