AVCapturePhotoOutput

To capture photos with the AVCapturePhotoOutput class, follow these steps:

1. Create an AVCapturePhotoOutput object. Use its properties to determine supported capture settings and to enable certain features (for example, whether to capture Live Photos).

2. Create and configure an AVCapturePhotoSettings object to choose features and settings for a specific capture (for example, whether to enable image stabilization or flash).

3. Capture an image by passing your photo settings object to the capturePhotoWithSettings:delegate: method along with a delegate object implementing the AVCapturePhotoCaptureDelegate protocol. The photo capture output then calls your delegate to notify you of significant events during the capture process.

Some photo capture settings, such as the flashMode property, include options for automatic behavior. For such settings, the photo output determines whether to use that feature at the moment of capture—you don’t know when requesting a capture whether the feature will be enabled when the capture completes. When the photo capture output calls your AVCapturePhotoCaptureDelegate methods with information about the completed or in-progress capture, it also provides an AVCaptureResolvedPhotoSettings object that details which automatic features have been set for that capture. The resolved settings object’s uniqueID property matches the uniqueID value of the AVCapturePhotoSettings object you used to request capture.

Enabling certain photo features (Live Photo capture and high resolution capture) requires a reconfiguration of the capture render pipeline. To opt into these features, set the highResolutionCaptureEnabled, livePhotoCaptureEnabled, and livePhotoAutoTrimmingEnabled properties before calling your AVCaptureSession object’s startRunning method. Changing any of these properties while the session is running disrupts the capture render pipeline: Live Photo captures in progress end immediately, unfulfilled photo requests abort, and video preview temporarily freezes.

Using a photo capture output adds other requirements to your AVCaptureSession object:

• A capture session cannot support both Live Photo capture and movie file output. If your capture session includes an AVCaptureMovieFileOutput object, the livePhotoCaptureSupported property becomes NO. (As an alternative, you can use the AVCaptureVideoDataOutput class to output video buffers at the same resolution as a simultaneous Live Photo capture.)

• A capture session cannot contain both an AVCapturePhotoOutput object and an AVCaptureStillImageOutput object. The AVCapturePhotoOutput class includes all functionality of (and deprecates) the AVCaptureStillImageOutput class.

The AVCapturePhotoOutput class implicitly supports wide-gamut color photography. If the source AVCaptureDevice object’s activeColorSpace value is AVCaptureColorSpace_P3_D65, the capture output produces photos with wide color information (unless your AVCapturePhotoSettings object specifies an output format that does not support wide color).