Annotate crosshairs at user-specified world (xyz) coordinates

Usage

annotate_crosshairs(
  xyz,
  color = "white",
  linewidth = 0.4,
  alpha = 0.7,
  linetype = "dashed",
  tol = 1,
  ...
)

Arguments

xyz: A numeric matrix or data.frame with columns x, y, and z giving world-space coordinates (in mm) at which to draw crosshairs.
color: Line color for the crosshairs. Default: "white".
linewidth: Line width passed to ggplot2::annotate. Default: 0.4.
alpha: Line alpha. Default: 0.7.
linetype: Line type (e.g., "dashed"). Default: "dashed".
tol: Tolerance (in mm) for matching a coordinate to a displayed slice along its slicing axis. Default: 1.
...: Additional arguments passed to ggplot2::annotate for the crosshair segments.

Value

A ggb object with action "add_annotations"

Details

Crosshairs are drawn on slices whose slicing axis (e.g., z for axial) falls within tol mm of the requested coordinate. If the coordinate on the slicing axis is NA, the crosshair is shown on all slices along that axis where the remaining two axes match. For example, x=0, y=0, z=NA will show a crosshair on every axial slice at x/y=0 (within the nearest in-plane voxel). Coordinates are provided in world space to match the slices() API.

Examples

if (FALSE) { # \dontrun{
# Show crosshairs on any axial slice at x/y = 0
ggbrain() +
  images(c(underlay = underlay_2mm)) +
  slices(c("z = 20", "z = 40")) +
  geom_brain("underlay") +
  annotate_crosshairs(data.frame(x = 0, y = 0, z = NA), linewidth = 0.6)
} # }