cubic_spline

Interpolation method for computation of cubic spline points within the range of a discrete set of known points.

Online documentation Demo

Example

use cubic_spline::{Points, Point, SplineOpts, TryFrom};


fn main() {
  let source = vec![(10.0, 200.0), (256.0, 390.0), (512.0, 10.0), (778.0, 200.0)];
  
  let opts = SplineOpts::new()
    .tension(0.5);
  
  let mut points = Points::try_from(&source).expect("expect valid points but");
  let result = points.calc_spline(&opts).expect("cant construct spline points");
  
  assert_eq!(result.get_ref().len(), 49);
  
  let inner_vec: &mut Vec<Point> = points.get_mut();
  inner_vec.push(Point::new(7.7, 1.3));
  inner_vec[1].x += 0.79;
  inner_vec.last_mut().iter_mut().for_each(|mut p| {p.tension = Some(0.7);});
  
  points.invert_vertically(400.0);
  
  assert_eq!(points.get_ref()[1].y, 10.0);
  
  let calculated_points = points
    .calc_spline(&opts.num_of_segments(33))
    .unwrap();
  
  assert_eq!(calculated_points.into_inner().len(), 133);

}

For information on how a curve can be constructed and which points to accept, see the appropriate structures.

Custom points

If you already have some points you can implement From trait for Point struct and pass your points directly.

Example

use cubic_spline::{SplineOpts, Point, Points};

#[derive(Default)]
struct MyPoint {
  vertical: u8,
  horizontal: u8,
  color: String,
}

impl<'a> From<&'a MyPoint> for Point {
  fn from(p: &'a MyPoint) -> Self {
    Point::new(p.horizontal as f64, p.vertical as f64)
  }
}

fn main() {
  let my_points: Vec<MyPoint> = vec![MyPoint::default(),MyPoint::default()];
  let spline = Points::from(&my_points)
    .calc_spline(&SplineOpts::default())
    .unwrap();
  
  assert_eq!(spline.get_ref().len(), 17);
}

Use in Javascript

It also compiled as wasm module. And you can use it in your js code but not completely. Now available only one function

import { getCurvePoints } from 'cubic-spline-rs'

const NUM_OF_SEGMENTS = 22

const points = [10.0, 200.0, 256.0, 390.0, 512.0, 10.0, 778.0, 200.0]

const curvePoints = getCurvePoints( points, {
  num_of_segments: NUM_OF_SEGMENTS, // *optional
  // tension: 0.5, // *optional
  // ...  
} )

If you want to draw result points to canvas - code like this:

const ctx = getMyCanvas2DContext()

ctx.beginPath()
ctx.lineWidth = 3
ctx.strokeStyle = '#ffcc00'

ctx.moveTo(curvePoints[0], curvePoints[1])
const length = curvePoints.length - 1
for (let i = 2; i < length; i += 2) {
  ctx.lineTo(curvePoints[i], curvePoints[i + 1])
}

ctx.stroke()
ctx.closePath()

See example here.

Options

| Name | Type | Default | Description | | --------------------- | :-----------------: | :-----: | ------------------------------------------------------------------------------------------- | | tension | f64 | 0.5 | Tension | | num_of_segments | u32 | 16 | Number of calculated points between known points | | hidden_point_at_start | Option<(f64,f64)> | None | A point that will not be drawn, but the beginning of the graph will bend as if it is there. | | hidden_point_at_end | Option<(f64,f64)> | None | A point that will not be drawn, but the end of the graph will bend as if it is there. |

use cubic_spline::{SplineOpts};

fn main() {
  let options = SplineOpts::new()
    .tension(0.6)
    .num_of_segments(54)
    // .hidden_point_at_start((1.2, 3.1))
    // .hidden_point_at_end((397.9, 105.5))
    ;

}

License

This module is MIT licensed.