为何不能释放资源?看看这段代码

为何不能释放资源?看看这段代码
请指点
var
  ps: PAINTSTRUCT;
  DC, drawDC1, drawDC2: HDC;
  drawBMP1, drawBMP2, oldBMP1, oldBMP2: HBitmap;
  iWidth, iHeight, ibmpWidth, ibmpHeight, I, J, K, W: integer;
begin
  FInterDrawing := True;
  try
    BeginPaint(Self.Handle, Ps);
    try      DC := Ps.hdc;
      iWidth := ClientWidth;
      iHeight := ClientHeight;
      drawDC1 := CreateCompatibleDC(DC);
      drawBMP1 := CreateCompatibleBitmap(DC, iWidth, iHeight);
      oldBMP1 := SelectObject(drawDC1, drawBMP1);      SendMessage(Handle, WM_PAINT, drawDC1, 0);      drawDC2 := CreateCompatibleDC(DC);
      drawBMP2 := CreateCompatibleBitmap(DC, iWidth, iHeight);
      oldBMP2 := SelectObject(drawDC2, drawBMP2);      iBmpWidth := Background.Width;
      iBmpHeight := Background.Height;
      K := ClientWidth div iBmpWidth;
      W := ClientHeight div iBmpHeight;
      for I := 0 to K do
        for J := 0 to W do
          BitBlt(drawDC2, I * iBmpWidth, J * iBmpHeight, iBmpWidth, iBmpHeight, Background.Canvas.Handle, 0, 0, SRCCOPY);      TransparentBlt(drawDC2, 0, 0, iWidth, iHeight, drawDC1, 0, 0, iWidth, iHeight, ColorToRGB(clWindow));
      BitBlt(DC, 0, 0, iWidth, iHeight, drawDC2, 0, 0, SRCCOPY);      SelectObject(drawDC1, oldBMP1);
      DeleteObject(drawBMP1);      SelectObject(drawDC2, oldBMP2);      DeleteObject(drawBMP2);    finally
      ReleaseDC(self.Handle,DC);
      DeleteDC(drawDC1);
      DeleteDC(drawDC2);      EndPaint(Handle, Ps);
    end;  finally
    FInterDrawing := False;
  end;