SIFT why it is invariant to affine tranlsation?

1. Is SIFT affine invariant?
2. Why is SIFT scale invariant?
3. How does SIFT extract scale invariant features?
4. Which of the following curve is invariant under an affine transformation?

Is SIFT affine invariant?

These deformations are locally well approximated by affine transforms of the image plane. rotation, the SIFT method succeeds in being fully invariant to four out of the six parameters of an affine transform.

Why is SIFT scale invariant?

This means that it finds the scale of the image which the feature will produce the highest response. Then, the descriptor is calculated in that scale. So when you use a smaller/larger version, it should still find the same scale for the feature.

How does SIFT extract scale invariant features?

SIFT keypoints of objects are first extracted from a set of reference images and stored in a database. An object is recognized in a new image by individually comparing each feature from the new image to this database and finding candidate matching features based on Euclidean distance of their feature vectors.

Which of the following curve is invariant under an affine transformation?

An important property of Bézier curves is that they are invariant under affine maps, which means that the following two procedures yield the same result: (1) first, compute the point bⁿ(t) and then apply an affine map to it; (2) first, apply an affine map to the control polygon and then evaluate the mapped polygon at ...