ultraface.h

#ifndef UltraFace_hpp
#define UltraFace_hpp

#pragma once

#include <MNN/Interpreter.hpp>

#include <MNN/MNNDefine.h>
#include <MNN/Tensor.hpp>
#include <MNN/ImageProcess.hpp>
#include <opencv2/opencv.hpp>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <memory>
#include <chrono>

#define num_featuremap 4
#define hard_nms 1
#define blending_nms 2 /* mix nms was been proposaled in paper blaze face, aims to minimize the temporal jitter*/
typedef struct FaceInfo {
    float x1;
    float y1;
    float x2;
    float y2;
    float score;

} FaceInfo;

class UltraFace {
public:
    UltraFace(const std::string& mnn_path,
        int input_width, int input_length, int num_thread_ = 4, float score_threshold_ = 0.7, float iou_threshold_ = 0.3,
        int topk_ = -1);

    ~UltraFace();

    int detect(cv::Mat& img, std::vector<FaceInfo>& face_list);

private:
    void generateBBox(std::vector<FaceInfo>& bbox_collection, MNN::Tensor* scores, MNN::Tensor* boxes);

    void nms(std::vector<FaceInfo>& input, std::vector<FaceInfo>& output, int type = blending_nms);

private:

    std::shared_ptr<MNN::Interpreter> ultraface_interpreter;
    MNN::Session* ultraface_session = nullptr;
    MNN::Tensor* input_tensor = nullptr;

    int num_thread;
    int image_w;
    int image_h;

    int in_w;
    int in_h;
    int num_anchors;

    float score_threshold;
    float iou_threshold;


    const float mean_vals[3] = { 127, 127, 127 };
    const float norm_vals[3] = { 1.0 / 128, 1.0 / 128, 1.0 / 128 };

    const float center_variance = 0.1;
    const float size_variance = 0.2;
    const std::vector<std::vector<float>> min_boxes = {
            {10.0f,  16.0f,  24.0f},
            {32.0f,  48.0f},
            {64.0f,  96.0f},
            {128.0f, 192.0f, 256.0f} };
    const std::vector<float> strides = { 8.0, 16.0, 32.0, 64.0 };
    std::vector<std::vector<float>> featuremap_size;
    std::vector<std::vector<float>> shrinkage_size;
    std::vector<int> w_h_list;

    std::vector<std::vector<float>> priors = {};
};

#endif /* UltraFace_hpp */