Transform points between voxel and ``world'' coordinates

These functions are used to transform points from dimensionless pixel or voxel coordinates to ``real-world'' coordinates, typically in millimetres, and back. Actual pixel units can be obtained using the pixunits function. The origin function gives the voxel coordinates of the real-world origin.

voxelToWorld(points, image, simple = FALSE, ...)

worldToVoxel(points, image, simple = FALSE, ...)

origin(image, ...)

Arguments

points	A vector giving the coordinates of a point, or a matrix with one point per row.
image	The image in whose space the points are given, or a 4x4 numeric xform matrix.
simple	A logical value: if TRUE then the transformation is performed simply by rescaling the points according to the voxel dimensions recorded in the image. Otherwise the full xform matrix is used.
...	Additional arguments to xform.

Value

A vector or matrix of transformed points.

Note

Voxel coordinates are assumed by these functions to use R's indexing convention, beginning from 1.

See also

xform, pixdim, pixunits

Author

Jon Clayden <code@clayden.org>

Examples

im <- readNifti(system.file("extdata", "example.nii.gz", package="RNifti"))

# Find the origin
origin(im)
#> [1] 49.81356 39.07409 23.01525