Capture screenshot of desktop or window running on top using GetBackBuffer DirectX

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C++

DirectX

screenshot

Hi I am looking to capture screenshot of the window on top or the desktop that is presently running application on top using GetBackBuffer() method in DirectX. And instead of saving I want to display the screenshot in a window.

However I am new to DirectX programming and and am unclear in the order of functions to be called. I referred to a few blogs and threads and have compiled this code:

// include the basic windows header files and the Direct3D header file
#include <windows.h>
#include <windowsx.h>
#include <d3d9.h>
//#include "iostream.h"
#include <stdio.h>

// include the Direct3D Library file
#pragma comment (lib, "d3d9.lib")

// global declarations
LPDIRECT3D9 d3d;    // the pointer to our Direct3D interface
LPDIRECT3DDEVICE9 d3ddev;    // the pointer to the device class

// function prototypes
void initD3D(HWND hWnd);    // sets up and initializes Direct3D
void render_frame(void);    // renders a single frame
void cleanD3D(void);    // closes Direct3D and releases memory

// the WindowProc function prototype
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);


// the entry point for any Windows program
int WINAPI WinMain(HINSTANCE hInstance,
	HINSTANCE hPrevInstance,
	LPSTR lpCmdLine,
	int nCmdShow)
{
	HWND hWnd;
	WNDCLASSEX wc;

	ZeroMemory(&wc, sizeof(WNDCLASSEX));

	wc.cbSize = sizeof(WNDCLASSEX);
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc = WindowProc;
	wc.hInstance = hInstance;
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
	wc.lpszClassName = L"WindowClass";

	RegisterClassEx(&wc);

	hWnd = CreateWindowEx(NULL,
		L"WindowClass",
		L"Our First Direct3D Program",
		WS_OVERLAPPEDWINDOW,
		300, 300,
		800, 600,
		NULL,
		NULL,
		hInstance,
		NULL);

	ShowWindow(hWnd, nCmdShow);

	// set up and initialize Direct3D
	initD3D(hWnd);

	// enter the main loop:

	MSG msg;

	while (TRUE)
	{
		while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}

		if (msg.message == WM_QUIT)
			break;

		render_frame();
	}

	// clean up DirectX and COM
	cleanD3D();

	return msg.wParam;
}


// this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_DESTROY:
	{
		PostQuitMessage(0);
		return 0;
	} break;
	}

	return DefWindowProc(hWnd, message, wParam, lParam);
}


// this function initializes and prepares Direct3D for use
void initD3D(HWND hWnd)
{
	d3d = Direct3DCreate9(D3D_SDK_VERSION);    // create the Direct3D interface

	D3DPRESENT_PARAMETERS d3dpp;    // create a struct to hold various device information

	ZeroMemory(&d3dpp, sizeof(d3dpp));    // clear out the struct for use
	d3dpp.Windowed = TRUE;    // program windowed, not fullscreen
	d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;    // discard old frames
	d3dpp.hDeviceWindow = hWnd;    // set the window to be used by Direct3D


	// create a device class using this information and the info from the d3dpp stuct
	d3d->CreateDevice(D3DADAPTER_DEFAULT,
		D3DDEVTYPE_HAL,
		hWnd,
		D3DCREATE_SOFTWARE_VERTEXPROCESSING,
		&d3dpp,
		&d3ddev);
}


// this is the function used to render a single frame
void render_frame(void)
{
	// clear the window to a deep blue
	
	IDirect3DSurface9 *offscreenSurface = 0;
	IDirect3DSurface9 *destSurface = 0;
	
	
	d3ddev->CreateOffscreenPlainSurface(800, 600, D3DFMT_A8B8G8R8, D3DPOOL_SYSTEMMEM, &offscreenSurface, NULL);
	HRESULT hr = d3ddev->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO, &offscreenSurface);
	d3ddev->GetRenderTargetData(offscreenSurface, destSurface);

	HRESULT hr1 = d3ddev->CreateRenderTarget(800, 600, D3DFMT_A8R8G8B8, D3DMULTISAMPLE_NONE, 0, TRUE, &offscreenSurface, NULL);
	

	d3ddev->BeginScene();    // begins the 3D scene

	// do 3D rendering on the back buffer here

	d3ddev->EndScene();    // ends the 3D scene

	d3ddev->Present(NULL, NULL, NULL, NULL);   // displays the created frame on the screen
}


// this is the function that cleans up Direct3D and COM
void cleanD3D(void)
{
	d3ddev->Release();    // close and release the 3D device
	d3d->Release();    // close and release Direct3D
}

I understand that I am doing something wrong and been trying to figure that out for the past days but I could not fix my code to make it capture screenshot of the desktop.

So please suggest me what changes I need to make in the code so that it does what it is supposed to.