System setup • ggseg.extra

Using pre-built atlases requires nothing beyond R. Creating your own atlases may require external software depending on the pipeline.

What each pipeline needs

Pipeline	R packages	System tools
Cortical (annotation, labels)	`freesurferformats`	None
Cortical (neuromaps volume)	`freesurfer`, `neuromapr`	FreeSurfer
Subcortical	`freesurfer`, `magick`, `chromote`, `htmlwidgets`, `terra`, `smoothr`	FreeSurfer, ImageMagick
Whole-brain	`freesurfer`, `RNifti`, `magick`, `chromote`, `htmlwidgets`, `terra`, `smoothr`	FreeSurfer, ImageMagick
Tract	`RNifti`, `Rvcg`	None
GIFTI / CIFTI	`gifti` or `ciftiTools`	Connectome Workbench (CIFTI only)

The cortical mesh-projection pipeline is the lightest — it runs in seconds with no system tools and minimal R dependencies. All heavier packages (freesurfer, magick, chromote, terra, etc.) are in Suggests and only loaded when a pipeline actually needs them.

FreeSurfer

FreeSurfer is needed by the subcortical, whole-brain, and neuromaps volume pipelines. The cortical annotation pipeline needs the freesurferformats R package (not FreeSurfer itself) to read .annot and .label files.

On macOS, you also need:

XQuartz
Xcode command line tools

Verify your installation:

freesurfer::fs_dir()

ImageMagick

ImageMagick is used by the subcortical and whole-brain pipelines for image processing — isolating regions from screenshots, tracing contours, and converting them to polygons.

Not needed for cortical or tract pipelines.

Install via your package manager:

# macOS
brew install imagemagick

# Ubuntu/Debian
sudo apt-get install imagemagick

Chrome / Chromium

The subcortical and whole-brain pipelines take 3D screenshots using the chromote package, which needs Google Chrome or Chromium. Chrome is typically already installed. If not, chromote will attempt to download a suitable version automatically.

Not needed for cortical or tract pipelines.

Parallel processing

ggseg.extra uses the furrr package for parallel processing. By default, processing runs sequentially.

To enable parallel processing, set up a future plan before running atlas creation functions:

library(future)

plan(multisession, workers = 4)

Use multisession, not multicore. The subcortical pipeline uses chromote to take 3D brain screenshots via headless Chrome. multicore relies on process forking, which corrupts chromote’s websocket connections and causes crashes. multisession spawns independent R worker processes that each get their own clean Chrome instance.

If plan(multicore) is active when the pipeline runs, it will automatically switch to multisession and warn you.

To return to sequential processing:

plan(sequential)

Progress bars

ggseg.extra uses progressr to report progress during long-running operations. Progress reporting is disabled by default.

To enable progress bars:

library(progressr)

handlers("cli")
handlers(global = TRUE)

This gives you a cli-style progress bar that updates as each region or step completes. It works with both sequential and parallel execution.

Checking your setup

Run the setup report to verify everything is in place:

setup_sitrep()