function PtInPoly( const Points : Array of TPoint; X, Y : Integer ) : Boolean;
var
  Count,
  I,
  J : Integer;
begin
  Result := False;
  Count := Length(Points);
  J := Count-1;
  for I := 0 to Count-1 do begin
     if ((Points[I].Y <=Y) and (Y < Points[J].Y)) or
        ((Points[J].Y <=Y) and (Y < Points[I].Y)) then
     begin
        if (x < (Points[j].X - Points[i].X) * (y - Points[i].Y) /
           (Points[j].Y - Points[i].Y) + Points[i].X) then
          Result := not Result;
     end;
     J := I;
  end;
end;