Convert a ggseg atlas to the sf-optional polygon representation

Sets the single geom slot to the brain_polygons representation, converting from sf if needed. The result renders identically via the geom_polygon-based path in ggseg, but no longer depends on the sf class machinery in $data — useful for wasm builds and air-gapped installs.

Usage

as_polygon_atlas(atlas)

Arguments

atlas

A ggseg_atlas (or legacy brain_atlas) object.

Value

A ggseg_atlas whose $data$geom is a brain_polygons object.

Details

Conversion is lossless, so a single representation is kept (no redundant sf alongside polygons). To rehydrate sf for geometric operations later, use as_sf_atlas().

This doubles as the backward-compatible path for sf-optional installs: a lite-only ggseg that meets a still-sf-backed atlas converts it on the fly when sf is installed. When sf is not installed the geometry cannot be read, so the call aborts with a pointer to migrate_atlas_files() — which the atlas maintainer runs once (on a machine with sf) to ship the package in the polygon format.

Examples

if (FALSE) { # \dontrun{
poly <- as_polygon_atlas(dk())
is_atlas_polygon(poly) # TRUE
} # }