You can use ML Kit to recognize well-known landmarks in an image.
Before you begin
- If you haven't already, add Firebase to your Android project .
- Add the dependencies for the ML Kit Android libraries to your module
(app-level) Gradle file (usually
app/build.gradle):apply plugin : ' com . android . application ' apply plugin : ' com . google . gms . google - services ' dependencies { // ... implementation ' com . google . firebase : firebase - ml - vision : 24.0.3 ' }
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If you have not already enabled Cloud-based APIs for your project, do so now:
- Open the ML Kit APIs page of the Firebase console.
-
If you have not already upgraded your project to a 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.
- If Cloud-based APIs aren't already enabled, click Enable Cloud-based APIs .
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:
Java
FirebaseVisionCloudDetectorOptions options = new FirebaseVisionCloudDetectorOptions . Builder () . setModelType ( FirebaseVisionCloudDetectorOptions . LATEST_MODEL ) . setMaxResults ( 15 ) . build ();
Kotlin
val options = FirebaseVisionCloudDetectorOptions . Builder () . setModelType ( FirebaseVisionCloudDetectorOptions . LATEST_MODEL ) . setMaxResults ( 15 ) . build ()
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 aFirebaseVisionImage
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. -
Create a
FirebaseVisionImageobject from your image.-
To create a
FirebaseVisionImageobject from amedia.Imageobject, such as when capturing an image from a device's camera, pass themedia.Imageobject and the image's rotation toFirebaseVisionImage.fromMediaImage().If you use the CameraX library, the
OnImageCapturedListenerandImageAnalysis.Analyzerclasses calculate the rotation value for you, so you just need to convert the rotation to one of ML Kit'sROTATION_constants before callingFirebaseVisionImage.fromMediaImage():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 Kit Vision API // ... } }
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 Kit 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:
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 ; }
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 }
Then, pass the
media.Imageobject and the rotation value toFirebaseVisionImage.fromMediaImage():Java
FirebaseVisionImage image = FirebaseVisionImage . fromMediaImage ( mediaImage , rotation );
Kotlin
val image = FirebaseVisionImage . fromMediaImage ( mediaImage , rotation )
- To create a
FirebaseVisionImageobject from a file URI, pass the app context and file URI toFirebaseVisionImage.fromFilePath(). This is useful when you use anACTION_GET_CONTENTintent to prompt the user to select an image from their gallery app.Java
FirebaseVisionImage image ; try { image = FirebaseVisionImage . fromFilePath ( context , uri ); } catch ( IOException e ) { e . printStackTrace (); }
Kotlin
val image : FirebaseVisionImage try { image = FirebaseVisionImage . fromFilePath ( context , uri ) } catch ( e : IOException ) { e . printStackTrace () }
- To create a
FirebaseVisionImageobject from aByteBufferor a byte array, first calculate the image rotation as described above formedia.Imageinput.Then, create a
FirebaseVisionImageMetadataobject that contains the image's height, width, color encoding format, and rotation: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 ();
Kotlin
val metadata = FirebaseVisionImageMetadata . Builder () . setWidth ( 480 ) // 480x360 is typically sufficient for . setHeight ( 360 ) // image recognition . setFormat ( FirebaseVisionImageMetadata . IMAGE_FORMAT_NV21 ) . setRotation ( rotation ) . build ()
Use the buffer or array, and the metadata object, to create a
FirebaseVisionImageobject:Java
FirebaseVisionImage image = FirebaseVisionImage . fromByteBuffer ( buffer , metadata ); // Or: FirebaseVisionImage image = FirebaseVisionImage.fromByteArray(byteArray, metadata);
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