function PtInPolygon(const Points: TPoints; P: TPoint): Boolean;
var
 Cnt, I, J: Integer;
begin
 Result := False;
 Cnt := Length(Points);
 J := Cnt - 1;
 for I := 0 to Cnt - 1 do
 begin
   if ((Points[I].y <= P.y) and (P.y < Points[J].y)) or
     ((Points[J].y <= P.y) and (P.y < Points[I].y)) then
   begin
     if (P.x < (Points[J].x - Points[I].x) * (P.y - Points[I].y) /
       (Points[J].y - Points[I].y) + Points[I].x) then
       Result := not Result;
   end;
   J := I;
 end;
end;