I have this code which creates a picturebox during runtime and displays line graph but I always get an error in this line:
gr1.DrawImage(pic1.Image, -m_Dx, 0) 'it says Value cannot be null. Parameter name: image
code Code:
Public Class Form1 Private Const m_Dx As Single = 1 Dim data As Integer = 1 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim pic1 As New PictureBox pic1.Location = New Point(12, 12) pic1.Name = "pic1" pic1.Width = 142 pic1.Height = 102 pic1.Visible = True pic1.BackColor = Color.Black pic1.BorderStyle = BorderStyle.Fixed3D Controls.Add(pic1) Dim bm1 As New Bitmap(pic1.Width, pic1.Height) Dim gr1 As Graphics = Graphics.FromImage(bm1) gr1.DrawImage(pic1.Image, -m_Dx, 0) gr1.ScaleTransform(1, -101 / pic1.Height) gr1.TranslateTransform(0, -101) Dim new_value1 As Integer = Val(data) / 2 If new_value1 < 1 Then new_value1 = 1 gr1.DrawLine(Pens.Blue, _ pic1.Width - 1, 0, _ pic1.Width - 1, new_value1) For i As Integer = 20 To 80 Step 20 gr1.DrawLine(Pens.Red, pic1.Width - m_Dx, i, pic1.Width, i) Next i pic1.Image = bm1 End Sub Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick data = data + 1 End Sub End Class
Did I miss something?




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