xfm2param

extract rotation, translation, scale, and shear parameters from a MNI transform file

xfm2param file.xfm [file.mnc] [options]

DESCRIPTION

xfm2param reads a MNI .xfm transform file and decomposes it into human-readable transformation parameters: center of rotation, translations, rotations (in degrees), scales, and shears.

For concatenated transforms, each sub-transform is decomposed individually. For non-linear transforms (grid transforms, thin-plate spline transforms), the type is reported but only linear transforms are fully decomposed.

An optional MINC volume can be provided as the second argument. When given, the center of gravity (COG) of the volume is computed and used as the center of rotation and scaling for the decomposition.

This is the inverse operation of param2xfm, which creates a transform file from parameters.

OPTIONS

-center x y z

Specify the center of rotation and scaling for the decomposition. Default: 0 0 0.

-help

Print summary of command-line options and exit.

-version

Print the program’s version number and exit.

EXAMPLES

Decompose a linear transform:

xfm2param transform.xfm

Decompose a transform using a volume’s center of gravity as the rotation center:

xfm2param transform.xfm brain.mnc

OUTPUT FORMAT

The output is a set of parameter lines printed to standard output:

center:      cx cy cz
translation: tx ty tz
rotation:    rx ry rz
scale:       sx sy sz
shear:       shx shy shz

Rotations are given in degrees.

AUTHOR

Louis Collins - McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University.

SEE ALSO

param2xfm xfmconcat xfminvert minctracc