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Option Strict On

Public Class Form1
    ' Μπορείς να ζωγραφίσεις είτε στο paint event παίρνωντας το Graphics Object
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        Dim ctn As New Cartesian(e.Graphics)
        ''Dim X As Single
        ''Dim Y As Single

        ctn.Origin = New PointF(200, 200)

        e.Graphics.SmoothingMode = Drawing2D.SmoothingMode.HighSpeed

        ctn.DrawAxes()

        e.Graphics.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias

        ''For X = -10 To 50 Step 0.5!
        ''    Y = CType((Math.Sin(X)), Single)

        ''    ctn.Draw(New PointF(X, Y))
        ''Next

        ' Αν σε μπερδεύει το Delegate κάνε uncomment το προηγούμενο block
        ctn.Draw(AddressOf aFunction)
    End Sub

    ' Είτε στο OnPaint αν θές να κληρονομείται
    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        ' Μπλα Μπλα
        MyBase.OnPaint(e)
    End Sub

    ' Νπορείς επίσης να δημιουργήσεις Graphics Object όποτε το χρειάζεσαι.
    Private Sub cmdBitMap_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBitMap.Click
        Dim g As System.Drawing.Graphics = Me.CreateGraphics

        Me.BitmapPlot(g)
        g.Dispose()
    End Sub

    Private Sub cmdClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClear.Click
        Dim g As Drawing.Graphics = Me.CreateGraphics

        g.Clear(Me.BackColor)
        g.Dispose()
    End Sub

    Private Sub BitmapPlot(ByVal graphics As Drawing.Graphics)
        Dim bmp As New Bitmap(255, 255)

        ' Plot, Αν θές απόλυτο έλεγχο ανά pixel
        ' Δες και παράδειγμα με Lockbits αν θες καλύτερο perfomance
        ' http://msdn.microsoft.com/en-us/library/system.drawing.bitmap.lockbits.aspx

        For i As Integer = 0 To bmp.Width - 1
            For n As Integer = 0 To bmp.Height - 1
                bmp.SetPixel(i, n, Color.FromArgb(255, 255 - i, i, i))
            Next
        Next

        graphics.DrawImage(bmp, 0, 0)
        bmp.Dispose()
    End Sub

    Private Sub cmdPaint_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPaint.Click
        Me.Invalidate(False)
    End Sub

    Private Function aFunction(ByVal X As Single) As Single
        Return CType((Math.Sin(X)), Single)
    End Function
End Class

Public Class Cartesian
    Public Property Origin As PointF
    Public Property Graphics As System.Drawing.Graphics

    Private _PreviousPoint As PointF
    Private _bFirstTime As Boolean

    Public Sub New(ByVal graphics As System.Drawing.Graphics)
        Me._Graphics = graphics
        Me._bFirstTime = True
    End Sub

    Public Sub DrawAxes()
        Dim fnt As New Font("Arial", 8.0!)

        _Graphics.DrawLine(Pens.LightGray, 0, Origin.Y, 1000, Origin.Y)
        _Graphics.DrawLine(Pens.LightGray, Origin.X, 0, Origin.X, 1000)
        _Graphics.DrawString("(0,0)", fnt, Brushes.Orange, Origin)

        fnt.Dispose()
    End Sub

    Public Sub Draw(ByVal point As PointF)
        point.X *= 10 ' Ζουμαρε λίγο
        point.Y *= 10

        point = PointF.Add(point, New SizeF(Origin.X, Origin.Y - 2 * point.Y))

        If _bFirstTime Then
            _bFirstTime = False
            _PreviousPoint = point
            Return
        End If

        Dim pen As New Pen(Drawing.Color.Black, 1.6!)

        _Graphics.DrawLine(pen, _PreviousPoint, point)
        pen.Dispose()

        _PreviousPoint = point
    End Sub

    Public Sub Draw(ByVal MyFunction As Func(Of Single, Single))
        Dim X As Single
        Dim Y As Single

        For X = -10 To 50 Step 0.6!
            Y = MyFunction(X)
            Me.Draw(New PointF(X, Y))
        Next

        Me._bFirstTime = True
    End Sub
End Class