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};

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);

points.get_mut().push(Point::new(7.7, 1.3));
points.get_mut()[1].x += 0.79;
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)
  }
}

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);

Example for JS

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

use cubic_spline::{SplineOpts};

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))
  ;

Enjoy using!

License

This module is MIT licensed.