您可以使用机器学习套件识别图片中的知名地标。
准备工作
- 将 Firebase 添加到您的 Android 项目（如果尚未添加）。
- 将 Android 版机器学习套件库的依赖项添加到您的模块（应用级层）Gradle 文件（通常为
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' } -
如果您尚未为项目启用云端 API，请立即完成以下操作：
- 打开 Firebase 控制台的机器学习套件 API 页面。
-
如果您尚未将项目升级到 Blaze 定价方案，请点击升级以执行此操作。（只有在您的项目未采用 Blaze 方案时，系统才会提示您进行升级。）
只有 Blaze 级项目才能使用基于 Cloud 的 API。
- 如果尚未启用基于 Cloud 的 API，请点击启用基于 Cloud 的 API。
配置地标检测器
默认情况下，Cloud 检测器使用 STABLE 版本的模型，最多会返回 10 个结果。如需更改这两项设置中的任何一项，请使用 FirebaseVisionCloudDetectorOptions 对象进行指定。
例如，如需更改这两项默认设置，请按照以下示例构建 FirebaseVisionCloudDetectorOptions 对象：
Java
FirebaseVisionCloudDetectorOptions options =
new FirebaseVisionCloudDetectorOptions.Builder()
.setModelType(FirebaseVisionCloudDetectorOptions.LATEST_MODEL)
.setMaxResults(15)
.build();
Kotlin+KTX
val options = FirebaseVisionCloudDetectorOptions.Builder()
.setModelType(FirebaseVisionCloudDetectorOptions.LATEST_MODEL)
.setMaxResults(15)
.build()
如需使用默认设置，可以在下一步中使用 FirebaseVisionCloudDetectorOptions.DEFAULT。
运行地标检测器
如需识别图片中的地标，请基于设备上的以下资源创建FirebaseVisionImage 对象：Bitmap、media.Image、ByteBuffer、字节数组或文件。然后，将 FirebaseVisionImage 对象传递给 FirebaseVisionCloudLandmarkDetector 的 detectInImage 方法。
基于图片创建
FirebaseVisionImage对象。-
如需基于
media.Image对象创建FirebaseVisionImage对象（例如从设备的相机捕获图片时），请将media.Image对象和图片的旋转角度传递给FirebaseVisionImage.fromMediaImage()。如果您使用 CameraX 库，
OnImageCapturedListener和ImageAnalysis.Analyzer类会为您计算旋转角度值，因此您只需在调用FirebaseVisionImage.fromMediaImage()之前将旋转角度转换为机器学习套件的ROTATION_常量之一：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+KTX
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 // ... } } }如果您没有使用可提供图片旋转角度的相机库，可以根据设备的旋转角度和设备中相机传感器的朝向来计算旋转角度：
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+KTX
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 }然后，将
media.Image对象及旋转角度值传递给FirebaseVisionImage.fromMediaImage()：Java
FirebaseVisionImage image = FirebaseVisionImage.fromMediaImage(mediaImage, rotation);
Kotlin+KTX
val image = FirebaseVisionImage.fromMediaImage(mediaImage, rotation)
- 如需基于文件 URI 创建
FirebaseVisionImage对象，请将应用上下文和文件 URI 传递给FirebaseVisionImage.fromFilePath()。如果您使用ACTION_GET_CONTENTIntent 提示用户从图库应用中选择图片，这一操作会非常有用。Java
FirebaseVisionImage image; try { image = FirebaseVisionImage.fromFilePath(context, uri); } catch (IOException e) { e.printStackTrace(); }Kotlin+KTX
val image: FirebaseVisionImage try { image = FirebaseVisionImage.fromFilePath(context, uri) } catch (e: IOException) { e.printStackTrace() } - 如需基于
ByteBuffer或字节数组创建FirebaseVisionImage对象，请先按上述media.Image输入的说明计算图片旋转角度。然后，创建一个包含图片的高度、宽度、颜色编码格式和旋转角度的
FirebaseVisionImageMetadata对象：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+KTX
val metadata = FirebaseVisionImageMetadata.Builder() .setWidth(480) // 480x360 is typically sufficient for .setHeight(360) // image recognition .setFormat(FirebaseVisionImageMetadata.IMAGE_FORMAT_NV21) .setRotation(rotation) .build()使用缓冲区或数组以及元数据对象来创建
FirebaseVisionImage对象：Java
FirebaseVisionImage image = FirebaseVisionImage.fromByteBuffer(buffer, metadata); // Or: FirebaseVisionImage image = FirebaseVisionImage.fromByteArray(byteArray, metadata);
Kotlin+KTX
val image = FirebaseVisionImage.fromByteBuffer(buffer, metadata) // Or: val image = FirebaseVisionImage.fromByteArray(byteArray, metadata)
- 如需基于
Bitmap对象创建FirebaseVisionImage对象，请运行以下代码：以Java
FirebaseVisionImage image = FirebaseVisionImage.fromBitmap(bitmap);
Kotlin+KTX
val image = FirebaseVisionImage.fromBitmap(bitmap)
Bitmap对象表示的图片必须保持竖直，不需要额外的旋转。
-
获取
FirebaseVisionCloudLandmarkDetector的一个实例：Java
FirebaseVisionCloudLandmarkDetector detector = FirebaseVision.getInstance() .getVisionCloudLandmarkDetector(); // Or, to change the default settings: // FirebaseVisionCloudLandmarkDetector detector = FirebaseVision.getInstance() // .getVisionCloudLandmarkDetector(options);Kotlin+KTX
val detector = FirebaseVision.getInstance() .visionCloudLandmarkDetector // Or, to change the default settings: // val detector = FirebaseVision.getInstance() // .getVisionCloudLandmarkDetector(options)最后，将图片传递给
detectInImage方法：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 // ... } });Kotlin+KTX
val result = detector.detectInImage(image) .addOnSuccessListener { firebaseVisionCloudLandmarks -> // Task completed successfully // ... } .addOnFailureListener { e -> // Task failed with an exception // ... }
获取识别出的地标的相关信息
如果地标识别操作成功，系统会向成功监听器传递一组FirebaseVisionCloudLandmark 对象。每个 FirebaseVisionCloudLandmark 对象代表一个在图片中识别出的地标。对于每个地标，您可以获取它在输入图片中的边界坐标、地标名称、地标的经纬度、地标的知识图谱实体 ID（如果有）以及匹配的置信度分数。例如：
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();
}
}Kotlin+KTX
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
}
}后续步骤
- 在向生产环境中部署使用 Cloud API 的应用之前，您应该执行一些额外的步骤来防止未经授权的 API 访问并减轻这些访问造成的影响。