How to adjust RGB values using TTrackBars

Question

I would like to program an application in which you can control values of red, green and blue with trackbars. How can I do that?

Answer 1

Drop three TrackBars on a form. Set Min to 0, Max to 255. Drop a TImage on the form. Then try this code:

{ ... }
var
  Form1: TForm1;
  MyColor: LongWord;
  RedColor: LongWord = $00000000;
  GreenColor: LongWord = $00000000;
  BlueColor: LongWord = $00000000;

implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin
  DoImageFill;
end;

procedure TForm1.DoImageFill;
begin
  MyColor := RedColor or GreenColor or BlueColor;
  Image1.Canvas.Brush.Color := TColor(MyColor);
  Image1.Canvas.FillRect(Rect(0, 0, Image1.Width, Image1.Height));
end;

procedure TForm1.RedBarChange(Sender: TObject);
begin
  RedColor := RedBar.Position;
  DoImageFill;
end;

procedure TForm1.GreenBarChange(Sender: TObject);
begin
  GreenColor := GreenBar.Position shl 8;
  DoImageFill;
end;

procedure TForm1.BlueBarChange(Sender: TObject);
begin
  BlueColor := BlueBar.Position shl 16;
  DoImageFill;
end;

end.

Tip by Sue D. Nom

Answer 2

Each color value ranges from 0 to 255. Set the three trackbars with this range. You can use the RGB function to create a color from these values.

{ ... }
  type
    TForm1 = class(TForm)
      redTrackBar: TTrackBar;
      greenTrackBar: TTrackBar;
      blueTrackBar: TTrackBar;
      Panel1: TPanel;
      procedure blueTrackBarChange(Sender: TObject);
      procedure greenTrackBarChange(Sender: TObject);
      procedure redTrackBarChange(Sender: TObject);
    public
      procedure ChangeColor;
    end;

procedure TForm1.ChangeColor;
begin
  Panel1.Color := RGB(
    redTrackBar.Position, greenTrackBar.Position, blueTrackBar.Position
  );
end;

procedure TForm1.blueTrackBarChange(Sender: TObject);
begin
  ChangeColor;
end;

procedure TForm1.greenTrackBarChange(Sender: TObject);
begin
  ChangeColor;
end;

procedure TForm1.redTrackBarChange(Sender: TObject);
begin
  ChangeColor;
end;