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Fade out transparent image on top of a chart
Posted: Wed Sep 24, 2014 2:43 pm
by 16567885
TeeChart has a lot of funky stuff. I can place some good-looking text anywhere on my chart using the TAnnotationTool. Have a look:
- This is just text on top of the chart
- chartTextAnnotation.png (13 KiB) Viewed 7607 times
Now the time has come to place an
image on top of the chart. Not even that, I need to show it, and then slowly fade it out. How would one go about this? I'm a bit clueless. Have a look at these two images:
- fade1.png (19.74 KiB) Viewed 7590 times
- fade2.png (18.53 KiB) Viewed 7592 times
This is what I need it to look like.
My best try (this is how both pictures were made) is to place a VCL form with a slowly decreasing
AlphaBlendValue on top of the chart. The drawback of this approach is that I always have to monitor if the coordinates of my "overlay form" match with the
screen coordinates of my chart. I'd also need to monitor the chart's form of moving around, getting minimized, all kinds of stuff.
Are there any better ideas? I see I can easily place random components inside my chart
. But transparent components don't seem to keep their transparency when put in there.
Many thanks in advance.
Re: Fade out transparent image on top of a chart
Posted: Thu Sep 25, 2014 8:04 am
by yeray
Hello Jens,
What about using a TTimer to change the Transparency of your shape?
Here it is an example with a TRectangleTool:
Code: Select all
uses Series, TeeTools, TeePNGImage;
var myRectTool: TRectangleTool;
timerUp: Boolean;
procedure TForm1.FormCreate(Sender: TObject);
begin
Chart1.View3D:=false;
Chart1.AddSeries(TLineSeries).FillSampleValues();
myRectTool:=Chart1.Tools.Add(TRectangleTool) as TRectangleTool;
with myRectTool do
begin
Shape.Picture.LoadFromFile('E:\tmp\elephant_transparent.png');
Shape.Transparency:=0;
Shape.Left:=100;
Shape.Top:=100;
Shape.Width:=200;
Shape.Height:=200;
Shape.Pen.Visible:=false;
end;
Label1.Caption:='Transparency: 0 %';
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
timerUp:=myRectTool.Shape.Transparency=0;
with TTimer.Create(Self) do
begin
Interval:=50;
OnTimer:=MyTimerOnTimer;
Enabled:=true;
end;
end;
procedure TForm1.MyTimerOnTimer(Sender: TObject);
begin
if timerUp then
myRectTool.Shape.Transparency:=myRectTool.Shape.Transparency+5
else
myRectTool.Shape.Transparency:=myRectTool.Shape.Transparency-5;
Label1.Caption:='Transparency: ' + IntToStr(myRectTool.Shape.Transparency) + ' %';
Chart1.Draw;
if (myRectTool.Shape.Transparency=0) or (myRectTool.Shape.Transparency=100) then
(Sender as TTimer).Enabled:=false;
end;
Re: Fade out transparent image on top of a chart
Posted: Thu Sep 25, 2014 10:39 am
by 16567885
That is bloody beautiful! 
It never entered my mind the TRectangleTool can be textured. This is exactly what I want. And it looks really good.
By the way: I couldn't get the TeePNGImage-include to work. I found no binary dcu and hat to include some source file. After that, it didn't even work. Stepping through it, I found that it incorrectly read out the PNG headers from the stream and then bailed out with an exception. I now use the default unit of Vcl.Imaging.PngImage for loading a PNG image.
Thanks a ton!
Re: Fade out transparent image on top of a chart
Posted: Thu Sep 25, 2014 11:08 am
by yeray
Hi Jens,
You are welcome!
jens.mertelmeyer wrote:By the way: I couldn't get the TeePNGImage-include to work. I found no binary dcu and hat to include some source file. After that, it didn't even work. Stepping through it, I found that it incorrectly read out the PNG headers from the stream and then bailed out with an exception. I now use the default unit of Vcl.Imaging.PngImage for loading a PNG image.
I used TeePNGImage because I was using Delphi 7 to test this. However, you should change it for PNGImage unit if you are on Delphi 2009 or later because PNGImage unit shipped with the IDE since then.
Sorry for the confusion generated.