To a lot of Internet denizens, it was as if somebody had popped up and said, "By the way, I've got a patent on air, so please set aside a penny every time you breathe." The somebody was Unisys Corp., the huge computer company based in Blue Bell, Pa., which last month announced it was asserting patent rights over the graphics interchange format (GIF), a software standard that helps turn photographs and other images into digital data that can be stored on a disk or zipped across networks. Unisys said it had collected royalties from CompuServe Inc., the big on-line services company, and authorized it to sell the technology to others.

You can find GIF-based images -- everyone calls them GIFs -- just about anywhere you look on the Net, whether you're downloading photographs of the volcanic plume arising from Mexico's Mount Popocatepetl or of leather-clad couples performing acts that could make your mouse blush. With the growing popularity of the World-Wide Web, the Internet's multimedia-rich information system, GIFs have only become more important.

Just about as common as air, in fact.

So the idea that Unisys would try to impose what amounts to a "GIF tax" had the don't-tread-on-me cyber citizens fighting mad. They accused the computer giant, scrambling to make up for years of dwindling hardware sales, of greedily invoking a "submarine" patent: lurking silently as the standard became entrenched, then surfacing to attack -- and collect its booty.

An "open letter" from Pat Clawson, chief executive of Huntington Beach, Calif.-based TeleGrafix Communications Inc., called the move "the on-line communications community's equivalent of the sneak attack at Pearl Harbor." Many people on the Net were particularly galled to see the offensive coming from a company that is part of the shrinking mainframe market and has very little role in the explosion of the Web and other Internet services.

At issue is the GIF "compression" scheme, or portion of the software that helps cram the data-hog images into more manageable file sizes. The software, known as the Lempel Zev Welch algorithm, also is used in another popular graphics format known as TIFF, for tagged image file format. It originally was patented by Unisys about 10 years ago.

The technology quickly became a standard, and was widely disseminated in just about every computer program that displays pictures -- that includes high-end graphics packages costing hundreds of dollars and bargain "shareware" programs that are distributed for free, but with a request to pay the author something if they're kept and used. (Shareware has made big profits for some developers, but for many others it simply brings in enough cash to keep them supplied with Jolt cola and pizza.)

Now we discover that two years ago Unisys began negotiations with CompuServe over payments for use of the GIF format in so many images that the service carries. That settlement came though earlier this month; CompuServe then announced that it would pay royalties to Unisys and would offer GIF licenses to developers itself, and touched off the current furor.

When people started getting mad, Unisys went to the Net to say that -- as can happen when news begins bouncing around in cyberspace -- that the situation has been blown out of proportion and its position had been misunderstood. The company said it wasn't interested in collecting money directly from computer users; instead, it hoped to license its technology to software developers, leaving it up to them whether to pass along the cost to consumers. Unisys said that could add about 1 percent to a product's retail price.

That logic still didn't sit well with the Net. Then last week Unisys announced that it would not go after companies with "inadvertent infringement" of the patent in programs brought to market before 1995.

The company also pledged to limit its attempts to collect to commercial software developers, including shareware developers, and would not bother hobbyists who write and distribute software for free. The company said it also is trying to develop a simple contract for shareware developers.

Ultimately, Unisys could come out of this debacle with a bruised public image and precious little revenue to show for its pains. Net users last week were discussing a switch to free alternatives to the GIF format that could evade the patent problem. Some were talking about the joint photographics experts group format, known as JPEG. Others were promoting quick fixes to the compression scheme in GIFs to switch out the Unisys-owned software with a hastily written patch.

The lesson, learned painfully by Unisys and spreading throughout cyber-related industries: Anger the Net at your peril. It's feisty and unforgiving.

John Schwartz's e-mail address is schwartj@twp.com.

CAPTION: PLACES TO GO

To follow the GIF controversy, read two of the many Usenet newsgroups where discussion has been active: alt.internet.media-coverage and comp.infosystems.www.misc. CompuServe carries the Unisys and CompuServe statements (type GO GRAPHSUP).

You also can use a World-Wide Web browser to read the statements at http://www.compuserve.com. or http://www.unisys.com.