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isurf

SURF feature extractor

sf = isurf(im, options) returns a vector of SurfPointFeature objects representing scale and rotationally invariant interest points in the image im.

The SurfPointFeature object has many properties including:

u horizontal coordinate
v vertical coordinate
strength feature strength
descriptor feature descriptor (64x1 or 128x1)
sigma feature scale
theta feature orientation [rad]

Options

'nfeat', N set the number of features to return (default Inf)
'thresh', T set Hessian threshold. Increasing the threshold reduces the number of features computed and reduces computation time.
'octaves', N number of octaves to process (default 5)
'extended' return 128-element descriptor (default 64)
'upright' don't compute rotation invariance
'suppress', R set the suppression radius (default 0). Features are not returned if they are within R [pixels] of an earlier (stronger) feature.

Example

Load the image

im = iread('lena.pgm');

Find the 10 strongest SURF features

sf = isurf(im, 'nfeat', 10);

and overlay them on the original image as blue circles

idisp(im);
sf.plot_scale()

Notes

Reference

"SURF: Speeded Up Robust Features", Herbert Bay, Andreas Ess, Tinne Tuytelaars, Luc Van Gool, Computer Vision and Image Understanding (CVIU), Vol. 110, No. 3, pp. 346--359, 2008

See also

SurfPointFeature, isift, icorner


 

© 1990-2012 Peter Corke.