旋转

//此方法放在@interface XXXViewController 之前

static double radians (double degrees) {return degrees * M_PI/180;}

static double ScalingFactorForAngle(double angle, CGSize originalSize) {
    double oriWidth = originalSize.height;
    double oriHeight = originalSize.width;
    double horizontalSpace = fabs( oriWidth*cos(angle) ) + fabs( oriHeight*sin(angle) );
    double scalingFactor = oriWidth / horizontalSpace ;
    return scalingFactor;
}

CGColorSpaceRef rgbColorSpace = NULL;
CIContext *context = nil;
CIImage *ci_originalImage = nil;
CIImage *ci_transformedImage = nil;
CIImage *ci_userTempImage = nil;

static inline void RotatePixelBufferToAngle(CVPixelBufferRef thePixelBuffer, double theAngle) {

    @autoreleasepool {

        if (context==nil) {
            rgbColorSpace = CGColorSpaceCreateDeviceRGB();
            context = [CIContext contextWithOptions:@{kCIContextWorkingColorSpace: (__bridge id)rgbColorSpace,
                                                       kCIContextOutputColorSpace : (__bridge id)rgbColorSpace}];
        }

        long int w = CVPixelBufferGetWidth(thePixelBuffer);
        long int h = CVPixelBufferGetHeight(thePixelBuffer);

        ci_originalImage = [CIImage imageWithCVPixelBuffer:thePixelBuffer];
        ci_userTempImage = [ci_originalImage imageByApplyingTransform:CGAffineTransformMakeScale(0.6, 0.6)];
        //        CGImageRef UICG_image = [context createCGImage:ci_userTempImage fromRect:[ci_userTempImage extent]];

        double angle = theAngle;
        angle = angle+M_PI;
        double scalingFact = ScalingFactorForAngle(angle, CGSizeMake(w, h));


        CGAffineTransform transform =  CGAffineTransformMakeTranslation(w/2.0, h/2.0);
        transform = CGAffineTransformRotate(transform, angle);
        transform = CGAffineTransformTranslate(transform, -w/2.0, -h/2.0);

        //rotate it by applying a transform
        ci_transformedImage = [ci_originalImage imageByApplyingTransform:transform];

        CVPixelBufferLockBaseAddress(thePixelBuffer, 0);

        CGRect extentR = [ci_transformedImage extent];
        CGPoint centerP = CGPointMake(extentR.size.width/2.0+extentR.origin.x,
                                      extentR.size.height/2.0+extentR.origin.y);
        CGSize scaledSize = CGSizeMake(w*scalingFact, h*scalingFact);
        CGRect cropRect = CGRectMake(centerP.x-scaledSize.width/2.0, centerP.y-scaledSize.height/2.0,
                                     scaledSize.width, scaledSize.height);


        CGImageRef cg_img = [context createCGImage:ci_transformedImage fromRect:cropRect];
        ci_transformedImage = [CIImage imageWithCGImage:cg_img];

        ci_transformedImage = [ci_transformedImage imageByApplyingTransform:CGAffineTransformMakeScale(1.0/scalingFact, 1.0/scalingFact)];
        [context render:ci_transformedImage toCVPixelBuffer:thePixelBuffer bounds:CGRectMake(0, 0, w, h) colorSpace:NULL];

        CGImageRelease(cg_img);
        CVPixelBufferUnlockBaseAddress(thePixelBuffer, 0);
    }
}

使用方法：
//home键在右传270.home键在左传90
RotatePixelBufferToAngle(pixelBuffer, radians(self.leftAngle));

方向

//手机锁定方向或者app只支持竖屏，可使用此方式获取设备方向
@property (nonatomic, strong) CMMotionManager *mManager;//陀螺仪
@property (nonatomic, assign) BOOL isHomeKeyLeft;//是否横屏
@property (nonatomic, assign) int leftAngle;//旋转角度

NSTimeInterval updateInterval;
- (CMMotionManager *)mManager
{
    if (!_mManager) {
        updateInterval = 1.0/15.0;
        _mManager = [[CMMotionManager alloc] init];
    }
    return _mManager;
}
- (void)startUpdateAccelerometer{
    if ([self.mManager isAccelerometerAvailable] == YES) {
//回调会一直调用,建议获取到就调用下面的停止方法，需要再重新开始，当然如果需求是实时不间断的话可以等离开页面之后再stop
        NSMutableDictionary *dic = [[NSMutableDictionary alloc] init];
        [self.mManager setAccelerometerUpdateInterval:updateInterval];
        [self.mManager startAccelerometerUpdatesToQueue:[NSOperationQueue currentQueue] withHandler:^(CMAccelerometerData *accelerometerData, NSError *error)
         {
             double x = accelerometerData.acceleration.x;
             double y = accelerometerData.acceleration.y;
             if (fabs(y) >= fabs(x))
             {
                 if (y >= 0){
                     //Down
                     self.isHomeKeyLeft = false;
                 }
                 else{
                     //Portrait
                     self.isHomeKeyLeft = false;
                 }
             }
             else
             {
                 if (x >= 0){
                     //Right：home键在左
                     self.isHomeKeyLeft = true;
                     self.leftAngle = 90;
                 }
                 else{
                     //Left：home键在右
                     self.isHomeKeyLeft = true;
                     self.leftAngle = 270;
                 }
             }
         }];
    }
}
- (void)stopUpdate
{
    if ([self.mManager isAccelerometerActive] == YES)
    {
        [self.mManager stopAccelerometerUpdates];
    }
}
-(void)dealloc{
    self.mManager = nil;
}