// Customizing the Preview dialog of a TImageEnView
uses
  Previews;

procedure TMyForm.FormCreate(Sender: TObject);
begin
  ImageEnView1.Proc.OnPreview := ProcPreview;
end;

procedure TMyForm.ProcPreview(Sender: TObject; PreviewForm: TForm);
begin
  with TfPreviews(PreviewForm) do
  begin
    // Red dialog
    Color := clRed;

    // Caption of OK button
    OkButton.Caption := 'Yeah baby';

    // Replace custom button
    CancelButton.Visible := False;
    With TBitBtn.Create( PreviewForm ) do
    begin
      Parent := PreviewForm;
      Left := CancelButton.Left;
      Top := CancelButton.Top + CancelButton.Height + 8;
      Width := CancelButton.Width;
      Height := CancelButton.Height;
      Anchors := [akTop, akRight];
      Caption := 'My Cancel';
      ModalResult := 2;
    end;
  end;
end;