knot-toolbox/frontend/lib/math/curves.js

function distance([x1, y1], [x2, y2]) {
    return Math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
}

function midpoints([x1, y1], [x2, y2], count) {
    const dx = x2 - x1
    const dy = y2 - y1

    const polyline = []

    for (let i = 1; i < count; i++) {
        const ratio = i / count
        polyline.push([x1 + dx * ratio, y1 + dy * ratio])
    }

    return polyline
}

export function resampleCurve(curve, minDist, maxDist) {
    if (curve.length === 0) return []

    const newCurve = [curve[0]]

    let lastPt = curve[0]
    for (let i = 1; i < curve.length; i++) {
        const pt = curve[i]

        const segmentLength = distance(lastPt, pt)

        if (segmentLength < minDist) {
            // console.log('skipping point, segmentLength:', segmentLength)
            continue
        }
        if (segmentLength > maxDist) {
            // console.log('adding points, segmentLength:', segmentLength)
            newCurve.push(...midpoints(lastPt, pt, Math.floor(segmentLength / maxDist)))
        }

        newCurve.push(pt)
        lastPt = pt
    }

    if (lastPt !== curve.at(-1)) {
        newCurve.push(curve.at(-1))
    }

    return newCurve
}

export function simplifyCurve(curve, minDistance) {
    if (curve.length === 0) return []

    const newCurve = [curve[0]]

    let lastPt = curve[0]
    for (let i = 1; i < curve.length; i++) {
        const pt = curve[i]

        if (distance(lastPt, pt) >= minDistance) {
            newCurve.push(pt)
            lastPt = pt
        }
    }

    if (lastPt !== curve.at(-1)) {
        newCurve.push(curve.at(-1))
    }

    return newCurve
}