核心提示：函数需要 uses Direct3D9,D3DX9; 偶然发现一个函数可以直接保存表面到文件1！所以修改了一下，函数为：...

procedure CaptureScreen(Const FileName: string);
var
BitsPerPixel: Byte;
pD3D: IDirect3D9;
pSurface: IDirect3DSurface9;
g_pD3DDevice: IDirect3DDevice9;
D3DPP: TD3DPresentParameters;
ARect: TRect;
LockedRect: TD3DLockedRect;
BMP: TBitmap;
i, p: Integer;
begin
BitsPerPixel := GetDeviceCaps(Canvas.Handle, BITSPIXEL);
FillChar(d3dpp, SizeOf(d3dpp), 0);
D3DPP.Windowed := True;
D3DPP.Flags := D3DPRESENTFLAG_LOCKABLE_BACKBUFFER;
D3DPP.SwapEffect := D3DSWAPEFFECT_DISCARD;
D3DPP.BackBufferWidth := Screen.Width;
D3DPP.BackBufferHeight := Screen.Height;
D3DPP.BackBufferFormat := D3DFMT_X8R8G8B8;
pD3D := Direct3DCreate9(D3D_SDK_VERSION);
pD3D.CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, GetDesktopWindow,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, @D3DPP, g_pD3DDevice);
g_pD3DDevice.CreateOffscreenPlainSurface(Screen.Width, Screen.Height, D3DFMT_A8R8G8B8, D3DPOOL_SCRATCH, pSurface, nil);
g_pD3DDevice.GetFrontBufferData(0, pSurface);
// use D3D to save surface. Notes: D3DX%ab.dll is required!
// D3DXSaveSurfaceToFile('Desktop.bmp', D3DXIFF_BMP, pSurface, nil, nil);
// use Bitmap to save surface
ARect := Screen.DesktopRect;
pSurface.LockRect(LockedRect, @ARect, D3DLOCK_NO_DIRTY_UPDATE or D3DLOCK_NOSYSLOCK or D3DLOCK_READONLY);
BMP := TBitmap.Create;
BMP.Width := Screen.Width;
BMP.Height := Screen.Height;
case BitsPerPixel of
8: BMP.PixelFormat := pf8bit;
16: BMP.PixelFormat := pf16bit;
24: BMP.PixelFormat := pf24bit;
32: BMP.PixelFormat := pf32bit;
end;
p := Cardinal(LockedRect.pBits);
for i := 0 to Screen.Height - 1 do
begin
CopyMemory(BMP.ScanLine[i], Ptr(p), Screen.Width * BitsPerPixel div 8);
p := p + LockedRect.Pitch;
end;
BMP.SaveToFile(FileName);
BMP.Free;
pSurface.UnlockRect;
end;

procedure CaptureScreen(const FileName: string;Const FileType: TD3DXImageFileFormat);
var
pD3D: IDirect3D9;
pSurface: IDirect3DSurface9;
g_pD3DDevice: IDirect3DDevice9;
D3DPP: TD3DPresentParameters;
begin
FillChar(d3dpp, SizeOf(d3dpp), 0);
D3DPP.Windowed := True;
D3DPP.Flags := D3DPRESENTFLAG_LOCKABLE_BACKBUFFER;
D3DPP.SwapEffect := D3DSWAPEFFECT_DISCARD;
D3DPP.BackBufferWidth := Screen.Width;
D3DPP.BackBufferHeight := Screen.Height;
D3DPP.BackBufferFormat := D3DFMT_X8R8G8B8;
pD3D := Direct3DCreate9(D3D_SDK_VERSION);
pD3D.CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, GetDesktopWindow,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, @D3DPP, g_pD3DDevice);
g_pD3DDevice.CreateOffscreenPlainSurface(Screen.Width, Screen.Height, D3DFMT_A8R8G8B8, D3DPOOL_SCRATCH, pSurface, nil);
g_pD3DDevice.GetFrontBufferData(0, pSurface);
D3DX9.D3DXSaveSurfaceToFile(PChar(FileName),FileType,pSurface,nil,nil);
pSurface := nil;
g_pD3DDevice := nil;
pD3D := nil;
end;

传递两个参数，第一个参数指定为文件名，第二个参数指定为文件类型
支持7种类型
_D3DXIMAGE_FILEFORMAT = (
D3DXIFF_BMP {= 0},
D3DXIFF_JPG {= 1},
D3DXIFF_TGA {= 2},
D3DXIFF_PNG {= 3},
D3DXIFF_DDS {= 4},
D3DXIFF_PPM {= 5},
D3DXIFF_DIB {= 6}
);

再给一个使用dX8实现的，上面给的是用Dx9实现的函数
procedure CaptureScreen(const FileName: string;Const FileType: TD3DXImageFileFormat);
var
pD3D: IDirect3D8;
pSurface: IDirect3DSurface8;
g_pD3DDevice: IDirect3DDevice8;
D3DPP: TD3DPresentParameters;
begin
FillChar(d3dpp, SizeOf(d3dpp), 0);
D3DPP.Windowed := True;
D3DPP.Flags := D3DPRESENTFLAG_LOCKABLE_BACKBUFFER;
D3DPP.SwapEffect := D3DSWAPEFFECT_DISCARD;
D3DPP.BackBufferWidth := Screen.Width;
D3DPP.BackBufferHeight := Screen.Height;
D3DPP.BackBufferFormat := D3DFMT_X8R8G8B8;
pD3D := Direct3DCreate8(D3D_SDK_VERSION);
pD3D.CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, GetDesktopWindow,
D3DCREATE_SOFTWARE_VERTEXPROCESSING, D3DPP, g_pD3DDevice);
g_pD3DDevice.CreateImageSurface(Screen.Width, Screen.Height, D3DFMT_A8R8G8B8, pSurface);
g_pD3DDevice.GetFrontBuffer(pSurface);
D3DX8.D3DXSaveSurfaceToFile(PChar(FileName),FileType,pSurface,nil,nil);
pSurface := nil;
g_pD3DDevice := nil;
pD3D := nil;
end;

再给一个直接使用系统GDI实现的抓屏
procedure CaptureScreen(const FileName: string);overload;
var
nScreenWidth,nScreenHeight: integer;
ScreenDc,hCaptureDC: HDC;
bmp: TBitmap;
begin
nScreenWidth := GetSystemMetrics(SM_CXSCREEN);
nScreenHeight := GetSystemMetrics(SM_CYSCREEN);
ScreenDc := GetDC(GetDesktopWindow);
hCaptureDC := CreateCompatibleDC(ScreenDc);
bmp := TBitmap.Create;
bmp.Handle :=CreateCompatibleBitmap(ScreenDc,nScreenWidth, nScreenHeight);
SelectObject(hCaptureDC,bmp.Handle);
BitBlt(hCaptureDC,0,0,nScreenWidth,nScreenHeight,ScreenDc,0,0,SRCCOPY);
bmp.SaveToFile(fileName);
ReleaseDC(GetDesktopWindow,ScreenDc);
DeleteDC(hCaptureDC);
bmp.Free;
end;

通过上面这一步，我们可以很容易联想到用来抓取任何一个控件的表面图象，函数如下：
procedure CaptureControl(Control: TWinControl;const FileName: string);overload;
var
ControlWidth,ControlHeight: integer;
ControlDc,hCaptureDC: HDC;
bmp: TBitmap;
begin
ControlWidth := Control.ClientWidth;
ControlHeight := Control.ClientHeight;
ControlDc := GetDC(Control.Handle);
hCaptureDC := CreateCompatibleDC(ControlDc);
bmp := TBitmap.Create;
bmp.Handle :=CreateCompatibleBitmap(ControlDc,ControlWidth,ControlHeight);
SelectObject(hCaptureDC,bmp.Handle);
BitBlt(hCaptureDC,0,0,ControlWidth,ControlHeight,ControlDc,0,0,SRCCOPY);
bmp.SaveToFile(fileName);
ReleaseDC(GetDesktopWindow,ControlDc);
DeleteDC(hCaptureDC);
bmp.Free;
end;