paint/graphics on windows forms

Question

Dear programmers,

I made an application that displays a background bitmap on a windows form. When I click on any position of the bitmap a circle appears.

This is the main code:

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
Dim bild As New Bitmap("w:\test.bmp")
Dim feld As New Rectangle(0, 0, 800, 600)
e.Graphics.DrawImage(bild, feld, feld, GraphicsUnit.Pixel)

e.Graphics.DrawEllipse(Pens.Aqua, New Rectangle(x, y, 20, 20))

invalidate() is used to update the graphics on the form

However, I find it annoying that the bitmap flashes whenever the position of the circle is updated.
Obviously the bitmap is loaded every time I click the mouse.
Is there a way to avoid this flashing?

Thanks for your answers!

Yours,
Wolfgang Weirich

Answer 1

Man spricht deutsh. Das englischsprachige Visual Basic-Forum findest Du hier:
http://social.msdn.microsoft.com/Forums/en-US/vbgeneral/threads

Answer 2

Hallo Wolfgang,

Effizienter wird es, wenn Du einen BufferedGraphicsContext für die Bitmap verwendest:
http://msdn.microsoft.com/de-de/library/system.drawing.bufferedgraphics.aspx

Eine Alternative ist, die Bitmap der BackgroundImage Eigenschaft zuzuweisen
und nur die Ellipse im OnPaint zu zeichnen.

Gruß Elmar

Answer 3

Hallo Wolfgang,

Vesruch mal den bitmap background der Form mit

Form.Picture=LoadPicture(Pfad des bitmaps) laden und nacher den Zirkel zeichnen.

Mfg,

Robert