I'm looking for some basic SIFT implementation in MATLAB. I need to write it from first principles. Also, I'm looking for something which explains whats going on in the program. Vedali's code and David Lowe's code just go over my head.
If you are a Matlab user, you must know this excelent site web : Matlab File Exchange
There, you will find the following project : Feature Points In Image
I think this project will fully answer to all your questions about sift.
It also posible to have a look of the SIFT implementation of the opencv library.
Then, you can find a matlab implementation by the SIFT inventor here : D.LOW SIFT, I assume that you already know this implementation.
To understand SIFT, read this very good paper ASIFT wich explain the ASIFT algorithm. This paper start with a description of SIFT alogirthm.
You can have a look at this implementation by Yan-Tao Zheng, Ming Zhao, Shi-Yong Neo.
Also, I know that Scott Ettinger from Intel research made a Matlab implementation at some point.
来源：https://stackoverflow.com/questions/9211916/sift-implementation-in-matlab-tutorial