grid_2_log

Convert deformation field to log-domain velocity field (or compute exponent).

grid_2_log <input> <output> [options]

DESCRIPTION

grid_2_log converts a standard deformation field into its log-domain velocity field representation using an iterative Baker-Campbell-Hausdorff (BCH) approximation. The resulting velocity field can be exponentiated via scaling and squaring to recover the original deformation.

When the --exp flag is given, the tool performs the inverse operation: it exponentiates a velocity field to produce a deformation field. A scaling factor can be applied to the velocity field before exponentiation.

This tool is essential for log-domain diffeomorphic registration workflows where deformations must be represented as stationary velocity fields.

OPTIONS

--verbose

Print progress information during processing.

--clobber

Overwrite the output file if it already exists.

--iter n

Number of iterations for the BCH approximation (default: 10).

--sigma f

Smoothing sigma for regularization (default: 2).

--approx n

Number of BCH terms to use in the approximation (default: 3).

--steps n

Number of integration steps for scaling and squaring (default: 500).

--byte

Store output voxels as unsigned byte.

--short

Store output voxels as short integer.

--float

Store output voxels as single-precision floating point.

--exp

Compute the exponent of the velocity field instead of the logarithm.

--factor f

Multiply the velocity field by this factor before exponentiation.

EXAMPLES

# Convert a deformation field to a log-domain velocity field
grid_2_log deformation.mnc velocity.mnc

# Convert with custom iteration count and BCH terms
grid_2_log deformation.mnc velocity.mnc --iter 20 --approx 4

# Exponentiate a velocity field to recover the deformation
grid_2_log velocity.mnc deformation.mnc --exp

# Apply a scaling factor during exponentiation
grid_2_log velocity.mnc scaled_deformation.mnc --exp --factor 0.5

AUTHOR

Vladimir S. Fonov - McConnell Brain Imaging Centre, Montreal Neurological Institute.

COPYRIGHTS

Copyright © 2009-2024 by Vladimir S. Fonov

SEE ALSO

grid_proc , grid_statistics , LogDomainDemonsRegistration