线程中取屏幕且分为8*8块的问题

我正在做一个远程控制软件, 想把整个屏幕取下来并把它分为8*8个区块,以下是个完整的线程, 如果去掉分区块的部分代码, 速度可达每秒取屏80幅, 加上后速度降低到每两秒1幅. 分析得到, 从一个图像的区块拷贝到回一图像花费大量的时间, 各位有什么好的办法解决?unit Unit_Clt_CopyScrThread;interfaceuses
    Windows,SysUtils,Classes,Forms,Graphics;type
  TCopyScrThread = class(TThread)
  private
    DemoFullBmp: TBitmap;  // 整屏图像
    SplitedBmp: TBitmap;  // 块区临时图像    procedure CopyScreen; // 取整屏图像保存在DemoFullBmp
    procedure SplitBmp2Streams; // 把整屏图像分为8*8个区块, 保存在DemoStreams
  protected
    procedure DoTerminate;override;
    procedure Execute; override;
  public
    constructor Create(Suspended:Boolean);
    destructor Destroy(); override;
  end;implementation
var
   DemoStreams:array[0..63] of TMemoryStream; //保存获取的8*8个区图像流constructor TCopyScrThread.Create(Suspended:Boolean);
var
  i: integer;
begin
  inherited Create(Suspended);
  FreeOnTerminate := true;  DemoFullBmp := TBitmap.Create;  SplitedBmp := TBitmap.Create;
  SplitedBmp.PixelFormat := pf15bit;  for i:=0 to 63 do
    DemoStreams[i] := TMemoryStream.Create;
end;destructor TCopyScrThread.Destroy();
var
  i: integer;
begin
  inherited Destroy;
  DemoFullBmp.Free;
  SplitedBmp.Free;
  for i:=0 to 63 do
    DemoStreams[i].Free;
end;procedure TCopyScrThread.DoTerminate;
begin
  inherited DoTerminate;
end;procedure TCopyScrThread.Execute;
begin
  while not Terminated and not Suspended do
  begin
    Synchronize(CopyScreen);
    Application.ProcessMessages;
    Synchronize(SplitBmp2Streams);
    Application.ProcessMessages;
  end;
end;procedure TCopyScrThread.CopyScreen;
var
  hCursor:integer;
  ptCursor:TPoint;
  icoCursor:TIcon;
  iconInfoCursor:TIconInfo;
  intThreadld: dword;  hScreen:integer;
  dcScreen:integer;
  rectScreen:TRect;
begin
  hScreen := GetDesktopWindow();
  dcScreen := GetDC(hScreen);  Application.ProcessMessages;  GetWindowRect(hScreen, rectScreen);
  DemoFullBmp.Width := rectScreen.Right-rectScreen.Left;
  DemoFullBmp.Height := rectScreen.Bottom-rectScreen.Top;
  BitBlt(DemoFullBmp.Canvas.Handle, 0, 0, DemoFullBmp.Width, DemoFullBmp.Height, dcScreen, 0, 0, SRCCOPY);  
  Application.ProcessMessages;  ReleaseDC(hScreen, dcScreen);end;procedure TCopyScrThread.SplitBmp2Streams;
var
  BmpNo: integer;
  BmpX,BmpY: integer; //要拷贝的图像在整个图的行号和列号
  PreWidth,PreHeight: integer; //每块要拷贝的图像宽度和高度
  x1,x2,y1,y2: integer;  //要拷贝的图像的两起始角位置begin
  PreWidth := trunc(Screen.Width/8);
  PreHeight := trunc(Screen.Height/8);//http://www.delphibbs.com/delphibbs/dispq.asp?lid=440449  SplitedBmp.Width := PreWidth;
  SplitedBmp.Height := PreHeight;  for BmpY := 0 to 7 do
  begin
    for BmpX := 0 to 7 do
    begin
       x1 := PreWidth*BmpX;
       y1 := PreHeight*BmpY;
       x2 := x1 + PreWidth;
       y2 := y1 + PreHeight;       BmpNo := BmpY*8 + BmpX;
       
       //如果去掉以下一句, 速度将变得很快
       SplitedBmp.Canvas.CopyRect(Rect(0,0,PreWidth,PreHeight), DemoFullBmp.Canvas, Rect(x1,y1,x2,y2));
       Application.ProcessMessages;       DemoStreams[BmpNo].Clear;
       DemoStreams[BmpNo].Position := 0;       SplitedBmp.SaveToStream(DemoStreams[BmpNo]);       Application.ProcessMessages;
    end;
  end;end;end.