Draw Line and Rectangle on PictureBox using Mouse

[horia]

Hello!

I have an project created by vb.Net 2010.The ptoject has a PictureBox and I draw Grid in to PictureBox .Using Mouse to draw Polygons.
I want to draw Line and Rectangle only where the Line Crosses(x,y-axis).
Please help me!

Thank you!
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[XCODE]

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• Private Sub picTest_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picTest.MouseDown
• Dim hstep As Double = picTest.Width / 12
• Dim vstep As Double = picTest.Height / 12
• Dim myPen As New Pen(Color.Red, 3)
• Dim g As Graphics = Graphics.FromImage(gBitmap)
• picAG.Refresh()
• If e.Button = System.Windows.Forms.MouseButtons.Left Then
• points.Add(e.Location) ' add point on left click
• For i As Integer = 0 To points.Count - 1
• g.DrawRectangle(myPen, points(i).X - 2, points(i).Y - 2, 5, 5)
• Next
• End If
• If (NewPolygon IsNot Nothing) Then
• If (e.Button = MouseButtons.Right) Then
• gBitmap = Nothing
• ' Finish this polygon.
• If (NewPolygon.Count > 0) Then Polygons.Add(NewPolygon)
• NewPolygon = Nothing
• picTest.Image = gBitmap
• Else
• ' Add a point to this polygon.
• If (NewPolygon(NewPolygon.Count - 1) <> e.Location) Then
• Dim i As Integer
• For i = 0 To 12
• NewPolygon.Add(New Point(e.X, e.Y )'Here I think to use'hstep,vstep and i',but I don`t know how to do ?!
• picTest.Image = gBitmap
• Next i
• End If
• End If
• Else
• ' Start a new polygon.
• NewPolygon = New List(Of Point)()
• NewPolygon.Add(e.Location)
• NewPoint = (e.Location)
• End If
• ' Redraw.
• picTest.Invalidate()
• 'Dispose of objects
• myPen.Dispose()
• g.Dispose()
• Private Sub picTest_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picTest.MouseMove
• If (NewPolygon Is Nothing) Then Exit Sub
• NewPoint = e.Location
• ' Redraw.
• picTest.Invalidate()
• End Sub
• Private Sub picTest_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picTest.Paint
• Dim g As Graphics = e.Graphics
• Dim myPen As New Pen(Color.Red, 2)
• If (NewPolygon IsNot Nothing) Then
• ' Draw the new polygon.
• If (NewPolygon.Count > 1) Then
• e.Graphics.DrawLines(myPen, NewPolygon.ToArray())
• For i As Integer = 0 To points.Count - 1
• e.Graphics.FillEllipse(Brushes.Green, points(i).X - 2, points(i).Y - 2, 5, 5)
• Next
• End If
• End If
• Dim hstep As Double = picTest.Width / 12
• Dim vstep As Double = picTest.Height / 12
• 'Draw horizontal Line
• Dim X As Single = hstep
• For i As Integer = 0 To hstep
• g.DrawLine(New Pen(Color.Black, 2), New Point(X, 0), New Point(X, Height))
• X += hstep
• Next i
• Dim Y As Single = vstep
• For i As Integer = 0 To vstep
• 'Draw Vertical Line
• g.DrawLine(New Pen(Color.Black, 2), New Point(0, Y), New Point(Width, Y))
• Y += vstep
• Next i
• End Sub