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Re: Off-Screen-Painting

To: Getting Started <gettingstarted at lists dot realsoftware dot com>
Subject: Re: Off-Screen-Painting
From: Eirik Karlsen <eikarlse at online dot no>
Date: Thu, 10 Feb 2005 23:15:53 +0100
Delivered-to: gettingstarted at lists dot realsoftware dot com
References: <001801c50fb9$7ff00550$0100a8c0 at bremerb7sqedlr>
Maybe I can contribute my 2 pennies worth.....

Play a bit with this code, it works for me:
'********************
  GraphFront=newPicture(CanvasGraph.width,CanvasGraph.height,16)  'This is the
Graphs

  GraphFront.graphics.ForeColor=GraphBackColor  'if you want color
  GraphFront.graphics.FillRect 0,0,GraphFront.width,GraphFront.height  'fill
with color

'''''''''''''''
'your code here, i.e:
'GraphFront.graphics.drawline (GX1),(GY2),(GX2),(GY2)
'''''''''''''

CanvasGraph.graphics.DrawPicture GraphFront,0,0 'Draw modified (buffered)
picture to Graphcanvas
'**********************


Also note that there is a huge difference in speed depending on colordepth,
obviously 32bit is the slowest.
A quick test showed that at
32bit I got 41 frames/sec
8bit I got 122 frames/sec
1bit I got 583 frames/sec





Marc-Hendrik Bremer wrote:

> Hello,
>
> I have some methods painting some graphics-stuff in a canvas. That works
> fine but is quite slow.
> Now I want to use an extra buffer as mentioned here and in the docs. I have
> "Offg" (of class picture) as a property of my canvas-class and build it with
> a NewPicture(x,y,0) in an early method. But if I try to pass Offg.graphics
> to my painting methods, the Parameter they get is always "Nil" and I (of
> course) get an exception when they try to use the graphics-methods on it.
> Passing the parameter ByRef did not work either.
>
> What am I doing wrong?
>
> Any help would be realy nice!
>
> Regards,
>
> Marc-Hendrik

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Regards
Eirik Karlsen


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