ImageKeypoints

ImageKeypoints[image]

finds key features in image and returns their coordinates.

ImageKeypoints[image,prop]

gives the specified property prop for each keypoint.

Details and Options

  • ImageKeypoints[image] finds keypoints in image with image dimensions {w,h} and returns their image coordinates as a list of the form {{x1,y1},{x2,y2},}.
  • The following properties can be specified:
  • "Position"image coordinates {x,y} in the range ,
    "PixelPosition"pixel coordinates {x,y} in the range ,
    "Scale"keypoint scale
    "Orientation"orientation angle, given in radians
    "Strength"blob response, given as a positive number
    "Descriptor"keypoint descriptor
    "OrientedDescriptor"keypoint oriented descriptor
    "ContrastSign" if the keypoint is lighter than its surroundings, otherwise
  • ImageKeypoints sorts the results based on the "Strength" property of the keypoints.
  • ImageKeypoints[image,{prop1,prop2,}] returns multiple properties.
  • The feature descriptors returned by ImageKeypoints are numerically robust against translation, rotation, and scale changes.
  • The following options can be specified:
  • KeypointStrength0minimum strength of the keypoints
    MaskingAllregion of interest
    MaxFeaturesAllmaximum number of keypoints
    Method"SURF"type of keypoint to return
  • With a setting MaxFeatures->n, at most n keypoints with largest "Strength" are returned.
  • Possible method settings include:
  • "AGAST"Adaptive and Generic Accelerated Segment Test
    "AKAZE"Accelerated KAZE and binary descriptors
    "BRISK"Binary Robust Invariant Scalable Keypoints
    "FAST"Features from Accelerated Segment Test
    "KAZE"nonlinear scale-space detector and descriptor
    "ORB"FAST detector and Binary Robust Independent Elementary Features (BRIEF) descriptor
    "SURF"Speeded-Up Robust Features
  • When a property is not available with a specified method, the corresponding element in the result is set to Missing["NotAvailable"]. » »

Examples

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Basic Examples  (2)

Find keypoints in an image:

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Highlight keypoints on the image:

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Count the number of points of interest in an image:

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Scope  (11)

Options  (9)

Applications  (5)

Properties & Relations  (7)

See Also

ImageCorrespondingPoints  CornerFilter  ImageCorners  ImageSaliencyFilter  ImageAlign

Introduced in 2010
(8.0)
| Updated in 2017
(11.1)