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Crosshatch pattern fill

Source: R/fill.R
fill_crosshatch.Rd

fill_crosshatch() builds a grid::pattern() fill value that renders two mirror-symmetric hatch lines, at angle and -angle, forming an "X" inside each tile.

Usage

fill_crosshatch(
  color = "black",
  angle = 45,
  spacing = 0.1,
  aspect = NULL,
  linewidth = 1,
  extend = "repeat"
)

Arguments

color

One or more line colours. A vector of length 2 colours the two lines independently; a single colour (the default) colours both the same, matching the original behaviour. Longer vectors are recycled to length 2. Default "black".

angle

Hatch angle in degrees, measured counterclockwise from the positive x-axis. Default 45.

spacing

Baseline tile size, as a fraction of the target's bounding box. Must be a positive number. Default 0.1.

aspect

Width-to-height ratio of the target polygon's bounding box. Must be a positive number, or NULL (the default) to resolve it automatically from the real target's own bounding-box aspect ratio at draw() time – see the fill class. Passing a fixed number instead computes the pattern once, immediately, against that value only.

linewidth

Line width. Must be a positive number. Default 1.

extend

Passed to grid::pattern(). Default "repeat".

Value

A pattern object as returned by grid::pattern(), suitable for use as the fill argument to grid::gpar().

Details

It shares fill_hatch()'s tile-shape technique: both lines are drawn as the two corner-to-corner diagonals of a single rectangular tile (rather than at an arbitrary baked-in slope), so both tile seamlessly under extend = "repeat", and the tile's width/height ratio – not the diagonals' own coordinates – determines the rendered angle. See fill_hatch()'s details for why this matters.

Because both lines share one tile shape, they are only perpendicular when angle = 45 (the classic crosshatch look); for other angles the two lines are symmetric about the horizontal axis but not at right angles to each other. Genuinely perpendicular hatching at an arbitrary angle would need two differently-shaped tiles layered as separate fills, which this function does not attempt.

At angle a multiple of 90 degrees, the two mirrored diagonals would coincide, so this case is handled separately by drawing a horizontal line and a vertical line instead (a simple grid).

See also

Other fill helpers: fill(), fill_charcoal(), fill_checker(), fill_flow(), fill_gradient(), fill_halftone(), fill_hatch(), fill_image(), fill_marble(), fill_noise(), fill_none(), fill_scatter(), fill_scribble(), fill_solid(), fill_stipple(), fill_stripe(), fill_vignette()

Examples

draw(shape_circle(fill = fill_crosshatch(angle = 30)))


# at a multiple of 90 degrees, the mirrored diagonals would coincide,
# so a plain horizontal/vertical grid is drawn instead
draw(shape_circle(fill = fill_crosshatch(angle = 0, spacing = 0.15)))


# only angle = 45 gives genuinely perpendicular lines; other angles are
# symmetric about the horizontal axis but not at right angles
draw(shape_circle(fill = fill_crosshatch(angle = 20, spacing = 0.12)))


# a two-colour vector colours the two lines independently
draw(shape_circle(
  fill = fill_crosshatch(color = c("steelblue", "tomato"), angle = 45)
))