Question

使用OpenCV-2.4.5-android-sdk，我尝试将两个图像与特征检测（ORB检测器和汉明匹配器）匹配。不幸的是，我在计算描述符时总是得到一个NullPointerException。我究竟做错了什么？

        FeatureDetector detector = FeatureDetector.create("ORB");
        DescriptorExtractor descriptor = DescriptorExtractor.create("ORB");
        BFMatcher matcher = new BFMatcher(Hamming.normType, true);

        KeyPoint keypoints1 = new KeyPoint();
        KeyPoint keypoints2 = new KeyPoint();
        CvMat[] descriptors = new CvMat[2];

        //ORB orb = new ORB();

        //orb.detect(image1, null, keypoints1);
        detector.detect(image1, keypoints1, null);
        descriptor.compute(image1, keypoints1, descriptors[0]);

        detector.detect(image2, keypoints2, null);
        //orb.detect(image2, null, keypoints2);
        descriptor.compute(image2, keypoints2, descriptors[1]);

        // matcher should include 2 different image's descriptors
        DMatch matches = new DMatch();
        matcher.match(descriptors[0], descriptors[1], matches, null);

我想知道，如果我在没有android-ndk的情况下在Android上使用openCV进行功能检测。您是否建议尝试编写和集成本机c ++代码？

更新：重新构建项目的设置后，按照以下http://docs.opencv.org/trunk/doc/tutorials/introduction/android_binary_package/dev_with_OCV_on_Android.html#dev-with-ocv-on-android说明进行操作，代码如下所示：

    FeatureDetector detector = FeatureDetector.create(FeatureDetector.ORB);
    DescriptorExtractor descriptor = DescriptorExtractor.create(DescriptorExtractor.ORB);
    DescriptorMatcher matcher = DescriptorMatcher.create(DescriptorMatcher.BRUTEFORCE_HAMMING);

    MatOfKeyPoint keypoints1 = new MatOfKeyPoint();
    MatOfKeyPoint keypoints2 = new MatOfKeyPoint();
    Mat[] descriptors = new Mat[2];

    //ORB orb = new ORB();
    //orb.detect(image1, null, keypoints1);
    detector.detect(image1, keypoints1, null);
    descriptor.compute(image1, keypoints1, descriptors[0]);

    detector.detect(image2, keypoints2, null);
    //orb.detect(image2, null, keypoints2);
    descriptor.compute(image2, keypoints2, descriptors[1]);

    // matcher should include 2 different image's descriptors
    MatOfDMatch matches = new MatOfDMatch();
    matcher.match(descriptors[0], descriptors[1], matches);

NPE仍然存在。

Answer 1

您似乎错过了将对象分配给descriptors[]数组。

    descriptors[0] = new CvMat();
    descriptors[1] = new CvMat();

Answer 2

分配对象，例如。

Mat descriptortwo = new Mat();

然后从可选的mask参数中删除null参数，如下所示：

detector.detect(image1,keypoints1);

认为它应该做的伎俩:)

OpenCV 2.4.5 android，FeatureDetector，DescriptorExtractor

2 个答案: