B4J Question How to Draw Waveforms of WAV Files

Private Sub Compress(data() As Double) As Double()
    Dim times As Int = data.Length / 5000
    Dim compressed(5000) As Double
    For i = 0 To compressed.Length - 1
        compressed(i) = data(i*times)
    Next
    Return compressed
End Sub

Dim times As Float = (data.Length - 1) / (5000 - 1)

Sub Class_Globals
    Private fx As JFX
    Private xui As XUI
End Sub

'Initializes the object. You can add parameters to this method if needed.
Public Sub Initialize
    
End Sub

Public Sub Draw(data() As Short) As B4XBitmap
    data = Compress(data)
    Dim normalized() As Float= Normalize(data)
    Dim bc As BitmapCreator
    bc.Initialize(3000,500)
    Dim height As Int = 500 - 200
    Dim NbSamples As Int = normalized.Length
    For i = 0 To NbSamples - 1
        If i = NbSamples - 1 Then
            Exit
        End If
        Dim centerY As Double = 250
        Dim x1 As Int = i
        Dim y1 As Double = centerY + normalized(i)*height
        Dim x2 As Int = i+1
        Dim y2 As Double = centerY + normalized(i+1)*height
        bc.DrawLine(x1,y1,x2,y2,xui.Color_Red,1)
    Next
    Return bc.Bitmap
End Sub

Private Sub Compress(data() As Short) As Short()
    Dim times As Int
    If data.Length > 3000 Then
        times = data.Length / 3000
    Else
        Return data
    End If
    Dim compressed(3000) As Short
    For i = 0 To compressed.Length - 1
        compressed(i) = data(i*times)
    Next
    Return compressed
End Sub

Private Sub Normalize(data() As Short) As Float()
    Dim normalized(data.Length) As Float
    Dim maxValue As Short = 0
    For i = 0 To data.Length - 1
        Dim value As Short = data(i)
        maxValue = Max(maxValue,value)
    Next
    For i = 0 To data.Length - 1
        normalized(i) = data(i) / maxValue
    Next
    Return normalized
End Sub