orb

ORB Feature descriptor. More...

Functions
AFAPI void	orb (features &feat, array &desc, const array &image, const float fast_thr=20.f, const unsigned max_feat=400, const float scl_fctr=1.5f, const unsigned levels=4, const bool blur_img=false)
	C++ Interface for ORB feature descriptor. More...
AFAPI af_err	af_orb (af_features *feat, af_array *desc, const af_array in, const float fast_thr, const unsigned max_feat, const float scl_fctr, const unsigned levels, const bool blur_img)
	C Interface for ORB feature descriptor. More...

Detailed Description

ORB Feature descriptor.

Extract ORB descriptors from FAST features that hold higher Harris responses. FAST does not compute orientation, thus, orientation of features is calculated using the intensity centroid. As FAST is also not multi-scale enabled, a multi-scale pyramid is calculated by downsampling the input image multiple times followed by FAST feature detection on each scale.

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Function Documentation

af_orb()

AFAPI af_err af_orb	(	af_features *	feat,
		af_array *	desc,
		const af_array	in,
		const float	fast_thr,
		const unsigned	max_feat,
		const float	scl_fctr,
		const unsigned	levels,
		const bool	blur_img
	)

C Interface for ORB feature descriptor.

Parameters

[out]	feat	af_features struct composed of arrays for x and y coordinates, score, orientation and size of selected features
[out]	desc	Nx8 array containing extracted descriptors, where N is the number of selected features
[in]	in	array containing a grayscale image (color images are not supported)
[in]	fast_thr	FAST threshold for which a pixel of the circle around the central pixel is considered to be brighter or darker
[in]	max_feat	maximum number of features to hold (will only keep the max_feat features with higher Harris responses)
[in]	scl_fctr	factor to downsample the input image, meaning that each level will hold prior level dimensions divided by scl_fctr
[in]	levels	number of levels to be computed for the image pyramid
[in]	blur_img	blur image with a Gaussian filter with sigma=2 before computing descriptors to increase robustness against noise if true

orb()

AFAPI void orb	(	features &	feat,
		array &	desc,
		const array &	image,
		const float	fast_thr = 20.f,
		const unsigned	max_feat = 400,
		const float	scl_fctr = 1.5f,
		const unsigned	levels = 4,
		const bool	blur_img = false
	)

C++ Interface for ORB feature descriptor.

Parameters

[out]	feat	features object composed of arrays for x and y coordinates, score, orientation and size of selected features
[out]	desc	Nx8 array containing extracted descriptors, where N is the number of selected features
[in]	image	array containing a grayscale image (color images are not supported)
[in]	fast_thr	FAST threshold for which a pixel of the circle around the central pixel is considered to be brighter or darker
[in]	max_feat	maximum number of features to hold (will only keep the max_feat features with higher Harris responses)
[in]	scl_fctr	factor to downsample the input image, meaning that each level will hold prior level dimensions divided by scl_fctr
[in]	levels	number of levels to be computed for the image pyramid
[in]	blur_img	blur image with a Gaussian filter with sigma=2 before computing descriptors to increase robustness against noise if true