issue about keypoint localization

[LiUzHiAn]

Hi, @SamL98

I got a little confused about the Line 43 in keypoints.py, it wrote offset = -LA.inv(HD).dot(J). You defined the HD as a 3 by 3 array, and the shape of J is 1 by 3. How that possible to use a dot operation between them?

[SamL98]

The shape of J is actually 3x1 as 1D arrays are treated as column vectors by default. Therefore, performing a dot product between a 3x3 array, or matrix, and a 3x1 vector simply results in a 3x1 vector. To be able to fully understand the code and SIFT in general, linear algebra knowledge is quite important.

Also, as a side note, I do not maintain this repository anymore. I believe this fork: https://github.com/HamidNE/machines-vision-sift-algorithm, is currently maintained.