meta_info: Lightweight metadata for neuroimaging files

Description

`meta_info()` provides a simple, CRAN-friendly way to retrieve essential image metadata without teaching S4 details up front. It accepts a file path or a `FileMetaInfo` object and returns a normalized list containing common fields like dimensions, spacing, origin, and transform.

The function does not read image data; it only parses header information.

Usage

meta_info(x)
# S4 method for FileMetaInfo
meta_info(x)
# S4 method for character
meta_info(x)

Value

A named list with the following elements:

`dim` Integer vector of image dimensions.
`spacing` Numeric voxel spacing (mm).
`origin` Numeric coordinate origin.
`trans` 4x4 transformation matrix mapping grid to world (mm).
`path` Data file path.
`filename` Basename of `path`.
`format` File format label (e.g., "NIFTI", "AFNI").
`dtype` Storage data type label.
`bytes_per_element` Bytes per element.
`nvox` Number of voxels in the spatial volume (prod of first 3 dims).
`nvol` Number of volumes (4th dim if present, else 1).
`size_bytes` Approximate uncompressed size in bytes (`nvox * nvol * bytes_per_element`).
`time_step` Time step (TR in seconds) if available for NIfTI, else `NA_real_`.

Arguments

x: A character file path (e.g., `"image.nii.gz"`) or an object of class FileMetaInfo.

Details

Summarize Image Metadata

Examples

Run this code

# \donttest{
f <- system.file("extdata", "global_mask_v4.nii", package = "neuroim2")
mi <- meta_info(f)
mi$dim
mi$spacing
mi$origin
mi$filename
# 4x4 transform
mi$trans
# }