如果您需要使用其他画布,则必须分配HDC,例如

var

WindowHandle:HWND;

ScreenCanvas,BufferCanvas: TCanvas;

r,r2: TRect;

ScreenDC,BufferDC :HDC;

BufferBitmap : HBITMAP;

begin

WindowHandle := 0;

ScreenCanvas := TCanvas.Create;

BufferCanvas := TCanvas.Create;

ScreenDC:=GetWindowDC(WindowHandle);

ScreenCanvas.Handle := ScreenDC;

BufferDC := CreateCompatibleDC(ScreenDC);

BufferCanvas.Handle := BufferDC;

BufferBitmap := CreateCompatibleBitmap(ScreenDC,GetDeviceCaps(ScreenDC,HORZRES),VERTRES));

SelectObject(BufferDC,BufferBitmap);

try

r := Rect(0,200);

BufferCanvas.CopyRect(r,ScreenCanvas,r);

form1.Canvas.CopyRect(r,BufferCanvas,r);

finally

ReleaseDC(WindowHandle,ScreenCanvas.Handle);

DeleteDC(BufferDC);

DeleteObject(BufferBitmap);

BufferCanvas.Free;

ScreenCanvas.Free;

end;

end;