isift

SIFT feature extractor

sf = isift(im, options) is a vector of SiftPointFeature objects representing scale and rotationally invariant interest points in the image im.

Options

'nfeat', N	set the number of features to return (default Inf)
'suppress', R	set the suppression radius (default 0)
'id', V	set the image_id of all features

The SiftPointFeature object has many properties including:

u	horizontal coordinate
v	vertical coordinate
strength	feature strength
descriptor	feature descriptor (128x1)
sigma	feature scale
theta	feature orientation [rad]
image_id	a value passed as an option to ISIFT

The SiftPointFeature object has many methods including:

See SiftPointFeature and PointFeature classes for more details.

Greyscale images only, double or integer pixel format.
Features are returned in descending strength order.
Wraps a MEX file from www.vlfeat.org
Corners are processed in order from strongest to weakest.
If IM is HxWxN it is considered to be an image sequence and F is a cell array with N elements, each of which is the feature vectors for the corresponding image in the sequence.
The SIFT algorithm is covered by US Patent 6,711,293 (March 23, 2004) held by the Univerity of British Columbia.
ISURF is a functional equivalent.

"Distinctive image features from scale-invariant keypoints", David G. Lowe, International Journal of Computer Vision, 60, 2 (2004), pp. 91-110.