bData.ByteData(ii) = CByte(bData.ByteData(ii) + (amount * (255 - bData.ByteData(ii)))) 'blue

Public Sub Brightness(Optional ByVal amount As Single = 0)
        OnFilterStarted()
        If amount = 0 Then Return
        Dim bData = BitmapData.LockBits(b)
        If amount > 0 Then
            For ii = bData.ByteData.GetLowerBound(0) To bData.ByteData.GetUpperBound(0) Step 4
                bData.ByteData(ii) = CByte(bData.ByteData(ii) + (amount * (255 - bData.ByteData(ii)))) 'blue
                bData.ByteData(ii + 1) = CByte(bData.ByteData(ii + 1) + (amount * (255 - bData.ByteData(ii + 1)))) 'green
                bData.ByteData(ii + 2) = CByte(bData.ByteData(ii + 2) + (amount * (255 - bData.ByteData(ii + 2)))) 'red
            Next
        Else
            For ii = bData.ByteData.GetLowerBound(0) To bData.ByteData.GetUpperBound(0) Step 4
                bData.ByteData(ii) = CByte(bData.ByteData(ii) - (Math.Abs(amount) * bData.ByteData(ii))) 'blue
                bData.ByteData(ii + 1) = CByte(bData.ByteData(ii + 1) - (Math.Abs(amount) * bData.ByteData(ii + 1))) 'green
                bData.ByteData(ii + 2) = CByte(bData.ByteData(ii + 2) - (Math.Abs(amount) * bData.ByteData(ii + 2))) 'red
            Next
        End If
        bData.UnlockBits()
        OnFilterFinished()
    End Sub

Dim b As Byte
    Dim a As Single

    b = 128
    a = 30

    b += a * (255 - b)