Re: [Lazarus] TAChart with transparent background
The image is a 30KB png, not much. It is smaller than the area, so it gets actually stretched. Can I use Draw instead of StretchDraw if I make the image exactly the size I need? I can force the form size. I think that tens of milliseconds can be actually relevant, because I am plotting data received (and processed) every 50ms from a serial port. R# 2014-09-16 0:07 GMT+02:00 Werner Pamler : > I added some simple time measuring code (using GetTickCount) to the > background image tutorial to see the speed loss that you mention: Without > the backgrounds (Lazarus logo and gradient) the GetTickCount reports 0 ms > between the OnBeforeDrawBackground and OnAfterPaint events, while with the > backgrounds it reports 16 ms, sometimes 0 ms. Replacing the StretchDraw by > a simple Draw in the painting of the logo, brings down the time also to 0. > Therefore I'd guess that the background painting is not perceivable unless > you squeeze a 20 mega-pixel photo into the chart area or load the image > during the painting event. > > What exactly are you doing? > > > -- > ___ > Lazarus mailing list > Lazarus@lists.lazarus.freepascal.org > http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus > -- ___ Lazarus mailing list Lazarus@lists.lazarus.freepascal.org http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
Re: [Lazarus] TAChart with transparent background
Though really late, I can confirm that the solution is working fine.
I still have to add some profiling code to measure it, though with added
background it seems perceivably slower even on a recent PC (core i5 vpro).
Are BGRA or other backends known to be faster?
thanks anyway for the help!
R#
2014-09-04 1:08 GMT+02:00 Roberto P. :
> Thank you very much.
> I need a background image, therefore as soon as I am back at the office
> I'll try your code.
> Thank you again!
>
> R#
>
>
> 2014-09-02 18:18 GMT+02:00 Werner Pamler :
>
>> It is not fully clear to me what you mean by "a chart with transparent
>> background". Do you want to see the form underneath the chart? I fear this
>> is not easily possible. Or do you want to have a background image in the
>> chart? For the latter case this code is working fine with me:
>>
>> type
>> TForm1 = class(TForm)
>> Chart1: TChart;
>> procedure Chart1BeforeDrawBackground(ASender: TChart; ACanvas:
>> TCanvas;
>> const ARect: TRect; var ADoDefaultDrawing: Boolean);
>> procedure Chart1BeforeDrawBackWall(ASender: TChart; ACanvas: TCanvas;
>> const ARect: TRect; var ADoDefaultDrawing: Boolean);
>> procedure FormCreate(Sender: TObject);
>> procedure FormDestroy(Sender: TObject);
>> private
>> { private declarations }
>> FBackImage: TPicture;
>> public
>> { public declarations }
>> end;
>>
>> procedure TForm1.Chart1BeforeDrawBackWall(ASender: TChart; ACanvas:
>> TCanvas;
>> const ARect: TRect; var ADoDefaultDrawing: Boolean);
>> begin
>> ADoDefaultDrawing := false;
>> ACanvas.StretchDraw(ARect, FBackImage.Graphic);
>> end;
>>
>> procedure TForm1.Chart1BeforeDrawBackground(ASender: TChart; ACanvas:
>> TCanvas;
>> const ARect: TRect; var ADoDefaultDrawing: Boolean);
>> begin
>> ACanvas.GradientFill(ARect, clSkyBlue, clWhite, gdVertical);
>> ADoDefaultDrawing := false;
>> end;
>>
>> procedure TForm1.FormCreate(Sender: TObject);
>> begin
>> FBackImage := TPicture.Create;
>> FBackImage.LoadFromFile('C:\lazarus-svn\images\splash_logo.png');
>> // please adapt this path to your lazarus installation
>> end;
>>
>> procedure TForm1.FormDestroy(Sender: TObject);
>> begin
>> FBackImage.Free;
>> end;
>>
>> The basic idea is to assign a handler to the chart events
>> OnBeforeDrawBackWall or OnBeforeDrawBackground and disable the default
>> background painting by setting ADoDefaultDrawing to false. The first event
>> replaces painting of the area enclosed by the chart's frame ("Back wall"),
>> the other one replaces painting of the entire chart background. Above
>> example paints the Lazarus splash-logo as BackWall and a gradient as
>> background.
>>
>> Maybe I'll once write a tutorial on this topic...
>>
>>
>> --
>> ___
>> Lazarus mailing list
>> Lazarus@lists.lazarus.freepascal.org
>> http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
>>
>
>
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___
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Re: [Lazarus] TAChart with transparent background
Thank you very much.
I need a background image, therefore as soon as I am back at the office
I'll try your code.
Thank you again!
R#
2014-09-02 18:18 GMT+02:00 Werner Pamler :
> It is not fully clear to me what you mean by "a chart with transparent
> background". Do you want to see the form underneath the chart? I fear this
> is not easily possible. Or do you want to have a background image in the
> chart? For the latter case this code is working fine with me:
>
> type
> TForm1 = class(TForm)
> Chart1: TChart;
> procedure Chart1BeforeDrawBackground(ASender: TChart; ACanvas:
> TCanvas;
> const ARect: TRect; var ADoDefaultDrawing: Boolean);
> procedure Chart1BeforeDrawBackWall(ASender: TChart; ACanvas: TCanvas;
> const ARect: TRect; var ADoDefaultDrawing: Boolean);
> procedure FormCreate(Sender: TObject);
> procedure FormDestroy(Sender: TObject);
> private
> { private declarations }
> FBackImage: TPicture;
> public
> { public declarations }
> end;
>
> procedure TForm1.Chart1BeforeDrawBackWall(ASender: TChart; ACanvas:
> TCanvas;
> const ARect: TRect; var ADoDefaultDrawing: Boolean);
> begin
> ADoDefaultDrawing := false;
> ACanvas.StretchDraw(ARect, FBackImage.Graphic);
> end;
>
> procedure TForm1.Chart1BeforeDrawBackground(ASender: TChart; ACanvas:
> TCanvas;
> const ARect: TRect; var ADoDefaultDrawing: Boolean);
> begin
> ACanvas.GradientFill(ARect, clSkyBlue, clWhite, gdVertical);
> ADoDefaultDrawing := false;
> end;
>
> procedure TForm1.FormCreate(Sender: TObject);
> begin
> FBackImage := TPicture.Create;
> FBackImage.LoadFromFile('C:\lazarus-svn\images\splash_logo.png');
> // please adapt this path to your lazarus installation
> end;
>
> procedure TForm1.FormDestroy(Sender: TObject);
> begin
> FBackImage.Free;
> end;
>
> The basic idea is to assign a handler to the chart events
> OnBeforeDrawBackWall or OnBeforeDrawBackground and disable the default
> background painting by setting ADoDefaultDrawing to false. The first event
> replaces painting of the area enclosed by the chart's frame ("Back wall"),
> the other one replaces painting of the entire chart background. Above
> example paints the Lazarus splash-logo as BackWall and a gradient as
> background.
>
> Maybe I'll once write a tutorial on this topic...
>
>
> --
> ___
> Lazarus mailing list
> Lazarus@lists.lazarus.freepascal.org
> http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
>
--
___
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