Splash screen - Slow image display

Question

I'm trying to display a splash screen before running the installer (Inno Installer). Everything works ok, but I would like the image to appear incrementally and then disappear incrementally. Then the installer starts. Does anyone know what parameter to use for the splash screen ?

Thanks for any advice

Continued display of the splash screen image before launching the installer. Example: [] 2

   // Show splash
  SplashForm := CreateCustomForm;
  SplashForm.BorderStyle := bsNone;
  SplashBitmap := TBitmapImage.Create(SplashForm);
  SplashBitmap.AutoSize := True;
  SplashBitmap.Align := alClient;
  SplashBitmap.Left := 0;
  SplashBitmap.Top := 0;
  SplashBitmap.Stretch := True;
  SplashBitmap.Parent := SplashForm;
  ExtractTemporaryFile('Dahlia.bmp');
  SplashBitmap.Bitmap.LoadFromFile(ExpandConstant('{tmp}') + '\Dahlia.bmp');
  SplashForm.Width := SplashBitmap.Width;
  SplashForm.Height := SplashBitmap.Height;
  SplashForm.SizeAndCenterOnShow := True;
  SplashForm.Show;
  SplashForm.Refresh;
  Sleep(8000);
  SplashForm.Close;