Screenshot of game window - c++

Question

How can i take a screenshot of a full screen game in c++? I know it can be done with directx and i have written a simple code which can take a screenshot of a window but i don't know how to get a HWND of game.
Here is my code.
#include <d3dx9.h>
#include <d3dx9tex.h>
#include <stdio.h>
#pragma comment(lib,"d3d9.lib")
#pragma comment(lib,"d3dx9.lib")
int main()
{
IDirect3DSurface9 *surface;
IDirect3DDevice9 *g_pd3dDevice;
IDirect3D9 *g_pD3D;
D3DDISPLAYMODE d3ddm;
D3DPRESENT_PARAMETERS d3dpp;
HWND hWnd = GetConsoleWindow();
if((g_pD3D = Direct3DCreate9(D3D_SDK_VERSION)) == NULL)
{
printf("fail 1");
}
if(FAILED(g_pD3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &d3ddm)))
{
printf("fail 2");
}
ZeroMemory(&d3dpp, sizeof(D3DPRESENT_PARAMETERS));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.BackBufferFormat = d3ddm.Format;
d3dpp.BackBufferHeight = d3ddm.Height;
d3dpp.BackBufferWidth = d3ddm.Width;
if(FAILED(g_pD3D->CreateDevice(D3DADAPTER_DEFAULT,
D3DDEVTYPE_HAL, hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp, &g_pd3dDevice)))
{
printf("fail 3");
}
g_pd3dDevice->CreateOffscreenPlainSurface(800, 600, D3DFMT_A8R8G8B8, D3DPOOL_SCRATCH, &surface, NULL);
g_pd3dDevice->GetFrontBufferData(0, surface);
D3DXSaveSurfaceToFile("c:\\tmp\\output.jpg", D3DXIFF_JPG, surface, NULL, NULL);
surface->Release();
return 0;
}

Answer 1

I don't have any experience with Direct3D, but with OpenGL.
But both APIs provide almost the same functionality.
You should read back the back buffer (using Direct3D and not some Windows functionality) to host memory. Then simply save that bitmap to a file using an image library or something like that.
It's actually an extremely simple process.
These two links might be helpful to you:
http://www.mvps.org/directx/articles/screengrab.htm
How to save backbuffer to file in DirectX 10?