opencv/modules/dnn/src/nms.inl.hpp
2017-10-25 13:40:56 +03:00

101 lines
3.3 KiB
C++

// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
//
// Copyright (C) 2017, Intel Corporation, all rights reserved.
// Third party copyrights are property of their respective owners.
#ifndef OPENCV_DNN_NMS_INL_HPP
#define OPENCV_DNN_NMS_INL_HPP
#include <opencv2/dnn.hpp>
namespace cv {
namespace dnn {
namespace
{
template <typename T>
static inline bool SortScorePairDescend(const std::pair<float, T>& pair1,
const std::pair<float, T>& pair2)
{
return pair1.first > pair2.first;
}
} // namespace
// Get max scores with corresponding indices.
// scores: a set of scores.
// threshold: only consider scores higher than the threshold.
// top_k: if -1, keep all; otherwise, keep at most top_k.
// score_index_vec: store the sorted (score, index) pair.
inline void GetMaxScoreIndex(const std::vector<float>& scores, const float threshold, const int top_k,
std::vector<std::pair<float, int> >& score_index_vec)
{
CV_DbgAssert(score_index_vec.empty());
// Generate index score pairs.
for (size_t i = 0; i < scores.size(); ++i)
{
if (scores[i] > threshold)
{
score_index_vec.push_back(std::make_pair(scores[i], i));
}
}
// Sort the score pair according to the scores in descending order
std::stable_sort(score_index_vec.begin(), score_index_vec.end(),
SortScorePairDescend<int>);
// Keep top_k scores if needed.
if (top_k > 0 && top_k < (int)score_index_vec.size())
{
score_index_vec.resize(top_k);
}
}
// Do non maximum suppression given bboxes and scores.
// Inspired by Piotr Dollar's NMS implementation in EdgeBox.
// https://goo.gl/jV3JYS
// bboxes: a set of bounding boxes.
// scores: a set of corresponding confidences.
// score_threshold: a threshold used to filter detection results.
// nms_threshold: a threshold used in non maximum suppression.
// top_k: if not > 0, keep at most top_k picked indices.
// indices: the kept indices of bboxes after nms.
template <typename BoxType>
inline void NMSFast_(const std::vector<BoxType>& bboxes,
const std::vector<float>& scores, const float score_threshold,
const float nms_threshold, const float eta, const int top_k,
std::vector<int>& indices, float (*computeOverlap)(const BoxType&, const BoxType&))
{
CV_Assert(bboxes.size() == scores.size());
// Get top_k scores (with corresponding indices).
std::vector<std::pair<float, int> > score_index_vec;
GetMaxScoreIndex(scores, score_threshold, top_k, score_index_vec);
// Do nms.
float adaptive_threshold = nms_threshold;
indices.clear();
for (size_t i = 0; i < score_index_vec.size(); ++i) {
const int idx = score_index_vec[i].second;
bool keep = true;
for (int k = 0; k < (int)indices.size() && keep; ++k) {
const int kept_idx = indices[k];
float overlap = computeOverlap(bboxes[idx], bboxes[kept_idx]);
keep = overlap <= adaptive_threshold;
}
if (keep)
indices.push_back(idx);
if (keep && eta < 1 && adaptive_threshold > 0.5) {
adaptive_threshold *= eta;
}
}
}
}// dnn
}// cv
#endif