a multi-start optimizer for affine registration

Searches over the sphere to find a good initialization for further registration refinement, if needed. This is a wrapper for the ANTs function antsAffineInitializer.

affineInitializer(
  fixedImage,
  movingImage,
  searchFactor = 20,
  radianFraction = 0.1,
  usePrincipalAxis = FALSE,
  localSearchIterations = 10,
  mask,
  txfn,
  num_threads = 1
)

Arguments

fixedImage

the fixed reference image
movingImage

the moving image to be mapped to the fixed space
searchFactor

degree of increments on the sphere to search
radianFraction

between zero and one, defines the arc to search over
usePrincipalAxis

boolean to initialize by principal axis
localSearchIterations

gradient descent iterations
mask

optional mask to restrict registration
txfn

filename for the transformation
num_threads

will execute Sys.setenv(ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS = num_threads) before running to attempt a more reproducible result. See https://github.com/ANTsX/ANTs/wiki/antsRegistration-reproducibility-issues for discussion. If NULL, will not set anything.

Value

transformationMatrix

Note

See https://github.com/ANTsX/ANTs/issues/444 for reproducibility discussion

Author

Avants BB

Examples


fi <- antsImageRead(getANTsRData("r16"))
mi <- antsImageRead(getANTsRData("r27"))
tx <- affineInitializer( fi, mi )

mi2 = resampleImage(mi, c(1.25, 1.25))
tx <- affineInitializer( fi, mi2 )
tx2 <- affineInitializer( fi, mi2 )
if ('R.matlab' %in% installed.packages()) {
tx_hdr = R.matlab::readMat(tx)
trans = tx_hdr$AffineTransform.double.2.2
fixed = tx_hdr$fixed

tx2_hdr = R.matlab::readMat(tx2)
trans2 = tx2_hdr$AffineTransform.double.2.2
fixed2 = tx2_hdr$fixed

testthat::expect_equal(tx_hdr, tx2_hdr)
}