bmp := TIEBitmap.Create();
  try
    bmp.Read( 'D:\Alpha2.png' );
    if bmp.HasAlphaChannel(True) and bmp.AlphaChannel.IsAllBlack() then
      ShowMessage( 'Image is completely transparent' )
    else
      ShowMessage( 'Image NOT transparent' );
  finally
    bmp.free;
  end;