Nicks LineString Tools
(Rust Version)

Contents

• 1. Introduction
• 2. Struct LineStringMeasured
  • 2.1. Constructing
  • 2.2. .cut()
  • 2.3. .cut_twice()
  • 2.4. .interpolate()
  • 2.5. .offset_basic()
  • 2.6. Converting to Vec<Vector2>
  • 2.7. Converting to Vec<(f64,f64)>
  • 2.8. Converting to Vec<(f64,f64,f64)>
• 3. Struct Vector2

1. Introduction

This is a library for basic operations on LineStrings.

This library provides the following structs:

1. Vector,
2. LineStringMeasured
3. LineSegmentMeasured (meant for internal use, read source if curious. It is small),

Most core functionality is implemented on LineStringMeasured.

This is a partial port of my previous python library nicks_line_tools which in turn is a partial implementation of the method described by Xu-Zheng Liu, Jun-Hai Yong, Guo-Qin Zheng, Jia-Guang Sun. An offset algorithm for polyline curves. Computers in Industry, Elsevier, 2007, 15p. inria-00518005. I wrote up a decent-ish summary of the psudocode on the python version.

My plan for this repo is to either abandon it and start again, or totally re-write it using the rust geo-types/geo ecosystem as a dependancy. My main use for this repo is as a dependancy for my other project nicklinref_rust which I am also considering abandoning.

The new hotness is megalinref which is a python library built with a rust binary which does the same thing but without the overhead of hosting a rest service on localhost. I need an offsetting algorithim for that project, but I am using geo-types / geo in that project.

2. Struct LineStringMeasured

2.1. Constructing

No constructor is provided currently. Instead the From<Vec<Vector2>> trait can be used to create an instance as follows:

use line_string_measured::LineStringMeasured;
use vector2::Vector2;

let ls:LineStringMeasured = vec![
	Vector2::new(0f64, 0f64),
	Vector2::new(1f64, 0f64),
	Vector2::new(1f64, 1f64),
].into();

OR

let ls = LineStringMeasured::from(vec![
	Vector2::new(0f64, 0f64),
	Vector2::new(1f64, 0f64),
	Vector2::new(1f64, 1f64),
]);

2.2. .cut()

Splits a linestring at a fraction of its length and returns two new linestrings

let (a:Option<LineStringMeasured>, b:Option<LineStringMeasured>) = ls.cut(0.25f64);

2.3. .cut_twice()

Splits a linestring twice at a fractions of its length and returns three new linestrings

let (a:Option<LineStringMeasured>, b:Option<LineStringMeasured>, c:Option<LineStringMeasured>) = ls.cut(0.25f64, 0.66f64);

2.4. .interpolate()

Gets a point at some fraction of the distance along a linestring. Fails with zero length linestrings.

let a:Option<Vector2> = ls.interpolate(0.25f64);

2.5. .offset_basic()

Returns Some(LineString) at some offset distance from the original. Returns None if the linestring has fewer than two points.

let c:Option<LineString> = ls.offset_basic(0.5f64);

2.6. Converting to Vec<Vector2>

User code may find it easier to handle Vec<Vector2> objects. Rust does not provide an elegant way to call the Into trait, therefore the following helper function is provided:

let back_to_vec = ls.into_vector2();

assert!(
	back_to_vec,
	vec![
		Vector2::new(0f64, 0f64),
		Vector2::new(1f64, 0f64),
		Vector2::new(1f64, 1f64),
	]
);

2.7. Converting to Vec<(f64,f64)>

Use the into_tuples() function to convert a multi line string into Vec<(f64,f64)> objects.

let into_tuples = ls.into_tuples();

assert_eq!(
	into_tuples,
	vec![
		(0f64, 0f64),
		(1f64, 0f64),
		(1f64, 1f64),
	]
);

2.8. Converting to Vec<(f64,f64,f64)>

Use the into_tuples_measured() function to convert a multi line string into Vec<(f64,f64,f64)> objects.

let into_tuples_measured = ls.into_tuples_measured(2.0, 10.0);

assert_eq!(
	into_tuples_measured,
	vec![
		(0f64, 0f64, 2f64),
		(1f64, 0f64, 6f64),
		(1f64, 1f64, 10f64),
	]
);

3. Struct Vector2

A simple vector manipulation class implementing PartialEq, Clone, Copy, Deserialize and Serialise:

pub struct Vector2 {
	pub x: f64,
	pub y: f64,
}