isAffine {RNiftyReg}

Create, test for and print affine matrices

Description

isAffine returns a logical value indicating whether its argument is, or resembles, a 4x4 affine matrix. asAffine converts other objects to the affine class, attaching or updating the source and target image attributes. Affine transformations are a class of linear transformations which preserve points, straight lines and planes, and may consist of a combination of rotation, translation, scale and skew operations.

Usage

isAffine(object, strict = FALSE)

asAffine(object, source = NULL, target = NULL, ...)

## S3 method for class 'niftyreg'
asAffine(object, source = NULL, target = NULL, i = 1L,
  ...)

## S3 method for class 'niftyregRDS'
asAffine(object, source = NULL, target = NULL, ...)

## S3 method for class 'affine'
asAffine(object, source = NULL, target = NULL, ...)

## S3 method for class 'niftiImage'
asAffine(object, source = attr(object, "source"),
  target = attr(object, "target"), ...)

## Default S3 method:
asAffine(object, source = NULL, target = NULL, ...)

## S3 method for class 'affine'
print(x, ...)

Arguments

object

An R object.

strict

If TRUE, this function just tests whether the object is of class "affine". Otherwise it also tests for an affine-like 4x4 matrix.

source, target

New source and target images for the transformation.

...

Additional parameters to methods.

i

The transformation number, for niftyreg objects containing more than one.

x

An "affine" object.

Details

NiftyReg's convention is for affine matrices to transform world coordinates (in the sense of voxelToWorld) from TARGET to SOURCE space, although transforms are logically applied the other way.

Value

For isAffine, a logical value, which is TRUE if object appears to be an affine matrix. For asAffine, a classed affine object with source and target attributes set appropriately.

Note

2D affines are a subset of 3D affines, and are stored in a 4x4 matrix for internal consistency, even though a 3x3 matrix would suffice.

Author(s)

Jon Clayden <[e-mail]>