INSTRUCTIONS:
To compile, cd into the hadoop folder and execute the build.sh script. 
To run the program, modify and execute the run.sh script to take the desired input 
image, or use a command of the format shown in the run.sh script.

First, you should really read the handout for information about how the contrast enhancement works.

The main() that runs is in driver/Driver.java.
expand(), reduce(), etc is in transform/PGMTransform.java.
reading, writing and getting the pixels of .pgm files is in image/PGMImage.java.
A high level overview of the process is in contrast/PGMContrast.java

When you implement your hadoop version, you will probably want to reuse PGMImage.java.
If not, feel free to reinvent the wheel.