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#include "mediapipe/framework/calculator_framework.h"
#include "mediapipe/framework/formats/detection.pb.h"
#include "tensorflow/lite/interpreter.h"
namespace mediapipe {
class BlazeFacePostprocessorCalculator : public CalculatorBase {
public:
static absl::Status GetContract(CalculatorContract* cc);
absl::Status Open(CalculatorContext* cc) override;
absl::Status Process(CalculatorContext* cc) override;
private:
std::vector<std::pair<float, float>> GenerateAnchors();
std::vector<float> DecodeBox(
const float* box_data,
const std::pair<float, float>& anchor);
std::vector<std::pair<float, float>> DecodeKeypoints(
const float* keypoint_data,
const std::pair<float, float>& anchor,
const std::vector<float>& box);
std::vector<int> NonMaxSuppression(
const std::vector<std::vector<float>>& boxes,
const std::vector<float>& scores,
float nms_threshold);
float score_threshold_ = 0.5f;
float min_suppression_threshold_ = 0.3f;
int num_keypoints_ = 6;
int num_anchors_ = 896;
std::vector<std::pair<float, float>> anchors_;
};
absl::Status BlazeFacePostprocessorCalculator::Open(CalculatorContext* cc) {
const auto& options = cc->Options<BlazeFaceOptions>();
score_threshold_ = options.score_threshold();
min_suppression_threshold_ = options.min_suppression_threshold();
num_keypoints_ = options.num_keypoints();
anchors_ = GenerateAnchors();
return absl::OkStatus();
}
absl::Status BlazeFacePostprocessorCalculator::Process(CalculatorContext* cc) {
if (cc->Inputs().Tag("TENSORS").IsEmpty()) {
return absl::OkStatus();
}
const auto& tensors = cc->Inputs().Tag("TENSORS").Get<std::vector<TfLiteTensor>>();
const float* box_data = tensors[0].data.f;
const float* score_data = tensors[1].data.f;
const float* keypoint_data = tensors[2].data.f;
std::vector<std::vector<float>> all_boxes;
std::vector<float> all_scores;
for (int i = 0; i < num_anchors_; ++i) {
float score = score_data[i];
if (score < score_threshold_) {
continue;
}
auto box = DecodeBox(box_data + i * 16, anchors_[i]);
all_boxes.push_back(box);
all_scores.push_back(score);
}
auto keep_indices = NonMaxSuppression(
all_boxes, all_scores, min_suppression_threshold_);
auto detections = absl::make_unique<std::vector<Detection>>();
for (int idx : keep_indices) {
Detection detection;
auto* bbox = detection.mutable_location_data()->mutable_relative_bounding_box();
bbox->set_xmin(all_boxes[idx][0]);
bbox->set_ymin(all_boxes[idx][1]);
bbox->set_width(all_boxes[idx][2] - all_boxes[idx][0]);
bbox->set_height(all_boxes[idx][3] - all_boxes[idx][1]);
detection.set_score(all_scores[idx]);
detection.set_label_id(0);
auto keypoints = DecodeKeypoints(
keypoint_data + idx * num_keypoints_ * 2,
anchors_[idx],
all_boxes[idx]);
for (const auto& kp : keypoints) {
auto* keypoint = detection.mutable_location_data()->add_relative_keypoints();
keypoint->set_x(kp.first);
keypoint->set_y(kp.second);
}
detections->push_back(detection);
}
cc->Outputs().Tag("DETECTIONS").Add(detections.release(), cc->InputTimestamp());
return absl::OkStatus();
}
std::vector<float> BlazeFacePostprocessorCalculator::DecodeBox(
const float* box_data,
const std::pair<float, float>& anchor) {
float x_center = box_data[0] / 128.0f + anchor.first;
float y_center = box_data[1] / 128.0f + anchor.second;
float width = box_data[2];
float height = box_data[3];
float xmin = x_center - width / 2.0f;
float ymin = y_center - height / 2.0f;
float xmax = x_center + width / 2.0f;
float ymax = y_center + height / 2.0f;
return {xmin, ymin, xmax, ymax};
}
std::vector<int> BlazeFacePostprocessorCalculator::NonMaxSuppression(
const std::vector<std::vector<float>>& boxes,
const std::vector<float>& scores,
float nms_threshold) {
std::vector<int> indices;
std::vector<bool> suppressed(boxes.size(), false);
std::vector<int> order(scores.size());
std::iota(order.begin(), order.end(), 0);
std::sort(order.begin(), order.end(),
[&scores](int a, int b) { return scores[a] > scores[b]; });
for (int i : order) {
if (suppressed[i]) continue;
indices.push_back(i);
for (int j : order) {
if (suppressed[j]) continue;
float iou = CalculateIoU(boxes[i], boxes[j]);
if (iou > nms_threshold) {
suppressed[j] = true;
}
}
}
return indices;
}
REGISTER_CALCULATOR(BlazeFacePostprocessorCalculator);
}
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