即前面两节讲的安卓开发的基本过程后我们来讲一下移动计算方面的，个人认为移动计算，手机等设备不只是进行消息传递及获取信息的工具而是具有一定的计算能力.这里我们主要介绍在手机端进行图像处理，利用的是OPENCV库。
首先我们来试一下opencv for Android里面的sample例子。
这里给出opencvforAndroid 官网教程地址：https://docs.opencv.org/2.4/doc/tutorials/introduction/android_binary_package/O4A_SDK.html#opencv4android-sdk
官网上教程的版本比较老，还是用eclipse开发的，我们要对其进行一些移植来适合Android studio。
这里我选用的opencv版本是3.4.0，安卓sdk版本为26
先进行移植的是samples下的tutorial-1-camerapreview
首先新建一个工程，将opencv的sdk导入工程中，选择File->Import Module 选择opencvforandroid下的\sdk\java文件

再在Project Structure中添加Opencv库的依赖，选择Modules中的app，选择Dependencies，点击加号，选择Models Dependency，选择其中的Opencv


接下来，将MainActivity改成：

package com.example.lenovo.myapplication;

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.Mat;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.CameraBridgeViewBase.CvCameraViewListener2;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MenuItem;
import android.view.SurfaceView;
import android.view.WindowManager;


public class MainActivity extends Activity implements CvCameraViewListener2 {
    
    private static final String TAG = "OCVSample::Activity";

    private CameraBridgeViewBase mOpenCvCameraView;
    private boolean mIsJavaCamera = true;
    private MenuItem  mItemSwitchCamera = null;

    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;
            }
        }
    };

    public MainActivity() {
    
        Log.i(TAG, "Instantiated new " + this.getClass());
    }

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
    
        Log.i(TAG, "called onCreate");
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.tutorial1_surface_view);

        mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.tutorial1_activity_java_surface_view);

        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();
    }

    public void onCameraViewStarted(int width, int height) {
    
    }

    public void onCameraViewStopped() {
    
    }

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    
        return inputFrame.rgba();
    }
}

主要改动是将opencv的版本号换成对应的版本号：

OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_4_0, this, mLoaderCallback);

下面是其页面布局文件：

<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/tutorial1_activity_java_surface_view"

        opencv:show_fps="true"
        opencv:camera_id="any" />

</FrameLayout>

在AndersonManif.xml中要声明对相机的权限：

<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"/>

接下来build 然后运行，这里在电脑上的模拟器上运行会出现不能调用摄像头的问题，可以用在手机上实验，安装时会提示要安装opencv manage之类的软件，这个可以通过将\sdk\native文件目录下的jniLibs文件夹放到安卓项目中的app\src\main\下

这个sample最后的结果是手机屏幕中间会显示拍摄的画面，而且画面是旋转90°的，这个可以对工程下openCVLibrary340/src/main/java/org.opencv/android中CamerabridgeViewBase类中的deliverAndDrawFrame函数进行修改

protected void deliverAndDrawFrame(CvCameraViewFrame frame) {
    
        Mat modified;

        if (mListener != null) {
    
            modified = mListener.onCameraFrame(frame);
        } else {
    
            modified = frame.rgba();
        }

        boolean bmpValid = true;
        if (modified != null) {
    
            try {
    
                Utils.matToBitmap(modified, mCacheBitmap);
            } catch(Exception e) {
    
                Log.e(TAG, "Mat type: " + modified);
                Log.e(TAG, "Bitmap type: " + mCacheBitmap.getWidth() + "*" + mCacheBitmap.getHeight());
                Log.e(TAG, "Utils.matToBitmap() throws an exception: " + e.getMessage());
                bmpValid = false;
            }
        }

        if (bmpValid && mCacheBitmap != null) {
    
            Canvas canvas = getHolder().lockCanvas();
            if (canvas != null) {
    
                canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                canvas.rotate(90,0,0);
                float scale = canvas.getWidth() / (float)mCacheBitmap.getHeight();
                float scale2 = canvas.getHeight() / (float)mCacheBitmap.getWidth();
                if(scale2 > scale){
    
                    scale = scale2;
                }
                if (scale != 0) {
    
                    canvas.scale(scale, scale,0,0);
                }
                canvas.drawBitmap(mCacheBitmap, 0, -mCacheBitmap.getHeight(), null);
                if (BuildConfig.DEBUG)
                    Log.d(TAG, "mStretch value: " + mScale);
                    if (mFpsMeter != null) {
    
                    mFpsMeter.measure();
                    mFpsMeter.draw(canvas, 20, 30);
                }
                getHolder().unlockCanvasAndPost(canvas);
            }
        }
    }

最后结果：