[Lazarus] Fast drawing to canvas

[dhkblaszyk at zeelandnet.nl]

I have played with Image.Update, .Invalidate and .Repaint, but none
of them seem to work for me. Only when I put Application.ProcessMessages
the painted images show on screen. See below for the testloop code. The
images are streamed from a file cache. For 24 frames this seems
overkill, but running at 24fps the memeory requirements quickly get very
large! 

Image.Transparent is also set to false btw, which is default.
Otherwise the drawing on the canvas is even messed up. 

Regards, Darius


procedure TForm1.Button1Click(Sender: TObject);
var
 s: TDateTime;
 i:
Integer;
begin
 s := now;
 for i := 1 to 24 do
 begin
 if
filecache_get_from_cache(i, png) then
 begin

Image1.Picture.Bitmap.LoadFromRawImage(png.RawImage, False);

Application.ProcessMessages;
 end;
 end; 

 ShowMessage(FloatToStr(24 /
((now - s) * 24 * 3600)))
end; 

On 8 feb '12, Flávio Etrusco wrote: 

>
On Wed, Feb 8, 2012 at 7:39 AM, Sven Barth wrote:
> 
>> Am 08.02.2012
01:07, schrieb dhkblaszyk at zeelandnet.nl: [1] 
>> 
>>> Hi, I'm drawing a
bitmap to the canvas by using LoadFromRawImage in combination with a
TImage. The OnPaint code below works just fine. When I move the
scrollbar, the images are drawn to the canvas, however there is still a
bit of flicker. procedure TForm1.Image1Paint(Sender: TObject); begin
Image1.Picture.Bitmap.LoadFromRawImage(bitmaplist[ScrollBar1.Position].RawImage,
False); Application.ProcessMessages; end;
>> Why are you calling
"Application.ProcessMessages" here? Regards, Sven
> 
> Good catch. I
guess the OP has used this previously to repaint
> controls/images
during a long-running procedure... (and even there
> it's often not the
best solution)
> @dhlblaszyk: when you want to force the repaint of the
whole control,
> call Image1.Repaint. If you want to just repaint some
invalidated part
> of it, call Image1.Update (not sure TGraphicControl
has Update, so you
> may need to use Parent.Update instead). Of course
you should do this
> *outside* the OnPaint. Also, is Image1.Transparent
set to false?
> BTW what do you mean by "The images are streamed
continuously from disk"?
> 
> Regards,
> Flávio
> 
> --
>
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