Transparentes Gif mit diesem Tutorial erstellen ?

[thomas2009]

Ich habe folgendes gemach:

Delphi-Quellcode:

procedure TForm1.Button2Click(Sender: TObject);
var
  GIF: TGIFImage;
  Ext: TGIFGraphicControlExtension;
begin
  GIF := TGIFImage.Create;
  try
    // Convert bitmap to GIF
    GIF.Assign(image1.Picture.Bitmap);

    // Create an extension to set the transparency flag
    Ext := TGIFGraphicControlExtension.Create(GIF.Images[0]);
    Ext.Transparent := True;

    // Set transparent color to lower left pixel color
    Ext.TransparentColorIndex := GIF.Images[0].Pixels[0, GIF.Height-1];

    // Do something with the GIF here...
    gif.SaveToFile('c:\MyBitmap_trans.GIF');
  finally
    GIF.Free;
  end;
end;

Error: Invalid Pixel coordinates