Multi Filter

multi-filter.swift

var filterCaches: [String: [CGFloat]] = [:]
func filter(_ value: CGFloat, for seconds: CGFloat, smooth: Bool = true, id: String) -> CGFloat {
    guard filterCaches[id] != nil else {
        filterCaches[id] = [value]
        return value
    }
    filterCaches[id]!.append(value)
    let frameCount = Int(seconds * CGFloat(60))
    if filterCaches[id]!.count > frameCount {
        filterCaches[id]!.remove(at: 0)
    }
    guard filterCaches[id]!.count > 1 else {
        return filterCaches[id]![0]
    }
    guard filterCaches[id]!.count > 2 else {
        return (filterCaches[id]![0] + filterCaches[id]![1]) / 2
    }
    var filteredValue: CGFloat = 0.0
    var weight: CGFloat = smooth ? 0.0 : CGFloat(filterCaches[id]!.count)
    for (i, val) in filterCaches[id]!.enumerated() {
        let fraction = CGFloat(i) / CGFloat(filterCaches[id]!.count - 1)
        let smoothWeight: CGFloat = 1.0 - (cos(fraction * .pi * 2) / 2 + 0.5)
        filteredValue += val * (smooth ? smoothWeight : 1.0)
        weight += smoothWeight
    }
    filteredValue /= weight
    return filteredValue
}