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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）进行匹配。不幸的是，我在计算描述符时总是得到 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 执行特征检测进行更改。您是否建议尝试编写和集成本机 C++ 代码？

更新：重组项目的设置后，如下：http ://docs.opencv.org/trunk/doc/tutorials/introduction/android_binary_package/dev_with_OCV_on_Android.html#dev-with-ocv-on-android描述，代码看起来像这个：

    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 仍然发生。

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3 回答 3

1

您似乎错过了将对象分配给descriptors[]数组。

    descriptors[0] = new CvMat();
    descriptors[1] = new CvMat();
于 2014-03-25T22:50:09.323 回答
0

分配对象，例如。 

Mat descriptortwo = new Mat();

然后从可选的掩码参数中删除 null 参数，如下所示： 

detector.detect(image1,keypoints1);

认为它应该可以解决问题:)

于 2015-03-15T09:50:23.277 回答
0

尝试初始化 thouse 矩阵。而不是说Mat[] descriptors = new Mat[2];

尝试： Mat descriptors1= new Mat(); Mat descriptors2= new Mat();

于 2015-08-24T10:49:07.527 回答