WaveView.kt

import javafx.scene.canvas.Canvas

class WaveView(width:Double, height:Double) : Canvas(width, height){
  fun draw(waveData:ByteArray){
    val c        = getGraphicsContext2D()!!
    val zoom     = 2.0
    val height   = getHeight().toDouble()
    val byteSize = 256
    val originY  = height / 2

    val moveToInitialZero = { c.moveTo(0.0, originY) }
    val lineToInitialZero = { c.lineTo(0.0, originY) }
    val lineToFinalZero   = { c.lineTo((waveData.size-1) * zoom, originY) }
    val calculateSampleY  = { (i:Int) -> waveData[i] * height / byteSize }
    val drawUpperHalf     = { for(i in waveData.indices)            c.lineTo(i * zoom,  calculateSampleY(i) + originY) }
    val drawLowerHalf     = { for(i in waveData.indices.reversed()) c.lineTo(i * zoom, -calculateSampleY(i) + originY) }

    moveToInitialZero()
    drawUpperHalf()
    lineToFinalZero()
    drawLowerHalf()
    lineToInitialZero()

    c.fill()
  }
}