There are many SIFT blogs either on cnnblog or csdn. I reviewed many. However, in my view, there are not in details. Mainly that they
do not offer a good feeling and real touching to the fundamentals underlying the math.
So I try to present the direct feeling and real touches.
2D feature extracted, satisfy:
1. scale invarient;
2. rotation invarient.
Naive Thinking: Minimal point or Maximum Point, Local;
Now you are given a grey img. Just a Matrix with element value range from 0,1,.., to255.
It is a finite discrete set.
The details looks like this: