Huawei_Technology
/
mindspore

## Demo of Image Segmentation

The following describes how to use the MindSpore Lite C++ APIs (Android JNIs) and MindSpore Lite image segmentation models to perform on-device inference, classify the content captured by a device camera, and display the most possible segmentation result on the application's image preview screen.

### Running Dependencies

- Android Studio 3.2 or later (Android 4.0 or later is recommended.)
- Native development kit (NDK) 21.3
- CMake 3.10.2 [CMake](https://cmake.org/download)
- Android software development kit (SDK) 26 or later
- JDK 1.8 or later

### Building and Running

1. Load the sample source code to Android Studio and install the corresponding SDK. (After the SDK version is specified, Android Studio automatically installs the SDK.)

    ![start_home](images/home.png)

    Start Android Studio, click `File > Settings > System Settings > Android SDK`, and select the corresponding SDK. As shown in the following figure, select an SDK and click `OK`. Android Studio automatically installs the SDK.

    ![start_sdk](images/sdk_management.png)

    If you have any Android Studio configuration problem when trying this demo, please refer to item 5 to resolve it.

2. Connect to an Android device and runs the image segmentation application.

    Connect to the Android device through a USB cable for debugging. Click `Run 'app'` to run the sample project on your device.

    ![run_app](images/run_app.PNG)

    For details about how to connect the Android Studio to a device for debugging, see <https://developer.android.com/studio/run/device?hl=zh-cn>.

    The mobile phone needs to be turn on "USB debugging mode" before Android Studio can recognize the mobile phone. Huawei mobile phones generally turn on "USB debugging model" in Settings > system and update > developer Options > USB debugging.

3. Continue the installation on the Android device. After the installation is complete, you can view the content captured by a camera and the inference result.

    ![result](images/app_result.jpg)

4. The solutions of Android Studio configuration problems:

    |      | Warning                                                         | Solution                                                     |
    | ---- | ------------------------------------------------------------ | ------------------------------------------------------------ |
    | 1    | Gradle sync failed: NDK not configured.                      | Specify the installed ndk directory in local.properties：ndk.dir={ndk的安装目录} |
    | 2    | Requested NDK version did not match the version requested by ndk.dir | Manually download corresponding [NDK Version](https://developer.android.com/ndk/downloads)，and specify the sdk directory in Project Structure - Android NDK location.（You can refer to the figure below.） |
    | 3    | This version of Android Studio cannot open this project, please retry with Android Studio or newer. | Update Android Studio Version in Tools - help - Checkout for Updates.                 |
    | 4    | SSL peer shut down incorrectly                               | Run this demo again.                                                     |

    ![project_structure](images/project_structure.png)

## Detailed Description of the Sample Program  

This image segmentation sample program on the Android device includes a Java layer and a JNI layer. At the Java layer, the Android Camera 2 API is used to enable a camera to obtain image frames and process images. At the JNI layer, the model inference process is completed in [Runtime](https://www.mindspore.cn/tutorial/lite/en/master/use/runtime.html).

### Sample Program Structure

```text
app
│
├── src/main
│   ├── assets # resource files
|   |   └── deeplabv3.ms # model file
│   |
│   ├── cpp # main logic encapsulation classes for model loading and prediction
|   |   |
|   |   ├── MindSporeNetnative.cpp # JNI methods related to MindSpore calling
│   |   └── MindSporeNetnative.h # header file
│   |
│   ├── java # application code at the Java layer
│   │   └── com.mindspore.himindsporedemo
│   │       ├── gallery.classify # implementation related to image processing and MindSpore JNI calling
│   │       │   └── ...
│   │       └── widget # implementation related to camera enabling and drawing
│   │           └── ...
│   │
│   ├── res # resource files related to Android
│   └── AndroidManifest.xml # Android configuration file
│
├── CMakeList.txt # CMake compilation entry file
│
├── build.gradle # Other Android configuration file
├── download.gradle # MindSpore version download
└── ...
```

### Configuring MindSpore Lite Dependencies

When MindSpore C++ APIs are called at the Android JNI layer, related library files are required. You can use MindSpore Lite [source code compilation](https://www.mindspore.cn/tutorial/lite/en/master/use/build.html) to generate the MindSpore Lite version. In this case, you need to use the compile command of generate with image preprocessing module.

In this example, the build process automatically downloads the `mindspore-lite-1.0.1-runtime-arm64-cpu` by the `app/download.gradle` file and saves in the `app/src/main/cpp` directory.

Note: if the automatic download fails, please manually download the relevant library files and put them in the corresponding location.

mindspore-lite-1.0.1-runtime-arm64-cpu.tar.gz [Download link](https://ms-release.obs.cn-north-4.myhuaweicloud.com/1.0.1/lite/android_aarch64/mindspore-lite-1.0.1-runtime-arm64-cpu.tar.gz)

```text
android{
    defaultConfig{
        externalNativeBuild{
            cmake{
                arguments "-DANDROID_STL=c++_shared"
            }
        }

        ndk{
            abiFilters'armeabi-v7a', 'arm64-v8a'  
        }
    }
}
```

Create a link to the `.so` library file in the `app/CMakeLists.txt` file:

```text
# ============== Set MindSpore Dependencies. =============
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp)
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/third_party/flatbuffers/include)
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION})
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/include)
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/include/ir/dtype)
include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/include/schema)

add_library(mindspore-lite SHARED IMPORTED )
add_library(minddata-lite SHARED IMPORTED )

set_target_properties(mindspore-lite PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/lib/libmindspore-lite.so)
set_target_properties(minddata-lite PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/cpp/${MINDSPORELITE_VERSION}/lib/libminddata-lite.so)
# --------------- MindSpore Lite set End. --------------------

# Link target library.
target_link_libraries(
    ...
     # --- mindspore ---
        minddata-lite
        mindspore-lite
    ...
)
```

### Downloading and Deploying a Model File

In this example, the  download.gradle File configuration auto download `deeplabv3.ms`and placed in the 'app/libs/arm64-v8a' directory.

Note: if the automatic download fails, please manually download the relevant library files and put them in the corresponding location.

deeplabv3.ms [deeplabv3.ms]( https://download.mindspore.cn/model_zoo/official/lite/deeplabv3_openimage_lite/deeplabv3.ms)

### Compiling On-Device Inference Code

Call MindSpore Lite Java APIs to implement on-device inference.

The inference code process is as follows. For details about the complete code, see `src/java/TrackingMobile.java`.

1. Load the MindSpore Lite model file and build the context, session, and computational graph for inference.

    - Load a model file. Import and configure the context for model inference.

    ```Java
    // Create context and load the .ms model named 'IMAGESEGMENTATIONMODEL'
    model = new Model();
    if (!model.loadModel(Context, IMAGESEGMENTATIONMODEL)) {
      Log.e(TAG, "Load Model failed");
      return;
    }
    ```

    - Create a session.

    ```Java
    // Create and init config.
    msConfig = new MSConfig();
    if (!msConfig.init(DeviceType.DT_CPU, 2, CpuBindMode.MID_CPU)) {
      Log.e(TAG, "Init context failed");
      return;
    }

    // Create the MindSpore lite session.
    session = new LiteSession();
    if (!session.init(msConfig)) {
      Log.e(TAG, "Create session failed");
      msConfig.free();
      return;
    }
    msConfig.free();
    ```

    - Compile graph for inference.

    ```Java
    if (!session.compileGraph(model)) {
      Log.e(TAG, "Compile graph failed");
      model.freeBuffer();
      return;
    }
    // Note: when use model.freeBuffer(), the model can not be complile graph again.
    model.freeBuffer();
    ```

2. Convert the input image into the Tensor format of the MindSpore model.

    ```Java
    List<MSTensor> inputs = session.getInputs();
    if (inputs.size() != 1) {
      Log.e(TAG, "inputs.size() != 1");
      return null;
    }

    // `bitmap` is the picture used to infer.
    float resource_height = bitmap.getHeight();
    float resource_weight = bitmap.getWidth();
    ByteBuffer contentArray = bitmapToByteBuffer(bitmap, imageSize, imageSize, IMAGE_MEAN, IMAGE_STD);

    MSTensor inTensor = inputs.get(0);
    inTensor.setData(contentArray);
    ```

3. Perform inference on the input tensor based on the model, obtain the output tensor, and perform post-processing.

    - Perform graph execution and on-device inference.

    ```Java
    // After the model and image tensor data is loaded, run inference.
    if (!session.runGraph()) {
      Log.e(TAG, "Run graph failed");
      return null;
    }
    ```

    - Obtain the output data.

    ```Java
    // Get output tensor values, the model only outputs one tensor.
    List<String> tensorNames = session.getOutputTensorNames();
    MSTensor output = session.getOutputByTensorName(tensorNames.front());
    if (output == null) {
      Log.e(TAG, "Can not find output " + tensorName);
      return null;
    }
    ```

    - Perform post-processing of the output data.

    ```Java
    // Show output as pictures.
    float[] results = output.getFloatData();

    ByteBuffer bytebuffer_results = floatArrayToByteArray(results);

    Bitmap dstBitmap = convertBytebufferMaskToBitmap(bytebuffer_results, imageSize, imageSize, bitmap, dstBitmap, segmentColors);
    dstBitmap = scaleBitmapAndKeepRatio(dstBitmap, (int) resource_height, (int) resource_weight);
    ```

4. The process of image and output data can refer to methods showing bellow.

    ```Java
    Bitmap scaleBitmapAndKeepRatio(Bitmap targetBmp, int reqHeightInPixels, int reqWidthInPixels) {
      if (targetBmp.getHeight() == reqHeightInPixels && targetBmp.getWidth() == reqWidthInPixels) {
        return targetBmp;
      }

      Matrix matrix = new Matrix();
      matrix.setRectToRect(new RectF(0f, 0f, targetBmp.getWidth(), targetBmp.getHeight()),
                           new RectF(0f, 0f, reqWidthInPixels, reqHeightInPixels), Matrix.ScaleToFit.FILL;

        return Bitmap.createBitmap(targetBmp, 0, 0, targetBmp.getWidth(), targetBmp.getHeight(), matrix, true);
    }

    ByteBuffer bitmapToByteBuffer(Bitmap bitmapIn, int width, int height, float mean, float std) {
      Bitmap bitmap = scaleBitmapAndKeepRatio(bitmapIn, width, height);
      ByteBuffer inputImage = ByteBuffer.allocateDirect(1 * width * height * 3 * 4);
      inputImage.order(ByteOrder.nativeOrder());
      inputImage.rewind();
      int[] intValues = new int[width * height];
      bitmap.getPixels(intValues, 0, width, 0, 0, width, height);
      int pixel = 0;
      for (int y = 0; y < height; y++) {
        for (int x = 0; x < width; x++) {
          int value = intValues[pixel++];
          inputImage.putFloat(((float) (value >> 16 & 255) - mean) / std);
          inputImage.putFloat(((float) (value >> 8 & 255) - mean) / std);
          inputImage.putFloat(((float) (value & 255) - mean) / std);
        }
      }
      inputImage.rewind();
      return inputImage;
    }

    ByteBuffer floatArrayToByteArray(float[] floats) {
      ByteBuffer buffer = ByteBuffer.allocate(4 * floats.length);
      FloatBuffer floatBuffer = buffer.asFloatBuffer();
      floatBuffer.put(floats);
      return buffer;
    }

    Bitmap convertBytebufferMaskToBitmap(ByteBuffer inputBuffer, int imageWidth, int imageHeight, Bitmap backgroundImage, int[] colors) {
      Bitmap.Config conf = Bitmap.Config.ARGB_8888;
      Bitmap dstBitmap = Bitmap.createBitmap(imageWidth, imageHeight, conf);
      Bitmap scaledBackgroundImage = scaleBitmapAndKeepRatio(backgroundImage, imageWidth, imageHeight);
      int[][] mSegmentBits = new int[imageWidth][imageHeight];
      inputBuffer.rewind();
      for (int y = 0; y < imageHeight; y++) {
        for (int x = 0; x < imageWidth; x++) {
          float maxVal = 0f;
          mSegmentBits[x][y] = 0;
          // NUM_CLASSES is the number of labels, the value here is 21.
          for (int i = 0; i < NUM_CLASSES; i++) {
            float value = inputBuffer.getFloat((y * imageWidth * NUM_CLASSES + x * NUM_CLASSES + i) * 4);
            if (i == 0 || value > maxVal) {
              maxVal = value;
              // Check wether a pixel belongs to a person whose label is 15.
              if (i == 15) {
                mSegmentBits[x][y] = i;
              } else {
                mSegmentBits[x][y] = 0;
              }
            }
          }
          itemsFound.add(mSegmentBits[x][y]);

          int newPixelColor = ColorUtils.compositeColors(
                  colors[mSegmentBits[x][y] == 0 ? 0 : 1],
                  scaledBackgroundImage.getPixel(x, y)
          );
          dstBitmap.setPixel(x, y, mSegmentBits[x][y] == 0 ? colors[0] : scaledBackgroundImage.getPixel(x, y));
        }
      }
      return dstBitmap;
    }
    ```