通过WMI的方式去设置LCD背光亮度

code例如以下：

#include "stdafx.h"
#include <objbase.h>
#include <windows.h>                                    
#include <stdio.h>
#include <wbemidl.h>
#include <comdef.h>

#pragma comment(lib, "wbemuuid.lib")
#pragma comment(lib, "comsuppw.lib")

int _tmain(int argc, _TCHAR* argv[])
{
    IWbemLocator 	* pLocator = NULL;
    IWbemServices 	* pNamespace = 0;
    IWbemClassObject * pClass = NULL;
    IWbemClassObject * pInClass = NULL;
    IWbemClassObject * pInInst = NULL;
	IEnumWbemClassObject *pEnum = NULL;
	HRESULT hr = S_OK;
 
    BSTR path = SysAllocString(L"root\wmi");
    BSTR ClassPath = SysAllocString(L"WmiMonitorBrightnessMethods");
    BSTR MethodName = SysAllocString(L"WmiSetBrightness");
    BSTR ArgName0 = SysAllocString(L"Timeout");
	BSTR ArgName1 = SysAllocString(L"Brightness");
	BSTR bstrQuery = SysAllocString(L"Select * from WmiMonitorBrightnessMethods");

	if (!path || ! ClassPath || !MethodName || ! ArgName0)
	{
		printf("SysAllocString failed. Out of memory.
");
		{printf("
[-] Err: xxx");goto cleanup;}
	}

    // Initialize COM and connect up to CIMOM

    hr = CoInitialize(0);
	if (FAILED(hr))
	{
		printf("CoInitialize returned 0x%x:", hr);
		{printf("
[-] Err: CoInitialize");goto cleanup;}
	}

	//  NOTE:
	//  When using asynchronous WMI API's remotely in an environment where the "Local System" account
	//  has no network identity (such as non-Kerberos domains), the authentication level of
	//  RPC_C_AUTHN_LEVEL_NONE is needed. However, lowering the authentication level to
	//  RPC_C_AUTHN_LEVEL_NONE makes your application less secure. It is wise to
	// use semi-synchronous API's for accessing WMI data and events instead of the asynchronous ones.

    hr = CoInitializeSecurity(NULL,
							-1,
							NULL,
							NULL,
							RPC_C_AUTHN_LEVEL_DEFAULT,
							RPC_C_IMP_LEVEL_IMPERSONATE,
							NULL,
							EOAC_NONE, //change to EOAC_NONE if you change dwAuthnLevel to RPC_C_AUTHN_LEVEL_NONE
							NULL );
	if (FAILED(hr))
	{
		printf("CoInitializeSecurity returned 0x%x:", hr);
		{printf("
[-] Err: CoInitializeSecurity");goto cleanup;}
	}

    hr = CoCreateInstance(CLSID_WbemLocator,
						0,
						CLSCTX_INPROC_SERVER,
						IID_IWbemLocator,
						(LPVOID *) &pLocator);
	if (FAILED(hr))
	{
		printf("CoCreateInstance returned 0x%x:", hr);
		{printf("
[-] Err: CoCreateInstance");goto cleanup;}
	}
    hr = pLocator->ConnectServer(path,
								NULL,
								NULL,
								NULL,
								0, 
								NULL,
								NULL, 
								&pNamespace);
    printf("
ConnectServer returned 0x%x:", hr);
    if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: ConnectServer");goto cleanup;}

	hr = CoSetProxyBlanket(pNamespace,
						RPC_C_AUTHN_WINNT,
						RPC_C_AUTHZ_NONE,
						NULL,
						RPC_C_AUTHN_LEVEL_CALL,
						RPC_C_IMP_LEVEL_IMPERSONATE,
						NULL,
						EOAC_NONE);

    if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: CoSetProxyBlanket");goto cleanup;}

	hr =pNamespace->ExecQuery(_bstr_t(L"WQL"), //Query Language
							bstrQuery, //Query to Execute
							WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, //Make a semi-synchronous call
							NULL, //Context
							&pEnum /*Enumeration Interface*/);

   if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: ExecQuery");goto cleanup;}
 
	hr = WBEM_S_NO_ERROR;

	ULONG ulReturned;
	IWbemClassObject *pObj;
	DWORD retVal = 0;

	//Get the Next Object from the collection
	hr = pEnum->Next(WBEM_INFINITE, //Timeout
					1, //No of objects requested
					&pObj, //Returned Object
					&ulReturned /*No of object returned*/);

	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: Next");goto cleanup;}

	// Get the class object
	hr = pNamespace->GetObject(ClassPath, 0, NULL, &pClass, NULL);
	printf("
GetObject returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: GetObject");goto cleanup;}

	// Get the input argument and set the property
	hr = pClass->GetMethod(MethodName, 0, &pInClass, NULL);
	printf("
GetMethod returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: GetMethod");goto cleanup;}

	hr = pInClass->SpawnInstance(0, &pInInst);
	printf("
SpawnInstance returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: SpawnInstance");goto cleanup;}

	VARIANT var1;
	VariantInit(&var1);

	V_VT(&var1) = VT_BSTR;
	V_BSTR(&var1) = SysAllocString(L"0");
	hr = pInInst->Put(ArgName0,
					0,
					&var1,
					CIM_UINT32); //CIM_UINT64

	//var1.vt = VT_I4;
	//var1.ullVal = 0;
	//hr = pInInst->Put(ArgName0, 0, &var1, 0);
	printf("
Put ArgName0 returned 0x%x:", hr);
	VariantClear(&var1);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: Put ArgName0");goto cleanup;}

	VARIANT var;
	VariantInit(&var);

	V_VT(&var) = VT_BSTR;
	V_BSTR(&var) = SysAllocString(L"100");
	hr = pInInst->Put(ArgName1,
					0,
					&var,
					CIM_UINT8); 

	//var.vt=VT_UI1;
	//var.uiVal = 100;
	//hr = pInInst->Put(ArgName1, 0, &var, 0); 
	VariantClear(&var);
	printf("
Put ArgName1 returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: Put ArgName1");goto cleanup;}
	// Call the method

	VARIANT pathVariable;
	VariantInit(&pathVariable);

	hr = pObj->Get(_bstr_t(L"__PATH"),
				0,
				&pathVariable,
				NULL,
				NULL);
	printf("
pObj Get returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: Get");goto cleanup;}

	hr =pNamespace->ExecMethod(pathVariable.bstrVal,
							MethodName,
							0,
							NULL, 
							pInInst,
							NULL, 
							NULL);
	VariantClear(&pathVariable);
	printf("
ExecMethod returned 0x%x:", hr);
	if(hr != WBEM_S_NO_ERROR)
		{printf("
[-] Err: ExecMethod");goto cleanup;}

	printf("Terminating normally
");

// Free up resources
cleanup:
    SysFreeString(path);
    SysFreeString(ClassPath);
    SysFreeString(MethodName);
    SysFreeString(ArgName0);
	SysFreeString(ArgName1);
	SysFreeString(bstrQuery);

	if (pClass)	pClass->Release();
	if (pInInst) pInInst->Release();
	if (pInClass) pInClass->Release();
	if (pLocator) pLocator->Release();
	if (pNamespace) pNamespace->Release();
	
    CoUninitialize();
    
	return 0;
}