Corner Detection
The Sobel and Scharr first derivative operators are to be used to take
the x and y derivatives of an image. Then a small region of interest (ROI) is to be
defined to detect corners in.
A 2x2 matrix of sums of the 
x
and y
derivatives is created as
follows: Solving 
where λ is a column vector of the eigen values and
I
is the identity
matrix, gives the eigen values. For the 2x2 matrix of the equation above, the solutions
may be written in a closed form: If , >
λ
1
λ
2
t
, where t
is some threshold, then a corner is considered to be found at that location. This can be
very useful for object or shape recognition.