OpenCv iOS相机预览单一方向,无需拉伸

视图控制器

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    // Initialize imageView to fullscreen
    imageView = [[UIImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    [self.view addSubview:imageView];
    [imageView setContentMode:UIViewContentModeScaleAspectFill];
    [imageView setClipsToBounds:YES];

    self.videoCamera = [[FixedCvVideoCamera alloc] initWithParentView:imageView];
    self.videoCamera.delegate = self;
    self.videoCamera.defaultAVCaptureDevicePosition = AVCaptureDevicePositionBack;
    self.videoCamera.defaultAVCaptureSessionPreset = AVCaptureSessionPresetHigh;
    self.videoCamera.defaultAVCaptureVideoOrientation =  AVCaptureVideoOrientationPortrait;
    self.videoCamera.defaultFPS = 30;
    self.videoCamera.grayscaleMode = NO;

    [self.videoCamera start];
}

FixedCvVideoCamera：CvVideoCamera

- (void)layoutPreviewLayer;
{
    if (self.parentView != nil)
    {
        CALayer* layer = self->customPreviewLayer;
        CGRect bounds = self->customPreviewLayer.bounds;
        NSLog(@"[FixedCvVideoCamera]Custom Preview Layer bounds %fx%f",bounds.size.width,bounds.size.height);

        float previewAspectRatio = bounds.size.height / bounds.size.width;
        NSLog(@"[FixedCvVideoCamera]Preview aspect ratio %f",previewAspectRatio);

        //int rotation_angle = 0;

        layer.position = CGPointMake(self.parentView.frame.size.width/2.,self.parentView.frame.size.height/2.);
        //layer.affineTransform = CGAffineTransformMakeRotation( DEGREES_RADIANS(rotation_angle) );

        // Get video feed's resolutions
        NSArray* devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
        AVCaptureDevice* device = nil;
        for (AVCaptureDevice *d in devices) {
            // Get the default camera device - should be either front of back camera device
            if ([d position] == self.defaultAVCaptureDevicePosition) {
                device = d;
            }
        }

        // Set the default device if not found
        if (!device) {
            device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
        }

        CMVideoDimensions dimensions = CMVideoFormatDescriptionGetDimensions(device.activeFormat.formatDescription);
        CGSize resolution = CGSizeMake(dimensions.width,dimensions.height);
        if (self.defaultAVCaptureVideoOrientation == AVCaptureVideoOrientationPortrait || self.defaultAVCaptureVideoOrientation == AVCaptureVideoOrientationPortraitUpsideDown) {
            resolution = CGSizeMake(resolution.height,resolution.width);
        }
        NSLog(@"[FixedCvVideoCamera]Video feed resolution is %fx%f",resolution.width,resolution.height);

        float videoFeedAspectRatio = resolution.height / resolution.width;
        NSLog(@"[FixedCvVideoCamera]Video feed's aspect ratio is %f",videoFeedAspectRatio);

        // Set layer bounds to ASPECT FILL by expanding either the width or the height
        if (previewAspectRatio > videoFeedAspectRatio) {
            NSLog(@"[FixedCvVideoCamera] Preview is more rectangular than the video feed aspect ratio. Expanding width to maintain aspect ratio.");
            float newWidth = bounds.size.height / videoFeedAspectRatio;
            layer.bounds = CGRectMake(0,newWidth,bounds.size.height);
        } else {
            NSLog(@"[FixedCvVideoCamera] Preview is equally or less rectangular (wider) than the video feed's aspect ratio. Expanding height bound to maintain aspect ratio.");
            float newHeight = bounds.size.width * videoFeedAspectRatio;
            layer.bounds = CGRectMake(0,newHeight);
        }
    }
}