可以用C改变屏幕亮度吗？

Question

在Linux中使用C语言，可以改变观看屏幕的亮度吗？除了在我安装的 Ubuntu 和 Fedora 上运行之外，预计它不会是可移植的。我问的是如何与操作系统交互来改变亮度。

Answer 1

我首先从下面的 ubuntu 软件包列表中进行选择，该工具允许您管理屏幕亮度（提示：这取决于品牌）

nvidia-settings - Tool of configuring the NVIDIA graphics driver
smartdimmer - Change LCD brightness on Geforce cards
armada-backlight - adjust backlight of Compaq Armada laptops (E300, M500, M700)
ddccontrol - a program to control monitor parameters
eeepc-acpi-scripts - Scripts to support suspend and hotkeys on the Asus Eee PC laptop
fnfxd - ACPI and hotkey daemon for Toshiba laptops
gddccontrol - a program to control monitor parameters
spicctrl - Sony Vaio controller program to set LCD backlight brightness
tpb - program to use the IBM ThinkPad(tm) special keys
xfce4-power-manager - power manager for Xfce desktop
xfce4-power-manager-plugins - power manager plugins for Xfce panel
xvattr - Utility to change Xv attributes

一旦您选择了它，

sudo apt-get build-dep <pkgname>
apt-get source --compile <pkgname> 

应该会让您走上正确的道路

Answer 2

戳/sys/class/backlight/*/brightness。是的，即使是在 C 语言中。

Answer 3

是的，但不可移植——你需要一个特定于平台的函数，C 标准库中没有任何东西。

Answer 4

查看 xbacklight 源。例如，以下代码将屏幕亮度设置为 50%。

// brightness.c
// gcc -o brightness brightness.c -lXrandr -lX11

#include <X11/Xatom.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xrandr.h>

#define BRIGHTNESS 0.5 // Target brightness between 0.0 and 1.0

int main(int argc, char *argv[])
{
        Display *dpy;
        static Atom backlight;
        int screen = 0, o = 0;
        Window root;
        XRRScreenResources *resources;
        RROutput output;
        XRRPropertyInfo *info;
        double min, max;
        long value;

        dpy = XOpenDisplay(NULL);
        backlight = XInternAtom (dpy, "Backlight", True);
        root = RootWindow(dpy, screen);
        resources = XRRGetScreenResources(dpy, root);
        output = resources->outputs[o];
        info = XRRQueryOutputProperty(dpy, output, backlight);
        min = info->values[0];
        max = info->values[1];
        XFree(info); // Don't need this anymore
        XRRFreeScreenResources(resources); // or this

        value = BRIGHTNESS * (max - min) + min;

        XRRChangeOutputProperty(dpy, output, backlight, XA_INTEGER,
                        32, PropModeReplace, (unsigned char *) &value, 1);
        XFlush(dpy);
        XSync(dpy, False);
        return 0;
}