Recognize Landmarks with Firebase ML on Android

This page describes an old version of recognizing well-known landmarks in images using the deprecated Firebase ML Vision SDK. As an alternative, you may call Cloud Vision APIs using Firebase Auth and Callable Functions to allow only users logged into your app to access the API.

You can use Firebase ML to recognize well-known landmarks in an image.

Use of the Cloud Vision APIs is subject to the Google Cloud Platform License Agreement and Service Specific Terms, and billed accordingly. For billing information, see the Pricing page.

Before you begin

1. If you haven't already, add Firebase to your Android project.
2. In your module (app-level) Gradle file (usually <project>/<app-module>/build.gradle.kts or <project>/<app-module>/build.gradle), add the dependency for the Firebase ML Vision library for Android. We recommend using the Firebase Android BoM to control library versioning.

   dependencies {
       // Import the BoM for the Firebase platform
       implementation(platform("com.google.firebase:firebase-bom:33.7.0"))
   
       // Add the dependency for the Firebase ML Vision library
       // When using the BoM, you don't specify versions in Firebase library dependencies
       implementation 'com.google.firebase:firebase-ml-vision'
   }

   By using the Firebase Android BoM, your app will always use compatible versions of Firebase Android libraries.

   (Alternative)  Add Firebase library dependencies without using the BoM

   If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line.

   Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.

   dependencies {
       // Add the dependency for the Firebase ML Vision library
       // When NOT using the BoM, you must specify versions in Firebase library dependencies
       implementation 'com.google.firebase:firebase-ml-vision:24.1.0'
   }

   Looking for a Kotlin-specific library module? Starting in October 2023 (Firebase BoM 32.5.0), both Kotlin and Java developers can depend on the main library module (for details, see the FAQ about this initiative).

3. If you have not already enabled Cloud-based APIs for your project, do so now:

   1. Open the Firebase ML APIs page of the Firebase console.

   2. If you have not already upgraded your project to the Blaze pricing plan, click Upgrade to do so. (You will be prompted to upgrade only if your project isn't on the Blaze plan.)

      Only Blaze-level projects can use Cloud-based APIs.

   3. If Cloud-based APIs aren't already enabled, click Enable Cloud-based APIs.
   Before you deploy to production an app that uses a Cloud API, you should take some additional steps to prevent and mitigate the effect of unauthorized API access.

Configure the landmark detector

By default, the Cloud detector uses the STABLE version of the model and returns up to 10 results. If you want to change either of these settings, specify them with a FirebaseVisionCloudDetectorOptions object.

For example, to change both of the default settings, build a FirebaseVisionCloudDetectorOptions object as in the following example:

Kotlin

val options = FirebaseVisionCloudDetectorOptions.Builder()
    .setModelType(FirebaseVisionCloudDetectorOptions.LATEST_MODEL)
    .setMaxResults(15)
    .build()
MainActivity.kt

Java

FirebaseVisionCloudDetectorOptions options =
        new FirebaseVisionCloudDetectorOptions.Builder()
                .setModelType(FirebaseVisionCloudDetectorOptions.LATEST_MODEL)
                .setMaxResults(15)
                .build();
MainActivity.java

To use the default settings, you can use FirebaseVisionCloudDetectorOptions.DEFAULT in the next step.

Run the landmark detector

To recognize landmarks in an image, create a FirebaseVisionImage object from either a Bitmap, media.Image, ByteBuffer, byte array, or a file on the device. Then, pass the FirebaseVisionImage object to the FirebaseVisionCloudLandmarkDetector's detectInImage method.

1. Create a FirebaseVisionImage object from your image.

   • To create a FirebaseVisionImage object from a media.Image object, such as when capturing an image from a device's camera, pass the media.Image object and the image's rotation to FirebaseVisionImage.fromMediaImage().

     If you use the CameraX library, the OnImageCapturedListener and ImageAnalysis.Analyzer classes calculate the rotation value for you, so you just need to convert the rotation to one of Firebase ML's ROTATION_ constants before calling FirebaseVisionImage.fromMediaImage():

     Kotlin

     private class YourImageAnalyzer : ImageAnalysis.Analyzer {
         private fun degreesToFirebaseRotation(degrees: Int): Int = when(degrees) {
             0 -> FirebaseVisionImageMetadata.ROTATION_0
             90 -> FirebaseVisionImageMetadata.ROTATION_90
             180 -> FirebaseVisionImageMetadata.ROTATION_180
             270 -> FirebaseVisionImageMetadata.ROTATION_270
             else -> throw Exception("Rotation must be 0, 90, 180, or 270.")
         }
     
         override fun analyze(imageProxy: ImageProxy?, degrees: Int) {
             val mediaImage = imageProxy?.image
             val imageRotation = degreesToFirebaseRotation(degrees)
             if (mediaImage != null) {
                 val image = FirebaseVisionImage.fromMediaImage(mediaImage, imageRotation)
                 // Pass image to an ML Vision API
                 // ...
             }
         }
     }

     Java

     private class YourAnalyzer implements ImageAnalysis.Analyzer {
     
         private int degreesToFirebaseRotation(int degrees) {
             switch (degrees) {
                 case 0:
                     return FirebaseVisionImageMetadata.ROTATION_0;
                 case 90:
                     return FirebaseVisionImageMetadata.ROTATION_90;
                 case 180:
                     return FirebaseVisionImageMetadata.ROTATION_180;
                 case 270:
                     return FirebaseVisionImageMetadata.ROTATION_270;
                 default:
                     throw new IllegalArgumentException(
                             "Rotation must be 0, 90, 180, or 270.");
             }
         }
     
         @Override
         public void analyze(ImageProxy imageProxy, int degrees) {
             if (imageProxy == null || imageProxy.getImage() == null) {
                 return;
             }
             Image mediaImage = imageProxy.getImage();
             int rotation = degreesToFirebaseRotation(degrees);
             FirebaseVisionImage image =
                     FirebaseVisionImage.fromMediaImage(mediaImage, rotation);
             // Pass image to an ML Vision API
             // ...
         }
     }

     If you don't use a camera library that gives you the image's rotation, you can calculate it from the device's rotation and the orientation of camera sensor in the device:

     Kotlin

     private val ORIENTATIONS = SparseIntArray()
     
     init {
         ORIENTATIONS.append(Surface.ROTATION_0, 90)
         ORIENTATIONS.append(Surface.ROTATION_90, 0)
         ORIENTATIONS.append(Surface.ROTATION_180, 270)
         ORIENTATIONS.append(Surface.ROTATION_270, 180)
     }
     /**
      * Get the angle by which an image must be rotated given the device's current
      * orientation.
      */
     @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
     @Throws(CameraAccessException::class)
     private fun getRotationCompensation(cameraId: String, activity: Activity, context: Context): Int {
         // Get the device's current rotation relative to its "native" orientation.
         // Then, from the ORIENTATIONS table, look up the angle the image must be
         // rotated to compensate for the device's rotation.
         val deviceRotation = activity.windowManager.defaultDisplay.rotation
         var rotationCompensation = ORIENTATIONS.get(deviceRotation)
     
         // On most devices, the sensor orientation is 90 degrees, but for some
         // devices it is 270 degrees. For devices with a sensor orientation of
         // 270, rotate the image an additional 180 ((270 + 270) % 360) degrees.
         val cameraManager = context.getSystemService(CAMERA_SERVICE) as CameraManager
         val sensorOrientation = cameraManager
             .getCameraCharacteristics(cameraId)
             .get(CameraCharacteristics.SENSOR_ORIENTATION)!!
         rotationCompensation = (rotationCompensation + sensorOrientation + 270) % 360
     
         // Return the corresponding FirebaseVisionImageMetadata rotation value.
         val result: Int
         when (rotationCompensation) {
             0 -> result = FirebaseVisionImageMetadata.ROTATION_0
             90 -> result = FirebaseVisionImageMetadata.ROTATION_90
             180 -> result = FirebaseVisionImageMetadata.ROTATION_180
             270 -> result = FirebaseVisionImageMetadata.ROTATION_270
             else -> {
                 result = FirebaseVisionImageMetadata.ROTATION_0
                 Log.e(TAG, "Bad rotation value: $rotationCompensation")
             }
         }
         return result
     }
     VisionImage.kt

     Java

     private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
     static {
         ORIENTATIONS.append(Surface.ROTATION_0, 90);
         ORIENTATIONS.append(Surface.ROTATION_90, 0);
         ORIENTATIONS.append(Surface.ROTATION_180, 270);
         ORIENTATIONS.append(Surface.ROTATION_270, 180);
     }
     
     /**
      * Get the angle by which an image must be rotated given the device's current
      * orientation.
      */
     @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
     private int getRotationCompensation(String cameraId, Activity activity, Context context)
             throws CameraAccessException {
         // Get the device's current rotation relative to its "native" orientation.
         // Then, from the ORIENTATIONS table, look up the angle the image must be
         // rotated to compensate for the device's rotation.
         int deviceRotation = activity.getWindowManager().getDefaultDisplay().getRotation();
         int rotationCompensation = ORIENTATIONS.get(deviceRotation);
     
         // On most devices, the sensor orientation is 90 degrees, but for some
         // devices it is 270 degrees. For devices with a sensor orientation of
         // 270, rotate the image an additional 180 ((270 + 270) % 360) degrees.
         CameraManager cameraManager = (CameraManager) context.getSystemService(CAMERA_SERVICE);
         int sensorOrientation = cameraManager
                 .getCameraCharacteristics(cameraId)
                 .get(CameraCharacteristics.SENSOR_ORIENTATION);
         rotationCompensation = (rotationCompensation + sensorOrientation + 270) % 360;
     
         // Return the corresponding FirebaseVisionImageMetadata rotation value.
         int result;
         switch (rotationCompensation) {
             case 0:
                 result = FirebaseVisionImageMetadata.ROTATION_0;
                 break;
             case 90:
                 result = FirebaseVisionImageMetadata.ROTATION_90;
                 break;
             case 180:
                 result = FirebaseVisionImageMetadata.ROTATION_180;
                 break;
             case 270:
                 result = FirebaseVisionImageMetadata.ROTATION_270;
                 break;
             default:
                 result = FirebaseVisionImageMetadata.ROTATION_0;
                 Log.e(TAG, "Bad rotation value: " + rotationCompensation);
         }
         return result;
     }
     VisionImage.java

     Then, pass the media.Image object and the rotation value to FirebaseVisionImage.fromMediaImage():

     Kotlin

     val image = FirebaseVisionImage.fromMediaImage(mediaImage, rotation)
     VisionImage.kt

     Java

     FirebaseVisionImage image = FirebaseVisionImage.fromMediaImage(mediaImage, rotation);
     VisionImage.java

   • To create a FirebaseVisionImage object from a file URI, pass the app context and file URI to FirebaseVisionImage.fromFilePath(). This is useful when you use an ACTION_GET_CONTENT intent to prompt the user to select an image from their gallery app.

     Kotlin

     val image: FirebaseVisionImage
     try {
         image = FirebaseVisionImage.fromFilePath(context, uri)
     } catch (e: IOException) {
         e.printStackTrace()
     }
     VisionImage.kt

     Java

     FirebaseVisionImage image;
     try {
         image = FirebaseVisionImage.fromFilePath(context, uri);
     } catch (IOException e) {
         e.printStackTrace();
     }
     VisionImage.java

   • To create a FirebaseVisionImage object from a ByteBuffer or a byte array, first calculate the image rotation as described above for media.Image input.

     Then, create a FirebaseVisionImageMetadata object that contains the image's height, width, color encoding format, and rotation:

     Kotlin

     val metadata = FirebaseVisionImageMetadata.Builder()
         .setWidth(480) // 480x360 is typically sufficient for
         .setHeight(360) // image recognition
         .setFormat(FirebaseVisionImageMetadata.IMAGE_FORMAT_NV21)
         .setRotation(rotation)
         .build()
     VisionImage.kt

     Java

     FirebaseVisionImageMetadata metadata = new FirebaseVisionImageMetadata.Builder()
             .setWidth(480)   // 480x360 is typically sufficient for
             .setHeight(360)  // image recognition
             .setFormat(FirebaseVisionImageMetadata.IMAGE_FORMAT_NV21)
             .setRotation(rotation)
             .build();
     VisionImage.java

     Use the buffer or array, and the metadata object, to create a FirebaseVisionImage object:

     Kotlin

     val image = FirebaseVisionImage.fromByteBuffer(buffer, metadata)
     // Or: val image = FirebaseVisionImage.fromByteArray(byteArray, metadata)
     VisionImage.kt

     Java

     FirebaseVisionImage image = FirebaseVisionImage.fromByteBuffer(buffer, metadata);
     // Or: FirebaseVisionImage image = FirebaseVisionImage.fromByteArray(byteArray, metadata);
     VisionImage.java

   • To create a FirebaseVisionImage object from a Bitmap object:

     Kotlin

     val image = FirebaseVisionImage.fromBitmap(bitmap)
     VisionImage.kt

     Java

     FirebaseVisionImage image = FirebaseVisionImage.fromBitmap(bitmap);
     VisionImage.java

     The image represented by the Bitmap object must be upright, with no additional rotation required.

2. Get an instance of FirebaseVisionCloudLandmarkDetector:

   Kotlin

   val detector = FirebaseVision.getInstance()
       .visionCloudLandmarkDetector
   // Or, to change the default settings:
   // val detector = FirebaseVision.getInstance()
   //         .getVisionCloudLandmarkDetector(options)
   LandmarkRecognitionActivity.kt

   Java

   FirebaseVisionCloudLandmarkDetector detector = FirebaseVision.getInstance()
           .getVisionCloudLandmarkDetector();
   // Or, to change the default settings:
   // FirebaseVisionCloudLandmarkDetector detector = FirebaseVision.getInstance()
   //         .getVisionCloudLandmarkDetector(options);
   LandmarkRecognitionActivity.java

3. Finally, pass the image to the detectInImage method:

   Kotlin

   val result = detector.detectInImage(image)
       .addOnSuccessListener { firebaseVisionCloudLandmarks ->
           // Task completed successfully
           // ...
       }
       .addOnFailureListener { e ->
           // Task failed with an exception
           // ...
       }
   LandmarkRecognitionActivity.kt

   Java

   Task<List<FirebaseVisionCloudLandmark>> result = detector.detectInImage(image)
           .addOnSuccessListener(new OnSuccessListener<List<FirebaseVisionCloudLandmark>>() {
               @Override
               public void onSuccess(List<FirebaseVisionCloudLandmark> firebaseVisionCloudLandmarks) {
                   // Task completed successfully
                   // ...
               }
           })
           .addOnFailureListener(new OnFailureListener() {
               @Override
               public void onFailure(@NonNull Exception e) {
                   // Task failed with an exception
                   // ...
               }
           });
   LandmarkRecognitionActivity.java

Get information about the recognized landmarks

If the landmark recognition operation succeeds, a list of FirebaseVisionCloudLandmark objects will be passed to the success listener. Each FirebaseVisionCloudLandmark object represents a landmark that was recognized in the image. For each landmark, you can get its bounding coordinates in the input image, the landmark's name, its latitude and longitude, its Knowledge Graph entity ID (if available), and the confidence score of the match. For example:

Kotlin

for (landmark in firebaseVisionCloudLandmarks) {
    val bounds = landmark.boundingBox
    val landmarkName = landmark.landmark
    val entityId = landmark.entityId
    val confidence = landmark.confidence

    // Multiple locations are possible, e.g., the location of the depicted
    // landmark and the location the picture was taken.
    for (loc in landmark.locations) {
        val latitude = loc.latitude
        val longitude = loc.longitude
    }
}
LandmarkRecognitionActivity.kt

Java

for (FirebaseVisionCloudLandmark landmark: firebaseVisionCloudLandmarks) {

    Rect bounds = landmark.getBoundingBox();
    String landmarkName = landmark.getLandmark();
    String entityId = landmark.getEntityId();
    float confidence = landmark.getConfidence();

    // Multiple locations are possible, e.g., the location of the depicted
    // landmark and the location the picture was taken.
    for (FirebaseVisionLatLng loc: landmark.getLocations()) {
        double latitude = loc.getLatitude();
        double longitude = loc.getLongitude();
    }
}
LandmarkRecognitionActivity.java

Next steps

• Before you deploy to production an app that uses a Cloud API, you should take some additional steps to prevent and mitigate the effect of unauthorized API access.