Google plans shortly to release a beta version of Picasa for Mac OS X, helping Apple fans catch up to Windows and Linux users already employing the free tool for editing, cataloguing and uploading photos.

The Mac version largely matches the features in Picasa 3 for Windows, said Jason Cook, Picasa's marketing manager. Though the company has been scrambling to include some secondary features such as geotagging and the ability to get photos printed, the core abilities of Picasa are present, he said.

Picasa lets people edit and print photos, create collages and movies, and add labels, star ratings and tags. More significantly, given Google's cloud-computing focus, it also lets people upload their images to the company's online Picasa Web Albums site where images can be shared. Google acquired Picasa in 2004.

"We have many Mac users," Cook said, though declining to offer any estimates, "and we think they'll be excited about this. It makes the Picasa Web Albums experience better."

Online photo sites are great for several reasons, but problems can arise when people manage separate and different sets of images. They often upload only a selection of photos on a PC, for example. Sometimes people upload images to an online site that never make it to the PC. And sometimes people add tags, captions and titles online but not to the versions on their computers.

Picasa takes one important step in dealing with this potential rat's nest: when a person edits a photo on the PC, Picasa updates the version stored online. The reverse isn't true, though, but bidirectional synchronisation is "something we're thinking about", Cook said. "We want to make sync as useful as possible."

Synchronisation with the Mac's bundled iPhoto software is another area where people should tread carefully, though Picasa offers cautionary alerts to try to avert any trouble, Cook said. Picasa for the Mac doesn't interfere with iPhoto, he said, but for example when a person uses Picasa to edit a photo, iPhoto still shows the original, which Picasa preserves. And Picasa will read ratings and tags from iPhoto, but not vice versa.

"We play nice. We take a hands-off, read-only approach with the iPhoto library," Cook said. "You can experiment with Picasa, and it won't screw up the images in the iPhoto library."

Before the Picasa for Mac was released, Google offered Mac users two other options for getting photos to Picasa Web Albums: an iPhoto plug-in and standalone upload tool.