picodet_mnn.cpp

// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// reference from https://github.com/RangiLyu/nanodet/tree/main/demo_mnn

#include "picodet_mnn.h"

using namespace std;

PicoDet::PicoDet(const std::string &mnn_path,
                 int input_width,
                 int input_length,
                 int num_thread_,
                 float score_threshold_,
                 float nms_threshold_) {
  num_thread = num_thread_;
  in_w = input_width;
  in_h = input_length;
  score_threshold = score_threshold_;
  nms_threshold = nms_threshold_;

  PicoDet_interpreter = std::shared_ptr<MNN::Interpreter>(
      MNN::Interpreter::createFromFile(mnn_path.c_str()));
  MNN::ScheduleConfig config;
  config.numThread = num_thread;
  MNN::BackendConfig backendConfig;
  backendConfig.precision = (MNN::BackendConfig::PrecisionMode)2;
  config.backendConfig = &backendConfig;

  PicoDet_session = PicoDet_interpreter->createSession(config);

  input_tensor = PicoDet_interpreter->getSessionInput(PicoDet_session, nullptr);
}

PicoDet::~PicoDet() {
  PicoDet_interpreter->releaseModel();
  PicoDet_interpreter->releaseSession(PicoDet_session);
}

int PicoDet::detect(cv::Mat &raw_image, std::vector<BoxInfo> &result_list) {
  if (raw_image.empty()) {
    std::cout << "image is empty ,please check!" << std::endl;
    return -1;
  }

  image_h = raw_image.rows;
  image_w = raw_image.cols;
  cv::Mat image;
  cv::resize(raw_image, image, cv::Size(in_w, in_h));

  PicoDet_interpreter->resizeTensor(input_tensor, {1, 3, in_h, in_w});
  PicoDet_interpreter->resizeSession(PicoDet_session);
  std::shared_ptr<MNN::CV::ImageProcess> pretreat(MNN::CV::ImageProcess::create(
      MNN::CV::BGR, MNN::CV::BGR, mean_vals, 3, norm_vals, 3));
  pretreat->convert(image.data, in_w, in_h, image.step[0], input_tensor);

  auto start = chrono::steady_clock::now();

  // run network
  PicoDet_interpreter->runSession(PicoDet_session);

  // get output data
  std::vector<std::vector<BoxInfo>> results;
  results.resize(num_class);

  for (const auto &head_info : heads_info) {
    MNN::Tensor *tensor_scores = PicoDet_interpreter->getSessionOutput(
        PicoDet_session, head_info.cls_layer.c_str());
    MNN::Tensor *tensor_boxes = PicoDet_interpreter->getSessionOutput(
        PicoDet_session, head_info.dis_layer.c_str());

    MNN::Tensor tensor_scores_host(tensor_scores,
                                   tensor_scores->getDimensionType());
    tensor_scores->copyToHostTensor(&tensor_scores_host);

    MNN::Tensor tensor_boxes_host(tensor_boxes,
                                  tensor_boxes->getDimensionType());
    tensor_boxes->copyToHostTensor(&tensor_boxes_host);

    decode_infer(&tensor_scores_host,
                 &tensor_boxes_host,
                 head_info.stride,
                 score_threshold,
                 results);
  }

  auto end = chrono::steady_clock::now();
  chrono::duration<double> elapsed = end - start;
  cout << "inference time:" << elapsed.count() << " s, ";

  for (int i = 0; i < (int)results.size(); i++) {
    nms(results[i], nms_threshold);

    for (auto box : results[i]) {
      box.x1 = box.x1 / in_w * image_w;
      box.x2 = box.x2 / in_w * image_w;
      box.y1 = box.y1 / in_h * image_h;
      box.y2 = box.y2 / in_h * image_h;
      result_list.push_back(box);
    }
  }
  cout << "detect " << result_list.size() << " objects." << std::endl;
  ;

  return 0;
}

void PicoDet::decode_infer(MNN::Tensor *cls_pred,
                           MNN::Tensor *dis_pred,
                           int stride,
                           float threshold,
                           std::vector<std::vector<BoxInfo>> &results) {
  int feature_h = in_h / stride;
  int feature_w = in_w / stride;

  for (int idx = 0; idx < feature_h * feature_w; idx++) {
    const float *scores = cls_pred->host<float>() + (idx * num_class);
    int row = idx / feature_w;
    int col = idx % feature_w;
    float score = 0;
    int cur_label = 0;
    for (int label = 0; label < num_class; label++) {
      if (scores[label] > score) {
        score = scores[label];
        cur_label = label;
      }
    }
    if (score > threshold) {
      const float *bbox_pred =
          dis_pred->host<float>() + (idx * 4 * (reg_max + 1));
      results[cur_label].push_back(
          disPred2Bbox(bbox_pred, cur_label, score, col, row, stride));
    }
  }
}

BoxInfo PicoDet::disPred2Bbox(
    const float *&dfl_det, int label, float score, int x, int y, int stride) {
  float ct_x = (x + 0.5) * stride;
  float ct_y = (y + 0.5) * stride;
  std::vector<float> dis_pred;
  dis_pred.resize(4);
  for (int i = 0; i < 4; i++) {
    float dis = 0;
    float *dis_after_sm = new float[reg_max + 1];
    activation_function_softmax(
        dfl_det + i * (reg_max + 1), dis_after_sm, reg_max + 1);
    for (int j = 0; j < reg_max + 1; j++) {
      dis += j * dis_after_sm[j];
    }
    dis *= stride;
    dis_pred[i] = dis;
    delete[] dis_after_sm;
  }
  float xmin = (std::max)(ct_x - dis_pred[0], .0f);
  float ymin = (std::max)(ct_y - dis_pred[1], .0f);
  float xmax = (std::min)(ct_x + dis_pred[2], (float)in_w);
  float ymax = (std::min)(ct_y + dis_pred[3], (float)in_h);
  return BoxInfo{xmin, ymin, xmax, ymax, score, label};
}

void PicoDet::nms(std::vector<BoxInfo> &input_boxes, float NMS_THRESH) {
  std::sort(input_boxes.begin(), input_boxes.end(), [](BoxInfo a, BoxInfo b) {
    return a.score > b.score;
  });
  std::vector<float> vArea(input_boxes.size());
  for (int i = 0; i < int(input_boxes.size()); ++i) {
    vArea[i] = (input_boxes.at(i).x2 - input_boxes.at(i).x1 + 1) *
               (input_boxes.at(i).y2 - input_boxes.at(i).y1 + 1);
  }
  for (int i = 0; i < int(input_boxes.size()); ++i) {
    for (int j = i + 1; j < int(input_boxes.size());) {
      float xx1 = (std::max)(input_boxes[i].x1, input_boxes[j].x1);
      float yy1 = (std::max)(input_boxes[i].y1, input_boxes[j].y1);
      float xx2 = (std::min)(input_boxes[i].x2, input_boxes[j].x2);
      float yy2 = (std::min)(input_boxes[i].y2, input_boxes[j].y2);
      float w = (std::max)(float(0), xx2 - xx1 + 1);
      float h = (std::max)(float(0), yy2 - yy1 + 1);
      float inter = w * h;
      float ovr = inter / (vArea[i] + vArea[j] - inter);
      if (ovr >= NMS_THRESH) {
        input_boxes.erase(input_boxes.begin() + j);
        vArea.erase(vArea.begin() + j);
      } else {
        j++;
      }
    }
  }
}

string PicoDet::get_label_str(int label) { return labels[label]; }

inline float fast_exp(float x) {
  union {
    uint32_t i;
    float f;
  } v{};
  v.i = (1 << 23) * (1.4426950409 * x + 126.93490512f);
  return v.f;
}

inline float sigmoid(float x) { return 1.0f / (1.0f + fast_exp(-x)); }

template <typename _Tp>
int activation_function_softmax(const _Tp *src, _Tp *dst, int length) {
  const _Tp alpha = *std::max_element(src, src + length);
  _Tp denominator{0};

  for (int i = 0; i < length; ++i) {
    dst[i] = fast_exp(src[i] - alpha);
    denominator += dst[i];
  }

  for (int i = 0; i < length; ++i) {
    dst[i] /= denominator;
  }

  return 0;
}