procedure ScaleBitmap(aBitmap: TBitmap;Scale: Single);
var
  tmp: TBitmap;
begin
  tmp := TBitmap.Create;
  try
    tmp.Width := Round(aBitmap.Width * Scale);
    tmp.Height := Round(aBitmap.Height * Scale);
    tmp.Canvas.StretchDraw(Bounds(0,0,tmp.Width,tmp.Height), aBitmap);
    aBitmap.Assign(tmp);
  finally
    tmp.Free;
  end;
end;