delphi – 将透明消息绘制到屏幕提供了超出系统资源

为什么首先使用此代码可以正常工作,但是经过几十次调用后,它会提供系统资源.
?它似乎免费BM好,我没有看到它分配其他资源.

procedure ttsplash.UpdateSplash(const Str: string);
var
  R: TRect;
  P: TPoint;
  S: TPoint;
  bm: TBitmap;
  bf: TBlendFunction;
  EXSTYLE: DWORD;
  x,y: integer;
  pixel: PRGBQuad;
  TextRed,TextGreen,TextBlue: byte;
begin

if str='' then exit;

  EXSTYLE := GetWindowLong(Handle,GWL_EXSTYLE);
  SetWindowLong(Handle,GWL_EXSTYLE,EXSTYLE or $80000);

  R := ClientRect;

  bm := TBitmap.Create;
  try
    bm.PixelFormat := pf32bit;
//    bm.SetSize(ClientWidth,ClientHeight);
    bm.Width := clientwidth;
        bm.height := clientheight;

    bm.Canvas.Brush.Color := clBlack;
    bm.Canvas.FillRect(ClientRect);

    bm.Canvas.Font.Assign(Self.Font);
    bm.Canvas.Font.Color := clWhite;
    DrawText(bm.Canvas.Handle,PChar(Str),Length(Str),R,DT_SINGLELINE or DT_VCENTER or DT_CENTER or DT_WORD_ELLIPSIS);

    TextRed := GetRValue(ColorToRGB(Font.Color));
    TextGreen := GetGValue(ColorToRGB(Font.Color));
    TextBlue := GetBValue(ColorToRGB(Font.Color));

    for y := 0 to bm.Height - 1 do
    begin
      pixel := bm.ScanLine[y];
      x := 0;
      while x < bm.Width do
      begin
        with pixel^ do
        begin
          rgbReserved := (rgbRed + rgbGreen + rgbBlue) div 3;

          rgbBlue := TextBlue * rgbReserved div 255;
          rgbGreen := TextGreen * rgbReserved div 255;
          rgbRed := TextRed * rgbReserved div 255;
        end;

        inc(pixel);
        inc(x);
      end;
    end;      

    P := Point(0,0);
    S := Point(bm.Width,bm.Height);
    bf.BlendOp := AC_SRC_OVER;
    bf.BlendFlags := 0;
    bf.SourceConstantAlpha := 255;
    bf.AlphaFormat := AC_SRC_ALPHA;
    UpdateLayeredWindow(Handle,nil,@S,bm.Canvas.Handle,@P,@bf,ULW_ALPHA)
  finally
    bm.Free;
  end;
end;