Title: An easy pulsing effect
Question: How can I create a pulsing effect on a color in my program easily?
Answer:
-First sorry for my English.
It is easy because you only have to set a TDateTime variable at the beginning of your program, and then you are able to use pulsing colors like in QBASIC the color codes after 16. But it's finer.
So I show a program code. On Form1 there is a Timer1. Its interval is 50. Then the code should look like:
{___________Creating pulsing colors - the easiest way
____________by Attila Tanyi (tatil@freemail.hu)
}
unit uPulse;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;
type
TForm1 = class(TForm)
Timer1: TTimer;
procedure FormCreate(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
{the .interval should be about 50, if it's high,
the framerate will be low}
private
{ Private declarations }
public
{ Public declarations }
end;
TFadingMode=(fmFlash,fmPulse);{Two types of the effect.}
var
Form1: TForm1;
Starting_Time:TDateTime;
implementation
{$R *.dfm}
procedure TForm1.FormCreate(Sender: TObject);
begin
Starting_Time:=Now;
end;
function TimeElapsed(Since:TDateTime):integer;
var h,m,s,ms:Word;
begin
DecodeTime(Now-Since,h,m,s,ms);
Result:=m*60000+s*1000+ms;
{
It may be: Result:=h*3600000+m*60000+s*1000+ms;
But not necessary.
}
end;
procedure TForm1.Timer1Timer(Sender: TObject);
const PulsingRate=500; FadingMode=fmPulse;
{Modify these to get different results}
var f:Byte; {the formula}
begin
case FadingMode of
{fades from color1 to color2 then turns back to color1}
fmFlash:f:=255*(TimeElapsed(Starting_Time) mod PulsingRate) div PulsingRate;
{fades from color1 to color2 then fades back to color1}
fmPulse:f:=255*Abs(TimeElapsed(Starting_Time) mod PulsingRate*2 - PulsingRate) div PulsingRate;
end;
{Then set the color with the RGB function}
Canvas.Brush.Color:=RGB(f,0,0);
{
currently modifying RED, but you can get other colors like:
RGB(f,0,0) - black-red
RGB(255-f,0,0) - red-black
RGB(0,f,0) - black-green
RGB(50,150,f) - green-blue
RGB(f,f,0) - yellow-black
RGB(f,f,f) - white-black
}
{then do the job... paint something etc.}
Canvas.Ellipse(50,50,150,150);
end;
end.
It's good because you can refresh the screen anytimes, the result depends only on the time elapsed. You don't have to declare a lot of variables.
And you can use the formula everywhere where is a color used. Just refresh it often!