Detects keypoints in an image or image set.

keypoints = obj.detect(img)
keypoints = obj.detect(imgs)
[...] = obj.detect(..., 'OptionName',optionValue, ...)

Input

• img Image (first variant).
• imgs Image set (second variant), cell array of images.

Output

• keypoints The detected keypoints. In the first variant, a 1-by-N structure array. In the second variant of the method, keypoints{i} is a set of keypoints detected in imgs{i}. Each keypoint is a struct 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).

Options

• Mask A mask specifying where to look for keypoints (optional). It must be a logical or 8-bit integer matrix with non-zero values in the region of interest. In the second variant, it is a cell-array of masks for each input image, masks{i} is a mask for imgs{i}. Not set by default.