Steema Central

Posted: **Wed Jul 03, 2019 9:39 am**

Hello,

I have been using TeeChart for a long time but I am dealing with a slow display problem when I want to display a 2 millions points serie.

By reading documentations, I am using a TFastLineSeries serie with some particular options in order to speed up display:

Code: Select all

      DrawAllPoints:= False ;
      DrawAllPointsStyle:= daMinMax ;
      FastPen:= False ;
      AutoRepaint:= False ;

I also tried to set Min/Max before adding data to serie but it didn't improve display.

The display is very slow while the filling of the serie is fast.

Here is the link of my project with datas to display:
https://drive.google.com/open?id=1z_0AU ... 4yodkAj12U

Does someone has an idea or some tips to improve display ?

Regards

Posted: **Wed Jul 10, 2019 1:57 pm**

Hello,

I've added a couple of extra columns to check the drawing speed and the number of values in the series:

Code: Select all

var tmpDraw: Int64 ;

procedure TForm1.va(Sender: TObject);
begin
  tmpDraw:= GetTickCount64 ;
end;

procedure TForm1.Chart1AfterDraw(Sender: TObject);
begin
  StringGrid1.Cells[2, StringGrid1.RowCount-2]:= IntToStr(GetTickCount64 - tmpDraw) ;
end;

procedure TForm1.ListBox1HddDblClick(Sender: TObject);
//...
  StringGrid1.Cells[2,0]:= 'Chart draw' ;
  StringGrid1.Cells[3,0]:= 'Points' ;
  //...
    StringGrid1.Cells[3, StringGrid1.RowCount-1]:= IntToStr(k) ;
  //...

Here the results I get:
- Drawing all the points (DrawAllPoints=True):

: Project1_2019-07-10_15-40-47.png (73.07 KiB) Viewed 9003 times

- Using daMinMax algorithm:

: Project1_2019-07-10_15-35-09.png (73.45 KiB) Viewed 9003 times

- Using daFirst:

: Project1_2019-07-10_15-36-34.png (72.01 KiB) Viewed 9003 times

We can see that, for the given data and configuration, the daMinMax algorithm doesn't improve the drawing speed, but the daFirst algorithm has a significant impact on the drawing speed.

Another alternative is to use the TSmoothingFunction, which takes some time to calculate, but improves the drawing speed with a result more similar to the original series:

Code: Select all

    DownSampleSerie := TFastLineSeries.Create(Nil) ;
    with DownSampleSerie do
    begin
      ParentChart:= Chart1 ;
      Color:=IntensiteSerie.Color;

      DownSampleFun := TDownSamplingFunction.Create(nil);
      SetFunction(DownSampleFun);

      DownSampleFun.Tolerance := 4;
      DownSampleFun.DownSampleMethod := dsAverage;

      DataSource := IntensiteSerie;
    end;

: Project1_2019-07-10_15-55-25.png (63.54 KiB) Viewed 9003 times

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