Come usare la computer vision in un’app iOS



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Se volete armeggiare da soli e imparare lungo la strada, vi suggerisco di seguire questo articolo che ho trovato su Medium. This approach is using native Swift code to extract camera frame, then you can process that frame with your own code.

  1. import UIKit 
  2. import AVFoundation 
  3. protocol FrameExtractorDelegate: class { 
  4. func captured(image: UIImage) 
  5. } 
  6. class FrameExtractor: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate { 
  7. private let position = AVCaptureDevicePosition.front 
  8. private let quality = AVCaptureSessionPresetMedium 
  9. private var permissionGranted = false 
  10. private let sessionQueue = DispatchQueue(label: "session queue") 
  11. private let captureSession = AVCaptureSession() 
  12. private let context = CIContext() 
  13. weak var delegate: FrameExtractorDelegate? 
  14. override init() { 
  15. super.init() 
  16. checkPermission() 
  17. sessionQueue.async { [unowned self] in 
  18. self.configureSession() 
  19. self.captureSession.startRunning() 
  20. } 
  21. } 
  22. // MARK: AVSession configuration 
  23. private func checkPermission() { 
  24. switch AVCaptureDevice.authorizationStatus(forMediaType: AVMediaTypeVideo) { 
  25. case .authorized: 
  26. permissionGranted = true 
  27. case .notDetermined: 
  28. requestPermission() 
  29. default: 
  30. permissionGranted = false 
  31. } 
  32. } 
  33. private func requestPermission() { 
  34. sessionQueue.suspend() 
  35. AVCaptureDevice.requestAccess(forMediaType: AVMediaTypeVideo) { [unowned self] granted in 
  36. self.permissionGranted = granted 
  37. self.sessionQueue.resume() 
  38. } 
  39. } 
  40. private func configureSession() { 
  41. guard permissionGranted else { return } 
  42. captureSession.sessionPreset = quality 
  43. guard let captureDevice = selectCaptureDevice() else { return } 
  44. guard let captureDeviceInput = try? AVCaptureDeviceInput(device: captureDevice) else { return } 
  45. guard captureSession.canAddInput(captureDeviceInput) else { return } 
  46. captureSession.addInput(captureDeviceInput) 
  47. let videoOutput = AVCaptureVideoDataOutput() 
  48. videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "sample buffer")) 
  49. guard captureSession.canAddOutput(videoOutput) else { return } 
  50. captureSession.addOutput(videoOutput) 
  51. guard let connection = videoOutput.connection(withMediaType: AVFoundation.AVMediaTypeVideo) else { return } 
  52. guard connection.isVideoOrientationSupported else { return } 
  53. guard connection.isVideoMirroringSupported else { return } 
  54. connection.videoOrientation = .portrait 
  55. connection.isVideoMirrored = position == .front 
  56. } 
  57. private func selectCaptureDevice() -> AVCaptureDevice? { 
  58. return AVCaptureDevice.devices().filter { 
  59. ($0 as AnyObject).hasMediaType(AVMediaTypeVideo) && 
  60. ($0 as AnyObject).position == position 
  61. }.first as? AVCaptureDevice 
  62. } 
  63. // MARK: Sample buffer to UIImage conversion 
  64. private func imageFromSampleBuffer(sampleBuffer: CMSampleBuffer) -> UIImage? { 
  65. guard let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return nil } 
  66. let ciImage = CIImage(cvPixelBuffer: imageBuffer) 
  67. guard let cgImage = context.createCGImage(ciImage, from: ciImage.extent) else { return nil } 
  68. return UIImage(cgImage: cgImage) 
  69. } 
  70. // MARK: AVCaptureVideoDataOutputSampleBufferDelegate 
  71. func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) { 
  72. guard let uiImage = imageFromSampleBuffer(sampleBuffer: sampleBuffer) else { return } 
  73. DispatchQueue.main.async { [unowned self] in 
  74. self.delegate?.captured(image: uiImage) 
  75. } 
  76. } 
  77. } 

iOS — Camera Frames Extraction – iOS App Development – Medium