# Homework Help: Perona-Malik Diffusion Equation

1. Dec 7, 2011

### pearpan

1. The problem statement, all variables and given/known data
Implement the non-linear de-noising algorithm of Perona-Malik. Consider a noisy image, u, with pixel values referenced by u(i,j). Non-linear de-noising can be achieved by solving the following non-linear diffusion equation:

∇ · (g(∇u)∇u) = 0

with g(s) = ((K^2)v) / ((K^2) + |s|)

where v and K are parameters controlling the amount of diffusion.

Write down the linear system associated with this discretization.

My question is how do I do this? How can I take the gradient of a pixel? It isn't a function so how can I do partial derivative with respect to x and y to it?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Dec 7, 2011

### pearpan

I have no idea what to do here. If I could have shown work I would have, but I have no work done. I just need a nudge in the right direction here.