M-File Help: SiftPointFeature View code for SiftPointFeature

SiftPointFeature

SIFT point corner feature object

A subclass of PointFeature for SIFT features.

Methods

plot Plot feature position
plot_scale Plot feature scale
distance Descriptor distance
match Match features
ncc Descriptor similarity
uv Return feature coordinate
display Display value
char Convert value to string

Properties

u horizontal coordinate
v vertical coordinate
strength feature strength
theta feature orientation [rad]
scale feature scale
descriptor feature descriptor (vector)
image_id index of image containing feature

Properties of a vector of SiftCornerFeature objects are returned as a vector. If F is a vector (Nx1) of SiftCornerFeature objects then F.u is a 2xN matrix with each column the corresponding u coordinate.

Notes

References

"Distinctive image features from scale-invariant keypoints", D.Lowe, Int. Journal on Computer Vision, vol.60, pp.91-110, Nov. 2004.

See also

isift, PointFeature, ScalePointFeature, SurfPointFeature


SiftPointFeature.SiftPointFeature

Create a SIFT point feature object

f = SiftPointFeature() is a point feature object with null parameters.

f = PointFeature(u, v) is a point feature object with specified coordinates.

f = PointFeature(u, v, strength) as above but with specified strength.

See also

isift



SiftPointFeature.match

Match SIFT point features

m = F.match(f2, options) is a vector of FeatureMatch objects that describe candidate matches between the two vectors of SIFT features F and f2. Correspondence is based on descriptor similarity.


SiftPointFeature.plot_scale

Plot feature scale

F.plot_scale(options) overlay a marker to indicate feature point position and scale.

F.plot_scale(options, ls) as above but the optional line style arguments ls are passed to plot.

If F is a vector then each element is plotted.

Options

'circle' Indicate scale by a circle (default)
'clock' Indicate scale by circle with one radial line for orientation
'arrow' Indicate scale and orientation by an arrow
'disk' Indicate scale by a translucent disk
'color', C Color of circle or disk (default green)
'alpha', A Transparency of disk, 1=opaque, 0=transparent (default 0.2)

SiftPointFeature.support

Support region of feature

out = F.support(im, w) is an image of the support region of the feature F, extracted from the image im in which the feature appears. The support region is scaled to WxW and rotated so that the feature's orientation axis is upward.

out = F.support(images, w) as above but if the features were extracted from an image sequence images then the feature is extracted from the appropriate image in the same sequence.

[out,T] = F.support(images, w) as above but returns the pose of the feature as a 3x3 homogeneous transform in SE(2) that comprises the feature position and orientation.

F.support(im, w) as above but the support region is displayed.

See also

SiftPointFeature


 

© 1990-2012 Peter Corke.