Striped pattern fill

fill_stripe() builds a grid::pattern() fill value that renders repeating solid bands, at a given angle, generalized from two colours to an arbitrary palette.

Usage

fill_stripe(
  color = c("black", "white"),
  angle = 45,
  spacing = 0.2,
  aspect = NULL,
  extend = "repeat"
)

Arguments

color

Two or more stripe colours, one equal-width band each (see details for biasing band widths). Default c("black", "white").

angle

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

spacing

One full period through all of color, as a fraction of the target's bounding box. Must be a positive number. Default 0.2.

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.

extend

Passed to the inner grid::linearGradient(), controlling what happens beyond the colour stops – not to the outer grid::pattern() call, which always uses extend = "repeat" (see details). Default "repeat".

Value

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

Details

Unlike fill_hatch(), this doesn't use the corner-to-corner-diagonal tile-shape technique at all – because a filled band, unlike a thin hatch line, needs every point along a tile's edge to match its neighbour, not just the points where a thin line happens to cross, a single diagonal split of a tile turns out not to tile seamlessly at an arbitrary angle the way a thin hatch line does. Instead, fill_stripe() sidesteps grid::pattern()'s tile-copy repetition altogether: the stripe angle and period come from a grid::linearGradient() with hard colour stops (no smooth transition) and extend = "repeat", which repeats itself continuously along its own axis – a fundamentally different (and for this purpose, simpler) mechanism than tiling a rasterised copy. grid::pattern() is still used around this gradient, but only once, as a single square (automatically aspect-corrected – see fill_hatch()'s own aspect docs) tile spanning the whole target shape, exactly as fill_gradient() does by default – not to create repetition, which the gradient already provides.

Each of the n = length(color) colours gets an equal-width band by default (1/n of the period); there's no separate argument for unequal bands – repeat a colour in color instead (e.g. c("steelblue", "steelblue", "white") gives a 2:1 ratio between the two colours), which reuses the same recycling mechanism rather than adding a second one.

See also

Other fill helpers: fill(), fill_charcoal(), fill_checker(), fill_crosshatch(), 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_vignette()

Examples

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


# repeating a colour biases the band widths, rather than a separate argument
draw(shape_circle(
  fill = fill_stripe(color = c("steelblue", "steelblue", "white"))
))


# narrower spacing gives more, thinner stripes
draw(shape_circle(fill = fill_stripe(angle = 90, spacing = 0.08)))


# three or more colours repeat through the same period
draw(shape_circle(
  fill = fill_stripe(color = c("steelblue", "white", "tomato"), angle = 30)
))