Fade out colors

[overseer21]

I am new in visual basic and I have one little problem.I want when the mouse is moving on the form to paint a red line.Every point of this line must start to fade out 1 second after being painted and to disappear after 3 seconds.I appreciate if anyone can help me.

[Illuminator]

Here is a little funtions that draw and fades circles on a picture box

'Place this code in a Module
Type point
    X As Integer
    Y As Integer
    life As Single
End Type

Public points() As point
Public point_count As Integer

'Place this in a Picture Box mousemove function
Dim i As Integer
If Button = 1 Then
    i = 0

    'find and use dead points
    While i < point_count
      If points(i).life <= 0.1 Then
        points(i).X = X
        points(i).Y = Y
        points(i).life = 4
      End If
      i = i + 1
    Wend
    
    'Need a new point
    If i = point_count Then
       point_count = point_count + 1
       ReDim Preserve points(point_count) As point
       i = point_count
       points(i).X = X
       points(i).Y = Y
       points(i).life = 4
    End If
    
    Picture1.Circle (points(i).X, points(i).Y), 2, RGB(255, 0, 0)
End If
End Sub


'place this in a Timer with interval = 100
Dim i As Integer
For i = 0 To point_count - 1
    If points(i).life >= 0.1 Then
      points(i).life = points(i).life - 0.1
    Else
      points(i).life = 0

    End If
    
    If points(i).life < 2 And points(i).life > 0 Then
        Picture1.Circle (points(i).X, points(i).Y), 2, RGB(255 * points(i).life / 2, 0, 0)
    End If
Next i

'Place this in form load
point_count = 0
ReDim points(point_count)

It doesn't draw lines beacause of replacement of dead points.
This does use minimal memory though because it does not waste space with points you cant see.

[Jotaf98]

Well, here's another idea. You'll need a timer (don't forget to set its interval to something low like 10ms), and to set the form's ScaleMode to Pixels.

Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long
Private Declare Function SetPixelV Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long, ByVal crColor As Long) As Long

Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
    If Button = vbLeftButton Then Picture1.PSet (X, Y), 255
End Sub

Private Sub Timer1_Timer()
    Dim X As Long, Y As Long, Temp As Long
        For X = 0 To Picture1.Width
            For Y = 0 To Picture1.Height
                Temp = GetPixel(Picture1.hdc, X, Y)
                Temp = Temp And 255
                Temp = Temp - 32
                If Temp < 0 Then Temp = 0
                SetPixelV Picture1.hdc, X, Y, Temp
            Next Y
    Next X
End Sub

The only problem is that it's a bit slow with large pictures...