VB.NET_Graph_Triming_Test_TrimPosition set with SlideBar

Dobon_bitmap_trim_00.vb

Public Class Form1

    Dim totalPlot As Bitmap
    Dim tg As Graphics

    Private Sub plotSlider(ByVal startNo As Integer)
        '画像の一部を切り取って（トリミングして）表示する
        Debug.Print(startNo)
        Dim timeScale As Integer = 3

        Dim canvas As New Bitmap(PictureBox1.Width, PictureBox1.Height) 'W=400,H=240
        Dim g As Graphics = Graphics.FromImage(canvas)

        Dim srcRect As New Rectangle(startNo, 0, 400, 210)
        '描画する部分の範囲を決定する。ここでは、位置(0,0)、大きさソース切取りサイズで描画する
        Dim desRect As New Rectangle(0, 0, srcRect.Width, srcRect.Height)
        '画像の一部を描画する
        g.DrawImage(totalPlot, desRect, srcRect, GraphicsUnit.Pixel)

        'Graphicsオブジェクトのリソースを解放する
        g.Dispose()

        'PictureBox1に表示する
        PictureBox2.Image = canvas
    End Sub

    Private Sub HScrollBar1_ValueChanged(sender As Object, e As EventArgs) Handles HScrollBar1.ValueChanged
        'maximum=1200 minimum=0
        Dim slideVal As Integer = HScrollBar1.Value
        plotSlider(slideVal)
        TextBox1.Text = CStr(slideVal)

    End Sub

    '元グラフを作成する
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        totalPlot = New Bitmap(PictureBox1.Width * 3, PictureBox1.Height)
        tg = Graphics.FromImage(totalPlot)
        Dim i As Integer

        For i = 1 To PictureBox1.Width * 3
                Dim px As Integer = i
                Dim py As Integer = Math.Sin(Math.PI / 30 * i) * 100 * (i / 1200) + 100
                tg.FillEllipse(Brushes.Red, px, py, 4, 4)

        Next i

        PictureBox1.Image = totalPlot

    End Sub
End Class