Function LoadSiftFeaturesFromTextFile

src/colmap/feature/sift.cc:1575–1621

}

void LoadSiftFeaturesFromTextFile(const std::filesystem::path& path,
                                  FeatureKeypoints* keypoints,
                                  FeatureDescriptors* descriptors) {
  THROW_CHECK_NOTNULL(keypoints);
  THROW_CHECK_NOTNULL(descriptors);

  std::ifstream file(path);
  THROW_CHECK_FILE_OPEN(file, path);
  file.imbue(std::locale::classic());

  std::string line;

  std::getline(file, line);
  std::istringstream header_line_stream(line);
  header_line_stream.imbue(std::locale::classic());

  point2D_t num_features;
  size_t dim;
  THROW_CHECK(header_line_stream >> num_features >> dim);

  THROW_CHECK_EQ(dim, kSiftDescriptorDim)
      << "SIFT features must have kSiftDescriptorDim dimensions";

  keypoints->resize(num_features);
  descriptors->data.resize(num_features, dim);
  descriptors->type = FeatureExtractorType::SIFT;

  for (size_t i = 0; i < num_features; ++i) {
    std::getline(file, line);
    std::istringstream feature_line_stream(line);
    feature_line_stream.imbue(std::locale::classic());

    float x, y, scale, orientation;
    THROW_CHECK(feature_line_stream >> x >> y >> scale >> orientation);

    (*keypoints)[i] = FeatureKeypoint(x, y, scale, orientation);

    // Descriptor
    for (size_t j = 0; j < dim; ++j) {
      float value;
      THROW_CHECK(feature_line_stream >> value);
      THROW_CHECK_GE(value, 0);
      THROW_CHECK_LE(value, 255);
      descriptors->data(i, j) = TruncateCast<float, uint8_t>(value);
    }
  }
}

}  //  namespace colmap