Как создать регион (HRNG) по маске

function BitmapToRgn(Image: TBitmap): HRGN;
var
  TmpRgn: HRGN;
  x, y: integer;
  ConsecutivePixels: integer;
  CurrentPixel: TColor;
  CreatedRgns: integer;
  CurrentColor: TColor;
begin
  CreatedRgns := 0;
  Result := CreateRectRgn(0, 0, Image.Width, Image.Height);
  inc(CreatedRgns);

  if (Image.Width = 0) or (Image.Height = 0) then
    exit;

  for y := 0 to Image.Height - 1 do
  begin
    CurrentColor := Image.Canvas.Pixels[0,y];
    ConsecutivePixels := 1;
    for x := 0 to Image.Width - 1 do
    begin
      CurrentPixel := Image.Canvas.Pixels[x,y];

      if CurrentColor = CurrentPixel then
        inc(ConsecutivePixels)
      else
      begin
        // Входим в новую зону
        if CurrentColor = clWhite then
        begin
          TmpRgn := CreateRectRgn(x-ConsecutivePixels, y, x, y+1);
          CombineRgn(Result, Result, TmpRgn, RGN_DIFF);
          inc(CreatedRgns);
          DeleteObject(TmpRgn);
        end;
        CurrentColor := CurrentPixel;
        ConsecutivePixels := 1;
      end;
    end;

    if (CurrentColor = clWhite) and (ConsecutivePixels > 0) then
    begin
      TmpRgn := CreateRectRgn(x-ConsecutivePixels, y, x, y+1);
      CombineRgn(Result, Result, TmpRgn, RGN_DIFF);
      inc(CreatedRgns);
      DeleteObject(TmpRgn);
    end;
  end;
end;