Question

Is there a way to adjust the Mac’s display brightness in Objective-C? I have sensitive eyes, and sometimes the display seems like it could be darker. Combine that with Jeff’s blog post about geeks and darkness, and it can get pretty annoying.

I think it would stand to reason that if the display could be set as a number value, it could get set lower than the regular screen brightness. I have Googled all over, but all of the things that came up were about the iPhone. Is there a way to do it for Mac?

Answer 1

just googled around and found this 🙂

Here is the code how to get brightness.

    // almost completely from: http://mattdanger.net/2008/12/adjust-mac-os-x-display-brightness-from-the-terminal/
- (float) get_brightness {
    CGDirectDisplayID display[kMaxDisplays];
    CGDisplayCount numDisplays;
    CGDisplayErr err;
    err = CGGetActiveDisplayList(kMaxDisplays, display, &numDisplays);

    if (err != CGDisplayNoErr)
        printf("cannot get list of displays (error %d)\n",err);
    for (CGDisplayCount i = 0; i < numDisplays; ++i) {


        CGDirectDisplayID dspy = display[i];
        CFDictionaryRef originalMode = CGDisplayCurrentMode(dspy);
        if (originalMode == NULL)
            continue;
        io_service_t service = CGDisplayIOServicePort(dspy);

        float brightness;
        err= IODisplayGetFloatParameter(service, kNilOptions, kDisplayBrightness,
                                        &brightness);
        if (err != kIOReturnSuccess) {
            fprintf(stderr,
                    "failed to get brightness of display 0x%x (error %d)",
                    (unsigned int)dspy, err);
            continue;
        }
        return brightness;
    }       
    return -1.0;//couldn't get brightness for any display
}

How to set the brightness.

// almost completely from: http://mattdanger.net/2008/12/adjust-mac-os-x-display-brightness-from-the-terminal/
- (void) set_brightness:(float) new_brightness {
    CGDirectDisplayID display[kMaxDisplays];
    CGDisplayCount numDisplays;
    CGDisplayErr err;
    err = CGGetActiveDisplayList(kMaxDisplays, display, &numDisplays);

    if (err != CGDisplayNoErr)
        printf("cannot get list of displays (error %d)\n",err);
    for (CGDisplayCount i = 0; i < numDisplays; ++i) {


        CGDirectDisplayID dspy = display[i];
        CFDictionaryRef originalMode = CGDisplayCurrentMode(dspy);
        if (originalMode == NULL)
            continue;
                io_service_t service = CGDisplayIOServicePort(dspy);

        float brightness;
        err= IODisplayGetFloatParameter(service, kNilOptions, kDisplayBrightness,
                                        &brightness);
        if (err != kIOReturnSuccess) {
            fprintf(stderr,
                    "failed to get brightness of display 0x%x (error %d)",
                    (unsigned int)dspy, err);
            continue;
        }

        err = IODisplaySetFloatParameter(service, kNilOptions, kDisplayBrightness,
                                         new_brightness);
        if (err != kIOReturnSuccess) {
            fprintf(stderr,
                    "Failed to set brightness of display 0x%x (error %d)",
                     (unsigned int)dspy, err);
            continue;
        }

        if(brightness > 0.0){
        }else{
        }
    }       

}

I found it here – http://www.alecjacobson.com/weblog/?tag=brightness.