Example code to grab a still image (photo) from a mac's FaceTime camera

ImageCaptureManager.swift

//
//  ImageCaptureManager.swift
//  ImageCapture
//
//  Created by Jeroen Wesbeek on 29/07/16.
//  Copyright © 2016 Jeroen Wesbeek. All rights reserved.
//

import Foundation
import AVFoundation
import AVKit

class ImageCaptureManager {
    static let sharedInstance = ImageCaptureManager()
    
    private var captureDevice: AVCaptureDevice?
    private var captureSession: AVCaptureSession?
    private var stillImageOutput: AVCaptureStillImageOutput?
    
    init() {
        do {
            // configure photo output
            let stillImageOutput = AVCaptureStillImageOutput()
            stillImageOutput.outputSettings = [
                AVVideoCodecKey: AVVideoCodecJPEG
            ]
            
            // create capture session
            let session = AVCaptureSession()
            
            // add input capture device
            let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
            let videoInput = try AVCaptureDeviceInput(device: captureDevice)
            session.addInput(videoInput)
            
            // add still image output
            session.sessionPreset = AVCaptureSessionPresetPhoto
            if session.canAddOutput(stillImageOutput) {
                session.addOutput(stillImageOutput)
            }
            
            // commit session
            session.commitConfiguration()
            
            // assign locally
            self.captureDevice = captureDevice
            self.captureSession = session
            self.stillImageOutput = stillImageOutput
        } catch let error as NSError {
            NSLog("Could not initialize image capture session (%@)", error.localizedDescription)
        }
    }
    
    func takePhoto() {
        guard let captureSession = self.captureSession else {
            return
        }
        
        captureSession.startRunning()

        // capture delayed for the exposure to set
        NSTimer.scheduledTimerWithTimeInterval(0.15, target: self, selector: #selector(grabStillImage), userInfo: nil, repeats: false)
    }
    
    @objc private func grabStillImage() {
        guard let captureSession = self.captureSession, stillImageOutput = self.stillImageOutput, videoConnection = stillImageOutput.connectionWithMediaType(AVMediaTypeVideo) else {
            return
        }
        
        stillImageOutput.captureStillImageAsynchronouslyFromConnection(videoConnection) { [weak self] buffer, error in
            let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
            self?.saveImage(withData: imageData)
            
            // stop capturing
            dispatch_async(dispatch_get_main_queue()) {
                captureSession.stopRunning()
            }
        }
    }
    
    private func saveImage(withData data: NSData) {
        let image = NSImage(data: data)
        if let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).first {
            // create image file name
            let formatter = NSDateFormatter()
            formatter.dateFormat = "yyyyMMddHHmmss"
            let dateString = formatter.stringFromDate(NSDate())
            let destinationPath = "\(documentsPath)/RickRoll-\(dateString).jpg"
            
            // write image
            let success = image?.savePNG(destinationPath) ?? false
            if !success {
                NSLog("Could not save still image from capture device")
            }
        }
    }
}