AVCam 自定义预览层

Question

这是我第一次使用 iOS 相机。我试图创建一个只能拍摄照片（静止图像）的简单应用程序。我正在使用来自 wwdc 的代码：

https://developer.apple.com/library/ios/samplecode/AVCam/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010112-Intro-DontLinkElementID_2

我想创建自定义照片尺寸，如图所示：
在此处输入图片描述

但结果是： enter image description here

如何固定到正方形的大小？

谢谢！

编辑： 我附上了结果的图片。 enter image description here 我该如何解决？

编辑 2：

CMPCameraViewController:

- (void)viewDidLoad
{
[super viewDidLoad];

// Disable UI. The UI is enabled if and only if the session starts running.
self.stillButton.enabled = NO;

// Create the AVCaptureSession.
self.session = [[AVCaptureSession alloc] init];

// Setup the preview view.
self.previewView.session = self.session;

// Communicate with the session and other session objects on this queue.
self.sessionQueue = dispatch_queue_create( "session queue", DISPATCH_QUEUE_SERIAL );

self.setupResult = AVCamSetupResultSuccess;


// Setup the capture session.
// In general it is not safe to mutate an AVCaptureSession or any of its inputs, outputs, or connections from multiple threads at the same time.
// Why not do all of this on the main queue?
// Because -[AVCaptureSession startRunning] is a blocking call which can take a long time. We dispatch session setup to the sessionQueue
// so that the main queue isn't blocked, which keeps the UI responsive.
dispatch_async( self.sessionQueue, ^{
    if ( self.setupResult != AVCamSetupResultSuccess ) {
        return;
    }

    self.backgroundRecordingID = UIBackgroundTaskInvalid;
    NSError *error = nil;

    AVCaptureDevice *videoDevice = [CMPCameraViewController deviceWithMediaType:AVMediaTypeVideo preferringPosition:AVCaptureDevicePositionBack];
    AVCaptureDeviceInput *videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];

    if ( ! videoDeviceInput ) {
        NSLog( @"Could not create video device input: %@", error );
    }

    [self.session beginConfiguration];

    if ( [self.session canAddInput:videoDeviceInput] ) {
        [self.session addInput:videoDeviceInput];
        self.videoDeviceInput = videoDeviceInput;

        dispatch_async( dispatch_get_main_queue(), ^{
            // Why are we dispatching this to the main queue?
            // Because AVCaptureVideoPreviewLayer is the backing layer for AAPLPreviewView and UIView
            // can only be manipulated on the main thread.
            // Note: As an exception to the above rule, it is not necessary to serialize video orientation changes
            // on the AVCaptureVideoPreviewLayer’s connection with other session manipulation.

            // Use the status bar orientation as the initial video orientation. Subsequent orientation changes are handled by
            // -[viewWillTransitionToSize:withTransitionCoordinator:].
            UIInterfaceOrientation statusBarOrientation = [UIApplication sharedApplication].statusBarOrientation;
            AVCaptureVideoOrientation initialVideoOrientation = AVCaptureVideoOrientationPortrait;
            if ( statusBarOrientation != UIInterfaceOrientationUnknown ) {
                initialVideoOrientation = (AVCaptureVideoOrientation)statusBarOrientation;
            }

            AVCaptureVideoPreviewLayer *previewLayer = (AVCaptureVideoPreviewLayer *)self.previewView.layer;
            previewLayer.connection.videoOrientation = initialVideoOrientation;
            previewLayer.bounds = _previewView.frame;
            //previewLayer.connection.videoOrientation = UIInterfaceOrientationLandscapeLeft;
        } );
    }
    else {
        NSLog( @"Could not add video device input to the session" );
        self.setupResult = AVCamSetupResultSessionConfigurationFailed;
    }

    AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
    AVCaptureDeviceInput *audioDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error];

    if ( ! audioDeviceInput ) {
        NSLog( @"Could not create audio device input: %@", error );
    }

    if ( [self.session canAddInput:audioDeviceInput] ) {
        [self.session addInput:audioDeviceInput];
    }
    else {
        NSLog( @"Could not add audio device input to the session" );
    }

    AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
    if ( [self.session canAddOutput:movieFileOutput] ) {
        [self.session addOutput:movieFileOutput];
        AVCaptureConnection *connection = [movieFileOutput connectionWithMediaType:AVMediaTypeVideo];
        if ( connection.isVideoStabilizationSupported ) {
            connection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
        }
        self.movieFileOutput = movieFileOutput;
    }
    else {
        NSLog( @"Could not add movie file output to the session" );
        self.setupResult = AVCamSetupResultSessionConfigurationFailed;
    }

    AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    if ( [self.session canAddOutput:stillImageOutput] ) {
        stillImageOutput.outputSettings = @{AVVideoCodecKey : AVVideoCodecJPEG};
        [self.session addOutput:stillImageOutput];
        self.stillImageOutput = stillImageOutput;
    }
    else {
        NSLog( @"Could not add still image output to the session" );
        self.setupResult = AVCamSetupResultSessionConfigurationFailed;
    }

    [self.session commitConfiguration];
} );    
}

CMPPreviewView:

 + (Class)layerClass
   {
   return [AVCaptureVideoPreviewLayer class];
   }

 - (AVCaptureSession *)session
 {
AVCaptureVideoPreviewLayer *previewLayer = (AVCaptureVideoPreviewLayer *)self.layer;
return previewLayer.session;
}

- (void)setSession:(AVCaptureSession *)session
{
AVCaptureVideoPreviewLayer *previewLayer = (AVCaptureVideoPreviewLayer *)self.layer;
previewLayer.session = session;
((AVPlayerLayer *)[self layer]).videoGravity = AVLayerVideoGravityResize;
   }

Answer 1

Apple 的 AVCam 代码是进入摄影开发的一个很好的起点。

您要做的是修改视频预览图层的大小。这是通过更改 videoGravity 设置来完成的。这是纵横比填充类型查看的示例：

[Swift 3]

previewView.videoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill

现在，对于填充到矩形的情况，您需要定义层边界然后使用 AVLayerVideoGravityResize。

请注意：这不会影响拍摄照片的尺寸。它只是修改视频预览层的大小。这是一个重要的区别。要修改拍摄照片的大小，您需要执行裁剪操作（可以通过多种方式轻松完成），但这似乎不是您的意图。

祝你好运。

编辑： 现在，您似乎有兴趣裁剪捕获的 UIImage。

[Swift 3] 
// I'm going to assume you've done something like this to store the captured data to a UIImage object 
//If not, I would do so
let myImage = UIImage(data: capturedImageData)! 

// using core graphics (the cg in cgImage) you can perform all kinds of image manipulations--crop, rotation, mirror, etc. 
// here's crop to a rectangle--fill in with your desired values 
let myRect = CGRect(x: ..., y: ..., width: ..., height: ...) 
myImage = myImage.cgImage?.cropping(to: myRect)

希望这能回答您的问题。

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