Delphi 2010 : Fast ScreenShot using DirectX

Question

everyone. I am developing a application using screenshot. Using Bitblt(StretchBlt) function gives me black screen image sometimes

procedure CaptureScreen_4(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;

So I used another method using directx

procedure CaptureScreen_1(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(Form3.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;

This method gives always me correct screenshot image. But this is very slow than using Bitblt method. Is there another one for fast and perfect capture screen?

If you want more speed don't save it to disc right away. Do that in the background. — Jens Borrisholt
No, saving time to disk is no problem. The main problem is in handling directX. — david chan

david chan david chan · Accepted Answer · 2016-01-05T15:57:26

I have found the way to solve my problem. Infact the reason I wanna help is blocking capture by special application. So I injected capture dll to the dest application. After injection of capture dll, the application didn't block capture anymore. Of course, I have used thread to capture image in the inject dll. Inject procedure is like my question [procedure CaptureScreen_4(const FileName: string);overload;] I wanna everyone reference my experience.

Delphi 2010 : Fast ScreenShot using DirectX

1 Answers