procedure TfrMain.btnCastColorClick(Sender: TObject);
begin
   CastColorOn := True;
   Screen.Cursor := crCross;
end;

procedure TfrMain.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
   fMouseDownX := X;
   fMouseDownY := Y;
end;

procedure TfrMain.Image1Click(Sender: TObject);
begin
   if CastColorOn then begin
      // it took a long time for the operation to complete compared to Microsoft method
      Image1.Proc.CastColor(Image1.XScr2Bmp(fMouseDownX), Image1.Yscr2Bmp(fMouseDownY), CreateRGB(255, 255, 255), 10); 
      CastColorOn := False;
      Screen.Cursor := crDefault;
   end;
end;

procedure TForm1.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton;
    Shift: TShiftState; X, Y: Integer);
const
  Tolerance = 10;
var
  clickColor, fromRGB, toRGB: TRGB;
begin
  // When the user clicks the image turn all image pixels of a similar color to white
  if fColorCasting then
  begin
    clickColor := ImageEnView1.IEBitmap.Pixels[ ImageEnView1.XScr2Bmp(x), ImageEnView1.Yscr2Bmp(y) ];

    fromRGB := CreateRGB( imax( 0, clickColor.r - Tolerance ),
                          imax( 0, clickColor.g - Tolerance ),
                          imax( 0, clickColor.B - Tolerance ));
    toRGB   := CreateRGB( imin( 255, clickColor.r + Tolerance ),
                          imin( 255, clickColor.g + Tolerance ),
                          imin( 255, clickColor.B + Tolerance ));

    ImageEnView1.Proc.CastColorRange( fromRGB, toRGB, CreateRGB(255, 255, 255));
  end;
end;