read.nrrd.header: Read the header of a file in NRRD format.

In freesurferformats: Read and Write 'FreeSurfer' Neuroimaging File Formats

Read the header of a file in NRRD format.

Description

Reads and parses the ASCII header of a NRRD file without touching the volume data. This is cheap, and it can be used to inspect a file, or to check its geometry, before deciding whether to read the data.

Usage

read.nrrd.header(filepath)

Arguments

filepath

character string, path to the NRRD file (.nrrd or .nhdr).

Value

named list, the parsed header. The fields of the file are available under their normalized names (e.g. space_directions for the field 'space directions'), and fields that this function does not interpret are collected in the other_fields entry. The derived entries are vox2ras_matrix (the 4x4 matrix that maps 0-based voxel indices to RAS+ coordinates, or NULL when the file states no geometry), vox2ras_source (how the matrix was derived: 'space directions' or 'spacings'), data_files (the resolved paths of the data files for a detached header, or NULL), data_offset (the byte offset of the data in the header file), gzipped_file (whether the whole file is gzip-compressed), header_size (the size of the header in bytes) and dwi (the parsed diffusion metadata, or NULL, see read.fs.volume.nrrd).

Examples

nrrd_file <- system.file("extdata", "nrrd", "vol_u8_raw.nrrd",
  package = "freesurferformats", mustWork = TRUE
)
hdr <- read.nrrd.header(nrrd_file)
hdr$sizes
hdr$vox2ras_matrix

freesurferformats documentation built on Sept. 25, 2026, 1:07 a.m.