On Thu, 29 Sep 2005 15:21:15 +0200
"Crause, Christo (JC)" <[EMAIL PROTECTED]> wrote:
> > I'm developing an osciloscope gui with Lazarus, so I need to
> > draw very
> > basic graphics (just lines to being with) to show the wave format.
> >
> > I have lots of dots that the hardware sends me (500 of them). What
> > component should I put on my form to draw on it's canvas? TImage or
> > TPaintBox? That is the difference between them?
> >
> > I've being trying without success since monday ... Can
> > someone provide
> > me an very basic example that will just draw 10 lines on an
> > white empty
> > drawing space??
> >
> > I could not find a very basic graphical example on the
> > examples folder
> > ... maybe I can add one after I get this stuff working...
> >
> > I thought I could just write to the canvas, and everything
> > would be ok.
> > I put a TImage on my form, added a OnPaint event to it and wrote:
> >
> > procedure TForm1.TelaPaint(Sender: TObject);
> > var
> > Bitmap: TBitmap;
> > x, y: Integer;
> > begin
> > Bitmap := TBitmap.Create;
> > try
> > Bitmap.PixelFormat := pf24bit;
> >
> > Bitmap.Canvas.Pen.Color := clBlack;
> > Bitmap.Canvas.MoveTo(0, 0);
> > for x := 0 to 499 do
> > begin
> > y := Medidas[x];
> > Bitmap.Canvas.LineTo(2 * x,y);
> > end;
> >
> > Tela.Canvas.Draw(0, 0, Bitmap);
> > finally
> > Bitmap.Free;
> > end;
> > end;
>
> The following code draws a blue line on red background on a Timage on a
> form:
>
> procedure TForm1.BitBtn1Click(Sender: TObject);
> begin
> // Fill in background
> Image1.Canvas.Brush.Color := clRed;
> Image1.Canvas.Rectangle(0, 0, Image1.Width, Image1.Height);
>
> // Draw a line
> Image1.Canvas.Pen.Color := clBlue;
> Image1.Canvas.MoveTo(0,0);
> Image1.Canvas.LineTo(50, 50);
> end;
Drawing to an image calls Invalidate. That's probably too much overhead for
drawing 500 lines.
The buffer approach above is faster. Don't set pf24bit, set Width and
Height.
Mattias
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