GraphicsDoubleBuffer

Introduction

This is a simple class i designed to remove flickering from painting controls with gdi+. The class removes flickering by double buffering the drawing. It draws on a separate bitmap canvas file. Once all drawing is complete, you can then push the drawing to the main drawing canvas all at once. This will kill most if not all flickering the drawing produces.

Code

Below is the simple class:

Public Class GraphicsDoubleBuffer

        Private P_Canvas As Bitmap

        Public Property [Canvas]() As Bitmap
            Get
                Return P_Canvas
            End Get
            Set(ByVal Value As Bitmap)
                P_Canvas = Value
            End Set
        End Property

        Public Sub New(ByVal CanvasWidth As Integer, 
                   ByVal CanvasHeight As Integer)
            P_Canvas = New Bitmap(CanvasWidth, CanvasHeight)
        End Sub

        Public Function Store() As Graphics

            Dim g As Graphics = Graphics.FromImage(P_Canvas)
            Return g

        End Function

        Public Sub Paint(ByVal Where As Object)

            Dim g As Graphics = Where.CreateGraphics()
            g.SmoothingMode = SmoothingMode.None
            Dim g2 As Graphics = Graphics.FromImage(P_Canvas)
            g2.SmoothingMode = SmoothingMode.None
            g.DrawImage(P_Canvas, 0, 0)
            g.Dispose()
            g2.Dispose()

        End Sub

        Public Sub [Dispose]()

            P_Canvas.Dispose()

        End Sub

    End Class

To use this class in your custom control add the following code to your project.

Dim g As New GraphicsDoubleBuffer(ClientRectangle.Width, 
    ClientRectangle.Height)
g.Store()
g.Paint(Me)
g.Dispose()

Start by declaring a constructor to the GraphicsDoubleBuffer() Class. Pass the the constructor the drawing dimensions of your canvas or form. Next use store() as your new gdi+ graphics object. You can do this several ways.

Example 1:

Dim g2 as graphics = g.store() 
g2.FillRectangle(New SolidBrush(Color.black), New Rectangle(20, 20, 20, 20))

Example 2:

g.store.FillRectangle(New SolidBrush(Color.black), 
    New Rectangle(20, 20, 20, 20))

After you have drawn to the store() graphics object, you then must push it to your main drawing canvas like so:

g.paint(Me)

"Me" must be the user control or form. After that we dispose() of the drawing object to clear it from memory.

g.dispose()

Resources

• http://windowsforms.net/articles/windowsformspainting.aspx

Conclusion

Well this concludes my simple double buffering class. If you use this class properly, it can be a vital resource to you. Latez, VectorX

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Very nice VaclavAntosik 12:49 27 Nov '07   Thanks for this article. I will use that for my new control. I hate computers Sign In·View Thread·PermaLink Are there a faster vb .net grapihcs masterdima 11:33 21 Jun '07   for my current project i'm using around 360 lines being redrawn continuously and their position being recalculate at the same rate. i'm using cos/sin functions to calculate their movement. Is the speed affected by the vb .net graphics abilities or the time for cos/sin function to calculate? Are there any alternate fast and easy graphics that i can use like directx(which is not easy) Sign In·View Thread·PermaLink Re: Are there a faster vb .net grapihcs [modified] VectorX 16:03 21 Jun '07   The only thing i can suggest is to get max performance out of GDI+ is to use global brushes,fonts,colors,pens,etc. and dont dispose of them until your app closes. Try to use paths if you can to draw your lines. Test your calculations without drawing them and see if it takes a long time. It might be your loops and calculations, instead of the drawing. See if you can globally store your calculations if they dont change. Try drawing like this example to a offscreen bitmap. Try to make the bitmap global and dont dispose of it on every pass, instead just paint over it with a background color rectangle. If your drawing has alot of colors then keep your graphics set on high quality, if not try moving the setting to low or anti. Another thing to check is bitmap width and height and make sure it is set to the size that you need and not some 2400px by 2400px size size has alot to do with memory and speed to render. Another trick of the trade for rendering is to draw like windows gui. Only draw a section rather than the entire whole bitmap. For example say only a small area of your drawing needs to be rendered but everything else stays the same. Draw a rectangle with those cords and paint the background color and then draw the new on top of it just for that location. i.e XXXXXXXXXXXXXXXXXXXXXXXXXXX X.Whole Bitmap or surface............X X.............................................X X.................xxxxxxxxxxxxx..........X X.................x Draw Only x..........X X.................x This!........x..........X X.................xxxxxxxxxxxxx..........X X.............................................X XXXXXXXXXXXXXXXXXXXXXXXXXXX This is usually the fastest drawing solution. If all else fails try using directx...but GDI+ should be fast enough to render almost game speed, 256 colors. -- modified at 21:15 Thursday 21st June, 2007 Sign In·View Thread·PermaLink It's a bit slow, is there a faster way masterdima 13:54 17 Jun '07   Right now i'm making a "game" that is drawn using lines. when i don't use the GraphicsDoubleBuffer the screen flickers, but it runs fairly fast. once i start using this, it becomes slows as hell.:( in vb6 i was able to get rid of this broblem just by changing form window option that was called AutoRedraw or something like that. Is there a way to do this faster,codewise or by changing some properties. thanks, i really need this. Sign In·View Thread·PermaLink Re: It's a bit slow, is there a faster way VectorX 16:00 17 Jun '07   Just use this and do all the painting yourself //Set the control styles---------------------------------- this.SetStyle(ControlStyles.DoubleBuffer, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.UserPaint, true); this.SetStyle(ControlStyles.SupportsTransparentBackColor, true); //-------------------------------------------------------- Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: It's a bit slow, is there a faster way masterdima 18:18 17 Jun '07   thanks man, i was just about to quit on vb.net and just go with c++ Sign In·View Thread·PermaLink thanks suchinoko 19:14 23 May '07   thanks!!! Sign In·View Thread·PermaLink Thanks netislander 10:37 19 Mar '07   helped with a problem I was having with merging graphics together. Worked like a champ. Thanks! Sign In·View Thread·PermaLink what about the SetStyles method ? alpha_centurian 18:45 4 Sep '06   as far as i know , the way to implement double buffering in VB.NET is : Public Sub New() MyBase.New() 'This call is required by the Windows Form Designer. InitializeComponent() 'Add any initialization after the InitializeComponent() call Me.SetStyle(ControlStyles.DoubleBuffer Or ControlStyles.UserPaint Or ControlStyles.AllPaintingInWmPaint, True) Me.UpdateStyles() End Sub but this is not working ... any help ? Sign In·View Thread·PermaLink 2.00/5 (1 vote) The really old days Giles 21:44 28 Jul '04   I remember when doing gui stuff on my old Atari ST years ago, having to sync with the vertical screen refresh. There was a system call to block until the begining of the new refresh. They were the days. None of this double buffering stuff. Just real men aligning there redraws with the hardware. "Je pense, donc je mange." - Rene Descartes 1689 - Just before his mother put his tea on the table. Shameless Plug - Distributed Database Transactions in .NET using COM+ Sign In·View Thread·PermaLink void xbios(26) ? Kochise 22:13 28 Jul '04   You then better had to draw quick to get the expected 1 VBL screen refresh rate. Double buffering was heavily used on ATARI, but the screen switch was sync with the hard, which made the double buffering even more efficient ! Kochise In Code we trust ! Sign In·View Thread·PermaLink Re: void xbios(26) ? Giles 12:25 29 Jul '04   Yep, XBIOS 26. Did not want to sound to geeky be know that when I mentioned it. Those days were really good fun for GUI stuff. It was when the switch statment rulled supreme for C based GUI's. And yes there was double buffering, but you had to be careful about it. I remember how much better the STe made things with it blitter chip. 68000's were lovely to code for. Intel got it wrong from the ground up with the ugliest assembeler going I think. Everythings the wrong way around. "Je pense, donc je mange." - Rene Descartes 1689 - Just before his mother put his tea on the table. Shameless Plug - Distributed Database Transactions in .NET using COM+ Sign In·View Thread·PermaLink or you could just Allen Anderson 15:30 28 Jul '04   use the system call that does the same thing. SetStyle( ControlStyles.AllPaintingInWmPaint | ControlStyles.ResizeRedraw | ControlStyles.Opaque | ControlStyles.UserPaint | ControlStyles.DoubleBuffer | ControlStyles.Selectable | ControlStyles.UserMouse, true ); Cheers, Allen Sign In·View Thread·PermaLink 2.00/5 (1 vote) Re: or you could just VectorX 17:36 28 Jul '04   Yea, but can you turn it off and on whenever you want throughout your class? Sign In·View Thread·PermaLink Re: or you could just Matthew Adams 9:09 30 Jul '04   Yes, just call SetStyle again. And presumably, you're only doing painting in your paint event, right? Although there is a good use for this: buffering up updates drawing onto your canvas from a secondary thread when there is a lot of calculation involved, and you can are not expecting to be able to do a complete redraw whenever a paint may be requested (e.g. because someone's dragged something over your window). You just blit 'last known good' in OnPaint(), and draw onto your back buffer wherever, switching your 'last known good' and backbuffer when you reach another 'good' state. It is still a good idea to enable the control styles in question, though, for more efficiency, and better behaviour when people decorate your painting themselves, as will typically occur if you can manipulate the content of the control (e.g. a drawing surface). Matthew Adams CTO Digital Healthcare Inc Sign In·View Thread·PermaLink Re: or you could just VectorX 11:16 30 Jul '04   When you turn off double buffering in your styles, doesn't it turn it off for the whole control or form? This can cause an undesirable flicker if more than one method is controlling style double buffering. Not everyone paints in the paint event. Some people think outside the box. Latez, VectorX Sign In·View Thread·PermaLink Re: or you could just Rhy Mednick 7:12 3 Aug '04   At first glance I thought that this class was a little redundant myself, but then I found another use for it. If you have a control that has multiple visual states, like a mouse_over or mouse_down state, then you could cache those states in multiple GraphicsDoubleBuffer objects and swap them out depending on what you need to display. Sure, it takes more memory than drawing fresh each time, but memory is cheap. Rhy Mednick Heart,Soul, Flesh, and Bones Chicken Scratch Software Because typing is for sissies http://www.ChickenScratchSoftware.com Sign In·View Thread·PermaLink

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