MediaPipe Android Archive

目录

• 1. 建立一个MediaPipe AAR的步骤
  • 1.1. 安装MediaPipe框架
  • 1.2. 编译MediaPipe得AAR包
• 2. Android Studio使用MediaPipe AAR步骤

1. 建立一个MediaPipe AAR的步骤

MediaPipe是用于构建跨平台多模态应用ML管道的框架，其包括快速ML推理，经典计算机视觉和媒体内容处理（如视频解码）。下面是用于对象检测与追踪的MediaPipe示例图，它由4个计算节点组成：PacketResampler计算单元；先前发布的ObjectDetection子图；围绕上述BoxTrakcing子图的ObjectTracking子图；以及绘制可视化效果的Renderer子图。

ObjectDetection子图仅在请求时运行，例如以任意帧速率或由特定信号触发。更具体地讲，在将视频帧传递到ObjectDetection之前，本示例中的PacketResampler将它们暂时采样为0.5 fps。你可以在PacketResampler中将这一选项配置为不同的帧速率。正是因为如此，在识别的时候可以抖动更少，而且可以跨帧维护对象ID。

1.1. 安装MediaPipe框架

参考Ubuntu下MediaPipe的环境配置（https://www.cnblogs.com/zhongzhaoxie/p/13359340.html）

1.2. 编译MediaPipe得AAR包

创建Mediapipe生成Android aar的编译文件，命令如下。

cd mediapipe/examples/android/src/java/com/google/mediapipe/apps/
mkdir buid_aar && cd buid_aar
vim BUILD

编译文件BUILD中内容如下，name是生成后aar的名字，calculators为使用的模型和计算单元，其他的模型和支持计算单元可以查看 mediapipe/graphs/目录下的内容，在这个目录都是Mediapipe支持的模型。其中目录hand_tracking就是使用到的模型，支持的计算单元需要查看该目录下的BUILD文件中的cc_library，这里我们是要部署到Android端的，所以选择Mobile的计算单元。本教程我们使用mobile_calculators，这个只检测一个手的关键点，如何想要检查多个收修改成这个计算单元multi_hand_mobile_calculators。

load("//mediapipe/java/com/google/mediapipe:mediapipe_aar.bzl", "mediapipe_aar")

mediapipe_aar(
    name = "mediapipe_hand_tracking",
    calculators = ["//mediapipe/graphs/hand_tracking:mobile_calculators"],
)

回到mediapipe根目录，执行以下命令生成Android的aar文件。执行成功，会生成该文件 bazel-bin/mediapipe/examples/android/src/java/com/google/mediapipe/apps/buid_aar/mediapipe_hand_tracking.aar

chmod -R 755 mediapipe/

bazel build -c opt --host_crosstool_top=@bazel_tools//tools/cpp:toolchain --fat_apk_cpu=arm64-v8a,armeabi-v7a 
//mediapipe/examples/android/src/java/com/google/mediapipe/apps/buid_aar:mediapipe_hand_tracking

执行以下命令生成Mediapipe的二进制图，命令参数同样是上面的BUILD中，其中路径不变，变的是路径后面的参数。这次我们需要寻找的是 mediapipe_binary_graph中的name，根据我们所要使用的模型，同样这个也是只检测单个手的关键点，多个手的使用multi_hand_tracking_mobile_gpu_binary_graph。选择对应的name。成功之后会生成 bazel-bin/mediapipe/graphs/hand_tracking/hand_tracking_mobile_gpu.binarypb。

bazel build -c opt mediapipe/graphs/hand_tracking:hand_tracking_mobile_gpu_binary_graph

2. Android Studio使用MediaPipe AAR步骤

(1) 在Android Studio中创建一个TestMediaPipe的空白项目。
(2) 复制上一步编译生成的aar文件到app/libs/目录下，该文件在mediapipe根目录下的以下路径：

bazel-bin/mediapipe/examples/android/src/java/com/google/mediapipe/apps/buid_aar/mediapipe_hand_tracking.aar

(3) 复制以下文件到app/src/main/assets/目录下。

bazel-bin/mediapipe/graphs/hand_tracking/hand_tracking_mobile_gpu.binarypb
mediapipe/models:handedness.txt
mediapipe/models/hand_landmark.tflite
mediapipe/models/palm_detection.tflite
mediapipe/models/palm_detection_labelmap.txt

(4)下载OpenCV SDK，下载地址如下，解压之后，把OpenCV-android-sdk/sdk/native/libs/目录下的arm64-v8a和armeabi-v7a复制到Android项目的app/src/main/jniLibs/目录下。(https://github.com/opencv/opencv/releases/download/3.4.3/opencv-3.4.3-android-sdk.zip)

(5) 在app/build.gradle添加以下依赖库，除了添加新的依赖库，还有在第一行添加'*.aar'，这样才能通过编译。还需要指定项目使用的Java版本为1.8。

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar", '*.aar'])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.13'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    // MediaPipe deps
    implementation 'com.google.flogger:flogger:0.3.1'
    implementation 'com.google.flogger:flogger-system-backend:0.3.1'
    implementation 'com.google.code.findbugs:jsr305:3.0.2'
    implementation 'com.google.guava:guava:27.0.1-android'
    implementation 'com.google.guava:guava:27.0.1-android'
    implementation 'com.google.protobuf:protobuf-java:3.11.4'
    // CameraX core library
    implementation "androidx.camera:camera-core:1.0.0-alpha06"
    implementation "androidx.camera:camera-camera2:1.0.0-alpha06"
}
	// android 中添加
    compileOptions {
        targetCompatibility = 1.8
        sourceCompatibility = 1.8
    }

(6) 在配置文件AndroidManifest.xml中添加相机权限。

<!-- For using the camera -->
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<!-- For MediaPipe -->
<uses-feature android:glEsVersion="0x00020000" android:required="true" />

(7) 修改页面代码和逻辑代码，MainActivity.java和activity_main.xml代码如下。以下为activity_main.xml代码，结构很简单，就一个FrameLayout包裹TextView，通常如何相机不正常才会显示TextView，一般情况下都会在FrameLayout显示相机拍摄的视频。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/preview_display_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/no_camera_access_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text="相机连接失败" />
    </FrameLayout>
</LinearLayout>

MainActivity.java代码，模型流的输出名请查看mediapipe/examples/android/src/java/com/google/mediapipe/apps/对应的Java代码。例如多个手的输出流名为multi_hand_landmarks。

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";

    // 资源文件和流输出名
    private static final String BINARY_GRAPH_NAME = "hand_tracking_mobile_gpu.binarypb";
    private static final String INPUT_VIDEO_STREAM_NAME = "input_video";
    private static final String OUTPUT_VIDEO_STREAM_NAME = "output_video";
    private static final String OUTPUT_HAND_PRESENCE_STREAM_NAME = "hand_presence";
    private static final String OUTPUT_LANDMARKS_STREAM_NAME = "hand_landmarks";

    private SurfaceTexture previewFrameTexture;
    private SurfaceView previewDisplayView;
    private EglManager eglManager;
    private FrameProcessor processor;
    private ExternalTextureConverter converter;
    private CameraXPreviewHelper cameraHelper;
    private boolean handPresence;
    // 所使用的摄像头
    private static final boolean USE_FRONT_CAMERA = false;

    // 因为OpenGL表示图像时假设图像原点在左下角，而MediaPipe通常假设图像原点在左上角，所以要翻转
    private static final boolean FLIP_FRAMES_VERTICALLY = true;

    // 加载动态库
    static {
        System.loadLibrary("mediapipe_jni");
        System.loadLibrary("opencv_java3");
    }

    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        previewDisplayView = new SurfaceView(this);
        setupPreviewDisplayView();
        // 获取权限
        PermissionHelper.checkAndRequestCameraPermissions(this);

        // 初始化assets管理器，以便MediaPipe应用资源
        AndroidAssetUtil.initializeNativeAssetManager(this);

        eglManager = new EglManager(null);
        // 通过加载获取一个帧处理器
        processor = new FrameProcessor(this,
                eglManager.getNativeContext(),
                BINARY_GRAPH_NAME,
                INPUT_VIDEO_STREAM_NAME,
                OUTPUT_VIDEO_STREAM_NAME);
        processor.getVideoSurfaceOutput().setFlipY(FLIP_FRAMES_VERTICALLY);

        // 获取是否检测到手模型输出
        processor.addPacketCallback(
                OUTPUT_HAND_PRESENCE_STREAM_NAME,
                (packet) -> {
                    handPresence = PacketGetter.getBool(packet);
                    if (!handPresence) {
                        Log.d(TAG, "[TS:" + packet.getTimestamp() + "] Hand presence is false, no hands detected.");
                    }
                });

        // 获取手的关键点模型输出
        processor.addPacketCallback(
                OUTPUT_LANDMARKS_STREAM_NAME,
                (packet) -> {
                    byte[] landmarksRaw = PacketGetter.getProtoBytes(packet);
                    try {
                        NormalizedLandmarkList landmarks = NormalizedLandmarkList.parseFrom(landmarksRaw);
                        if (landmarks == null || !handPresence) {
                            Log.d(TAG, "[TS:" + packet.getTimestamp() + "] No hand landmarks.");
                            return;
                        }
                        // 如果没有检测到手，输出的关键点是无效的
                        Log.d(TAG,
                                "[TS:" + packet.getTimestamp()
                                        + "] #Landmarks for hand: "
                                        + landmarks.getLandmarkCount());
                        Log.d(TAG, getLandmarksDebugString(landmarks));
                    } catch (InvalidProtocolBufferException e) {
                        Log.e(TAG, "Couldn't Exception received - " + e);
                    }
                });
    }

    @Override
    protected void onResume() {
        super.onResume();
        converter = new ExternalTextureConverter(eglManager.getContext());
        converter.setFlipY(FLIP_FRAMES_VERTICALLY);
        converter.setConsumer(processor);
        if (PermissionHelper.cameraPermissionsGranted(this)) {
            startCamera();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        converter.close();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        PermissionHelper.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    // 计算最佳的预览大小
    protected Size computeViewSize(int width, int height) {
        return new Size(width, height);
    }

    protected void onPreviewDisplaySurfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // 设置预览大小
        Size viewSize = computeViewSize(width, height);
        Size displaySize = cameraHelper.computeDisplaySizeFromViewSize(viewSize);
        // 根据是否旋转调整预览图像大小
        boolean isCameraRotated = cameraHelper.isCameraRotated();
        converter.setSurfaceTextureAndAttachToGLContext(
                previewFrameTexture,
                isCameraRotated ? displaySize.getHeight() : displaySize.getWidth(),
                isCameraRotated ? displaySize.getWidth() : displaySize.getHeight());
    }


    private void setupPreviewDisplayView() {
        previewDisplayView.setVisibility(View.GONE);
        ViewGroup viewGroup = findViewById(R.id.preview_display_layout);
        viewGroup.addView(previewDisplayView);

        previewDisplayView
                .getHolder()
                .addCallback(
                        new SurfaceHolder.Callback() {
                            @Override
                            public void surfaceCreated(SurfaceHolder holder) {
                                processor.getVideoSurfaceOutput().setSurface(holder.getSurface());
                            }

                            @Override
                            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
                                onPreviewDisplaySurfaceChanged(holder, format, width, height);
                            }

                            @Override
                            public void surfaceDestroyed(SurfaceHolder holder) {
                                processor.getVideoSurfaceOutput().setSurface(null);
                            }
                        });
    }

    // 相机启动后事件
    protected void onCameraStarted(SurfaceTexture surfaceTexture) {
        // 显示预览
        previewFrameTexture = surfaceTexture;
        previewDisplayView.setVisibility(View.VISIBLE);
    }

    // 设置相机大小
    protected Size cameraTargetResolution() {
        return null;
    }

    // 启动相机
    public void startCamera() {
        cameraHelper = new CameraXPreviewHelper();
        cameraHelper.setOnCameraStartedListener(this::onCameraStarted);
        CameraHelper.CameraFacing cameraFacing =
                USE_FRONT_CAMERA ? CameraHelper.CameraFacing.FRONT : CameraHelper.CameraFacing.BACK;
        cameraHelper.startCamera(this, cameraFacing, null, cameraTargetResolution());
    }

    // 解析关键点
    private static String getLandmarksDebugString(NormalizedLandmarkList landmarks) {
        int landmarkIndex = 0;
        StringBuilder landmarksString = new StringBuilder();
        for (NormalizedLandmark landmark : landmarks.getLandmarkList()) {
            landmarksString.append("		Landmark[").append(landmarkIndex).append("]: (").append(landmark.getX()).append(", ").append(landmark.getY()).append(", ").append(landmark.getZ()).append(")
");
            ++landmarkIndex;
        }
        return landmarksString.toString();
    }
}

效果如下：

参考文献

1. https://google.github.io/mediapipe/getting_started/android_archive_library.html
2. https://cloud.tencent.com/developer/article/1657637