The general answer to the character recognition problem is negative (currently not possible). However, several important subproblems are solvable. For example,

The general answer to the character recognition problem is negative (currently not possible). However, several important subproblems are solvable. For example, if you know that a particular image came from a printed text, or from handwriting, or a (printed) form, etc, there are some very good solvers. Not perfect (neither is a human, in case of handwriting or a poor fax), but good to very good. For further googling, see terms ICR, OCR, character recognition. As a user, I have had very good results with Finereader. Have not tried Tesseract. Parascript was good with online character recognition, but that market is small, and I have not looked at them for a while (disclaimer: I used to work in a previous incarnation of the company).