Calculate velocity from optic flow. More...

#include "std.h"
#include "inter_thread_data.h"
#include "lib/vision/image.h"
#include "lib/v4l/v4l2.h"

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Data Structures
struct	opticflow_t

Functions
void	opticflow_calc_init (struct opticflow_t *opticflow)
	Initialize the opticflow calculator. More...

void	opticflow_calc_frame (struct opticflow_t opticflow, struct opticflow_state_t state, struct image_t img, struct opticflow_result_t result)
	Run the optical flow on a new image frame. More...

void	calc_fast9_lukas_kanade (struct opticflow_t opticflow, struct opticflow_state_t state, struct image_t img, struct opticflow_result_t result)
	Run the optical flow with fast9 and lukaskanade on a new image frame. More...

void	calc_edgeflow_tot (struct opticflow_t opticflow, struct opticflow_state_t state, struct image_t img, struct opticflow_result_t result)
	Run the optical flow with EDGEFLOW on a new image frame. More...

void	kalman_filter_opticflow_velocity (float velocity_x, float velocity_y, float acceleration_measurement, float fps, float measurement_noise, float process_noise, bool reinitialize_kalman)
	Filter the velocity with a simple linear kalman filter, together with the accelerometers. More...

Detailed Description

Calculate velocity from optic flow.

Using images from a vertical camera and IMU sensor data.

Definition in file opticflow_calculator.h.

Data Structure Documentation

struct opticflow_t

Definition at line 40 of file opticflow_calculator.h.

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Data Fields
bool	derotation	Derotation switched on or off (depended on the quality of the gyroscope measurement)
float	derotation_correction_factor_x	Correction factor for derotation in x axis, determined from a fit from the gyros and flow rotation. (wrong FOV, camera not in center)
float	derotation_correction_factor_y	Correction factor for derotation in Y axis, determined from a fit from the gyros and flow rotation. (wrong FOV, camera not in center)
bool	fast9_adaptive	Whether the FAST9 threshold should be adaptive.
uint16_t	fast9_min_distance	Minimum distance in pixels between corners.
uint8_t	fast9_num_regions	The number of regions of interest the image is split into.
uint16_t	fast9_padding	Padding used in FAST9 detector.
bool	fast9_region_detect	Decides whether to detect fast9 corners in specific regions of interest or the whole image (only for feature management)
struct point_t *	fast9_ret_corners	Corners.
uint16_t	fast9_rsize	Amount of corners allocated.
uint8_t	fast9_threshold	FAST9 corner detection threshold.
bool	feature_management	Decides whether to keep track corners in memory for the next frame instead of re-detecting every time.
bool	got_first_img	If we got a image to work with.
struct image_t	img_gray	Current gray image frame.
bool	just_switched_method	Boolean to check if methods has been switched (for reinitialization)
bool	kalman_filter	Decide to use Kalman filter to filter velocity with accelerometers.
float	kalman_filter_process_noise	Process noise of the model used in the kalman filter.
uint8_t	max_iterations	The maximum amount of iterations the Lucas Kanade algorithm should do.
uint8_t	max_track_corners	Maximum amount of corners Lucas Kanade should track.
bool	median_filter	Decides to use a median filter on the velocity.
uint8_t	method	Method to use to calculate the optical flow.
struct image_t	prev_img_gray	Previous gray image frame.
struct FloatRates	prev_rates	Gyro Rates from the previous image frame.
struct timeval	prev_timestamp	Timestamp of the previous frame, used for FPS calculation.
uint8_t	pyramid_level	Number of pyramid levels used in Lucas Kanade algorithm (0 == no pyramids used)
uint16_t	resolution_factor	The resolution in EdgeFlow to determine the Divergence.
uint16_t	search_distance	Search distance for blockmatching alg.
uint16_t	subpixel_factor	The amount of subpixels per pixel.
uint8_t	threshold_vec	The threshold in x, y subpixels which the algorithm should stop.
uint16_t	window_size	Window size for the blockmatching algorithm (general value for all methods)

Function Documentation

void calc_edgeflow_tot	(	struct opticflow_t *	opticflow,
		struct opticflow_state_t *	cam_state,
		struct image_t *	img,
		struct opticflow_result_t *	result
	)

Run the optical flow with EDGEFLOW on a new image frame.

Parameters

[in]	*opticflow	The opticalflow structure that keeps track of previous images
[in]	*state	The state of the drone
[in]	*img	The image frame to calculate the optical flow from
[out]	*result	The optical flow result

Definition at line 519 of file opticflow_calculator.c.

Referenced by opticflow_calc_frame().

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void calc_fast9_lukas_kanade	(	struct opticflow_t *	opticflow,
		struct opticflow_state_t *	cam_state,
		struct image_t *	img,
		struct opticflow_result_t *	result
	)

Run the optical flow with fast9 and lukaskanade on a new image frame.

Parameters

[in]	*opticflow	The opticalflow structure that keeps track of previous images
[in]	*state	The state of the drone
[in]	*img	The image frame to calculate the optical flow from
[out]	*result	The optical flow result

Definition at line 256 of file opticflow_calculator.c.

Referenced by opticflow_calc_frame().

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void kalman_filter_opticflow_velocity	(	float *	velocity_x,
		float *	velocity_y,
		float *	acceleration_measurement,
		float	fps,
		float *	measurement_noise,
		float	kalman_process_noise,
		bool	reinitialize_kalman
	)

Filter the velocity with a simple linear kalman filter, together with the accelerometers.

Parameters

[in]	*velocity_x	Velocity in x direction of body fixed coordinates
[in]	*velocity_y	Belocity in y direction of body fixed coordinates
[in]	*acceleration_measurement	Measurements of the accelerometers
[in]	fps	Frames per second
[in]	*measurement_noise	Expected variance of the noise of the measurements
[in]	*measurement_noise	Expected variance of the noise of the model prediction
[in]	reinitialize_kalman	Boolean to reinitialize the kalman filter

Definition at line 772 of file opticflow_calculator.c.

References kalman_filter_linear_2D_float(), and model.

Referenced by opticflow_calc_frame().

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void opticflow_calc_frame	(	struct opticflow_t *	opticflow,
		struct opticflow_state_t *	cam_state,
		struct image_t *	img,
		struct opticflow_result_t *	result
	)

Run the optical flow on a new image frame.

Parameters

[in]	*opticflow	The opticalflow structure that keeps track of previous images
[in]	*state	The state of the drone
[in]	*img	The image frame to calculate the optical flow from
[out]	*result	The optical flow result