nr_polygon: Draw multiple polygons on a native raster image

In nara: Native Raster Image Tools

Draw multiple polygons on a native raster image

Description

Draw multiple polygons on a native raster image

Usage

nr_polygon(
  nr,
  x,
  y,
  id = NULL,
  fill = "black",
  color = NA,
  linewidth = 1,
  mitre_limit = linewidth,
  use_alpha = TRUE
)

Arguments

nr	native raster image
x, y	Vectors of point coordinates
id	integer vector used to separate coordinates into multiple polygons. Consecutive runs of the same id value belong to the same polygon. If NULL (the default) then all coordinates are assumed to be vertices of a single polygon.
fill	fill color
color	Color as a character string. Either a standard R color (e.g. 'blue', 'white') or a hex color of the form #rrggbbaa, #rrggbb, #rgba or #rgb
linewidth	Line linewidth. Default: 1. If linewidth = 1 then a naive version of Bresenham is used to draw the points. If linewidth is greater than 1, then the line is convert to a triangle strip and rendered as polygons.
mitre_limit	Limit the size of the mitre when two lines meet at an acute angle and linewidth is greater than 1. Default: same as line linewidth which mostly looks OK.
use_alpha	Use alpha channel when drawing? Logical. Default: TRUE

Value

Invisibly return the supplied native raster image which was been modified in-place

See Also

Other drawing functions: nr_circle(), nr_polyline(), nr_rect(), nr_tri_mesh()

Examples

w <- 200
h <- 150
nr <- nr_new(w, h, 'grey80')

N  <- 20
theta <- seq(0, 2 * pi, length.out = N)
xs <- w/2 + 50 * cos(theta)
ys <- h/2 + 50 * sin(theta)

nr_polygon(nr, xs, ys, fill = 'grey50', col = 'black')
nr_point(nr, xs, ys, col = 'red')
plot(nr)

nara documentation built on May 28, 2026, 5:07 p.m.