Detects keypoints and computes their descriptors

[keypoints, descriptors] = obj.detectAndCompute_elliptic(img)
[...] = obj.detectAndCompute_elliptic(..., 'OptionName',optionValue, ...)

Input

• img Image, input 8-bit grayscale image.

Output

• keypoints The detected keypoints (elliptic region around an interest point). A 1-by-N structure array with the following fields:
  • pt coordinates of the keypoint [x,y]
  • size diameter of the meaningful keypoint neighborhood
  • angle computed orientation of the keypoint (-1 if not applicable); it's in [0,360) degrees and measured relative to image coordinate system (y-axis is directed downward), i.e in clockwise.
  • response the response by which the most strong keypoints have been selected. Can be used for further sorting or subsampling.
  • octave octave (pyramid layer) from which the keypoint has been extracted.
  • class_id object class (if the keypoints need to be clustered by an object they belong to).
  • axes the lengths of the major and minor ellipse axes [ax1,ax2]
  • si the integration scale at which the parameters were estimated.
  • transf the transformation between image space and local patch space, 2x3 matrix.
• descriptors Computed descriptors.

Options

• Mask optional mask specifying where to look for keypoints. Not set by default.
• Keypoints If passed, then the method will use the provided vector of keypoints instead of detecting them, and the algorithm just computes their descriptors.

Detects keypoints and computes descriptors for their surrounding regions, after warping them into circles.