samples/opencv_mobilenet/MainActivity.java

package org.opencv.samples.opencv_mobilenet;

import android.content.Context;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.Point;
import org.opencv.core.Scalar;
import org.opencv.core.Size;
import org.opencv.dnn.Net;
import org.opencv.dnn.Dnn;
import org.opencv.imgproc.Imgproc;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity implements CvCameraViewListener2 {

    // Initialize OpenCV manager.
    private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS: {
                    Log.i(TAG, "OpenCV loaded successfully");
                    mOpenCvCameraView.enableView();
                    break;
                }
                default: {
                    super.onManagerConnected(status);
                    break;
                }
            }
        }
    };

    @Override
    public void onResume() {
        super.onResume();
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION, this, mLoaderCallback);
    }

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

        // Set up camera listener.
        mOpenCvCameraView = (CameraBridgeViewBase)findViewById(R.id.CameraView);
        mOpenCvCameraView.setVisibility(CameraBridgeViewBase.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);
    }

    // Load a network.
    public void onCameraViewStarted(int width, int height) {
        String proto = getPath("MobileNetSSD_deploy.prototxt", this);
        String weights = getPath("MobileNetSSD_deploy.caffemodel", this);
        net = Dnn.readNetFromCaffe(proto, weights);
        Log.i(TAG, "Network loaded successfully");
    }

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        final int IN_WIDTH = 300;
        final int IN_HEIGHT = 300;
        final float WH_RATIO = (float)IN_WIDTH / IN_HEIGHT;
        final double IN_SCALE_FACTOR = 0.007843;
        final double MEAN_VAL = 127.5;
        final double THRESHOLD = 0.2;

        // Get a new frame
        Mat frame = inputFrame.rgba();
        Imgproc.cvtColor(frame, frame, Imgproc.COLOR_RGBA2RGB);

        // Forward image through network.
        Mat blob = Dnn.blobFromImage(frame, IN_SCALE_FACTOR,
                new Size(IN_WIDTH, IN_HEIGHT),
                new Scalar(MEAN_VAL, MEAN_VAL, MEAN_VAL), /*swapRB*/false, /*crop*/false);
        net.setInput(blob);
        Mat detections = net.forward();

        int cols = frame.cols();
        int rows = frame.rows();

        detections = detections.reshape(1, (int)detections.total() / 7);

        for (int i = 0; i < detections.rows(); ++i) {
            double confidence = detections.get(i, 2)[0];
            if (confidence > THRESHOLD) {
                int classId = (int)detections.get(i, 1)[0];

                int left   = (int)(detections.get(i, 3)[0] * cols);
                int top    = (int)(detections.get(i, 4)[0] * rows);
                int right  = (int)(detections.get(i, 5)[0] * cols);
                int bottom = (int)(detections.get(i, 6)[0] * rows);

                // Draw rectangle around detected object.
                Imgproc.rectangle(frame, new Point(left, top), new Point(right, bottom),
                                  new Scalar(0, 255, 0));
                String label = classNames[classId] + ": " + confidence;
                int[] baseLine = new int[1];
                Size labelSize = Imgproc.getTextSize(label, Imgproc.FONT_HERSHEY_SIMPLEX, 0.5, 1, baseLine);

                // Draw background for label.
                Imgproc.rectangle(frame, new Point(left, top - labelSize.height),
                                  new Point(left + labelSize.width, top + baseLine[0]),
                                  new Scalar(255, 255, 255), Imgproc.FILLED);
                // Write class name and confidence.
                Imgproc.putText(frame, label, new Point(left, top),
                        Imgproc.FONT_HERSHEY_SIMPLEX, 0.5, new Scalar(0, 0, 0));
            }
        }
        return frame;
    }

    public void onCameraViewStopped() {}

    // Upload file to storage and return a path.
    private static String getPath(String file, Context context) {
        AssetManager assetManager = context.getAssets();

        BufferedInputStream inputStream = null;
        try {
            // Read data from assets.
            inputStream = new BufferedInputStream(assetManager.open(file));
            byte[] data = new byte[inputStream.available()];
            inputStream.read(data);
            inputStream.close();

            // Create copy file in storage.
            File outFile = new File(context.getFilesDir(), file);
            FileOutputStream os = new FileOutputStream(outFile);
            os.write(data);
            os.close();
            // Return a path to file which may be read in common way.
            return outFile.getAbsolutePath();
        } catch (IOException ex) {
            Log.i(TAG, "Failed to upload a file");
        }
        return "";
    }

    private static final String TAG = "OpenCV/Sample/MobileNet";
    private static final String[] classNames = {"background",
            "aeroplane", "bicycle", "bird", "boat",
            "bottle", "bus", "car", "cat", "chair",
            "cow", "diningtable", "dog", "horse",
            "motorbike", "person", "pottedplant",
            "sheep", "sofa", "train", "tvmonitor"};

    private Net net;
    private CameraBridgeViewBase mOpenCvCameraView;
}