特征提取与匹配案例代码、环境：Android studio + opencv for AndroidMainActivity.javapackage com.packtpub.masteringopencvandroid.chapter3;import android.app.Activity;import android.content.Intent;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import .Uri;import android.os.AsyncTask;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.widget.ImageView;import android.widget.TextView;import android.widget.Toast;import org.opencv.android.BaseLoaderCallback;import org.opencv.android.LoaderCallbackInterface;import org.opencv.android.OpenCVLoader;import org.opencv.android.Utils;import org.opencv.core.Core;import org.opencv.core.CvType;import org.opencv.core.Mat;import org.opencv.core.MatOfDMatch;import org.opencv.core.MatOfKeyPoint;import org.opencv.core.Point;import org.opencv.core.Scalar;import org.opencv.features2d.DMatch;import org.opencv.features2d.DescriptorExtractor;import org.opencv.features2d.DescriptorMatcher;import org.opencv.features2d.FeatureDetector;import org.opencv.features2d.Features2d;import org.opencv.highgui.Highgui;import org.opencv.imgproc.Imgproc;import java.io.FileNotFoundException;import java.io.InputStream;import java.util.Collections;import parator;import java.util.Date;import java.util.List;public class MainActivity extends Activity {private final int SELECT_PHOTO_1 = 1;private final int SELECT_PHOTO_2 = 2;private final int MAX_MATCHES = 50;private ImageView ivImage1;private TextView tvKeyPointsObject1, tvKeyPointsObject2, tvKeyPointsMatches, tvTime;private int keypointsObject1, keypointsObject2, keypointMatches;Mat src1, src2;static int ACTION_MODE = 0;private boolean src1Selected = false, src2Selected = false;private BaseLoaderCallback mOpenCVCallBack = new BaseLoaderCallback(this) { @Overridepublic void onManagerConnected(int status) {switch (status) {case LoaderCallbackInterface.SUCCESS://DO YOUR WORK/STUFF HERESystem.loadLibrary("nonfree");break;default:super.onManagerConnected(status);break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(yout.activity_main);getActionBar().setDisplayHomeAsUpEnabled(true);ivImage1 = (ImageView)findViewById(R.id.ivImage1);tvKeyPointsObject1 = (TextView) findViewById(KeyPointsObject1);tvKeyPointsObject2 = (TextView) findViewById(KeyPointsObject2);tvKeyPointsMatches = (TextView) findViewById(KeyPointsMatches);keypointsObject1 = keypointsObject2 = keypointMatches = -1;tvTime = (TextView) findViewById(Time);Intent intent = getIntent();if(intent.hasExtra("ACTION_MODE")){ACTION_MODE = intent.getIntExtra("ACTION_MODE", 0);}}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.menu_main, menu);return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {int id = item.getItemId();if (id == R.id.action_load_first_image) {Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);photoPickerIntent.setType("image/*");startActivityForResult(photoPickerIntent, SELECT_PHOTO_1);return true;} else if (id == R.id.action_load_second_image) {Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);photoPickerIntent.setType("image/*");startActivityForResult(photoPickerIntent, SELECT_PHOTO_2);return true;}return super.onOptionsItemSelected(item);}@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) {super.onActivityResult(requestCode, resultCode, imageReturnedIntent);switch(requestCode) {case SELECT_PHOTO_1:if(resultCode == RESULT_OK){try {final Uri imageUri = imageReturnedIntent.getData();final InputStream imageStream =getContentResolver().openInputStream(imageUri);final Bitmap selectedImage = BitmapFactory.decodeStream(imageStream);src1 = new Mat(selectedImage.getHeight(), selectedImage.getWidth(), CvType.CV_8UC4);// ivImage1.setImageBitmap(selectedImage);Utils.bitmapToMat(selectedImage, src1);src1Selected = true;} catch (FileNotFoundException e) {e.printStackTrace();}}break;case SELECT_PHOTO_2:if(resultCode == RESULT_OK){try {final Uri imageUri = imageReturnedIntent.getData();final InputStream imageStream = getContentResolver().openInputStream(imageUri);final Bitmap selectedImage = BitmapFactory.decodeStream(imageStream);src2 = new Mat(selectedImage.getHeight(), selectedImage.getWidth(), CvType.CV_8UC4);Utils.bitmapToMat(selectedImage, src2);src2Selected = true;} catch (FileNotFoundException e) {e.printStackTrace();}}break;}Toast.makeText(MainActivity.this, src1Selected + " " + src2Selected, Toast.LENGTH_SHORT).show();if(src1Selected && src2Selected){Log.d("com.packtpub.chapter3", "Before Execute");new AsyncTask<Void, Void, Bitmap>() {private long startTime, endTime;@Overrideprotected void onPreExecute() {super.onPreExecute();startTime = System.currentTimeMillis();}@Overrideprotected Bitmap doInBackground(Void... params) {return executeTask();}@Overrideprotected void onPostExecute(Bitmap bitmap) {super.onPostExecute(bitmap);endTime = System.currentTimeMillis();ivImage1.setImageBitmap(bitmap);tvKeyPointsObject1.setText("Object 1 : "+keypointsObject1);tvKeyPointsObject2.setText("Object 2 : "+keypointsObject2);tvKeyPointsMatches.setText("Keypoint Matches : "+keypointMatches);tvTime.setText("Time taken : "+(endTime-startTime)+" ms");}}.execute();}}private Bitmap executeTask(){Log.d("com.packtpub.chapter3", "Execute");FeatureDetector detector;MatOfKeyPoint keypoints1, keypoints2;DescriptorExtractor descriptorExtractor;Mat descriptors1, descriptors2;DescriptorMatcher descriptorMatcher;MatOfDMatch matches = new MatOfDMatch();keypoints1 = new MatOfKeyPoint();keypoints2 = new MatOfKeyPoint();descriptors1 = new Mat();descriptors2 = new Mat();Log.d("com.packtpub.chapter3", "before switch");switch (ACTION_MODE){case HomeActivity.MODE_SIFT:detector = FeatureDetector.create(FeatureDetector.SIFT);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.SIFT);descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_SL2);// descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.FLANNBASED);break;case HomeActivity.MODE_SURF:detector = FeatureDetector.create(FeatureDetector.SURF);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.SURF);descriptorMatcher =DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_SL2);break;case HomeActivity.MODE_ORB:detector = FeatureDetector.create(FeatureDetector.ORB);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.ORB);descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);break;case HomeActivity.MODE_BRISK:detector = FeatureDetector.create(FeatureDetector.BRISK);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.BRISK);descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);break;case HomeActivity.MODE_FREAK:detector = FeatureDetector.create(FeatureDetector.FAST);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.FREAK);descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);break;default:detector = FeatureDetector.create(FeatureDetector.FAST);descriptorExtractor = DescriptorExtractor.create(DescriptorExtractor.BRIEF);descriptorMatcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);break;}Log.d("com.packtpub.chapter3", "After switch");detector.detect(src2, keypoints2);detector.detect(src1, keypoints1);Log.d("com.packtpub.chapter3", CvType.typeToString(src1.type())+" "+CvType.typeToString(src2.type()));Log.d("com.packtpub.chapter3", keypoints1.toArray().length+" keypoints");Log.d("com.packtpub.chapter3", keypoints2.toArray().length+" keypoints");Log.d("com.packtpub.chapter3", "Detect");keypointsObject1 = keypoints1.toArray().length;keypointsObject2 = keypoints2.toArray().length;pute(src1, keypoints1, descriptors1);pute(src2, keypoints2, descriptors2);descriptorMatcher.match(descriptors1, descriptors2, matches);Log.d("com.packtpub.chapter3", matches.toArray().length+" matches");keypointMatches = matches.toArray().length;Collections.sort(matches.toList(), new Comparator<DMatch>() {@Overridepublic int compare(DMatch o1, DMatch o2) {if(o1.distance<o2.distance)return -1;if(o1.distance>o2.distance)return 1;return 0;}});List<DMatch> listOfDMatch = matches.toList();if(listOfDMatch.size()>MAX_MATCHES){matches.fromList(listOfDMatch.subList(0,MAX_MATCHES));}// Mat src3 = src1.clone();// Features2d.drawMatches(src1, keypoints1, src2, keypoints2, matches, src3);Mat src3 = drawMatches(src1, keypoints1, src2, keypoints2, matches, false);Log.d("com.packtpub.chapter3", CvType.typeToString(src3.type()));Bitmap image1 = Bitmap.createBitmap(src3.cols(), src3.rows(), Bitmap.Config.ARGB_8888);Utils.matToBitmap(src3, image1);Imgproc.cvtColor(src3, src3, Imgproc.COLOR_BGR2RGB);boolean bool = Highgui.imwrite(Environment.getExternalStorageDirectory()+"/Download/PacktBook/Chapter3/" +ACTION_MODE+".png", src3);Log.d("com.packtpub.chapter3", bool+" "+Environment.getExternalStorageDirectory()+"/Download/PacktBook/Chapter3/"+ACTION_MO DE+".png");return image1;}@Overrideprotected void onResume() {super.onResume();OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_10, this,mOpenCVCallBack);}static Mat drawMatches(Mat img1, MatOfKeyPoint key1, Mat img2, MatOfKeyPoint key2, MatOfDMatch matches, boolean imageOnly){//https:///mustafaakin/image-matcher/tree/master/src/in/mustafaak/imagematcher Mat out = new Mat();Mat im1 = new Mat();Mat im2 = new Mat();Imgproc.cvtColor(img1, im1, Imgproc.COLOR_BGR2RGB);Imgproc.cvtColor(img2, im2, Imgproc.COLOR_BGR2RGB);if ( imageOnly){MatOfDMatch emptyMatch = new MatOfDMatch();MatOfKeyPoint emptyKey1 = new MatOfKeyPoint();MatOfKeyPoint emptyKey2 = new MatOfKeyPoint();Features2d.drawMatches(im1, emptyKey1, im2, emptyKey2, emptyMatch, out);} else {Features2d.drawMatches(im1, key1, im2, key2, matches, out);}Bitmap bmp = Bitmap.createBitmap(out.cols(), out.rows(), Bitmap.Config.ARGB_8888);Imgproc.cvtColor(out, out, Imgproc.COLOR_BGR2RGB);Core.putText(out, "FRAME", new Point(img1.width() / 2,30), Core.FONT_HERSHEY_PLAIN, 2, new Scalar(0,255,255),3);Core.putText(out, "MATCHED", new Point(img1.width() + img2.width() / 2,30), Core.FONT_HERSHEY_PLAIN, 2, new Scalar(255,0,0),3);return out;}}HomeActivity.javapackage com.packtpub.masteringopencvandroid.chapter3;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.widget.Button;public class HomeActivity extends Activity {public static final int MODE_SIFT = 1;public static final int MODE_SURF = 2;public static final int MODE_ORB = 3;public static final int MODE_BRISK = 4;public static final int MODE_FREAK = 5;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(yout.activity_home);Button bSIFT, bSURF, bORB, bBRISK, bFREAK;bSIFT = (Button) findViewById(R.id.bSIFT);bSURF = (Button) findViewById(R.id.bSURF);bORB = (Button) findViewById(R.id.bORB);bBRISK = (Button) findViewById(R.id.bBRISK);bFREAK = (Button) findViewById(R.id.bFREAK);bSIFT.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent i = new Intent(getApplicationContext(), MainActivity.class);i.putExtra("ACTION_MODE", MODE_SIFT);startActivity(i);}});bSURF.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent i = new Intent(getApplicationContext(), MainActivity.class);i.putExtra("ACTION_MODE", MODE_SURF);startActivity(i);}});bORB.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent i = new Intent(getApplicationContext(), MainActivity.class);i.putExtra("ACTION_MODE", MODE_ORB);startActivity(i);}});bBRISK.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent i = new Intent(getApplicationContext(), MainActivity.class);i.putExtra("ACTION_MODE", MODE_BRISK);startActivity(i);}});bFREAK.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Intent i = new Intent(getApplicationContext(), MainActivity.class);i.putExtra("ACTION_MODE", MODE_FREAK);startActivity(i);}});}}。