procedure TPABorders(var TPA: TPointArray);
var
  h, i: Integer;
  a, b: T2DPointArray;
begin
  pp_TPABlob(TPA, sd8ways, a);
  h := High(a);
  SetLength(b, (h + 1));
  for i := 0 to h do
  begin
    pp_TPABorder(a[i]);
    pp_TPAFromPolygon(a[i], b[i]);
  end;
  SetLength(TPA, 0);
  pp_Merge(b, TPA);
  SetLength(a, 0);
  pp_TPABlob(TPA, sd8ways, a);
  h := High(a);
  for i := 0 to h do
    pp_TPABorder(a[i]);
  SetLength(TPA, 0);
  pp_Merge(a, TPA);
end;