Image.LayersAdd;
Image.Layers[1].Opacity:=0.5;

procedure TfmMain.ImageDrawBackBuffer(Sender: TObject);
var
  pts : TPointArray;
  i   : integer;
begin
  SetLength(pts,length(Warnings[0].Coordinates));

  for i:=0 to length(Warnings[0].Coordinates)-1 do
  begin
    pts[i].X:=map.LongitudeToBmpX(Warnings[0].Coordinates[i].Lon);
    pts[i].Y:=map.LatitudeToBmpY(Warnings[0].Coordinates[i].Lat);
  end;
  
  with Image.Layers[1].Bitmap.Canvas do
  begin
    Pen.Color:=clBlack;
    Brush.Style:=bsSolid;
    Brush.Color:=clYellow;
    Polygon(pts);
  end;
end;  

procedure ImageDrawLayer(Sender: TObject; Dest: TIEBitmap; LayerIndex: Integer);
var
  pts : TPointArray;
  i   : integer;
begin
  if LayerIndex=1 then
  begin
    SetLength(pts,length(Warnings[0].Coordinates));

    for i:=0 to length(Warnings[0].Coordinates)-1 do
    begin
      pts[i].X:=map.LongitudeToBmpX(Warnings[0].Coordinates[i].Lon);
      pts[i].Y:=map.LatitudeToBmpY(Warnings[0].Coordinates[i].Lat);
    end;

    with Dest.IECanvas do
    begin
      Pen.Mode := pmCopy;
      Pen.Width :=2;
      Pen.Style := psSolid;
      Pen.Color := clBlack;
      Pen.Transparency := 192;

      Brush.Color := clYellow;
      Brush.Style := bsSolid;
      Brush.Transparency := 128;
      Polygon(pts);
    end;
  end;
end;