Created
April 19, 2020 01:27
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one euro filter Typescript version
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/* eslint-disable max-classes-per-file */ | |
class LowPassFilter { | |
y: number | null; | |
s: number | null; | |
alpha = 0; | |
constructor(alpha: number) { | |
this.setAlpha(alpha); | |
this.y = null; | |
this.s = null; | |
} | |
setAlpha(alpha: number) { | |
if (alpha <= 0 || alpha > 1.0) { | |
throw new Error(); | |
} | |
this.alpha = alpha; | |
} | |
filter(value: number, timestamp: number, alpha: number) { | |
if (alpha) { | |
this.setAlpha(alpha); | |
} | |
let s; | |
if (!this.y) { | |
s = value; | |
} else { | |
s = this.alpha * value + (1.0 - this.alpha) * this.s!; | |
} | |
this.y = value; | |
this.s = s; | |
return s; | |
} | |
lastValue() { | |
return this.y; | |
} | |
} | |
export default class OneEuroFilter { | |
freq: number; | |
minCutOff: number; | |
beta: number; | |
dCutOff: number; | |
x: LowPassFilter; | |
dx: LowPassFilter; | |
lasttime: number | null; | |
constructor(freq: number, minCutOff = 1.0, beta = 0.0, dCutOff = 1.0) { | |
if (freq <= 0 || minCutOff <= 0 || dCutOff <= 0) { | |
throw new Error(); | |
} | |
this.freq = freq; | |
this.minCutOff = minCutOff; | |
this.beta = beta; | |
this.dCutOff = dCutOff; | |
this.x = new LowPassFilter(this.alpha(this.minCutOff)); | |
this.dx = new LowPassFilter(this.alpha(this.dCutOff)); | |
this.lasttime = null; | |
} | |
alpha(cutOff: number) { | |
const te = 1.0 / this.freq; | |
const tau = 1.0 / (2 * Math.PI * cutOff); | |
return 1.0 / (1.0 + tau / te); | |
} | |
filter(x: number, timestamp: number | null = null) { | |
if (this.lasttime && timestamp) { | |
this.freq = 1.0 / (timestamp - this.lasttime); | |
} | |
this.lasttime = timestamp; | |
const prevX = this.x.lastValue(); | |
const dx = !prevX ? 0.0 : (x - prevX) * this.freq; | |
const edx = this.dx.filter(dx, timestamp!, this.alpha(this.dCutOff)); | |
const cutOff = this.minCutOff + this.beta * Math.abs(edx); | |
return this.x.filter(x, timestamp!, this.alpha(cutOff)); | |
} | |
} |
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credits go to : https://gist.github.com/3846masa/5628f711e86fd62bea56b18e32177c60
I only converted to Typescript