c# - 使用KnnMatch返回2张图像之间的相似度

Question

我有来自emgu opencv包装器的以下示例

HomographyMatrix homography = null;
SURFDetector surfCPU = new SURFDetector(500,true);
        VectorOfKeyPoint modelKeyPoints;
        VectorOfKeyPoint observedKeyPoints;
        Matrix<int> indices;

        Matrix<byte> mask;
        int k = 2;
        double uniquenessThreshold = 0.9; //0.8

        //extract features from the object image
        modelKeyPoints = surfCPU.DetectKeyPointsRaw(modelImage, null);
        Matrix<float> modelDescriptors = surfCPU.ComputeDescriptorsRaw(modelImage, null, modelKeyPoints);
        modelImage.Dispose();                     


        // extract features from the observed image
        observedKeyPoints = surfCPU.DetectKeyPointsRaw(observedImage, null);
        Matrix<float> observedDescriptors = surfCPU.ComputeDescriptorsRaw(observedImage, null, observedKeyPoints);
        observedImage.Dispose();
        BruteForceMatcher<float> matcher = new BruteForceMatcher<float>(DistanceType.L2);
        matcher.Add(modelDescriptors);

        indices = new Matrix<int>(observedDescriptors.Rows, k);
        using (Matrix<float> dist = new Matrix<float>(observedDescriptors.Rows, k))
        {
            matcher.KnnMatch(observedDescriptors, indices, dist, k, null);
            mask = new Matrix<byte>(dist.Rows, 1);
            mask.SetValue(255);
            Features2DToolbox.VoteForUniqueness(dist, uniquenessThreshold, mask);
        }
        //...

应用KnnMatch后，如何获取匹配的关键点数量，以及非零像素计数与获取2张图像之间的相似性有什么关系？

Answer 1

指的是opencv doc http://www.opencv.org.cn/opencvdoc/2.3.2/html/modules/features2d/doc/common_interfaces_of_descriptor_matchers.html

void DescriptorMatcher::knnMatch(const Mat＆queryDescriptors，vector>＆match，int k，const vector＆masks = vector()，bool compactResult = false)

匹配项(在您的代码中为dist)–匹配项。对于同一查询描述符，每个matchs [i]是k个或更少的匹配项。
k –每个查询描述符找到的最佳匹配计数，如果查询描述符的总数少于k，则更少。

关于相似性(我不清楚这个问题)，代码使用的是L2距离。

BruteForceMatcher匹配器=新的BruteForceMatcher(DistanceType.L2);