Private Sub LinieZiehen(X1!, Y1!, X2!, Y2!)
  Dim DX!, DY!, a!, b!, X!, Y!
 
  DX = X2 - X1
  DY = Y2 - Y1
  If Abs(DX) > Abs(DY) Then
    a = DY / DX
    b = Y1 - a * X1
    For X = X1 To X2 Step Sgn(DX)
      Y = a * X + b
      Picture1.PSet (X, Y), vbWhite
    Next X
  Else
    a = DX / DY
    b = X1 - a * Y1
    For Y = Y1 To Y2 Step Sgn(DY)
      X = a * Y + b
      Picture1.PSet (X, Y), vbWhite
    Next Y
  End If
End Sub