安装JDK

网上一堆教程：略。

安装Android Studio

网上一堆教程：略。

安装OpenCV4Android

到opencv官网下载地址下载opencv4android包。这边下载3.4.4版本的Android pack。

下载后解压可以看到以下几个文件。

apk：opencv已经编译好的Android可执行程序，拷贝到手机上即可运行。

samples：生成这些apk的Android代码工程。

sdk：里面是opencv的Java的接口和JNI接口等。

在Android Studio上配置OpenCV环境

1.打开Android studio新建一个新的Android空工程。

2.在Android Studio的菜单选择File-->New-->Import Module。

3.选择opencv android pack解压出来的sdk目录下的java文件夹，点击下一步，出现三个复选框，都选上，点击Finish。

4.菜单栏选择File-->Project Structure。

5.按照如下图步骤操作，选择app-->Dependencies-->+-->3 Module dependency，点击ok退出，然后再点击ok退出。

6.修改build.gradle(Module:openCVLibrary344)文件，将compileSdkVersion，minSdkVersion，targetSdkVersion改成你对应安卓版本，这边目标为Android8.0，最低为Android7.0.

7.在工程目录下的app/src/main目录下新建文件夹jniLibs，将我们下载解压的OpenCV-android-sdk下的sdk/native/libs下的所有文件拷贝到jniLibs下。

8.到此，opencv环境配置完成。

在Android上使用opencv写图像处理算法

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.administrator.cv4andoird"
    android:orientation="vertical"
    >
    <Button
        android:id="@+id/select_btn"
        android:text="选择图片"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="fill_parent"
        android:layout_height="1388px"
        android:src="@mipmap/ic_launcher" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        >

        <Button
            android:id="@+id/src_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="2dp"
            android:layout_marginRight="2dp"
            android:orientation="horizontal"
            android:text="原图" />

        <Button
            android:id="@+id/process_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="2dp"
            android:layout_marginRight="2dp"
            android:orientation="horizontal"
            android:text="灰度" />

        <Button
            android:id="@+id/canny_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="2dp"
            android:layout_marginRight="2dp"
            android:orientation="horizontal"
            android:text="边缘" />

        <Button
            android:id="@+id/hsv_btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="2dp"
            android:layout_marginRight="2dp"
            android:orientation="horizontal"
            android:text="复古" />

    </LinearLayout>
</LinearLayout>

MainActivity.java

package com.example.administrator.cv4andoird;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import org.opencv.android.OpenCVLoader;
import org.opencv.android.Utils;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.imgproc.Imgproc;


import java.io.InputStream;

public class MainActivity extends AppCompatActivity {

    private double max_size = 1024;
    private int PICK_IMAGE_REQUEST = 1;
    private ImageView myImageView;
    private Bitmap selectbp;
    private Bitmap selectbptmp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        staticLoadCVLibraries();
        myImageView = (ImageView)findViewById(R.id.imageView);
        myImageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
        Button selectImageBtn = (Button)findViewById(R.id.select_btn);
        selectImageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // makeText(MainActivity.this.getApplicationContext(), "start to browser image", Toast.LENGTH_SHORT).show();
                selectImage();
            }
        });

        Button processBtn = (Button)findViewById(R.id.process_btn);
        processBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // makeText(MainActivity.this.getApplicationContext(), "hello, image process", Toast.LENGTH_SHORT).show();
                convertGray();
            }
        });

        Button cannyBtn = (Button)findViewById(R.id.canny_btn);
        cannyBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // makeText(MainActivity.this.getApplicationContext(), "hello, image process", Toast.LENGTH_SHORT).show();
                kayCanny();
            }
        });

        Button srcBtn = (Button)findViewById(R.id.src_btn);
        srcBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // makeText(MainActivity.this.getApplicationContext(), "hello, image process", Toast.LENGTH_SHORT).show();
                kaySrc();
            }
        });

        Button hsvBtn = (Button)findViewById(R.id.hsv_btn);
        hsvBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // makeText(MainActivity.this.getApplicationContext(), "hello, image process", Toast.LENGTH_SHORT).show();
                kayHsv();
            }
        });
    }

    private void staticLoadCVLibraries(){
        boolean load = OpenCVLoader.initDebug();
        if(load) {
            Log.i("CV", "Open CV Libraries loaded...");
        }
    }

    private void convertGray() {
        Mat src = new Mat();
        Mat temp = new Mat();
        Mat dst = new Mat();

        Utils.bitmapToMat(selectbp, src);
        Imgproc.cvtColor(src, temp, Imgproc.COLOR_BGRA2BGR);
        Log.i("CV", "image type:" + (temp.type() == CvType.CV_8UC3));
        Imgproc.cvtColor(temp, dst, Imgproc.COLOR_BGR2GRAY);
        Utils.matToBitmap(dst, selectbptmp);
        myImageView.setImageBitmap(selectbptmp);
    }

    private void kayCanny() {
        Mat src = new Mat();
        Mat temp = new Mat();
        Mat gray = new Mat();
        Mat dst = new Mat();
        Utils.bitmapToMat(selectbp, src);
        Imgproc.cvtColor(src, temp, Imgproc.COLOR_BGRA2BGR);
        Imgproc.cvtColor(temp, gray, Imgproc.COLOR_BGR2GRAY);

        Imgproc.Canny(gray, dst, 80, 90);

        Utils.matToBitmap(dst, selectbptmp);
        myImageView.setImageBitmap(selectbptmp);
    }

    private void kaySrc() {

        myImageView.setImageBitmap(selectbp);
    }

    private void kayHsv() {
        Mat src = new Mat();
        Mat temp = new Mat();
        Mat dst = new Mat();

        Utils.bitmapToMat(selectbp, src);
        Imgproc.cvtColor(src, temp, Imgproc.COLOR_BGRA2BGR);
        Log.i("CV", "image type:" + (temp.type() == CvType.CV_8UC3));
        Imgproc.cvtColor(temp, dst, Imgproc.COLOR_BGR2HSV);
        Utils.matToBitmap(dst, selectbptmp);
        myImageView.setImageBitmap(selectbptmp);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null && data.getData() != null) {
            Uri uri = data.getData();
            try {
                Log.d("image-tag", "start to decode selected image now...");
                InputStream input = getContentResolver().openInputStream(uri);
                BitmapFactory.Options options = new BitmapFactory.Options();
                options.inJustDecodeBounds = true;
                BitmapFactory.decodeStream(input, null, options);
                int raw_width = options.outWidth;
                int raw_height = options.outHeight;
                int max = Math.max(raw_width, raw_height);
                int newWidth = raw_width;
                int newHeight = raw_height;
                int inSampleSize = 1;
                if(max > max_size) {
                    newWidth = raw_width / 2;
                    newHeight = raw_height / 2;
                    while((newWidth/inSampleSize) > max_size || (newHeight/inSampleSize) > max_size) {
                        inSampleSize *=2;
                    }
                }

                options.inSampleSize = inSampleSize;
                options.inJustDecodeBounds = false;
                options.inPreferredConfig = Bitmap.Config.ARGB_8888;
                selectbp = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);
                selectbptmp = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);
                myImageView.setImageBitmap(selectbptmp);

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    private void selectImage() {
        Intent intent = new Intent();
        intent.setType("image/*");
        intent.setAction(Intent.ACTION_GET_CONTENT);
        startActivityForResult(Intent.createChooser(intent,"选择图像..."), PICK_IMAGE_REQUEST);
    }
}