Pairwise term for Graphcut

Very fast, vectorized code for calculating the pairwise term for algorithms like Graph cuts.

This code is inspired by Steve's post on Neighborhood indexing:

http://blogs.mathworks.com/steve/2007/03/28/neighbor-indexing/

Four-connected neighborhood implementing the color difference between adjacent pixels in RGB space as a way to encode to similarity.

1/(norm(I1(:)- I2(:))+1)

Example:

timeit(@() pairwise_term(imread('peppers.png')))

ans =

0.2037

Please obtain the timeit function from here:

http://www.mathworks.com/matlabcentral/fileexchange/18798