R: Transform points between voxel and "world" coordinates

voxelToWorld {RNifti} | R Documentation

## Transform points between voxel and “world” coordinates

### Description

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.

### Usage

    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.

### Author(s)

Jon Clayden <code@clayden.org>

### See Also

`xform`, `pixdim`, `pixunits`

### Examples

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

    # Find the origin
    origin(im)

[Package RNifti version 1.2.2 Index]