camera orientation

camera

手机相机录视频或者拍照，需要考虑设备的方向，主要在两方面

1. 采集过程中，无论手机什么方向采集，采集画面都是正着看，不用侧头
2. 录制/或者拍照后，视频/图片在正常手持设备的情况下正常显示，不用横着手机

正常手持一般都是竖着拿手机，所以就算横着拍摄，竖着拿手机也需要正常显示，不理解可以参考下系统相机。

所以这里就存在一个方向修正的问题。

device orientation

苹果手机，如果设置里锁定了方向，是没办法通过 [UIDevice currentDevice].orientation这个方法拿到的，同样UIDeviceOrientationDidChangeNotification这个通知也获取不到。同理 [[UIApplication sharedApplication] statusBarOrientation]; 跟 **UIApplicationDidChangeStatusBarOrientationNotification** 也是不可用的。

可以通过 CMMotionManager 监听设备的方向

_motionManager = [[CMMotionManager alloc] init];
_motionManager.deviceMotionUpdateInterval = 1/15.0;
if (!_motionManager.deviceMotionAvailable) {
    _motionManager = nil;
    return self;
}
OBJC_WEAK(self)
[_motionManager startDeviceMotionUpdatesToQueue:[NSOperationQueue currentQueue] withHandler: ^(CMDeviceMotion
*motion, NSError *error){
    
    [weak_self performSelectorOnMainThread:@selector(handleDeviceMotion:) withObject:motion waitUntilDone:YES];
}];

- (void)handleDeviceMotion:(CMDeviceMotion *)deviceMotion {
    double x = deviceMotion.gravity.x;
    double y = deviceMotion.gravity.y;
    if (fabs(y) >= fabs(x)) {
        if (y >= 0) {
            _deviceOrientation = UIDeviceOrientationPortraitUpsideDown;
            _videoOrientation  = AVCaptureVideoOrientationPortraitUpsideDown;
        } else {
            _deviceOrientation = UIDeviceOrientationPortrait;
            _videoOrientation  = AVCaptureVideoOrientationPortrait;
        }
    } else {
        if (x >= 0) {
            _deviceOrientation = UIDeviceOrientationLandscapeRight;
            _videoOrientation  = AVCaptureVideoOrientationLandscapeRight;
        } else {
            _deviceOrientation = UIDeviceOrientationLandscapeLeft;
            _videoOrientation  = AVCaptureVideoOrientationLandscapeLeft;
        }
    }
}

capture

项目中需要支持设置滤镜、特效等等，所以显示采集的图像需要自己渲染，通过官方的AVCaptureSession配置好采集流程，不管是竖着还是横着采集，获取到的pixelBuffer都是横向的，因为默认就是home键在右边采集图像，但是显示的视图一般都是竖向，所以这里要做一个90°的旋转处理,OPENGL 就是一个旋转矩阵。

void main()
{
   // z
   mat4 rotationMatrix = mat4(cos(angle) , sin(angle) , 0.0, 0.0,
                              -sin(angle) , cos(angle) , 0.0, 0.0,
                              0.0, 0.0, 1.0, 0.0,
                              0.0, 0.0, 0.0, 1.0);
   
   vec4 outPosition =  rotationMatrix * position;
   gl_Position = outPosition;
   textureCoordinate = inputTextureCoordinate.xy;
}

如果只是解决采集画面显示，也可以通过设置connection.videoOrientation = [self currentVideoOrientation]; 来解决
项目中没有用这个，因为后面还需要录制视频导出视频文件。

// 当前设备取向
- (AVCaptureVideoOrientation)currentVideoOrientation{
    AVCaptureVideoOrientation orientation;
    switch (self.motionManager.deviceOrientation) { 
        case UIDeviceOrientationPortrait:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
        case UIDeviceOrientationLandscapeLeft:
            orientation = AVCaptureVideoOrientationLandscapeRight;
            break;
        case UIDeviceOrientationLandscapeRight:
            orientation = AVCaptureVideoOrientationLandscapeLeft;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            orientation = AVCaptureVideoOrientationPortraitUpsideDown;
            break;
        default:
            orientation = AVCaptureVideoOrientationPortrait;
            break;
    }
    return orientation;
}

Record

录制过程通过AVAssetWriterInput *writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:obj outputSettings:options]; 和[self.mPixelBufferAdaptor appendPixelBuffer:pixelBuffer withPresentationTime:ts] 来积累pixelBuffer， 为了保障导出的视频可以正常显示，需要记录视频的方向，通过设置writerInput.transform[ = self transformFromCurrentVideoOrientationToOrientation:AVCaptureVideoOrientationPortrait],系统自动帮我们做转换

// 旋转视频方向函数实现
- (CGAffineTransform)transformFromCurrentVideoOrientationToOrientation:(AVCaptureVideoOrientation)orientation {
    CGFloat orientationAngleOffset = [self angleOffsetFromPortraitOrientationToOrientation:orientation];
    CGFloat videoOrientationAngleOffset = [self angleOffsetFromPortraitOrientationToOrientation:self.currentOrientation];
    CGFloat angleOffset;
    if (self.position == AVCaptureDevicePositionBack)  {
        angleOffset = videoOrientationAngleOffset - orientationAngleOffset + M_PI_2;
    } else {
        angleOffset = orientationAngleOffset - videoOrientationAngleOffset + M_PI_2;
    }
    CGAffineTransform transform = CGAffineTransformMakeRotation(angleOffset);
    return transform;
}

- (CGFloat)angleOffsetFromPortraitOrientationToOrientation:(AVCaptureVideoOrientation)orientation {
    CGFloat angle = 0.0;
    switch (orientation) {
        case AVCaptureVideoOrientationPortrait:
            angle = 0.0;
            break;
        case AVCaptureVideoOrientationPortraitUpsideDown:
            angle = M_PI;
            break;
        case AVCaptureVideoOrientationLandscapeRight:
            angle = -M_PI_2;
            break;
        case AVCaptureVideoOrientationLandscapeLeft:
            angle = M_PI_2;
            break;
    }
    return angle;
}

主要就是通过录制视频时候的设备方向跟显示方向计算一下transform

Pic

拍照生成图片是同样的道理，直接给出方法，主要就是图片方向的旋转

- (UIImageOrientation)getImageRotationOrientationFromCaptureVideoOrientation:(AVCaptureVideoOrientation)orientation {
    UIImageOrientation imageOrientation;
    switch (orientation) {
        case AVCaptureVideoOrientationPortrait:
            imageOrientation = UIImageOrientationRight;
            break;
        case AVCaptureVideoOrientationPortraitUpsideDown:
            imageOrientation = UIImageOrientationLeft;
            break;
        case AVCaptureVideoOrientationLandscapeRight:
            imageOrientation = UIImageOrientationUp;
            break;
        case AVCaptureVideoOrientationLandscapeLeft:
            imageOrientation = UIImageOrientationDown;
            break;
    }
    return imageOrientation;
}

+ (UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation {
    long double rotate = 0.0;
    CGRect rect;
    float translateX = 0;
    float translateY = 0;
    float scaleX = 1.0;
    float scaleY = 1.0;
    
    switch (orientation) {
        case UIImageOrientationLeft:
            rotate = M_PI_2;
            rect = CGRectMake(0, 0, image.size.height, image.size.width);
            translateX = 0;
            translateY = -rect.size.width;
            scaleY = rect.size.width/rect.size.height;
            scaleX = rect.size.height/rect.size.width;
            break;
        case UIImageOrientationRight:
            rotate = -M_PI_2;
            rect = CGRectMake(0, 0, image.size.height, image.size.width);
            translateX = -rect.size.height;
            translateY = 0;
            scaleY = rect.size.width/rect.size.height;
            scaleX = rect.size.height/rect.size.width;
            break;
        case UIImageOrientationDown:
            rotate = M_PI;
            rect = CGRectMake(0, 0, image.size.width, image.size.height);
            translateX = -rect.size.width;
            translateY = -rect.size.height;
            break;
        default:
            rotate = 0.0;
            rect = CGRectMake(0, 0, image.size.width, image.size.height);
            translateX = 0;
            translateY = 0;
            break;
    }
    
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    //做CTM变换
    CGContextTranslateCTM(context, 0.0, rect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextRotateCTM(context, rotate);
    CGContextTranslateCTM(context, translateX, translateY);
    
    CGContextScaleCTM(context, scaleX, scaleY);
    //绘制图片
    CGContextDrawImage(context, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);
    
    UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();
    
    return newPic;
}