如何在Qt中调节显示屏的亮度

Question

我想实现一个使用Qt调整所有显示器亮度的程序。我是一个初学者，找了很久的资料。谁能给我一些想法吗？谢谢！

    BOOL CGammaRamp::SetBrightness(HDC hDC, WORD wBrightness)
{
    /*
    Changes the brightness of the entire screen.
    This function may not work properly in some video cards.

    The wBrightness value should be a number between 0 and 255.
    128 = Regular brightness
    above 128 = brighter
    below 128 = darker

    If hDC is NULL, SetBrightness automatically load and release
    the display device context for you.

    */
    BOOL bReturn = FALSE;
    HDC hGammaDC = hDC;

    //Load the display device context of the entire screen if hDC is NULL.
    if (hDC == NULL)
        hGammaDC = GetDC(NULL);

    if (hGammaDC != NULL)
    {
        //Generate the 256-colors array for the specified wBrightness value.
        WORD GammaArray[3][256];

        for (int iIndex = 0; iIndex < 256; iIndex++)
        {
            int iArrayValue = iIndex * (wBrightness + 128);

            if (iArrayValue > 65535)
                iArrayValue = 65535;

            GammaArray[0][iIndex] =
            GammaArray[1][iIndex] =
            GammaArray[2][iIndex] = (WORD)iArrayValue;

        }

        //Set the GammaArray values into the display device context.
        bReturn = SetDeviceGammaRamp(hGammaDC, GammaArray);
    }

    if (hDC == NULL)
        ReleaseDC(NULL, hGammaDC);

    return bReturn;
}

这是我之前尝试过的，使用 SetDeviceGammaRamp 调整伽玛值可以在克隆模式下的单显示器或多显示器中正常工作。但是，当有多个显示器时，即使我为每个显示器获取了相应的 HDC，它也没有任何影响。

我还找到了另一种方法，但不幸的是，它只适用于外部屏幕，不适用于我的笔记本电脑屏幕。

    
#include "Ioctl.h"
#define _CRT_SECURE_NO_WARNINGS
#include <windows.h>
#include <iostream>
#include <Ntddvdeo.h>
#include "QDebug"

#define IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS  CTL_CODE(FILE_DEVICE_VIDEO, 0x125, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS    CTL_CODE(FILE_DEVICE_VIDEO, 0x126, METHOD_BUFFERED, FILE_ANY_ACCESS)
#define IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS      CTL_CODE(FILE_DEVICE_VIDEO, 0x127, METHOD_BUFFERED, FILE_ANY_ACCESS)

int Ioctl::setBrightness(int level)
{
    HANDLE h;
    DWORD nOutBufferSize = 256;
    BYTE SupportedBrightness[256];
    DWORD g_supportedLevelCount;
    DISPLAY_BRIGHTNESS DisplayBrightness;

    memset(SupportedBrightness, 0, sizeof(SupportedBrightness));

    /* use createfile function to open lcd.
    * url from microsoft about IOCTL code.
    *  http://msdn.microsoft.com/en-us/library/windows/desktop/aa372703%28v=vs.85%29.aspx
    */

    /*
    * char* 和 wchar_t* 互相转换参考博客
    * https://www.cnblogs.com/icqw/p/4614877.html
    */
    /*
    * c++代码参考博客
    * https://blog.csdn.net/weixin_34111819/article/details/86328019
    */
    char temchar[] = "\\\\.\\LCD";
    char* szSour = temchar;
    WCHAR Temp[128] = { 0 };
    mbstowcs(Temp, szSour, strlen(szSour));
    h = CreateFileW(Temp, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, 0);
    if (h == INVALID_HANDLE_VALUE) {
        qDebug()<<"Open \\\\.\\LCD error";
        exit(1);
    }

    /* Query for display supported level */
    if (!DeviceIoControl(h, IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS, NULL, 0, SupportedBrightness, nOutBufferSize, &g_supportedLevelCount, NULL)) {
        qDebug()<<"IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize;
        exit(1);
    }
    if (g_supportedLevelCount == 0)     /* 0 means not supported */
    {
        qDebug()<<"\nLCD not support LEVEL COUNT", g_supportedLevelCount;
        exit(1);
    }

    DisplayBrightness.ucDisplayPolicy = 0;
    DisplayBrightness.ucACBrightness = level;
    DisplayBrightness.ucDCBrightness = level;

    /* Set display backlight level */
    nOutBufferSize = sizeof(DisplayBrightness);
    if (!DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, (DISPLAY_BRIGHTNESS*)&DisplayBrightness, nOutBufferSize, NULL, 0, &nOutBufferSize, NULL)) {
        qDebug()<<"IOCTL_VIDEO_SET_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize;
        exit(1);
    }

    Sleep(500); /* delay for some time while wmi event changed */
    nOutBufferSize = sizeof(DisplayBrightness);
    if (!DeviceIoControl(h, IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS, NULL, 0, (DISPLAY_BRIGHTNESS*)&DisplayBrightness, nOutBufferSize, &nOutBufferSize, NULL)) {
        qDebug()<<"IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS error - %d, - buffer: %d ", g_supportedLevelCount, nOutBufferSize;
        exit(1);
    }
    qDebug()<<"\nBrightness_AC: %d\nBrightness_DC: %d", DisplayBrightness.ucACBrightness, DisplayBrightness.ucDCBrightness;
}

Answer 1

使用 Qt 无法做到这一点。您必须使用本机 Windows API。

以下是有关如何使用 Win32 API 为 Windows 执行操作的各种示例： https://github.com/alervd/monitor

您将找到有关如何枚举显示以及如何控制它们的代码示例。