The maker of the popular photo-editing software Photoshop on Thursday launched a basic version available for free online.

Registered users will have 2 GB of storage available as well. Once you sign up, you get a “personal sharing URL,” such as http://xxxx.photoshop.com. And before you ask, no, you can’t edit local files, only files that are uploaded to your account – or at other sites (more on that below).

Annoyingly, they use Flash for everything, including login, which means Roboform, my password / auto-login program, won’t work. Sigh.

Web-based software is increasingly popular, and Adobe knows it’s got to get on that train, said Kathleen Maher, an analyst at Jon Peddie Research.

Many kinds of software are available for use online in a trend known as “software as a service,” or “cloud computing.” The earliest were e-mail programs, but they now include services to create and manage content and even whole operating systems. And they don’t require time-consuming upgrades because they’re maintained by the service provider.

Google Inc. provides a host of such services, as do Microsoft Corp. and others.

“This is the battlefield where Adobe and Microsoft and Google are going to fight some pretty big battles,” Maher said.