文章目录
前言
最近遇到了新的需求，需要通过代码去改变显示器的亮度。通过调研发现，改变显示器亮度的方式有三种
1.调节伽马值
2.使用WMI
3.使用DDC/CI协议
然而这三个方法都各有缺点：
第一个方式：调节伽马值，效果会收到显示器的影响，有的显示器，或者驱动，会去校准显示器亮度。如果你改变了伽马值，在你的鼠标脱离程序的时候，屏幕亮度就会被校准回去。
第二个方式：使用WMI。使用WMI是不支持台式电脑的，只能在笔记本上面生效。这个也是我在调试的时候发现的，总是被拒绝访问，去查了才知道台式不支持。然后在笔记本下做了校验，发现确实是可以实现的。
第三个方式：使用DDC/CI协议。DDC/CI，全称为 Display Data Channel / Command Interface，是一种用于计算机显示设备（如显示器、投影仪等）之间通信的协议。它允许计算机与显示器共享信息，使得计算机能够读取显示器的状态和特性，例如分辨率、色彩特性等。
DDC/CI 的构成
DDC/CI 协议主要构建在两个较早的标准之上：
DDC (Display Data Channel):
DDC 是一种用于监视器和计算机之间通信的协议，允许计算机访问显示器的 EDID（Extended Display Identification Data）信息，EDID 是描述显示器特性的标准化数据结构。
CI (Command Interface):
Command Interface 允许计算机向显示器发送命令，包括但不限于调节明亮度、对比度、开启或关闭显示器等功能。
DDC/CI 的工作原理
I²C 通信: DDC/CI 的底层协议使用 I²C（Inter-Integrated Circuit）总线，使其可以支持主设备和从设备的双向通信。通常情况下，计算机作为主设备，显示器作为从设备。
EDID 读取: 计算机在启动时通过 DDC 读取显示器的 EDID，以确定最佳的分辨率和刷新率等设置。
命令发送: 计算机可以通过 DDC/CI 向显示器发送各种控制命令，比如：
调整亮度和对比度
切换输入信号源（如 HDMI、DisplayPort 等）
查询显示器当前的状态和设置
DDC/CI 的应用
显示器控制: DDC/CI 允许用户通过软件来控制显示器的许多设置，例如调节亮度、对比度和色温。许多监视器和显示器厂商都提供支持 DDC/CI 的软件工具来实现这些功能。
自动化脚本: 一些高级用户和系统管理员可以利用 DDC/CI 编写自动化脚本，以便远程管理和控制多个显示器的设置。
多显示器支持: 在多显示器环境中，DDC/CI 使得通过计算机系统统一管理多个显示器的设置成为可能。
如何使用 DDC/CI
软件工具
有几种工具可以帮助用户利用 DDC/CI 控制显示器：
DDC/CI 控制工具: 许多开源和商业软件，如 Monitorian （Windows 上的应用程序），可以通过 DDC/CI 来调整监视器的亮度和其他设置。
命令行工具: 例如 ddcutil 在 Linux 平台上，可以用来通过命令行与 DDC/CI 兼容的显示器进行交互。
注意事项
显示器支持: 并非所有显示器都支持 DDC/CI，因此确保你的显示器具有此功能。
驱动问题: 某些情况下，操作系统或显卡驱动程序可能需要支持 DDC/CI，以确保正常工作。
使用WMI调节显示器亮度
直接上代码吧，代码其实都是差不多的，主要在于你执行怎样的WQL操作，做什么样的操作。其余步骤都是差不多的。
头文件
cpp
#pragma once
#include <QtWidgets/QMainWindow>
#include "ui_QtTestPro.h"
class QtTestPro : public QMainWindow
{
Q_OBJECT
public:
QtTestPro(QWidget *parent = Q_NULLPTR);
int Init();
int GetBrightness();
void PrintError(HRESULT hres);
int SetBrightness(int brightness);
void Cleanup();
~QtTestPro();
private slots:
void on_btnUp_clicked();
void on_btnDown_clicked();
private:
Ui::QtTestProClass ui;
};cpp文件
cpp
#include "QtTestPro.h"
#include <QPushButton>
#include <iostream>
#include <string>
#include <windows.h>
#include <objbase.h>
#include <wbemidl.h>
#include <comdef.h>
#include <mutex>
#include<QDebug>
#pragma comment(lib, "wbemuuid.lib")
#pragma comment(lib, "comsuppw.lib")
using namespace std;
// wmi namespace
IWbemLocator* wmiLocator = NULL;
IWbemServices* wmiNamespace = 0;
BSTR wmiPath = SysAllocString(L"root\\wmi");
HRESULT hr = S_OK;
// brightnessAdjustmentClass
IWbemClassObject* brightnessAdjustmentClass = NULL;
IWbemClassObject* brightnessAdjustmentClassInstant = NULL;
IWbemClassObject* brightnessAdjustmentClassObject = NULL;
IWbemClassObject* brightnessAdjustmentMethodInstant = NULL;
IEnumWbemClassObject* brightnessAdjustmentClassEnum = NULL;
BSTR brightnessAdjustmentClassPath = SysAllocString(L"WmiMonitorBrightnessMethods");
BSTR brightnessAdjustmentMethodName = SysAllocString(L"WmiSetBrightness");
BSTR brightnessAdjustmentMethodArgName1 = SysAllocString(L"Timeout");
BSTR brightnessAdjustmentMethodArgName2 = SysAllocString(L"Brightness");
BSTR brightnessAdjustmentClassQuery = SysAllocString(L"Select * from WmiMonitorBrightnessMethods");
// brightnessClass
IEnumWbemClassObject* brightnessClassEnum = NULL;
//IWbemClassObject *brightnessClass = NULL;
IWbemClassObject* brightnessClassObject = NULL;
BSTR brightnessClassPath = SysAllocString(L"WmiMonitorBrightness");
BSTR brightnessVariableName = SysAllocString(L"CurrentBrightness");
BSTR brightnessQuery = SysAllocString(L"Select * from WmiMonitorBrightness");
QtTestPro::QtTestPro(QWidget* parent)
: QMainWindow(parent)
{
ui.setupUi(this);
connect(ui.btnUp, &QPushButton::clicked, this, &QtTestPro::on_btnUp_clicked);
connect(ui.btnDown, &QPushButton::clicked, this, &QtTestPro::on_btnDown_clicked);
// 全局唯一
//auto m = CreateMutexA(NULL, TRUE, "{CAF16FA1-1E0C-419B-9D45-99B5719ED318}");
//if (ERROR_ALREADY_EXISTS == GetLastError())
// return;
int r = Init();
if (r != 0)
return;
}
QtTestPro::~QtTestPro() {
// 清理
//UnregisterHotKey(hwnd, hotKeyId1);
//UnregisterHotKey(hwnd, hotKeyId2);
//GlobalDeleteAtom(hotKeyId1);
//GlobalDeleteAtom(hotKeyId2);
//Cleanup();
}
//
int QtTestPro::Init()
{
// Initialize COM and connect up to CIMOM
hr = CoInitialize(0);
if (FAILED(hr))
return -1;
hr = CoInitializeSecurity(NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_DEFAULT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, NULL);
if (FAILED(hr))
return -1;
hr = CoCreateInstance(CLSID_WbemLocator, 0, CLSCTX_INPROC_SERVER, IID_IWbemLocator, (LPVOID*)&wmiLocator);
if (FAILED(hr))
return -1;
hr = wmiLocator->ConnectServer(_bstr_t(L"ROOT\\WMI"), NULL, NULL, NULL, 0, NULL, NULL, &wmiNamespace);
if (hr != WBEM_S_NO_ERROR)
return -1;
hr = CoSetProxyBlanket(wmiNamespace, 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)
return -1;
//_bstr_t(L"ROOT\\CIMV2");
// query variable enum
hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), _bstr_t(L"Select * from WmiMonitorBrightnessMethods"), WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessAdjustmentClassEnum);
if (hr != WBEM_S_NO_ERROR)
return -1;
/*hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), brightnessQuery, WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessClassEnum);
if (hr != WBEM_S_NO_ERROR)
return -1;*/
// get class obj
ULONG ret;
hr = brightnessAdjustmentClassEnum->Next(WBEM_INFINITE, 1, &brightnessAdjustmentClassObject, &ret);
if (hr != WBEM_S_NO_ERROR)
{
qDebug() << "Failed to retrieve the next object. Error code = 0x"
<< hex << hr << dec << endl;
return -1;
}
hr = wmiNamespace->GetObject(brightnessAdjustmentClassPath, 0, NULL, &brightnessAdjustmentClass, NULL);
if (hr != WBEM_S_NO_ERROR)
return -1;
// get brightness adjust method instant
hr = brightnessAdjustmentClass->GetMethod(brightnessAdjustmentMethodName, 0, &brightnessAdjustmentClassInstant, NULL);
if (hr != WBEM_S_NO_ERROR)
return -1;
hr = brightnessAdjustmentClassInstant->SpawnInstance(0, &brightnessAdjustmentMethodInstant);
if (hr != WBEM_S_NO_ERROR)
return -1;
return 0;
//HRESULT hres;
Step 1: --------------------------------------------------
Initialize COM. ------------------------------------------
hres = CoInitializeEx(0, COINIT_MULTITHREADED);
//hres = CoInitialize(0);
//if (FAILED(hres))
//{
// PrintError(hres);
// qDebug() << "Failed to initialize COM library. Error code = 0x"
// << hex << hres << endl;
// return 1; // Program has failed.
//}
Step 2: --------------------------------------------------
Set general COM security levels --------------------------
//hres = CoInitializeSecurity(
// NULL,
// -1, // COM authentication
// NULL, // Authentication services
// NULL, // Reserved
// RPC_C_AUTHN_LEVEL_DEFAULT, // Default authentication
// RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation
// NULL, // Authentication info
// EOAC_NONE, // Additional capabilities
// NULL // Reserved
// );
//if (FAILED(hres))
//{
// cout << "Failed to initialize security. Error code = 0x"
// << hex << hres << endl;
// CoUninitialize();
// return 1; // Program has failed.
//}
Step 3: ---------------------------------------------------
Obtain the initial locator to WMI -------------------------
//IWbemLocator *pLoc = NULL;
//hres = CoCreateInstance(
// CLSID_WbemLocator,
// 0,
// CLSCTX_INPROC_SERVER,
// IID_IWbemLocator, (LPVOID *)&pLoc);
//if (FAILED(hres))
//{
// cout << "Failed to create IWbemLocator object."
// << " Err code = 0x"
// << hex << hres << endl;
// CoUninitialize();
// return 1; // Program has failed.
//}
Step 4: -----------------------------------------------------
Connect to WMI through the IWbemLocator::ConnectServer method
//IWbemServices *pSvc = NULL;
Connect to the root\cimv2 namespace with
the current user and obtain pointer pSvc
to make IWbemServices calls.
//hres = pLoc->ConnectServer(
// _bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
// NULL, // User name. NULL = current user
// NULL, // User password. NULL = current
// 0, // Locale. NULL indicates current
// NULL, // Security flags.
// 0, // Authority (for example, Kerberos)
// 0, // Context object
// &pSvc // pointer to IWbemServices proxy
// );
//if (FAILED(hres))
//{
// cout << "Could not connect. Error code = 0x"
// << hex << hres << endl;
// pLoc->Release();
// CoUninitialize();
// return 1; // Program has failed.
//}
//cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;
Step 5: --------------------------------------------------
Set security levels on the proxy -------------------------
//hres = CoSetProxyBlanket(
// pSvc, // Indicates the proxy to set
// RPC_C_AUTHN_WINNT, // RPC_C_AUTHN_xxx
// RPC_C_AUTHZ_NONE, // RPC_C_AUTHZ_xxx
// NULL, // Server principal name
// RPC_C_AUTHN_LEVEL_CALL, // RPC_C_AUTHN_LEVEL_xxx
// RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
// NULL, // client identity
// EOAC_NONE // proxy capabilities
// );
//if (FAILED(hres))
//{
// cout << "Could not set proxy blanket. Error code = 0x"
// << hex << hres << endl;
// pSvc->Release();
// pLoc->Release();
// CoUninitialize();
// return 1; // Program has failed.
//}
Step 6: --------------------------------------------------
Use the IWbemServices pointer to make requests of WMI ----
For example, get the name of the operating system
//IEnumWbemClassObject* pEnumerator = NULL;
//hres = pSvc->ExecQuery(
// bstr_t("WQL"),
// bstr_t("SELECT * FROM Win32_DesktopMonitor"),//L"Select * from WmiMonitorBrightnessMethods "SELECT * FROM Win32_OperatingSystem" "SELECT * FROM Win32_DesktopMonitor"
// WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
// NULL,
// &pEnumerator);
//if (FAILED(hres))
//{
// cout << "Query for operating system name failed."
// << " Error code = 0x"
// << hex << hres << endl;
// pSvc->Release();
// pLoc->Release();
// CoUninitialize();
// return 1; // Program has failed.
//}
Step 7: -------------------------------------------------
Get the data from the query in step 6 -------------------
//IWbemClassObject *pclsObj = NULL;
//ULONG uReturn = 0;
//while (pEnumerator)
//{
// HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1,
// &pclsObj, &uReturn);
// if (0 == uReturn)
// {
// break;
// }
// VARIANT vtProp;
// VariantInit(&vtProp);
// // Get the value of the Name property
// hr = pclsObj->Get(L"Name", 0, &vtProp, 0, 0);
// qDebug() << " OS Name : " << vtProp.bstrVal << endl;
// VariantClear(&vtProp);
// pclsObj->Release();
//}
Cleanup
========
//pSvc->Release();
//pLoc->Release();
//pEnumerator->Release();
//CoUninitialize();
//return 0; // Program successfully completed.
}
void QtTestPro::PrintError(HRESULT hres)
{
LPVOID lpMsgBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
hres,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPWSTR)&lpMsgBuf,
0, NULL);
qDebug()<< L"Error: " << (LPWSTR)lpMsgBuf << endl;
LocalFree(lpMsgBuf);
}
int QtTestPro::GetBrightness()
{
// 每次都需要查询
if (brightnessClassEnum) brightnessClassEnum->Release();
if (brightnessClassObject) brightnessClassObject->Release();
HRESULT hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), brightnessQuery, WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessClassEnum);
if (hr != WBEM_S_NO_ERROR)
return -1;
DWORD ret;
hr = brightnessClassEnum->Next(WBEM_INFINITE, 1, &brightnessClassObject, &ret);
if (hr != WBEM_S_NO_ERROR)
return -1;
// 获得亮度值
VARIANT brightnessValue;
VariantInit(&brightnessValue);
hr = brightnessClassObject->Get(brightnessVariableName, 0, &brightnessValue, 0, 0);
if (hr != WBEM_S_NO_ERROR)
return -1;
ui.label->setText(QString::number(brightnessValue.uintVal));
return brightnessValue.uintVal;
}
int QtTestPro::SetBrightness(int brightness)
{
// 亮度范围是 [0, 100]
brightness = min(max(brightness, 0), 100);
// write brightness adjust params
VARIANT var;
VariantInit(&var);
V_VT(&var) = VT_BSTR;
// write timeout param
V_BSTR(&var) = SysAllocString(L"0");
hr = brightnessAdjustmentMethodInstant->Put(brightnessAdjustmentMethodArgName1, 0, &var, CIM_UINT32);
if (hr != WBEM_S_NO_ERROR)
return -1;
// write brightness param
V_BSTR(&var) = SysAllocString(to_wstring(brightness).c_str());
hr = brightnessAdjustmentMethodInstant->Put(brightnessAdjustmentMethodArgName2, 0, &var, CIM_UINT8);
VariantClear(&var);
if (hr != WBEM_S_NO_ERROR)
return -1;
// 获取 method instant path 和 execute
VARIANT pathVariable;
VariantInit(&pathVariable);
hr = brightnessAdjustmentClassObject->Get(_bstr_t(L"__PATH"), 0, &pathVariable, NULL, NULL);
if (hr != WBEM_S_NO_ERROR)
return -1;
hr = wmiNamespace->ExecMethod(pathVariable.bstrVal, brightnessAdjustmentMethodName, 0, NULL, brightnessAdjustmentMethodInstant, NULL, NULL);
VariantClear(&pathVariable);
if (hr != WBEM_S_NO_ERROR)
return -1;
return 0;
}
void QtTestPro::Cleanup()
{
// 清理
SysFreeString(wmiPath);
SysFreeString(brightnessAdjustmentClassPath);
SysFreeString(brightnessAdjustmentMethodName);
SysFreeString(brightnessAdjustmentMethodArgName1);
SysFreeString(brightnessAdjustmentMethodArgName2);
SysFreeString(brightnessAdjustmentClassQuery);
SysFreeString(brightnessClassPath);
SysFreeString(brightnessVariableName);
SysFreeString(brightnessQuery);
brightnessAdjustmentClass->Release();
brightnessAdjustmentMethodInstant->Release();
brightnessAdjustmentClassInstant->Release();
brightnessAdjustmentClassObject->Release();
brightnessAdjustmentClassEnum->Release();
//if (brightnessClass) brightnessClass->Release();
brightnessClassObject->Release();
brightnessClassEnum->Release();
wmiNamespace->Release();
wmiLocator->Release();
CoUninitialize();
}
// 亮度进阶值
void QtTestPro::on_btnUp_clicked() {
GetBrightness();
SetBrightness(ui.lineEdit->text().toInt());
}
void QtTestPro::on_btnDown_clicked() {
GetBrightness();
SetBrightness(ui.lineEdit->text().toInt());
}