In what ways did the pigs in Animal Farm change during the course of the story?

Over the course of the George Orwell novel, Animal Farm, the pigs change from being oppressed workers in a capitalist system to framers of a socialist system in which all animals would be equal, to ultimately being the oppressors in a system much like the one from which they freed themselves at the beginning of the novel. 

In a capitalist society, wealth is enjoyed by the few and the means of production are also an asset of the owner. The workers themselves do not enjoy the same profit as the owner.  This is the system in place on the farm under Mr. Jones.  The animals produced for Mr. Jones and were treated very poorly.  They did not enjoy any of the fruits of their labor.  When they were no longer of any use, Mr. Jones disposed of them. After the revolution, the animals put a socialist system in place.  All animals were equal and the fruit of their labor was divided among them.  After some time, the pigs began to take on the practices of Mr. Jones and the animals lost their equal footing on the farm.  The seven commandments were changed to read that some animals were more equal then others. The fruits of labor were enjoyed by the pigs only, while rations and living conditions for the other animals declined rapidly. 

By the end of the novel, the pigs had completely transformed from the oppressed to the oppressors on the farm.