efficient fixed-point optical-flow calculation More...

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <string.h>
#include "lucas_kanade.h"

Include dependency graph for lucas_kanade.c:

Functions
struct flow_t *	opticFlowLK (struct image_t new_img, struct image_t old_img, struct point_t points, uint16_t points_cnt, uint16_t half_window_size, uint16_t subpixel_factor, uint8_t max_iterations, uint8_t step_threshold, uint8_t max_points, uint8_t pyramid_level, uint8_t keep_bad_points)

struct flow_t *	opticFlowLK_flat (struct image_t new_img, struct image_t old_img, struct point_t points, uint16_t points_cnt, uint16_t half_window_size, uint16_t subpixel_factor, uint8_t max_iterations, uint8_t step_threshold, uint16_t max_points, uint8_t keep_bad_points)
	Compute the optical flow of several points using the Lucas-Kanade algorithm by Yves Bouguet The initial fixed-point implementation is doen by G. More...

Detailed Description

efficient fixed-point optical-flow calculation

Compute the optical flow of several points using the pyramidal Lucas-Kanade algorithm by Yves Bouguet The initial fixed-point implementation is done by G.

Initial fixed-point C implementation by G. de Croon
Algorithm: Lucas-Kanade by Yves Bouguet

Publication: http://robots.stanford.edu/cs223b04/algo_tracking.pdf

de Croon and is adapted by Freek van Tienen for the implementation in Paparazzi. Pyramids implementation and related development done by Hrvoje Brezak.

Parameters

[in]	*new_img	The newest grayscale image (TODO: fix YUV422 support)
[in]	*old_img	The old grayscale image (TODO: fix YUV422 support)
[in]	*points	Points to start tracking from
[in,out]	points_cnt	The amount of points and it returns the amount of points tracked
[in]	half_window_size	Half the window size (in both x and y direction) to search inside
[in]	subpixel_factor	The subpixel factor which calculations should be based on
[in]	max_iterations	Maximum amount of iterations to find the new point
[in]	step_threshold	The threshold of additional subpixel flow at which the iterations should stop
[in]	max_points	The maximum amount of points to track, we skip x points and then take a point.
[in]	pyramid_level	Level of pyramid used in computation (0 == no pyramids used)
[in]	keep_bad_points	Do not filter out bad points. The error field will be set accordingly.

Returns: The vectors from the original *points in subpixels

Pyramidal implementation of Lucas-Kanade feature tracker.

Uses input images to build pyramid of padded images.

For every pyramid level:

For all points:

(1) determine the subpixel neighborhood in the old image
(2) get the x- and y- gradients
(3) determine the 'G'-matrix [sum(Axx) sum(Axy); sum(Axy) sum(Ayy)], where sum is over the window
(4) iterate over taking steps in the image to minimize the error:
- [a] get the subpixel neighborhood in the new image
- [b] determine the image difference between the two neighborhoods
- [c] calculate the 'b'-vector
- [d] calculate the additional flow step and possibly terminate the iteration
(5) use calculated flow as initial flow estimation for next level of pyramid

Definition in file lucas_kanade.c.

Function Documentation

◆ opticFlowLK()

struct flow_t* opticFlowLK	(	struct image_t *	new_img,
		struct image_t *	old_img,
		struct point_t *	points,
		uint16_t *	points_cnt,
		uint16_t	half_window_size,
		uint16_t	subpixel_factor,
		uint8_t	max_iterations,
		uint8_t	step_threshold,
		uint8_t	max_points,
		uint8_t	pyramid_level,
		uint8_t	keep_bad_points
	)

Definition at line 74 of file lucas_kanade.c.

References flow_t::error, flow_t::flow_x, flow_t::flow_y, image_t::h, image_calculate_g(), image_create(), image_difference(), image_free(), IMAGE_GRADIENT, image_gradients(), IMAGE_GRAYSCALE, image_multiply(), image_subpixel_window(), LARGE_FLOW_ERROR, opticFlowLK_flat(), p, patch_size, flow_t::pos, pyramid_build(), image_t::w, point_t::x, and point_t::y.

Referenced by calc_fast9_lukas_kanade().

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◆ opticFlowLK_flat()

struct flow_t* opticFlowLK_flat	(	struct image_t *	new_img,
		struct image_t *	old_img,
		struct point_t *	points,
		uint16_t *	points_cnt,
		uint16_t	half_window_size,
		uint16_t	subpixel_factor,
		uint8_t	max_iterations,
		uint8_t	step_threshold,
		uint16_t	max_points,
		uint8_t	keep_bad_points
	)

Compute the optical flow of several points using the Lucas-Kanade algorithm by Yves Bouguet The initial fixed-point implementation is doen by G.

de Croon and is adapted by Freek van Tienen for the implementation in Paparazzi.

Parameters

[in]	*new_img	The newest grayscale image (TODO: fix YUV422 support)
[in]	*old_img	The old grayscale image (TODO: fix YUV422 support)
[in]	*points	Points to start tracking from
	[in/out]	points_cnt The amount of points and it returns the amount of points tracked
[in]	half_window_size	Half the window size (in both x and y direction) to search inside
[in]	subpixel_factor	The subpixel factor which calculations should be based on
[in]	max_iteration	Maximum amount of iterations to find the new point
[in]	step_threshold	The threshold at which the iterations should stop
[in]	max_point	The maximum amount of points to track, we skip x points and then take a point.

Returns: The vectors from the original *points in subpixels

Definition at line 275 of file lucas_kanade.c.

References flow_t::error, FALSE, flow_t::flow_x, flow_t::flow_y, image_t::h, image_calculate_g(), image_create(), image_difference(), image_free(), IMAGE_GRADIENT, image_gradients(), IMAGE_GRAYSCALE, image_multiply(), image_subpixel_window(), LARGE_FLOW_ERROR, p, patch_size, flow_t::pos, TRUE, image_t::w, point_t::x, and point_t::y.

Referenced by opticFlowLK().