gistfile1.txt

import Darwin

let Max = 5000.0

func log(_ x: Double, base: Double) -> Double {
    let result = log(x + 1.0) / log(base + 1.0)
    print("  log(\(x), base: \(base)) -> \(result)")
   return result
}


func scale(_ x: Double) -> UInt8 {
    print("  scale(\(x))")
    let inverseX = Double(Max - x)
    print("  inverseX: \(inverseX)")
    let inverseLog = log(inverseX, base: Max)
    print("  inverseLog: \(inverseLog)")
    let result = 255 - UInt8(inverseLog * 255.0)
    print("  result: \(result)")

    return result
}

func unscale(_ x: UInt8) -> Double {
    let inverseX = Double(255 - x)
    let inverseLog = log(inverseX, base: 255)  // Convert to range 0.0 ... 1.0

    return Max - (inverseLog * Max)
}

for i: UInt8 in 0...255 {
    let unscaled = unscale(i)
    let scaled = scale(unscaled)
    print("\(i) -> \(unscaled) -> \(scaled)")
}