学习笔记：基于OpenCV的Android拍照功能的实现

利用OpenCV For Android利用org.opencv.android.JavaCameraView实现拍照功能，并对正在处理的图片根据选择实现灰度显示、RGB显示和Canny边缘显示。

1.配置AndroidManefest.xml文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.userhu2012.app.camera">

    <supports-screens android:resizeable="true"
        android:smallScreens="true"
        android:normalScreens="true"
        android:largeScreens="true"
        android:anyDensity="true" />

    <uses-permission android:name="android.permission.CAMERA"/>

    <uses-feature android:name="android.hardware.camera" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.autofocus" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front.autofocus" android:required="false"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
      
        <!--android:screenOrientation设置屏幕方向
            android:configChanges:设置配置变化键盘隐藏|定位
        -->
        <activity android:name=".CameraActivity"
            android:screenOrientation="landscape"
            android:configChanges="keyboardHidden|orientation"
            >
           <intent-filter> 
                <action android:name="android.intent.action.MAIN" /> 
                <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
        </activity>
    </application>

</manifest>

2.定义活动对应的布局文件activity_main.xml

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

    <org.opencv.android.JavaCameraView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"
        android:id="@+id/javaCameraView"
        opencv:show_fps="true"
        opencv:camera_id="any" />

</FrameLayout>

3.res/menu/main.xml菜单定义

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/grayItem" android:title="@string/title_gray" />
    <item android:id="@+id/rgbItem" android:title="@string/title_rgb" />
    <item android:id="@+id/cannyItem" android:title="@string/title_canny" />
    <item android:id="@+id/exitItem" android:title="@string/title_exit" />
</menu>

4.定义活动

package com.userhu2012.app.camera;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewFrame;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;
import org.opencv.imgproc.Imgproc;

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.SurfaceView;
import android.view.WindowManager;
import android.widget.Toast;

import static chenyi.ncu.edu.cn.ch01.MainActivity.MY_PERMISSIONS_REQUEST_CAMERA;

public class CameraActivity extends AppCompatActivity implements CvCameraViewListener2 {
    private static final String TAG = "CameraActivity";

    private CameraBridgeViewBase mOpenCvCameraView;
    private boolean              mIsJavaCamera = true;
    private MenuItem             mItemSwitchCamera = null;
    private static final int       VIEW_MODE_RGBA     = 0;
    private static final int       VIEW_MODE_GRAY     = 1;
    private static final int       VIEW_MODE_CANNY    = 2;
    private static final int       VIEW_MODE_FEATURES = 5;

    private int                    mViewMode;
    private Mat                    mRgba;
    private Mat                    mIntermediateMat;
    private Mat                    mGray;
    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;
            }
        }
    };

    /**
     * 第一次创建时调用
     * */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG, "called onCreate");
        //权限检查
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) !=        PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                            new String[]{Manifest.permission.CAMERA},
                            MY_PERMISSIONS_REQUEST_CAMERA);

        }
        //将窗口变亮
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        setContentView(R.layout.activity_camera);

        mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.javaCameraView);
        mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);

    }

    @Override
    public void onPause(){
        super.onPause();
        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

    @Override
    public void onResume(){
        super.onResume();
        if (!OpenCVLoader.initDebug()) {
            Log.d(TAG, "Internal OpenCV library not found. Using OpenCV Manager for initialization");
            OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_4_0, this, mLoaderCallback);
        } else {
            Log.d(TAG, "OpenCV library found inside package. Using it!");
            mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
        }
    }

    public void onDestroy() {
        super.onDestroy();
        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

    /**
      *创建菜单
      */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main,menu);
        return true;
    }
    
    /**
     *选择菜单项的处理
     */
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()){
            case R.id.grayItem:
                mViewMode = VIEW_MODE_GRAY;
                break;
            case R.id.rgbItem:
                mViewMode = VIEW_MODE_RGBA;
                break;
            case R.id.cannyItem:
                mViewMode = VIEW_MODE_CANNY;
                break;
            case R.id.exitItem: finish();
        }
        return true;
    }

    public void onCameraViewStarted(int width, int height) {
        mRgba = new Mat(height, width, CvType.CV_8UC4);
        mIntermediateMat = new Mat(height, width, CvType.CV_8UC4);
        mGray = new Mat(height, width, CvType.CV_8UC1);
    }

    public void onCameraViewStopped() {
        mRgba.release();
        mGray.release();
        mIntermediateMat.release();

    }

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        final int viewMode = mViewMode;
        switch (viewMode) {
            case VIEW_MODE_GRAY:
                Imgproc.cvtColor(inputFrame.gray(), mRgba, Imgproc.COLOR_GRAY2RGBA, 4);
                break;
            case VIEW_MODE_RGBA:
                mRgba = inputFrame.rgba();
                break;
            case VIEW_MODE_CANNY:
                mRgba = inputFrame.rgba();
                Imgproc.Canny(inputFrame.gray(), mIntermediateMat, 80, 100);
                Imgproc.cvtColor(mIntermediateMat, mRgba, Imgproc.COLOR_GRAY2RGBA, 4);
                break;
        }

        return mRgba;
    }
}