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#ifndef MEDIAPIPE_CALCULATORS_DETECTION_NMS_CALCULATOR_H_
#define MEDIAPIPE_CALCULATORS_DETECTION_NMS_CALCULATOR_H_
#include "mediapipe/framework/calculator_framework.h"
#include "mediapipe/framework/formats/detection.pb.h"
namespace mediapipe {
class NMSCalculator : public CalculatorBase {
public:
static absl::Status GetContract(CalculatorContract* cc) {
cc->Inputs().Tag("DETECTIONS").Set<std::vector<Detection>>();
cc->Outputs().Tag("DETECTIONS").Set<std::vector<Detection>>();
cc->Options<NMSOptions>();
return absl::OkStatus();
}
absl::Status Open(CalculatorContext* cc) override {
const auto& options = cc->Options<NMSOptions>();
iou_threshold_ = options.iou_threshold();
max_detections_ = options.max_detections();
sort_by_ = options.sort_by();
LOG(INFO) << "NMSCalculator initialized: "
<< "iou_threshold=" << iou_threshold_
<< ", max_detections=" << max_detections_;
return absl::OkStatus();
}
absl::Status Process(CalculatorContext* cc) override {
if (cc->Inputs().Tag("DETECTIONS").IsEmpty()) {
return absl::OkStatus();
}
const auto& detections =
cc->Inputs().Tag("DETECTIONS").Get<std::vector<Detection>>();
if (detections.empty()) {
return absl::OkStatus();
}
std::vector<int> indices(detections.size());
std::iota(indices.begin(), indices.end(), 0);
switch (sort_by_) {
case NMSOptions::SCORE:
std::sort(indices.begin(), indices.end(),
[&detections](int a, int b) {
return detections[a].score() > detections[b].score();
});
break;
case NMSOptions::AREA:
std::sort(indices.begin(), indices.end(),
[&detections](int a, int b) {
float area_a = (detections[a].xmax() - detections[a].xmin()) *
(detections[a].ymax() - detections[a].ymin());
float area_b = (detections[b].xmax() - detections[b].xmin()) *
(detections[b].ymax() - detections[b].ymin());
return area_a > area_b;
});
break;
case NMSOptions::NONE:
break;
}
std::vector<bool> suppressed(detections.size(), false);
std::vector<Detection> result;
for (int idx : indices) {
if (suppressed[idx]) continue;
result.push_back(detections[idx]);
if (result.size() >= max_detections_) {
break;
}
for (int j : indices) {
if (suppressed[j]) continue;
float iou = ComputeIOU(detections[idx], detections[j]);
if (iou > iou_threshold_) {
suppressed[j] = true;
}
}
}
LOG(INFO) << "NMS: " << detections.size() << " → " << result.size();
cc->Outputs().Tag("DETECTIONS").AddPacket(
MakePacket<std::vector<Detection>>(result).At(cc->InputTimestamp()));
return absl::OkStatus();
}
private:
float iou_threshold_ = 0.45f;
int max_detections_ = 100;
NMSOptions::SortBy sort_by_ = NMSOptions::SCORE;
float ComputeIOU(const Detection& a, const Detection& b) {
float x1 = std::max(a.xmin(), b.xmin());
float y1 = std::max(a.ymin(), b.ymin());
float x2 = std::min(a.xmax(), b.xmax());
float y2 = std::min(a.ymax(), b.ymax());
float intersection = std::max(0.0f, x2 - x1) * std::max(0.0f, y2 - y1);
float area_a = (a.xmax() - a.xmin()) * (a.ymax() - a.ymin());
float area_b = (b.xmax() - b.xmin()) * (b.ymax() - b.ymin());
float union_area = area_a + area_b - intersection;
if (union_area == 0) return 0.0f;
return intersection / union_area;
}
float SoftNMS(const std::vector<Detection>& detections,
float iou_threshold,
float sigma = 0.5,
float score_threshold = 0.5) {
std::vector<float> scores;
for (const auto& det : detections) {
scores.push_back(det.score());
}
std::vector<bool> suppressed(detections.size(), false);
std::vector<float> weights = scores;
for (int i = 0; i < detections.size(); ++i) {
if (suppressed[i]) continue;
for (int j = 0; j < detections.size(); ++j) {
if (i == j || suppressed[j]) continue;
float iou = ComputeIOU(detections[i], detections[j]);
if (iou > iou_threshold) {
float weight = exp(-(iou * iou) / sigma);
weights[j] *= weight;
}
}
}
for (int i = 0; i < detections.size(); ++i) {
detections[i].set_score(std::min(detections[i].score(), weights[i]));
}
return 0;
}
};
REGISTER_CALCULATOR(NMSCalculator);
}
#endif
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