The principle of Huffman coding is (roughly) to replace symbols in the original data (in your case the value of each pixel of the image) by a numeric code that is attributed according to the probability of the symbol. The most probable (i.e. the most common) symbol will be replaced by shorter codes in order to realize a compression of the data.
File list:
Assignment 3.pdf
cameraman.tif
Code.mat
Dictionary.mat
Water.jpg