procedure Tfmain.btnAddShapeMaskClick(Sender: TObject);
var
  prevLayer: TIELayer;
begin
  // Create a star shape, Fill area will be black for now
  ImageEnView1.LayersInsert( ImageEnView1.LayersCurrent + 1, iesStar5 );
  ImageEnView1.CurrentLayer.FillColor    := clBlack;
  ImageEnView1.CurrentLayer.BorderWidth  := 0;

  // Convert shape layer to an image layer
  ImageEnView1.CurrentLayer.ConvertToImageLayer( 1 );

  // Make 256 color and negative (so black becomes white transparency
  TIEImageLayer( ImageEnView1.CurrentLayer ).Bitmap.PixelFormat := ie8g;
  ImageEnView1.Proc.Negative();

  // Set this layer as a mask
  ImageEnView1.CurrentLayer.IsMask := True;

  // Layer must be hidden to work as mask
  ImageEnView1.CurrentLayer.Visible := False;

  // Make it the cover the underlying image
  prevLayer := ImageEnView1.Layers[ ImageEnView1.LayersCurrent - 1];
  ImageEnView1.CurrentLayer.PosX   := prevLayer.PosX;
  ImageEnView1.CurrentLayer.PosY   := prevLayer.PosY;
  ImageEnView1.CurrentLayer.Width  := prevLayer.Width;
  ImageEnView1.CurrentLayer.Height := prevLayer.Height;
end;