Forgent has added Microsoft to the list of companies it is suing for patent infringement of the ubiquitous Jpeg digital image format.

The addition of the software giant to the 31 other companies Forgent wants licensing fees from - including Apple, Dell, Kodak, HP, IBM, Macromedia and Xerox - comes after it failed to negotiate a licensing agreement with Microsoft, said Michael Noonan, director of investor relations at Forgent.

You have to question the logic of adding such a legally adept company to a lawsuit that is already punching about its weight. The patent in question, number 4,698,672, expires in October this year. It covers a data compression technique Forgent claims is used in the JPEG digital image standard.

It has had some success with its claims though. It persuaded Sony to pay it $16 million to license the format, and it has received an estimated $90 million in total from a variety of companies.

"We want them to pay a reasonable royalty rate for the technology they are using," Noonan said. "If a company uses Jpeg, they are using our patents."

In a pre-emptive strike, Microsoft sued Forgent subsidiary Compression Labs on Friday. Forgent may have bitten off more than it can chew here.