If anyone likes a challenge, there is a good image challenge in this thread over at the Image Processing Techniques on www.unmannedspaceflight.com
The guy has posted a piece of paper that he mailed to himself after printing out some soccer results with an inkjet printer.
Apparently, the ink soaks into the envelope and forensically, you can read the letter from the ink left on the envelope which has reacted with some chemical in the envelope paper. So the challenge is to get as good a result as you can from the reaction of the ink to the chemical in the envelope paper.
I thought it would be a useful exercise to try and do this. The image can be downloaded from the thread. Any takers?
They give their formulae for what they did, so you can either try theirs or try your own methods.