add SoftNMS implementation

modules/dnn/test/test_nms.cpp

@@ -37,4 +37,41 @@ TEST(NMS, Accuracy)
         ASSERT_EQ(indices[i], ref_indices[i]);
 }
 
+TEST(SoftNMS, Accuracy)
+{
+    //reference results are obtained using TF v2.7 tf.image.non_max_suppression_with_scores
+    std::string dataPath = findDataFile("dnn/soft_nms_reference.yml");
+    FileStorage fs(dataPath, FileStorage::READ);
+
+    std::vector<Rect> bboxes;
+    std::vector<float> scores;
+    std::vector<int> ref_indices;
+    std::vector<float> ref_updated_scores;
+
+    fs["boxes"] >> bboxes;
+    fs["probs"] >> scores;
+    fs["indices"] >> ref_indices;
+    fs["updated_scores"] >> ref_updated_scores;
+
+    std::vector<float> updated_scores;
+    const float score_thresh = .01f;
+    const float nms_thresh = .5f;
+    std::vector<int> indices;
+    const size_t top_k = 0;
+    const float sigma = 1.; // sigma in TF is being multiplied by 2, so 0.5 should be passed there
+    cv::dnn::softNMSBoxes(bboxes, scores, updated_scores, score_thresh, nms_thresh, indices, top_k, sigma);
+
+    ASSERT_EQ(ref_indices.size(), indices.size());
+    for(size_t i = 0; i < indices.size(); i++)
+    {
+        ASSERT_EQ(indices[i], ref_indices[i]);
+    }
+
+    ASSERT_EQ(ref_updated_scores.size(), updated_scores.size());
+    for(size_t i = 0; i < updated_scores.size(); i++)
+    {
+        EXPECT_NEAR(updated_scores[i], ref_updated_scores[i], 1e-7);
+    }
+}
+
 }} // namespace