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