Add Java and Python code for AKAZE local features matching tutorial. Fix incorrect uses of Mat.mul() in Java code.

Uniform Lowe's ratio test in the code.

doc/tutorials/features2d/akaze_matching/akaze_matching.markdown

@@ -7,8 +7,7 @@ Introduction
 In this tutorial we will learn how to use AKAZE @cite ANB13 local features to detect and match keypoints on
 two images.
 We will find keypoints on a pair of images with given homography matrix, match them and count the
-
+number of inliers (i.e. matches that fit in the given homography).
-number of inliers (i. e. matches that fit in the given homography).
 
 You can find expanded version of this example here:
 <https://github.com/pablofdezalc/test_kaze_akaze_opencv>
@@ -16,7 +15,7 @@ You can find expanded version of this example here:
 Data
 ----
 
-We are going to use images 1 and 3 from *Graffity* sequence of Oxford dataset.
+We are going to use images 1 and 3 from *Graffiti* sequence of [Oxford dataset](http://www.robots.ox.ac.uk/~vgg/data/data-aff.html).
 
 ![](images/graf.png)
 
@@ -27,107 +26,148 @@ Homography is given by a 3 by 3 matrix:
 3.4663091e-04  -1.4364524e-05   1.0000000e+00
 @endcode
 You can find the images (*graf1.png*, *graf3.png*) and homography (*H1to3p.xml*) in
-*opencv/samples/cpp*.
+*opencv/samples/data/*.
 
 ### Source Code
 
-@include cpp/tutorial_code/features2D/AKAZE_match.cpp
+@add_toggle_cpp
+-   **Downloadable code**: Click
+    [here](https://raw.githubusercontent.com/opencv/opencv/3.4/samples/cpp/tutorial_code/features2D/AKAZE_match.cpp)
+
+-   **Code at glance:**
+    @include samples/cpp/tutorial_code/features2D/AKAZE_match.cpp
+@end_toggle
+
+@add_toggle_java
+-   **Downloadable code**: Click
+    [here](https://raw.githubusercontent.com/opencv/opencv/3.4/samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java)
+
+-   **Code at glance:**
+    @include samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java
+@end_toggle
+
+@add_toggle_python
+-   **Downloadable code**: Click
+    [here](https://raw.githubusercontent.com/opencv/opencv/3.4/samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py)
+
+-   **Code at glance:**
+    @include samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py
+@end_toggle
 
 ### Explanation
 
--#  **Load images and homography**
+-   **Load images and homography**
-    @code{.cpp}
-    Mat img1 = imread("graf1.png", IMREAD_GRAYSCALE);
-    Mat img2 = imread("graf3.png", IMREAD_GRAYSCALE);
 
-    Mat homography;
+@add_toggle_cpp
-    FileStorage fs("H1to3p.xml", FileStorage::READ);
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp load
-    fs.getFirstTopLevelNode() >> homography;
+@end_toggle
-    @endcode
-    We are loading grayscale images here. Homography is stored in the xml created with FileStorage.
 
--#  **Detect keypoints and compute descriptors using AKAZE**
+@add_toggle_java
-    @code{.cpp}
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java load
-    vector<KeyPoint> kpts1, kpts2;
+@end_toggle
-    Mat desc1, desc2;
 
-    AKAZE akaze;
+@add_toggle_python
-    akaze(img1, noArray(), kpts1, desc1);
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py load
-    akaze(img2, noArray(), kpts2, desc2);
+@end_toggle
-    @endcode
-    We create AKAZE object and use it's *operator()* functionality. Since we don't need the *mask*
-    parameter, *noArray()* is used.
 
--#  **Use brute-force matcher to find 2-nn matches**
+We are loading grayscale images here. Homography is stored in the xml created with FileStorage.
-    @code{.cpp}
-    BFMatcher matcher(NORM_HAMMING);
-    vector< vector<DMatch> > nn_matches;
-    matcher.knnMatch(desc1, desc2, nn_matches, 2);
-    @endcode
-    We use Hamming distance, because AKAZE uses binary descriptor by default.
 
--#  **Use 2-nn matches to find correct keypoint matches**
+-   **Detect keypoints and compute descriptors using AKAZE**
-    @code{.cpp}
-    for(size_t i = 0; i < nn_matches.size(); i++) {
-        DMatch first = nn_matches[i][0];
-        float dist1 = nn_matches[i][0].distance;
-        float dist2 = nn_matches[i][1].distance;
 
-        if(dist1 < nn_match_ratio * dist2) {
+@add_toggle_cpp
-            matched1.push_back(kpts1[first.queryIdx]);
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp AKAZE
-            matched2.push_back(kpts2[first.trainIdx]);
+@end_toggle
-        }
-    }
-    @endcode
-    If the closest match is *ratio* closer than the second closest one, then the match is correct.
 
--#  **Check if our matches fit in the homography model**
+@add_toggle_java
-    @code{.cpp}
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java AKAZE
-    for(int i = 0; i < matched1.size(); i++) {
+@end_toggle
-        Mat col = Mat::ones(3, 1, CV_64F);
-        col.at<double>(0) = matched1[i].pt.x;
-        col.at<double>(1) = matched1[i].pt.y;
 
-        col = homography * col;
+@add_toggle_python
-        col /= col.at<double>(2);
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py AKAZE
-        float dist = sqrt( pow(col.at<double>(0) - matched2[i].pt.x, 2) +
+@end_toggle
-                           pow(col.at<double>(1) - matched2[i].pt.y, 2));
 
-        if(dist < inlier_threshold) {
+We create AKAZE and detect and compute AKAZE keypoints and descriptors. Since we don't need the *mask*
-            int new_i = inliers1.size();
+parameter, *noArray()* is used.
-            inliers1.push_back(matched1[i]);
-            inliers2.push_back(matched2[i]);
-            good_matches.push_back(DMatch(new_i, new_i, 0));
-        }
-    }
-    @endcode
-    If the distance from first keypoint's projection to the second keypoint is less than threshold,
-    then it it fits in the homography.
 
-    We create a new set of matches for the inliers, because it is required by the drawing function.
+-   **Use brute-force matcher to find 2-nn matches**
 
--#  **Output results**
+@add_toggle_cpp
-    @code{.cpp}
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp 2-nn matching
-    Mat res;
+@end_toggle
-    drawMatches(img1, inliers1, img2, inliers2, good_matches, res);
-    imwrite("res.png", res);
-    ...
-    @endcode
-    Here we save the resulting image and print some statistics.
 
-### Results
+@add_toggle_java
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java 2-nn matching
+@end_toggle
 
-Found matches
+@add_toggle_python
--------------
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py 2-nn matching
+@end_toggle
+
+We use Hamming distance, because AKAZE uses binary descriptor by default.
+
+-   **Use 2-nn matches and ratio criterion to find correct keypoint matches**
+@add_toggle_cpp
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp ratio test filtering
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java ratio test filtering
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py ratio test filtering
+@end_toggle
+
+If the closest match distance is significantly lower than the second closest one, then the match is correct (match is not ambiguous).
+
+-   **Check if our matches fit in the homography model**
+
+@add_toggle_cpp
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp homography check
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java homography check
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py homography check
+@end_toggle
+
+If the distance from first keypoint's projection to the second keypoint is less than threshold,
+then it fits the homography model.
+
+We create a new set of matches for the inliers, because it is required by the drawing function.
+
+-   **Output results**
+
+@add_toggle_cpp
+@snippet samples/cpp/tutorial_code/features2D/AKAZE_match.cpp draw final matches
+@end_toggle
+
+@add_toggle_java
+@snippet samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java draw final matches
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py draw final matches
+@end_toggle
+
+Here we save the resulting image and print some statistics.
+
+Results
+-------
+
+### Found matches
 
 ![](images/res.png)
 
-A-KAZE Matching Results
+Depending on your OpenCV version, you should get results coherent with:
------------------------
+
 @code{.none}
  Keypoints 1:   2943
  Keypoints 2:   3511
  Matches:       447
  Inliers:       308
- Inlier Ratio: 0.689038}
+ Inlier Ratio: 0.689038
 @endcode

doc/tutorials/features2d/table_of_content_features2d.markdown

@@ -98,6 +98,8 @@ OpenCV.
 
 -   @subpage tutorial_akaze_matching
 
+    *Languages:* C++, Java, Python
+
     *Compatibility:* \> OpenCV 3.0
 
     *Author:* Fedor Morozov

samples/cpp/tutorial_code/features2D/AKAZE_match.cpp

@@ -6,11 +6,12 @@
 using namespace std;
 using namespace cv;
 
-const float inlier_threshold = 2.5f; // Distance threshold to identify inliers
+const float inlier_threshold = 2.5f; // Distance threshold to identify inliers with homography check
 const float nn_match_ratio = 0.8f;   // Nearest neighbor matching ratio
 
 int main(int argc, char* argv[])
 {
+    //! [load]
     CommandLineParser parser(argc, argv,
                              "{@img1 | ../data/graf1.png | input image 1}"
                              "{@img2 | ../data/graf3.png | input image 2}"
@@ -21,20 +22,25 @@ int main(int argc, char* argv[])
     Mat homography;
     FileStorage fs(parser.get<String>("@homography"), FileStorage::READ);
     fs.getFirstTopLevelNode() >> homography;
+    //! [load]
 
+    //! [AKAZE]
     vector<KeyPoint> kpts1, kpts2;
     Mat desc1, desc2;
 
     Ptr<AKAZE> akaze = AKAZE::create();
     akaze->detectAndCompute(img1, noArray(), kpts1, desc1);
     akaze->detectAndCompute(img2, noArray(), kpts2, desc2);
+    //! [AKAZE]
 
+    //! [2-nn matching]
     BFMatcher matcher(NORM_HAMMING);
     vector< vector<DMatch> > nn_matches;
     matcher.knnMatch(desc1, desc2, nn_matches, 2);
+    //! [2-nn matching]
 
-    vector<KeyPoint> matched1, matched2, inliers1, inliers2;
+    //! [ratio test filtering]
-    vector<DMatch> good_matches;
+    vector<KeyPoint> matched1, matched2;
     for(size_t i = 0; i < nn_matches.size(); i++) {
         DMatch first = nn_matches[i][0];
         float dist1 = nn_matches[i][0].distance;
@@ -45,8 +51,12 @@ int main(int argc, char* argv[])
             matched2.push_back(kpts2[first.trainIdx]);
         }
     }
+    //! [ratio test filtering]
 
-    for(unsigned i = 0; i < matched1.size(); i++) {
+    //! [homography check]
+    vector<DMatch> good_matches;
+    vector<KeyPoint> inliers1, inliers2;
+    for(size_t i = 0; i < matched1.size(); i++) {
         Mat col = Mat::ones(3, 1, CV_64F);
         col.at<double>(0) = matched1[i].pt.x;
         col.at<double>(1) = matched1[i].pt.y;
@@ -63,12 +73,14 @@ int main(int argc, char* argv[])
             good_matches.push_back(DMatch(new_i, new_i, 0));
         }
     }
+    //! [homography check]
 
+    //! [draw final matches]
     Mat res;
     drawMatches(img1, inliers1, img2, inliers2, good_matches, res);
     imwrite("akaze_result.png", res);
 
-    double inlier_ratio = inliers1.size() * 1.0 / matched1.size();
+    double inlier_ratio = inliers1.size() / (double) matched1.size();
     cout << "A-KAZE Matching Results" << endl;
     cout << "*******************************" << endl;
     cout << "# Keypoints 1:                        \t" << kpts1.size() << endl;
@@ -80,6 +92,7 @@ int main(int argc, char* argv[])
 
     imshow("result", res);
     waitKey();
+    //! [draw final matches]
 
     return 0;
 }

samples/cpp/tutorial_code/features2D/feature_flann_matcher/SURF_FLANN_matching_Demo.cpp

@@ -46,7 +46,7 @@ int main( int argc, char* argv[] )
     std::vector<DMatch> good_matches;
     for (size_t i = 0; i < knn_matches.size(); i++)
     {
-        if (knn_matches[i].size() > 1 && knn_matches[i][0].distance / knn_matches[i][1].distance <= ratio_thresh)
+        if (knn_matches[i][0].distance < ratio_thresh * knn_matches[i][1].distance)
         {
             good_matches.push_back(knn_matches[i][0]);
         }

samples/cpp/tutorial_code/features2D/feature_homography/SURF_FLANN_matching_homography_Demo.cpp

@@ -48,7 +48,7 @@ int main( int argc, char* argv[] )
     std::vector<DMatch> good_matches;
     for (size_t i = 0; i < knn_matches.size(); i++)
     {
-        if (knn_matches[i].size() > 1 && knn_matches[i][0].distance / knn_matches[i][1].distance <= ratio_thresh)
+        if (knn_matches[i][0].distance < ratio_thresh * knn_matches[i][1].distance)
         {
             good_matches.push_back(knn_matches[i][0]);
         }

samples/java/tutorial_code/ImgTrans/distance_transformation/ImageSegmentationDemo.java

@@ -103,8 +103,9 @@ class ImageSegmentation {
 
         // Normalize the distance image for range = {0.0, 1.0}
         // so we can visualize and threshold it
-        Core.normalize(dist, dist, 0, 1., Core.NORM_MINMAX);
+        Core.normalize(dist, dist, 0.0, 1.0, Core.NORM_MINMAX);
-        Mat distDisplayScaled = dist.mul(dist, 255);
+        Mat distDisplayScaled = new Mat();
+        Core.multiply(dist, new Scalar(255), distDisplayScaled);
         Mat distDisplay = new Mat();
         distDisplayScaled.convertTo(distDisplay, CvType.CV_8U);
         HighGui.imshow("Distance Transform Image", distDisplay);
@@ -113,14 +114,14 @@ class ImageSegmentation {
         //! [peaks]
         // Threshold to obtain the peaks
         // This will be the markers for the foreground objects
-        Imgproc.threshold(dist, dist, .4, 1., Imgproc.THRESH_BINARY);
+        Imgproc.threshold(dist, dist, 0.4, 1.0, Imgproc.THRESH_BINARY);
 
         // Dilate a bit the dist image
         Mat kernel1 = Mat.ones(3, 3, CvType.CV_8U);
         Imgproc.dilate(dist, dist, kernel1);
         Mat distDisplay2 = new Mat();
         dist.convertTo(distDisplay2, CvType.CV_8U);
-        distDisplay2 = distDisplay2.mul(distDisplay2, 255);
+        Core.multiply(distDisplay2, new Scalar(255), distDisplay2);
         HighGui.imshow("Peaks", distDisplay2);
         //! [peaks]
 
@@ -144,11 +145,14 @@ class ImageSegmentation {
         }
 
         // Draw the background marker
-        Imgproc.circle(markers, new Point(5, 5), 3, new Scalar(255, 255, 255), -1);
+        Mat markersScaled = new Mat();
-        Mat markersScaled = markers.mul(markers, 10000);
+        markers.convertTo(markersScaled, CvType.CV_32F);
+        Core.normalize(markersScaled, markersScaled, 0.0, 255.0, Core.NORM_MINMAX);
+        Imgproc.circle(markersScaled, new Point(5, 5), 3, new Scalar(255, 255, 255), -1);
         Mat markersDisplay = new Mat();
         markersScaled.convertTo(markersDisplay, CvType.CV_8U);
         HighGui.imshow("Markers", markersDisplay);
+        Imgproc.circle(markers, new Point(5, 5), 3, new Scalar(255, 255, 255), -1);
         //! [seeds]
 
         //! [watershed]

samples/java/tutorial_code/features2D/akaze_matching/AKAZEMatchDemo.java

@@ -0,0 +1,163 @@
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+
+import org.opencv.core.Core;
+import org.opencv.core.CvType;
+import org.opencv.core.DMatch;
+import org.opencv.core.KeyPoint;
+import org.opencv.core.Mat;
+import org.opencv.core.MatOfDMatch;
+import org.opencv.core.MatOfKeyPoint;
+import org.opencv.core.Scalar;
+import org.opencv.features2d.AKAZE;
+import org.opencv.features2d.DescriptorMatcher;
+import org.opencv.features2d.Features2d;
+import org.opencv.highgui.HighGui;
+import org.opencv.imgcodecs.Imgcodecs;
+import org.w3c.dom.Document;
+import org.xml.sax.SAXException;
+
+class AKAZEMatch {
+    public void run(String[] args) {
+        //! [load]
+        String filename1 = args.length > 2 ? args[0] : "../data/graf1.png";
+        String filename2 = args.length > 2 ? args[1] : "../data/graf3.png";
+        String filename3 = args.length > 2 ? args[2] : "../data/H1to3p.xml";
+        Mat img1 = Imgcodecs.imread(filename1, Imgcodecs.IMREAD_GRAYSCALE);
+        Mat img2 = Imgcodecs.imread(filename2, Imgcodecs.IMREAD_GRAYSCALE);
+        if (img1.empty() || img2.empty()) {
+            System.err.println("Cannot read images!");
+            System.exit(0);
+        }
+
+        File file = new File(filename3);
+        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+        DocumentBuilder documentBuilder;
+        Document document;
+        Mat homography = new Mat(3, 3, CvType.CV_64F);
+        double[] homographyData = new double[(int) (homography.total()*homography.channels())];
+        try {
+            documentBuilder = documentBuilderFactory.newDocumentBuilder();
+            document = documentBuilder.parse(file);
+            String homographyStr = document.getElementsByTagName("data").item(0).getTextContent();
+            String[] splited = homographyStr.split("\\s+");
+            int idx = 0;
+            for (String s : splited) {
+                if (!s.isEmpty()) {
+                    homographyData[idx] = Double.parseDouble(s);
+                    idx++;
+                }
+            }
+        } catch (ParserConfigurationException e) {
+            e.printStackTrace();
+            System.exit(0);
+        } catch (SAXException e) {
+            e.printStackTrace();
+            System.exit(0);
+        } catch (IOException e) {
+            e.printStackTrace();
+            System.exit(0);
+        }
+        homography.put(0, 0, homographyData);
+        //! [load]
+
+        //! [AKAZE]
+        AKAZE akaze = AKAZE.create();
+        MatOfKeyPoint kpts1 = new MatOfKeyPoint(), kpts2 = new MatOfKeyPoint();
+        Mat desc1 = new Mat(), desc2 = new Mat();
+        akaze.detectAndCompute(img1, new Mat(), kpts1, desc1);
+        akaze.detectAndCompute(img2, new Mat(), kpts2, desc2);
+        //! [AKAZE]
+
+        //! [2-nn matching]
+        DescriptorMatcher matcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);
+        List<MatOfDMatch> knnMatches = new ArrayList<>();
+        matcher.knnMatch(desc1, desc2, knnMatches, 2);
+        //! [2-nn matching]
+
+        //! [ratio test filtering]
+        float ratioThreshold = 0.8f; // Nearest neighbor matching ratio
+        List<KeyPoint> listOfMatched1 = new ArrayList<>();
+        List<KeyPoint> listOfMatched2 = new ArrayList<>();
+        List<KeyPoint> listOfKeypoints1 = kpts1.toList();
+        List<KeyPoint> listOfKeypoints2 = kpts2.toList();
+        for (int i = 0; i < knnMatches.size(); i++) {
+            DMatch[] matches = knnMatches.get(i).toArray();
+            float dist1 = matches[0].distance;
+            float dist2 = matches[1].distance;
+            if (dist1 < ratioThreshold * dist2) {
+                listOfMatched1.add(listOfKeypoints1.get(matches[0].queryIdx));
+                listOfMatched2.add(listOfKeypoints2.get(matches[0].trainIdx));
+            }
+        }
+        //! [ratio test filtering]
+
+        //! [homography check]
+        double inlierThreshold = 2.5; // Distance threshold to identify inliers with homography check
+        List<KeyPoint> listOfInliers1 = new ArrayList<>();
+        List<KeyPoint> listOfInliers2 = new ArrayList<>();
+        List<DMatch> listOfGoodMatches = new ArrayList<>();
+        for (int i = 0; i < listOfMatched1.size(); i++) {
+            Mat col = new Mat(3, 1, CvType.CV_64F);
+            double[] colData = new double[(int) (col.total() * col.channels())];
+            colData[0] = listOfMatched1.get(i).pt.x;
+            colData[1] = listOfMatched1.get(i).pt.y;
+            colData[2] = 1.0;
+            col.put(0, 0, colData);
+
+            Mat colRes = new Mat();
+            Core.gemm(homography, col, 1.0, new Mat(), 0.0, colRes);
+            colRes.get(0, 0, colData);
+            Core.multiply(colRes, new Scalar(1.0 / colData[2]), col);
+            col.get(0, 0, colData);
+
+            double dist = Math.sqrt(Math.pow(colData[0] - listOfMatched2.get(i).pt.x, 2) +
+                    Math.pow(colData[1] - listOfMatched2.get(i).pt.y, 2));
+
+            if (dist < inlierThreshold) {
+                listOfGoodMatches.add(new DMatch(listOfInliers1.size(), listOfInliers2.size(), 0));
+                listOfInliers1.add(listOfMatched1.get(i));
+                listOfInliers2.add(listOfMatched2.get(i));
+            }
+        }
+        //! [homography check]
+
+        //! [draw final matches]
+        Mat res = new Mat();
+        MatOfKeyPoint inliers1 = new MatOfKeyPoint(listOfInliers1.toArray(new KeyPoint[listOfInliers1.size()]));
+        MatOfKeyPoint inliers2 = new MatOfKeyPoint(listOfInliers2.toArray(new KeyPoint[listOfInliers2.size()]));
+        MatOfDMatch goodMatches = new MatOfDMatch(listOfGoodMatches.toArray(new DMatch[listOfGoodMatches.size()]));
+        Features2d.drawMatches(img1, inliers1, img2, inliers2, goodMatches, res);
+        Imgcodecs.imwrite("akaze_result.png", res);
+
+        double inlierRatio = listOfInliers1.size() / (double) listOfMatched1.size();
+        System.out.println("A-KAZE Matching Results");
+        System.out.println("*******************************");
+        System.out.println("# Keypoints 1:                        \t" + listOfKeypoints1.size());
+        System.out.println("# Keypoints 2:                        \t" + listOfKeypoints2.size());
+        System.out.println("# Matches:                            \t" + listOfMatched1.size());
+        System.out.println("# Inliers:                            \t" + listOfInliers1.size());
+        System.out.println("# Inliers Ratio:                      \t" + inlierRatio);
+
+        HighGui.imshow("result", res);
+        HighGui.waitKey();
+        //! [draw final matches]
+
+        System.exit(0);
+    }
+}
+
+public class AKAZEMatchDemo {
+    public static void main(String[] args) {
+        // Load the native OpenCV library
+        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
+
+        new AKAZEMatch().run(args);
+    }
+}

samples/java/tutorial_code/features2D/feature_flann_matcher/SURFFLANNMatchingDemo.java

@@ -42,12 +42,12 @@ class SURFFLANNMatching {
         matcher.knnMatch(descriptors1, descriptors2, knnMatches, 2);
 
         //-- Filter matches using the Lowe's ratio test
-        float ratio_thresh = 0.7f;
+        float ratioThresh = 0.7f;
         List<DMatch> listOfGoodMatches = new ArrayList<>();
         for (int i = 0; i < knnMatches.size(); i++) {
             if (knnMatches.get(i).rows() > 1) {
                 DMatch[] matches = knnMatches.get(i).toArray();
-                if (matches[0].distance / matches[1].distance <= ratio_thresh) {
+                if (matches[0].distance < ratioThresh * matches[1].distance) {
                     listOfGoodMatches.add(matches[0]);
                 }
             }

samples/java/tutorial_code/features2D/feature_homography/SURFFLANNMatchingHomographyDemo.java

@@ -48,12 +48,12 @@ class SURFFLANNMatchingHomography {
         matcher.knnMatch(descriptorsObject, descriptorsScene, knnMatches, 2);
 
         //-- Filter matches using the Lowe's ratio test
-        float ratio_thresh = 0.75f;
+        float ratioThresh = 0.75f;
         List<DMatch> listOfGoodMatches = new ArrayList<>();
         for (int i = 0; i < knnMatches.size(); i++) {
             if (knnMatches.get(i).rows() > 1) {
                 DMatch[] matches = knnMatches.get(i).toArray();
-                if (matches[0].distance / matches[1].distance <= ratio_thresh) {
+                if (matches[0].distance < ratioThresh * matches[1].distance) {
                     listOfGoodMatches.add(matches[0]);
                 }
             }

samples/java/tutorial_code/photo/hdr_imaging/HDRImagingDemo.java

@@ -7,6 +7,7 @@ import java.util.List;
 import org.opencv.core.Core;
 import org.opencv.core.CvType;
 import org.opencv.core.Mat;
+import org.opencv.core.Scalar;
 import org.opencv.imgcodecs.Imgcodecs;
 import org.opencv.photo.CalibrateDebevec;
 import org.opencv.photo.MergeDebevec;
@@ -70,7 +71,7 @@ class HDRImaging {
 
         //! [Tonemap HDR image]
         Mat ldr = new Mat();
-        TonemapDurand tonemap = Photo.createTonemapDurand();
+        TonemapDurand tonemap = Photo.createTonemapDurand(2.2f, 4.0f, 1.0f, 2.0f, 2.0f);
         tonemap.process(hdr, ldr);
         //! [Tonemap HDR image]
 
@@ -81,8 +82,8 @@ class HDRImaging {
         //! [Perform exposure fusion]
 
         //! [Write results]
-        fusion = fusion.mul(fusion, 255);
+        Core.multiply(fusion, new Scalar(255,255,255), fusion);
-        ldr = ldr.mul(ldr, 255);
+        Core.multiply(ldr, new Scalar(255,255,255), ldr);
         Imgcodecs.imwrite("fusion.png", fusion);
         Imgcodecs.imwrite("ldr.png", ldr);
         Imgcodecs.imwrite("hdr.hdr", hdr);

samples/python/tutorial_code/features2D/akaze_matching/AKAZE_match.py

@@ -0,0 +1,81 @@
+from __future__ import print_function
+import cv2 as cv
+import numpy as np
+import argparse
+from math import sqrt
+
+## [load]
+parser = argparse.ArgumentParser(description='Code for AKAZE local features matching tutorial.')
+parser.add_argument('--input1', help='Path to input image 1.', default='../data/graf1.png')
+parser.add_argument('--input2', help='Path to input image 2.', default='../data/graf3.png')
+parser.add_argument('--homography', help='Path to the homography matrix.', default='../data/H1to3p.xml')
+args = parser.parse_args()
+
+img1 = cv.imread(args.input1, cv.IMREAD_GRAYSCALE)
+img2 = cv.imread(args.input2, cv.IMREAD_GRAYSCALE)
+if img1 is None or img2 is None:
+    print('Could not open or find the images!')
+    exit(0)
+
+fs = cv.FileStorage(args.homography, cv.FILE_STORAGE_READ)
+homography = fs.getFirstTopLevelNode().mat()
+## [load]
+
+## [AKAZE]
+akaze = cv.AKAZE_create()
+kpts1, desc1 = akaze.detectAndCompute(img1, None)
+kpts2, desc2 = akaze.detectAndCompute(img2, None)
+## [AKAZE]
+
+## [2-nn matching]
+matcher = cv.DescriptorMatcher_create(cv.DescriptorMatcher_BRUTEFORCE_HAMMING)
+nn_matches = matcher.knnMatch(desc1, desc2, 2)
+## [2-nn matching]
+
+## [ratio test filtering]
+matched1 = []
+matched2 = []
+nn_match_ratio = 0.8 # Nearest neighbor matching ratio
+for m, n in nn_matches:
+    if m.distance < nn_match_ratio * n.distance:
+        matched1.append(kpts1[m.queryIdx])
+        matched2.append(kpts2[m.trainIdx])
+## [ratio test filtering]
+
+## [homography check]
+inliers1 = []
+inliers2 = []
+good_matches = []
+inlier_threshold = 2.5 # Distance threshold to identify inliers with homography check
+for i, m in enumerate(matched1):
+    col = np.ones((3,1), dtype=np.float64)
+    col[0:2,0] = m.pt
+
+    col = np.dot(homography, col)
+    col /= col[2,0]
+    dist = sqrt(pow(col[0,0] - matched2[i].pt[0], 2) +\
+                pow(col[1,0] - matched2[i].pt[1], 2))
+
+    if dist < inlier_threshold:
+        good_matches.append(cv.DMatch(len(inliers1), len(inliers2), 0))
+        inliers1.append(matched1[i])
+        inliers2.append(matched2[i])
+## [homography check]
+
+## [draw final matches]
+res = np.empty((max(img1.shape[0], img2.shape[0]), img1.shape[1]+img2.shape[1], 3), dtype=np.uint8)
+cv.drawMatches(img1, inliers1, img2, inliers2, good_matches, res)
+cv.imwrite("akaze_result.png", res)
+
+inlier_ratio = len(inliers1) / float(len(matched1))
+print('A-KAZE Matching Results')
+print('*******************************')
+print('# Keypoints 1:                        \t', len(kpts1))
+print('# Keypoints 2:                        \t', len(kpts2))
+print('# Matches:                            \t', len(matched1))
+print('# Inliers:                            \t', len(inliers1))
+print('# Inliers Ratio:                      \t', inlier_ratio)
+
+cv.imshow('result', res)
+cv.waitKey()
+## [draw final matches]

samples/python/tutorial_code/features2D/feature_flann_matcher/SURF_FLANN_matching_Demo.py

@@ -29,7 +29,7 @@ knn_matches = matcher.knnMatch(descriptors1, descriptors2, 2)
 ratio_thresh = 0.7
 good_matches = []
 for m,n in knn_matches:
-    if m.distance / n.distance <= ratio_thresh:
+    if m.distance < ratio_thresh * n.distance:
         good_matches.append(m)
 
 #-- Draw matches

samples/python/tutorial_code/features2D/feature_homography/SURF_FLANN_matching_homography_Demo.py

@@ -29,7 +29,7 @@ knn_matches = matcher.knnMatch(descriptors_obj, descriptors_scene, 2)
 ratio_thresh = 0.75
 good_matches = []
 for m,n in knn_matches:
-    if m.distance / n.distance <= ratio_thresh:
+    if m.distance < ratio_thresh * n.distance:
         good_matches.append(m)
 
 #-- Draw matches