SDK Calibration Algorithms

class Metavision::BlinkingDotsGridDetectorAlgorithm

Class that detects a grid of blinking dots with specific frequencies, for example the Prophesee calibration shield.

Public Types

using OutputCb = std::function<void(timestamp, cv::Mat&, std::vector<cv::Point2f>&)>

Type for callback.

Public Functions

BlinkingDotsGridDetectorAlgorithm(int sensor_width, int sensor_height, const BlinkingDotsGridDetectorAlgorithmConfig &config)

Constructor.

Parameters

~BlinkingDotsGridDetectorAlgorithm()

Destructor.

template<typename InputIt>
void process_events(InputIt it_begin, InputIt it_end)

Detects a grid of blinking dots from input events. Calls the callback function according to the defined processing step.

Template Parameters

  • InputIt: Input event type. Works for events defining the fields: x, y, p (polarity), t (timestamp).

Parameters

  • it_begin: Iterator to first input event.

  • it_end: Iterator to past the last input event.

void set_output_callback(const OutputCb &output_cb)

Sets a callback to get the detection results. The callback provides:

  • Timestamp of grid detection.

  • Image showing the location of the events used to detect the grid.

  • std::vector with the points in the grid (empty if the grid was not correctly detected).

    Note

    The generated image and the vector will be passed to the callback as non constant references. The user is free to copy or swap them.

    Parameters

    • output_cb: Function to be set as callback.

class Metavision::BlinkingFrameGeneratorAlgorithm

Class that generates a frame from blinking events.

It accumulates events and keeps pixels which were activated with both polarities during the accumulating period, if enough of them are found. Outputs a binary frame representing blinking pixels (0 or 255).

Public Types

using OutputCb = std::function<void(timestamp, cv::Mat&)>

Type for callbacks called after each asynchronous process.

Public Functions

BlinkingFrameGeneratorAlgorithm(int sensor_width, int sensor_height, const BlinkingFrameGeneratorAlgorithmConfig &config)

Constructor.

Parameters

  • sensor_width: Sensor’s width

  • sensor_height: Sensor’s height

  • config: Blinking detector configuration

template<typename InputIt>
void process_events(InputIt it_begin, InputIt it_last)

Processes a buffer of events.

Template Parameters

  • InputIt: Input event type

Parameters

  • it_begin: Iterator to first input event

  • it_last: Iterator to past the last input event

void set_output_callback(const OutputCb &output_cb)

Sets a callback to get the mask.

Note

The generated image will be passed to the callback as a non constant reference, meaning that the user is free to copy it or swap it. In case of a swap with a non initialized image, it will be automatically initialized

class Metavision::DftHighFreqScorerAlgorithm

Class that computes and returns the Discrete Fourier Transform (DFT) of an image in addition to a score depending on the proportion of high frequencies.

Public Functions

DftHighFreqScorerAlgorithm(int width, int height, const DftHighFreqScorerAlgorithmConfig &dft_config)

Constructor.

Parameters

  • width: Sensor’s width (in pixels)

  • height: Sensor’s height (in pixels)

  • dft_config: Discrete Fourier Transform configuration file

bool process_frame(const timestamp ts, const cv::Mat &input_frame, float &output_score)

Computes the DFT and a high frequency score.

Parameters

  • ts: Timestamp

  • input_frame: Binary frame of accumulated blinking events (Either 0 or 1)

  • output_score: Ratio of the average DFT magnitude of high frequencies to the one for all frequencies

struct Metavision::PinholeMonoCalibratorSettings

Settings used to specify the calibration mode and its stopping criterion.

Public Functions

PinholeMonoCalibratorSettings(bool use_fisheye_lens = false, bool enable_tangential_estimation = false)

Constructor.

Parameters

  • use_fisheye_lens: Use fisheye lens in case of strong radial distortions

  • enable_tangential_estimation: By default, the tangential parameters and the third radial parameter are not estimated

Public Members

size_t delete_n_best_errors_ = 5

Number of frames with the highest error to remove.

size_t max_pts_to_delete_ = 20

Maximum number of frames to delete per estimation.

size_t min_frames_to_calibrate_ = 5

Minimum number of frames to perform calibration.

timestamp t_interval_us_ = 2e6

Minimal time interval between addition of two points (here, 2s by default)

double max_reproj_error_tolerated_ = 0.2

If the avg reprojection error is below this threshold, do not remove any more points

int cv_calibration_flags_

OpenCV flags used to configure the camera calibration. By default the tangential parameters and the third radial parameter are not estimated.

int cv_calibration_flags_fish_eye_

Flags used for cv::fisheye::calibrate:

bool use_fisheye_lens_

In case of strong radial distortions.

struct Metavision::PinholeMonoCalibratorPattern

Structure representing the geometry of the rigid 3D pattern used for calibration.

Public Functions

PinholeMonoCalibratorPattern(int n_cols, int n_rows, float dist_between_rows, float dist_between_cols)

Constructor using the physical size of cells.

Parameters

  • n_cols: Number of columns in the pattern (width)

  • n_rows: Number of rows of the pattern (height)

  • dist_between_rows: Distance between two consecutive rows of the pattern

  • dist_between_cols: Distance between two consecutive columns of the pattern

PinholeMonoCalibratorPattern(int n_cols, int n_rows, const std::vector<double> &coordinates_3d)

Constructor using a flattened vector of 3D coordinates.

Parameters

  • n_cols: Number of columns in the pattern (width)

  • n_rows: Number of rows of the pattern (height)

  • coordinates_3d: 3D positions of each point of the pattern, should be n_cols * n_rows * 3 size

PinholeMonoCalibratorPattern(int n_cols, int n_rows, const std::vector<cv::Point3f> &pts_3d)

Constructor using a vector of 3D points.

Parameters

  • n_cols: Number of columns in the pattern (width)

  • n_rows: Number of rows of the pattern (height)

  • pts_3d: 3D points of the pattern, should be n_cols * n_rows size

Public Members

int n_cols_

Pattern’s width.

int n_rows_

Pattern’s height.

int n_pts_

Nbr of points in pattern.

std::vector<cv::Point3f> base_3D_points_

3D positions of each point of the pattern

class Metavision::PinholeMonoCalibrator

Class that takes the 2D projection of a rigid 3D pattern to calibrate a camera (its intrinsics parameters) using a Pinhole camera model.

Public Functions

PinholeMonoCalibrator(int width, int height, const PinholeMonoCalibratorPattern &pattern, const PinholeMonoCalibratorSettings &settings)

Constructor.

Parameters

  • width: Sensor’s width (in pixels)

  • height: Sensor’s height (in pixels)

  • pattern: Geometry of a rigid 3D pattern

  • settings: Calibration mode and its stopping criterion

bool add_2d_detection(const timestamp ts, const std::vector<cv::Point2f> &img_points)

Adds a 2D detection of the 3D pattern.

Return

true if the detection has actually been added

Parameters

  • ts: Timestamp at which the 3D pattern was detected

  • img_points: 2D observations in the image of the 3D pattern’s keypoints

bool perform_calibration()

Does the calibration using OpenCV.

Return

True if the calibration has been successful

void write_full_calibration(std::string directory)

Writes the estimated camera matrix and the distortion coefficients.

Parameters

  • directory: Directory where to save all calibration files

bool add_multiple_detections(const std::vector<std::vector<cv::Point2f>> &img_points)

Adds already dumped detections.

Return

True if the detections where coherent with what was expected, false otherwise.

Parameters

  • img_points: 2D observations to be added