freesurferformats (version 1.1.0)

transform2ras: Convert a transformation to RAS world coordinates.

Description

ITK and the tools built on it (3D Slicer, ANTs, SimpleITK and the workflows that use them) work in world coordinates that are left-posterior-superior (LPS), while the other file formats of this package use right-anterior-superior (RAS) coordinates. The two conventions differ in the sign of the first two axes only, so converting a transformation between them neither needs nor uses the geometry of a volume, unlike the conversion between voxel and world coordinates, see transform2world. A transformation that is already in RAS coordinates is returned unchanged.

Usage

transform2ras(tf)

Value

an fs.transform instance whose matrix operates on RAS coordinates.

Arguments

tf

an fs.transform instance whose matrix operates on world coordinates, i.e. space_in and space_out are either 'lps' or 'ras'.

See Also

Other header coordinate space: invert.fs.transform(), is.fs.transform(), mghheader.is.ras.valid(), mghheader.ras2vox(), mghheader.ras2vox.tkreg(), mghheader.scanner2tkreg(), mghheader.tkreg2scanner(), mghheader.vox2ras(), mghheader.vox2ras.tkreg(), print.fs.transform(), read.fs.transform(), read.fs.transform.dat(), read.fs.transform.fslmat(), read.fs.transform.itk(), read.fs.transform.lta(), read.fs.transform.xfm(), sm0to1(), sm1to0(), summary.fs.transform(), transform2lps(), transform2voxel(), transform2world(), write.fs.transform(), write.fs.transform.dat(), write.fs.transform.fslmat(), write.fs.transform.itk(), write.fs.transform.lta(), write.fs.transform.xfm()

Examples

# An ITK transform operates on LPS coordinates, the FreeSurfer formats on RAS coordinates.
tf <- read.fs.transform(system.file("extdata", "talairach.xfm",
  package = "freesurferformats", mustWork = TRUE
))
summary(tf)$space_in
summary(transform2lps(tf))$space_in
summary(transform2ras(transform2lps(tf)))$space_in