Attribute VB_Name = "mdl_rgb_rndm"
' Replace imgsource with the pic/img box name
' Replace frmMain with the name of the form containing imgsource
' Add a timer interval=1,reference ColorUpdate()
' Replace Timer1 with the name of the timer.
' Add call to InitializeColors() in frmMain.load
' c_INITIALINTERVAL applies to first scan when no colors are changed
' c_RUNINTERVAL applies to all subsequent scans
' c_WAITINTERVAL set the period between scans

Option Explicit

Private Const c_RUNINTERVAL As Integer = 1 ' 20
Private Const c_INITIALINTERVAL As Integer = 1
Private Const c_WAITINTERVAL As Integer = 1  ' 10000

Private m_intW As Integer, m_intH As Integer
Private m_intL As Integer, m_intT As Integer
Private Y As Integer, k As Integer, X As Integer
Private r As Long, g As Long, b As Long
Private m_intDelta As Integer
Private m_bolRunning As Boolean
Private Declare Function GetSysColor Lib "user32" _
    (ByVal nIndex As Long) As Long
    
Public Sub InitializeColors()

    frmMain.Timer1.Interval = c_INITIALINTERVAL
    m_bolRunning = False
    With frmMain.imgSource
        m_intL = .Left
        m_intT = .Top
        m_intW = m_intL + .Width
        m_intH = m_intT + .Height
    End With
    Y = m_intT
    k = 1

End Sub
Public Sub ColorUpdate()
    
    If m_bolRunning Then
        frmMain.Timer1.Interval = c_RUNINTERVAL
    End If
    
    If Y > m_intH Or Y < m_intT Then
        Randomize
        m_intDelta = Int(256 * Rnd)
        k = -1 * k
        Y = Y + k
        frmMain.Timer1.Interval = c_WAITINTERVAL
        m_bolRunning = True
    End If
    For X = m_intL To m_intW
        Call BreakColor(frmMain.Point(X, Y), r, g, b)
        frmMain.PSet (X, Y), RGB(r, g, b)
    Next
    Y = Y + k
End Sub
' Break a color into is components.
Private Sub BreakColor(ByVal color As Long, ByRef r As Long, _
    ByRef g As Long, ByRef b As Long)

    If color = &HFFFFFFFF Then
        color = GetSysColor(color And &HFFFFFF)
    End If

    r = color And &HFF&
    g = (color And &HFF00&) \ &H100&
    b = (color And &HFF0000) \ &H10000
    
    r = (r + m_intDelta) Mod 256
    g = (g + m_intDelta) Mod 256
    b = (b + m_intDelta) Mod 256
    
End Sub