Read and write an 'ITK'/'ANTs' affine transform

write_ants_transform stores a \(4\times 4\) RAS-to-RAS affine (such as the transform returned by register_volume3d) as an 'ITK' .mat file (a 'MATLAB' level-5 binary, LPS convention) compatible with antsApplyTransforms. read_ants_transform reads such a file back into a \(4\times 4\) RAS matrix. The reader folds a non-zero ITK center of rotation into the translation, so transforms written by 'ANTs' are read correctly.

Usage

write_ants_transform(transform, file)

read_ants_transform(file)

Arguments

transform

a \(4\times 4\) (or \(3\times 4\)) RAS affine

file

path to the .mat file

Value

write_ants_transform returns file invisibly; read_ants_transform returns a \(4\times 4\) RAS matrix.

See also

register_volume3d, save_registration

Examples

tf <- tempfile(fileext = ".mat")
m <- diag(4); m[1:3, 4] <- c(3, -2, 1)
write_ants_transform(m, tf)
read_ants_transform(tf)
#>      [,1] [,2] [,3] [,4]
#> [1,]    1    0    0    3
#> [2,]    0    1    0   -2
#> [3,]    0    0    1    1
#> [4,]    0    0    0    1