prague12

   Dim g As Graphics = Me.PictureBox1.CreateGraphics()
    Dim p_blue As New Pen(Color.Blue, 1)
    Dim p_black As New Pen(Color.Black, 1)
    Dim p_red As New Pen(Color.Red, 1)

    Dim x_all = PictureBox1.Width

    Static xx1 As Integer
    Static yy1 As Integer

    Static yin As Integer

    yin = yin + 1
    yy1 = CInt(Math.Sin(yin * 0.01745) * 70) ' Y軸值大小  -70 ~ 70

    xx1 = xx1 + 1   'X方向遞增   但是GDI限定只能是整數點  最小間隔  1

    Dim scale_x = xx1 + CInt(Me.PictureBox1.Width / 2)     '重訂起始中心X座標   >> 正中間
    Dim scale_y = -yy1 + CInt(Me.PictureBox1.Height / 2)   '重訂起始中心Y座標

    Dim scale_x_0 = CInt(Me.PictureBox1.Width / 2)
    Dim scale_y_0 = CInt(Me.PictureBox1.Height / 2)   '中心

    Dim ppp As Pen '定義  ppp  物件是 pen  類別
    'yy1 = 100
    Static turn As Integer  ' 用來調換ppp 繪圖顏色的條件

    If xx1 Mod 180 = 0 Then   '每180度 清除圖表
    PictureBox1.Refresh()
    End If

    '---------------------------------------------------------------------

    If scale_x = Me.PictureBox1.Width Then  '當繪圖X方向到底  則跳往左半邊繼續畫

    turn = turn + 1 '紀錄第幾次跳換邊界
    xx1 = -CInt(Me.PictureBox1.Width / 2)

    End If
    '------------------------------------------------------------

    If turn Mod 2 = 1 Then
    ppp = p_blue    ' 指定ppp的顏色
    Else
    ppp = p_black
    End If

    '--------------------------------------------------------
    g.DrawEllipse(ppp, scale_x, scale_y, 2, 2)  '以ppp為畫筆  描點
    g.DrawLine(ppp, scale_x, CInt(Me.PictureBox1.Height / 2), scale_x, scale_y)  '描stem

    '  me.TextBox1.Text = yy1 & "," & me.TextBox1.Text   '測試用

    '-------標上刻度----------------------------------------------------
    Dim b_red As New SolidBrush(Color.Red)   '要先建立b_red 的  SolidBrush類別物件下面要用到Brush 

    ' ps: NET cf 下 沒有 BRUSHES 物件 ,只能自己以 SolidBrush 類別來創brush物件

    Dim interval = 30   '刻度範圍大小
    Dim interval_N = CInt(x_all / interval) '將 X軸 刻上 N個度
    For NN = 1 To interval_N
    g.DrawLine(p_red, NN * interval, scale_y_0 + 5, NN * interval, scale_y_0 - 5)  '畫刻度
    g.DrawString(NN * interval, Me.Font, b_red, NN * interval, scale_y_0 + 5)   '標數值

    Next
    '--------/標上刻度/----------------------------------------------

    g.DrawLine(p_black, 0, CInt(Me.PictureBox1.Height / 2), CInt(Me.PictureBox1.Width), CInt(Me.PictureBox1.Height / 2))  'x軸
    g.DrawLine(p_black, CInt(Me.PictureBox1.Width / 2), 0, CInt(Me.PictureBox1.Width / 2), CInt(Me.PictureBox1.Height))  'y軸
    g.DrawLine(p_black, CInt(0), 0, CInt(0), CInt(Me.PictureBox1.Height))   'y-左邊界
    g.DrawLine(p_black, CInt(Me.PictureBox1.Width - 1), 0, CInt(Me.PictureBox1.Width - 1), CInt(Me.PictureBox1.Height))  'y右邊界