[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Clear drawn image from a picturebox

Posted on 2009-04-22
4
Medium Priority
?
1,452 Views
Last Modified: 2012-05-07
Hi Experts

I have a picturebox in which I draw a sinewave or a squarewave depending on which radiobutton is clicked on.

I have included the two subroutines below.

My problem is that one draws over the other if I click on first one radiobutton and then the other. How do I clear the first drawing ready to draw the next??

The routines idealy should have something like:

pctWaveDisplay.clear

but there is nothing I can find.

Kind Regards

Simon
Private Sub drawSineWave()
 
 
        'I just draw a Sin graphics between 0-2p for example 
 
        Dim x0 As Single = 80.0F
 
        Dim y0 As Single = 50.0F
 
 
        'Assume the graphics width is 200pixels 
 
        'so there're 200 points 
 
        Dim points As PointF() = New PointF(199) {}
 
        For j As Integer = 0 To 199
 
 
            points(j) = New PointF()
 
            points(j).X = x0 + j
 
 
            points(j).Y = y0 - CSng((Math.Sin((2 * Math.PI * j) / 200) * (200 / (2 * Math.PI))))
 
        Next
 
        Using p As New Pen(Color.Blue)
 
            p.EndCap = LineCap.ArrowAnchor
 
            'Draw X-coordinate 
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0, x0 + 220, y0)
 
            'Draw(Y - coordinate)
 
            p.StartCap = LineCap.ArrowAnchor
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0 + 47, x0, y0 - 47)
 
            p.DashStyle = DashStyle.Dash
 
            p.Color = Color.Red
 
            p.StartCap = LineCap.NoAnchor
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0 - 32, x0 + 50, y0 - 32)
 
 
        End Using
 
        pctWaveDisplay.CreateGraphics.DrawString("0", SystemFonts.DefaultFont, Brushes.Blue, x0, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("p", SystemFonts.DefaultFont, Brushes.Blue, x0 + 95, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("2p", SystemFonts.DefaultFont, Brushes.Blue, x0 + 200, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("VOLTAGE", SystemFonts.DefaultFont, Brushes.Blue, x0 - 60, y0 - 43)
 
        pctWaveDisplay.CreateGraphics.SmoothingMode = SmoothingMode.AntiAlias
 
        pctWaveDisplay.CreateGraphics.DrawLines(Pens.Red, points)
 
    End Sub
 
    Private Sub drawSquareWave()
 
        'I just draw a Sin graphics between 0-2p for example 
 
        Dim x0 As Single = 80.0F
 
        Dim y0 As Single = 50.0F
 
 
        'Assume the graphics width is 200pixels 
 
        'so there're 200 points 
 
 
        Using p As New Pen(Color.Blue)
 
            p.EndCap = LineCap.ArrowAnchor
 
            'Draw X-coordinate 
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0, x0 + 220, y0)
 
            'Draw(Y - coordinate)
 
            p.StartCap = LineCap.ArrowAnchor
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0 + 47, x0, y0 - 47)
 
            'Draw the square wave.
 
            p.StartCap = LineCap.NoAnchor
            p.EndCap = LineCap.NoAnchor
 
            p.Color = Color.Red
 
            p.DashStyle = DashStyle.Solid
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0 - 10, y0, x0, y0)
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0, x0, y0 - 32)
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0, y0 - 32, x0 + 100, y0 - 32)
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0 + 100, y0 - 32, x0 + 100, y0)
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0 + 100, y0, x0 + 200, y0)
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0 + 200, y0, x0 + 200, y0 - 32)
 
            p.EndCap = LineCap.ArrowAnchor
 
            pctWaveDisplay.CreateGraphics.DrawLine(p, x0 + 200, y0 - 32, x0 + 210, y0 - 32)
 
        End Using
 
        pctWaveDisplay.CreateGraphics.DrawString("0", SystemFonts.DefaultFont, Brushes.Red, x0, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("p", SystemFonts.DefaultFont, Brushes.Red, x0 + 95, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("2p", SystemFonts.DefaultFont, Brushes.Red, x0 + 200, y0)
 
        pctWaveDisplay.CreateGraphics.DrawString("VOLTAGE", SystemFonts.DefaultFont, Brushes.Red, x0 - 60, y0 - 43)
 
        pctWaveDisplay.CreateGraphics.SmoothingMode = SmoothingMode.AntiAlias
 
 
 
    End Sub

Open in new window

0
Comment
Question by:si2030
  • 2
4 Comments
 
LVL 48

Accepted Solution

by:
Wayne Taylor (webtubbs) earned 2000 total points
ID: 24204052
Call the Refresh method of the PictureBox....

    pctWaveDisplay.Refresh()

...which forces a redraw of the control.

Wayne
0
 

Author Closing Comment

by:si2030
ID: 31618497
Wayne... Thankyou :)
0
 
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 24205463
You should be MANUALLY disposing of the graphics returned by your calls to CreateGraphics().  Additionally, you should use only ONE for the duration of your drawing:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.creategraphics(VS.71).aspx

    "The returned Graphics object must be disposed through a call to its Dispose method when it is no longer needed."

So something like:

    Dim G As Graphics = pctWaveDisplay.CreateGraphics()

    ' do ALL of your drawing with "G" in here
    G.DrawLine(...)
    G.DrawString(...)
    ' etc...

    G.Dispose()

If you want the graphics to be PERSISTENT and not get erased when the window is minimized or another window obscures yours then use the graphics supplied for you in the Paint() event of the PictureBox in the "e" parameter.
0
 
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 24205540
Nevermind...I see you have another question open where ABEL has already made these suggestions for you!  =)
0

Featured Post

Hire Technology Freelancers with Gigs

Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: Kraeven
Introduction Remote Share is a simple remote sharing tool, enabling you to see, add and remove remote or local shares. The application is written in VB.NET targeting the .NET framework 2.0. The source code and the compiled programs have been in…
1.0 - Introduction Converting Visual Basic 6.0 (VB6) to Visual Basic 2008+ (VB.NET). If ever there was a subject full of murkiness and bad decisions, it is this one!   The first problem seems to be that people considering this task of converting…
Integration Management Part 2
Loops Section Overview

873 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question