sift implementation matlab

I would like to know the answer to the following question regarding SIFT if anyone knows.

Before I start, I refer you to the implementation of David Lowe's paper through this link:

http://www.cs.ubc.ca/~lowe/keypoints/

T开发者_运维技巧he function declaration looks like this:

[image, descriptors, locs] = sift(image1);

I am not sure about the output parameter locs. Does it return the location of descriptor as the vector [x y scale orientation]?

If it gives the location, then x and y must be a whole numbers, but it gives fractional values.

SIFT uses subpixel accuracy when locating the keypoint. This can be seen in Section 4 Lowe's 2004 SIFT paper.