To the best of my knowledge there have been three programs that performed font recognition.
The first was FontFinder which I coauthored and published in 1994. We only sold a couple of hundred copies even though we got three mice from Publish Magazine and a rave review from Sign Business Magazine. It wasn't the most user friendly application I had ever used but it worked. The principle was simple enough. If you give the program a reasonably accurate measurement of the height and width of three or four characters from a printed sample, and then compare the height to width ratio to a stored database compiled from the metric data (AFM files) of all the fonts you can get hold of, you will come up with a unique fingerprint or a very short list of possibilities. It worked extremely well and we even had a field for inputting a numeric variable in case the font had been stretched or squeezed. About 75% of our customers were professional forensic document examiners ... including the FBI, the US Secret Service and the CIA. Sign guys viewed it as too much trouble. FontFinder is no longer on the market and it is doubtful it would even install on current operating systems.
The second was a Swiss program published by a German company and named FontExpert. My company was the US distributor for a couple of years. FontExpert is a very competent and user friendly application which will compare selected scanned characters against a stored database using a direct overlay of the pixels. It generates a percentage ranked list and a screen display of the font when you select each one from the list. It also includes their Database Generator thus allowing you to add in your own fonts. It lacks any ability, however, to adjust for width modifications, so if the font has been modified, the only recourse you have is to attempt to unmodify it in an image editor like Photoshop. Still, it will give you an accurate ID in a couple of minutes about 75% to 80% of the time and if you have some idea of what you are doing.
FontExpert is currently available from Smart Designs for $149.00.
The third is Imagaro Z who just released a new version that packs about 40,000 fonts in its database. The program is first and foremost marketed as an autotracing and vector editing application. It also will identify text and substitute it as part of the vectorization process (providing you own licensed versions of the fonts and in the particular way that they have them cataloged.) The application will also, according to claims made by the sellers, identify a font even if it has been modified. In a recent email exchange with the US distributor, he stated that the font substitution limitation is misunderstood and that the application will still tell you the font it thinks is the unknown sample. It just won't substitute it automatically unless you have met the program's requirements in proving that you own licensed versions. This from their website:
Let Imagaro Z tell you what typeface your text has. Scan the text and in seconds you will have the name of the correct font. Imagaro Z searches a built-in database of about 40,000 fonts.
The identified font is drawn on top of the scanned text so that you can be sure that the typeface is 100% correct. If the text is stretched or compressed, it can be very difficult to identify the font. Not so, with Imagaro Z you can just as easily search through all typefaces and let the software compress and stretch the text. The stretch or compression rate is displayed so that you can reproduce new texts with the same look.
Imagaro Z currently sells for $690.00. As far as I can tell, there is no capability to add you own fonts into their database in the event they haven't included some of them.