fast

FAST feature detector. More...

Functions
AFAPI features	fast (const array &in, const float thr=20.0f, const unsigned arc_length=9, const bool non_max=true, const float feature_ratio=0.05f, const unsigned edge=3)
	C++ Interface for FAST feature detector. More...
AFAPI af_err	af_fast (af_features *out, const af_array in, const float thr, const unsigned arc_length, const bool non_max, const float feature_ratio, const unsigned edge)
	C Interface for FAST feature detector. More...

Detailed Description

FAST feature detector.

A circle of radius 3 pixels, translating into a total of 16 pixels, is checked for sequential segments of pixels much brighter or much darker than the central one. For a pixel p to be considered a feature, there must exist a sequential segment of arc_length pixels in the circle around it such that all are greather than (p + thr) or smaller than (p - thr). After all features in the image are detected, if nonmax is true, the non-maximal suppression is applied, checking all detected features and the features detected in its 8-neighborhood and discard it if its score is non maximal.

---

Function Documentation

af_fast()

AFAPI af_err af_fast	(	af_features *	out,
		const af_array	in,
		const float	thr,
		const unsigned	arc_length,
		const bool	non_max,
		const float	feature_ratio,
		const unsigned	edge
	)

C Interface for FAST feature detector.

Parameters

[out]	out	struct containing arrays for x and y coordinates and score, while array orientation is set to 0 as FAST does not compute orientation, and size is set to 1 as FAST does not compute multiple scales
[in]	in	array containing a grayscale image (color images are not supported)
[in]	thr	FAST threshold for which a pixel of the circle around the central pixel is considered to be greater or smaller
[in]	arc_length	length of arc (or sequential segment) to be tested, must be within range [9-16]
[in]	non_max	performs non-maximal suppression if true
[in]	feature_ratio	maximum ratio of features to detect, the maximum number of features is calculated by feature_ratio * in.elements(). The maximum number of features is not based on the score, instead, features detected after the limit is reached are discarded
[in]	edge	is the length of the edges in the image to be discarded by FAST (minimum is 3, as the radius of the circle)

fast()

AFAPI features fast	(	const array &	in,
		const float	thr = 20.0f,
		const unsigned	arc_length = 9,
		const bool	non_max = true,
		const float	feature_ratio = 0.05f,
		const unsigned	edge = 3
	)

C++ Interface for FAST feature detector.

Parameters

[in]	in	array containing a grayscale image (color images are not supported)
[in]	thr	FAST threshold for which a pixel of the circle around the central pixel is considered to be greater or smaller
[in]	arc_length	length of arc (or sequential segment) to be tested, must be within range [9-16]
[in]	non_max	performs non-maximal suppression if true
[in]	feature_ratio	maximum ratio of features to detect, the maximum number of features is calculated by feature_ratio * in.elements(). The maximum number of features is not based on the score, instead, features detected after the limit is reached are discarded
[in]	edge	is the length of the edges in the image to be discarded by FAST (minimum is 3, as the radius of the circle)

Returns

features object containing arrays for x and y coordinates and score, while array orientation is set to 0 as FAST does not compute orientation, and size is set to 1 as FAST does not compute multiple scales