Accessing the ambient light sensor in iOS

Question

I'm working on a project in which it is really necessary to access the ambient light sensor.

I searched a lot in Google and Stackoverflow, but couldn't find any useful information. Is it even possible to do so?

I also tried to calculate the ambient light value by calculating the brightness out of the camera input, but the results aren't really precise, as the camera makes lot's of adjustments to the images, which distort the results.

Answer 1

To read the ambient light sensor data, you need to use IOHID in the IOKit framework (Reference)

http://iphonedevwiki.net/index.php/AppleISL29003

http://iphonedevwiki.net/index.php/IOKit.framework

Answer 2

I solve this problem With access to the camera

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection: (AVCaptureConnection *)connection
{
 CFDictionaryRef metadataDict = CMCopyDictionaryOfAttachments(NULL,
sampleBuffer, kCMAttachmentMode_ShouldPropagate);
NSDictionary *metadata = [[NSMutableDictionary alloc]
                          initWithDictionary:(__bridge NSDictionary*)metadataDict];
CFRelease(metadataDict);
NSDictionary *exifMetadata = [[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary] mutableCopy];
float brightnessValue = [[exifMetadata objectForKey:(NSString *)kCGImagePropertyExifBrightnessValue] floatValue];

//THIS IS INFORMATION THAT COMES FROM THE SENSOR
_Sensor = [[NSNumber numberWithFloat:brightnessValue] stringValue];
 NSLog(@" %@",_Sensor);

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){


        if ([_Sensor isEqualToString:@"-5.575654"]) {

       // YOU CODE HER

        }
        else {

       // YOU CODE HER
    }

});

}