Gian Paolo Ghilardi Gian Paolo Ghilardi - 4 months ago 19
Linux Question

Setting color brightness on Linux/Xorg

Is there any command (or API) to set X.Org/Linux color brightness?

In other words, I need something as handy as the xgamma command but for changing RGB brightness real-time.

Is this possibile?


Use the XF86VidMode* family of functions.

#include <X11/Xlib.h>
#include <X11/extensions/xf86vmode.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
    Display *display;
    int screen;
    int major, minor;
    int i;
    XF86VidModeGamma orig;

    display = XOpenDisplay(NULL);
    if (!display) return -1;
    screen = DefaultScreen(display);
    if (!XF86VidModeQueryVersion(display, &major, &minor)
            || major < 2 || major == 2 && minor < 0
            || !XF86VidModeGetGamma(display, screen, &orig)) {
        return -1;

    for (i = 0; i <= 32; i++) {
        XF86VidModeGamma gamma; = exp2f(2 - fabs(i - 16) / 4); =; =;
        if (!XF86VidModeSetGamma(display, screen, &gamma)) break;
        printf("gamma: %f %f %f",,,;
        if (!XF86VidModeGetGamma(display, screen, &gamma)) break;
        printf(" -> %f %f %f\n",,,;
    XF86VidModeSetGamma(display, screen, &orig);
    XF86VidModeGetGamma(display, screen, &orig);

    return 0;

This brings the gamma from 0.25 to 4.0 and back, and then restores the original gamma.

Or you could just repeatedly call system("xgamma -gamma %f"), with pretty much the same results.