unit UExtFloodFill;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Shape1: TShape;
    procedure Button1Click(Sender: TObject);
  private
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
  {set the color of the brush used for the flood fill}
  Canvas.Brush.Color := clLime;

  {fill the red square with the new brush color}
  ExtFloodFill(Canvas.Handle, 20, 20, clRed, FLOODFILLSURFACE);
end;

end.