harris

Harris corner detector. More...

Functions
AFAPI features	harris (const array &in, const unsigned max_corners=500, const float min_response=1e5f, const float sigma=1.f, const unsigned block_size=0, const float k_thr=0.04f)
	C++ Interface for Harris corner detector. More...
AFAPI af_err	af_harris (af_features *out, const af_array in, const unsigned max_corners, const float min_response, const float sigma, const unsigned block_size, const float k_thr)
	C Interface for Harris corner detector. More...

Detailed Description

Harris corner detector.

Compute corners using the Harris corner detector approach. For each pixel, a small window is used to calculate the determinant and trace of such a window, from which a response is calculated. Pixels are considered corners if they are local maximas and have a high positive response.

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Function Documentation

af_harris()

AFAPI af_err af_harris	(	af_features *	out,
		const af_array	in,
		const unsigned	max_corners,
		const float	min_response,
		const float	sigma,
		const unsigned	block_size,
		const float	k_thr
	)

C Interface for Harris corner detector.

Parameters

[out]	out	struct containing arrays for x and y coordinates and score (Harris response), while arrays orientation and size are set to 0 and 1, respectively, because Harris does not compute that information
[in]	in	array containing a grayscale image (color images are not supported)
[in]	max_corners	maximum number of corners to keep, only retains those with highest Harris responses
[in]	min_response	minimum response in order for a corner to be retained, only used if max_corners = 0
[in]	sigma	the standard deviation of a circular window (its dimensions will be calculated according to the standard deviation), the covariation matrix will be calculated to a circular neighborhood of this standard deviation (only used when block_size == 0, must be >= 0.5f and <= 5.0f)
[in]	block_size	square window size, the covariation matrix will be calculated to a square neighborhood of this size (must be >= 3 and <= 31)
[in]	k_thr	Harris constant, usually set empirically to 0.04f (must be >= 0.01f)

harris()

AFAPI features harris	(	const array &	in,
		const unsigned	max_corners = 500,
		const float	min_response = 1e5f,
		const float	sigma = 1.f,
		const unsigned	block_size = 0,
		const float	k_thr = 0.04f
	)

C++ Interface for Harris corner detector.

Parameters

[in]	in	array containing a grayscale image (color images are not supported)
[in]	max_corners	maximum number of corners to keep, only retains those with highest Harris responses
[in]	min_response	minimum response in order for a corner to be retained, only used if max_corners = 0
[in]	sigma	the standard deviation of a circular window (its dimensions will be calculated according to the standard deviation), the covariation matrix will be calculated to a circular neighborhood of this standard deviation (only used when block_size == 0, must be >= 0.5f and <= 5.0f)
[in]	block_size	square window size, the covariation matrix will be calculated to a square neighborhood of this size (must be >= 3 and <= 31)
[in]	k_thr	Harris constant, usually set empirically to 0.04f (must be >= 0.01f)

Returns

features object containing arrays for x and y coordinates and score (Harris response), while arrays orientation and size are set to 0 and 1, respectively, because Harris does not compute that information