svg2psp

The package provides functions to import SVG files into a spatstat R object.

Installation

You can install svg2psp from github with:

# install.packages("devtools")
devtools::install_github("xraynaud/svg2psp")

Usage

The main function is svg2psp and the only obligatory parameter is the path of the SVG file to import. The function only import SVG paths and understand absolute and relative SVG commands moveto, lineto, and curveto (quadratic and cubic bezier curves) as well as lineto shorthands horizontal and vertical.

library(svg2psp)
filepath = system.file("extdata","SVG.svg", package = "svg2psp")
svg = svg2psp(file=filepath,bezier = 10)
svg
#> planar line segment pattern: 419 line segments
#> window: rectangle = [0, 118.9211] x [0, 58.42246] mm

Imported data can be vizualised using spatstat functions.

plot(svg)

Quadratic bezier curves are approximated to cubic bezier curves. Cubic bezier curves are approximated by the De Casteljau algorithm. The number of iterations used for the approximation are passed using the bezier parameter.

svg_low = svg2psp(file=filepath,bezier = 1)
svg_low
#> planar line segment pattern: 59 line segments
#> window: rectangle = [0, 118.9211] x [0, 58.42246] mm
plot(svg_low)

By default, svg2psp assumes that the origin of coordinates is at the bottom left of the image. The parameter reverse can be use to flip the vertical coordinate so as to have the origin at the top left of the image, similarly to TIFF images. If the SVG contains size information, svg2psp also uses these informations to build the psp object (dimensions and units). The rescale parameter can be used to obtain a psp object in pixel coordinates.

svg2 = svg2psp(file=filepath,bezier = 10,reverse=F, rescale=F)
svg2
#> planar line segment pattern: 419 line segments
#> window: rectangle = [0, 421.374] x [0, 207.00872] units
plot(svg2)

The other function parameters are detailed in the help(svg2psp) help page.

The svg2psp package also provides 2 functions to manipulate the psp objects:

The cut method cut the segments of the psp object to smaller segments of size maxlength. Each segments is cut into n smaller segments of length maxlength plus a remainding segment of length < maxlength.

cut(svg,1) # Note the number of line segments.
#> planar line segment pattern: 747 line segments
#> window: rectangle = [0, 118.9211] x [0, 58.42246] mm

The connectedsets.psp function automatically define sets of segments based on their proximity and the angles they form. Two segments which have one end less or equal to conn.radius units apart and form and angle less or equal to conn.angle radian will be considered to belong to the same set.

plot(connectedsets.psp(svg,conn.radius=0,conn.angle=2*pi))