function IsInPoly(const ARegion: array of TPoint; const ASearchPoint:
  TPoint): Boolean;
var
  LPrevPoint, LCurPoint: TPoint;
  Li: Integer;
  DX, DY, StepX, StepY: Integer;
  Step: Double;
  Rotation: Double;
begin
  LPrevPoint := ARegion[0];
  Rotation := 0;
  for Li := 1 to Length(ARegion) - 1 do begin
    LCurPoint := ARegion[Li];
    DX := LCurPoint.X - LPrevPoint.X;
    DY := LCurPoint.Y - LPrevPoint.Y;
    StepX := LPrevPoint.X - ASearchPoint.X;
    StepY := LPrevPoint.Y - ASearchPoint.Y;
    if (StepX <> 0) or (StepY <> 0) then begin
      Step := (DX * StepY - DY * StepX) / (StepX * StepX + StepY * StepY);
      Rotation := Rotation + Step;
    end;
    LPrevPoint := LCurPoint;
  end;
  Result := (Abs(Rotation) > 5);
end;