cnt_skeleton {centerline} | R Documentation |
This function generates skeletons (centerlines) of closed polygon objects by applying Voronoi diagrams (Voronoi, 1908). A Voronoi diagram partitions space into regions based on the distance to the polygon's vertices. The edges of these cells form a network of lines (skeletons) that represent the structure of the polygon while preserving its overall shape.
cnt_skeleton(input, keep = 0.5)
input |
|
keep |
numeric, proportion of points to retain (0.05-Inf; default 0.5). See Details. |
If keep
equals 1, no transformation will occur. The
function will use the original geometry to find the skeleton.
If the keep
parameter is below 1, then the geos::geos_simplify()
function will be used. So the original input
geometry would be simplified, and the resulting skeleton will be cleaner but
maybe more edgy.
The current realisation of simplification is similar (but not identical)
to rmapshaper::ms_simplify()
one with Douglas-Peuker algorithm. However,
due to geos
superpower, it performs several times faster.
If you find that the built-in simplification algorithm performs poorly,
try rmapshaper::ms_simplify()
first and then find the polygon skeleton
with keep = 1
, i.e.
cnt_skeleton(rmapshaper::ms_simplify(polygon_sf), keep = 1)
If the keep
is above 1, then the densification
algorithm is applied using the geos::geos_densify()
function. This may
produce a very large object if keep is set more than 2. However, the
resulting skeleton would potentially be more accurate.
a sf
, sfc
, SpatVector
or geos_geometry
class object of a MULTILINESTRING
geometry
Voronoi, G. (1908). Nouvelles applications des paramètres continus à la théorie des formes quadratiques. Journal für die reine und angewandte Mathematik, 134, 198-287. doi:10.1515/crll.1908.134.198
library(sf)
polygon <-
sf::st_read(system.file("extdata/example.gpkg", package = "centerline"),
layer = "polygon",
quiet = TRUE
)
plot(polygon)
pol_skeleton <- cnt_skeleton(polygon)
plot(pol_skeleton)