Tiling-pattern fills

Create a pattern that fills a shape by tiling a grob. The grob is drawn once into a tile occupying the unit square (0..1 npc), then repeated across a cell of size width x height (in units) anchored at (x, y). Like gradients, the cell geometry is resolved against the viewport at draw time.

Usage

vl_pattern(
  grob,
  width = 0.1,
  height = 0.1,
  x = 0.5,
  y = 0.5,
  units = "npc",
  extend = "repeat"
)

Arguments

grob

A grob, or a list of grobs, drawn into the tile (their 0..1 npc coordinates map to the tile, painted in order).

width, height

Size of one tile cell (default 0.1 npc).

x, y

Cell centre (default centred).

units

Coordinate system for the geometry; see linear_gradient().

extend

Tiling mode: "repeat" (default), "reflect", or "pad". (SVG renders all modes as repeat.)

Value

A vellum_pattern object, suitable for vl_gpar(fill = ...).

Details

The tile is rendered to a raster image (sized from width/height at the scene's resolution) and embedded: PNG raster, SVG <image> in a <pattern>. The PDF backend has no image support yet, so a pattern degrades to the tile's average colour there.

Examples

dots <- circle_grob(r = 0.25, gp = vl_gpar(fill = "white", col = NA))
vl_pattern(dots, width = 0.08, height = 0.08)
#> $grob
#> <vellum::grob_circle>
#>  @ name  : NULL
#>  @ gp    : <vellum::vl_gpar>
#>  .. @ col       : logi NA
#>  .. @ fill      : chr "white"
#>  .. @ lwd       : NULL
#>  .. @ alpha     : NULL
#>  .. @ lty       : NULL
#>  .. @ lineend   : NULL
#>  .. @ linejoin  : NULL
#>  .. @ linemitre : NULL
#>  .. @ fontfamily: NULL
#>  .. @ fontface  : NULL
#>  .. @ fontsize  : NULL
#>  .. @ lineheight: NULL
#>  @ vp    : NULL
#>  @ id    : NULL
#>  @ role  : NULL
#>  @ keys  : NULL
#>  @ meta  : NULL
#>  @ x     : unit [1:1] 0.5npc
#>  @ y     : unit [1:1] 0.5npc
#>  @ r     : unit [1:1] 0.25npc
#>  @ sketch: NULL
#> 
#> $width
#> [1] 0.08
#> 
#> $height
#> [1] 0.08
#> 
#> $x
#> [1] 0.5
#> 
#> $y
#> [1] 0.5
#> 
#> $units
#> [1] "npc"
#> 
#> $extend
#> [1] "repeat"
#> 
#> attr(,"class")
#> [1] "vellum_pattern"