Camera detection

Camera Preview

To start using camera detection the app must first acquire the permission to open the camera from the user. This permission is not handled by the SDK.

Add the UI element that is responsible for rendering the camera frames:

func setupPreviewLayer() {
    guard videoLayer == nil else { return }
    if let videoLayer = passioSDK.getPreviewLayer() {
        self.videoLayer = videoLayer
        videoLayer.frame = view.bounds
        view.layer.insertSublayer(videoLayer, at: 0)

Start food detection

The SDK can detect 3 different categories: VISUAL, BARCODE and PACKAGED. The VISUAL recognition is powered by Passio's neural network and is used to recognize over 4000 food classes. BARCODE, as the name suggests, can be used to scan a barcode located on a branded food. Finally, PACKAGED can detect the name of a branded food. To choose one or more types of detection, a FoodDetectionConfiguration object is defined and the corresponding fields are set. The VISUAL recognition works automatically.

The type of food detection is defined by the FoodDetectionConfiguration object. To start the Food Recognition process a FoodRecognitionListener also has to be defined. The listener serves as a callback for all the different food detection processes defined by the FoodDetectionConfiguration. When the app is done with food detection, it should clear out the listener to avoid any unwanted UI updates.

In viewWillAppear request authorization to use the camera and start the recognition:

override func viewWillAppear(_ animated: Bool) {
    if AVCaptureDevice.authorizationStatus(for: .video) == .authorized {
    } else {
        AVCaptureDevice.requestAccess(for: .video) { (granted) in
            if granted {
                DispatchQueue.main.async {
            } else {
                print("The user didn't grant access to use camera")

Add the method startFoodDetection()

func startFoodDetection() {
    passioSDK.startFoodDetection(foodRecognitionDelegate: self) { ready in
        if !ready {
            print("SDK was not configured correctly")

Stop Food Detection in viewWillDisappear:

override func viewWillDisappear(_ animated: Bool) {
    videoLayer = nil

Implement the delegate FoodRecognitionDelegate:

extension PassioQuickStartViewController: FoodRecognitionDelegate {

  func recognitionResults(candidates: FoodCandidates?,
                          image: UIImage?) {
      if let detectedCandidates = candidates?.detectedCandidates {
         // Handle result


The FoodCandidates object that is returned in the recognition callbacks contains three lists:

  • detectedCandidates detailing the result of VISUAL detection

  • barcodeCandidates detailing the result of BARCODE detection

  • packagedFoodCandidates detailing the result of PACKAGED detection

Only the corresponding candidate lists will be populated (e.g. if you define detection types VISUAL and BARCODE, you will never receive a packagedFoodCandidates list in this callback).

Visual detection

A DetectedCandidate represents the result from running Passio's neural network, specialized for detecting foods like apples, salads, burgers etc. The properties of a detected candidate are:

  • name

  • passioID (unique identifier used to query the nutritional databse)

  • confidence (measure of how accurate is the candidate, ranges from 0 to 1)

  • boundingBox (a rectangle detailing the bounds of the recognised item within the image dimensions)

  • alternatives (list of alternative foods that are visually or contextually similar to the recognised food)

  • croppedImage (the image that the recognition was ran on)

To fetch the full nutrition data of a detected candidate use:

public func fetchFoodItemFor(passioID: PassioNutritionAISDK.PassioID, completion: @escaping (PassioNutritionAISDK.PassioFoodItem?) -> Void)

Example of an image that produces a DetectedCandidate:

Barcode detection

The SDK can detect barcodes located on the packaging of packaged foods. The BarcodeCandidate has only two properties, the value of the barcode and it's bounding box.

To fetch the full nutritional details of a DetectedCandidate use this api passing the barcode value:

public func fetchFoodItemFor(productCode: String, completion: @escaping ((PassioNutritionAISDK.PassioFoodItem?) -> Void))

Example of an image that produces multiple BarcodeCandidates:

Product food detection

Passio uses OCR to recognise names of branded foods. The packaged food detection works for users tha point the camera of their devices to the front facing side of a packaged food. The result of that process is a PackagedFoodCandidate that only holds two values, the packaged food code and a measure of confidence.

Use the same api as in Barcode detectionto retrieve the full nutritional data passing the packaged food code as the parameter.

Example of an image that produces a PackagedFoodCandidate:

Last updated