What does the SIFTPoints properties mean?

What do these properties mean? I tried looking up the documentation but I could not find much.

Thanks!

Answer 1

[Sarthak]

Hi Jessy,

As per my understanding, the SIFTPoints object enables you to pass data between the detectSIFTFeatures and extractFeatures functions. You can also use it to manipulate and plot the data returned by these functions. You can use the object to fill interest points interactively.

The SIFTPoints object itself has multiple properties:

1. Location: This property represents the (x, y) coordinates of the keypoints in the image. It is usually a 2D array of size N-by-2, where N is the number of keypoints and the first column represents the x-coordinates and the second column represents the y-coordinates.
2. Scale: This property represents the scale of the keypoints, which is usually determined by the size of the feature region around the keypoints. It is typically a scalar value or an array of size N-by-1, where N is the number of keypoints.
3. Orientation: This property represents the orientation or direction of the keypoints, which is typically computed based on the local image gradient information around the keypoints. It is usually a scalar value or an array of size N-by-1, where N is the number of keypoints.
4. Octave: This property represents the octave or scale level at which the keypoints were detected, which is used to represent the scale space pyramid used in the SIFT algorithm. It is usually a scalar value or an array of size N-by-1, where N is the number of keypoints.
5. Layer: This property represents the layer or sub-octave level at which the keypoints were detected, which is used to represent the scale space pyramid used in the SIFT algorithm. It is usually a scalar value or an array of size N-by-1, where N is the number of keypoints.
6. Metric: This property represents a metric or score associated with each keypoint, which is often used to represent the strength or quality of the keypoints. It is usually a scalar value or an array of size N-by-1, where N is the number of keypoints.

You can also refer to the following documentation. I hope this helps.

https://www.mathworks.com/help/vision/ref/siftpoints.html