cubic_spline

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

Online documentation Demo

Example

use cubic_spline::{CalcPoints, SplineOptsBuilder, SplineResult, SrcPoints};

let points = vec![(10.0, 200.0), (256.0, 390.0), (512.0, 10.0), (778.0, 200.0)];

let opts = SplineOptsBuilder::new()
  .num_of_segments(16)
  .take();

let pts: SrcPoints<(f64, f64)> = SrcPoints::new(&points);
let mut result = SplineResult::<(f64, f64)>::new();
pts.calc(&opts, &mut result);

assert_eq!(result.get().len(), 51);

//
// Same as:
//
use cubic_spline::{Spline};
let spline_points = Spline::from_tuples(&points, &opts);

assert_eq!(spline_points.len(), 51);

For now source and resulting points may be Vec<f64> - (vec![x,y,x,y,...]) or Vec<(f64, f64)> - (vec![(x,y),(x,y), ...]). For this types of points there are two helper functions Spline::from_flatten_points and Spline::from_tuples

Custom points

If you allready have some points to avoid unnecessary copying, creating new Vec etc. you can implement GetPoint trait. And if you need some particular result implement PushPoint.

Example

use cubic_spline::{CalcPoints,SrcPoints,SplineResult,PushPoint,GetPoint,SplineOpts};

struct MyPoint {
  pub top: f32,
  pub left: f32,
  pub label: Option<String>,
}

struct MyResult<T>(T);
struct MySrcPoints<T>(T);

impl<'a> GetPoint for MySrcPoints<SrcPoints<'a, MyPoint>> {
  fn get(&self, index: usize) -> Option<(f64, f64)> {
    self.0.pts().get(index).and_then(|p| {
      Some((f64::from(p.left), f64::from(p.top)))
    })
  }
  fn len(&self) -> usize {
    self.0.pts().len()
  }
}

impl PushPoint for MyResult<SplineResult<MyPoint>> {
  fn push_spline_point(&mut self, x: f64, y: f64) {
    let calculated_point = MyPoint { top: y as f32, left: x as f32, label: None };
    self.0.pts().push(calculated_point);
  }
}

impl<'a> CalcPoints for MySrcPoints<SrcPoints<'a, MyPoint>> {}


let points: Vec<MyPoint> = vec![];
let pts = MySrcPoints(SrcPoints::new(&points));
let mut result = MyResult(SplineResult::default());
pts.calc(&SplineOpts::default(), &mut result);

See here for implementation example

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, SplineOptsBuilder};
let opts = SplineOpts {
  tension: 0.6,
  ..Default.default()
};

// or use builder

let opts2 = SplineOptsBuilder::new()
  .num_of_segments(54)
  .invert_y_with_height(1080)
  .take();

Enjoy using!

License

This module is MIT licensed.