The NIfTI-1 and NIfTI-2 formats have a simple extension mechanism that allows additional metadata to be stored with their headers. The format of this extension data is unspecified by the NIfTI standard, but extension codes indicate what type of information is present. These functions provide access to this extension metadata.
extensions(image)extension(image, code, mode = c("raw", "character", "numeric", "double",
"integer", "logical", "complex"), ..., simplify = TRUE)
extensions(image) <- value
extension(image, code) <- value
For extensions, a list of raw vectors containing the bytes
stored in each available header. For extension, a list of vector
of values, converted to the required mode, for the extension code
specified. If the extension code is not used in the image, the return
value is NULL. The replacement forms return the modified image.
An image, in any acceptable form (see asNifti).
Integer value, expression or string specifying which extension code is required.
The required mode of the extracted data.
Additional arguments to readBin.
Logical value. If TRUE, the default, a single
extension will be returned as a vector; otherwise a list is always
returned.
New value for the extension(s).
Jon Clayden <code@clayden.org>
The plural version, extensions, extracts or replaces all extensions
at once. The retrieval form returns a list of raw vectors, each with the
corresponding code in an attribute, and the replacement form accepts a list
of atomic vectors with code attributes, or NULL, which removes all
extensions. The singular version, extension, gets all extensions with
the specified code, or appends an extension with that code. Valid extension
codes are stored in the ExtensionCodes vector.
NIfTI extensions are stored as a simple, unstructured byte stream, which is
naturally represented in R as a vector of mode "raw". However, these
functions will perform some conversion to and from other atomic types for
convenience. The NIfTI standard makes no guarantees about byte order within
the data stream, but the endian argument to readBin can
be passed through when converting to a non-raw type.
ExtensionCodes for the valid extension codes.