svg-to-poly

Converts an SVG into a Planar Straight Line Graph in the .poly format from Triangle.

The default output is a JSON with the same property names as struct triangulateio defined in triangle.h from Triangle.

An alternative output is a formatted string which could be written onto a .poly file.

A .poly file represents a PSLG, as well as some additional information. PSLG stands for Planar Straight Line Graph, a term familiar to computational geometers. By definition, a PSLG is just a list of vertices and segments. A .poly file can also contain information about holes and concavities, as well as regional attributes and constraints on the areas of triangles.

Full description of the .poly file format.

Install

npm install svg-to-poly

Example

const svgToPoly = require('svg-to-poly');
const loadSvg = require('load-svg');

loadSvg('./arrow460.svg', (err, svg) => {
  console.log(svgToPoly(svg));
});

Output:

{
  pointlist: [[0.86, -0.50], [0.83, -0.55] ...],
  segmentlist: [[0, 1], [1, 2] ...],
  holelist: [[0.23, -0.40]],
  numberofpoints: 115,
  numberofsegments: 115,
  numberofholes: 1
}

Alternative with format() to get a string in the .poly format:

const svgToPoly = require('svg-to-poly');
const loadSvg = require('load-svg');

loadSvg('./arrow460.svg', (err, svg) => {
  console.log(svgToPoly.format(svg));
});

Output:

# points
115 2 0 0
0 0.86 -0.50
1 0.83 -0.55
...
# segments
115 0
0 0 1
1 1 2
...
# holes
1
0 0.23 -0.40

Demo

svg-to-poly demo

Usage

svgToPoly(svg, options)

• svg an SVG element

• options

  • flat (default false) flatten nested arrays i.e. [[x, y], [x, y]] into [x, y, x, y]
  • normalize (default false) normalizes path to its bounding box, returns points in the -1.0 ... 1.0 range
  • threshold (default 0.2) threshold passed to simplify-js

Returns an object with the parsed properties.

svgToPoly.format(svg, options)

Same as above.

Returns a string in the .poly format.

Thanks

svg-to-poly benefits from the groundwork laid by some other great packages:

• extract-svg-path concatenates all <path> data from an SVG
• parse-svg-path splits paths into groups of instructions and values
• svg-path-contours converts paths into polylines
• simplify-path simplifies polylines
• point-in-polygon checks if a point is inside a polygon
• polylabel finds an optimal position inside a polygon

See Also

• Triangle - A Two-Dimensional Quality Mesh Generator and Delaunay Triangulator - Jonathan Shewchuk
• poly-parse - parse .poly into JSON

License

MIT, see LICENSE for details.