Google's Picasa for Macintosh (click for larger image)

Google on Monday announced the release of Picasa for Mac, a desktop photo editing and organization application that had previously been available only to Windows and Linux users.

"Picasa for Mac looks and works almost exactly like Picasa on other platforms," Google product manager Brian Axe said in a blog post. "It can keep track of photo files scattered across your hard drives, and will automatically account for new photos as you add them to your system. Picasa for Mac also features non-destructive editing, so you can explore different photo adjustments and effects without worry."

The beta-phase software includes a drag-and-drop photo collage tool, a retouching brush, a slide show moviemaker with easy YouTube uploading, and automatic red-eye removal.

Picasa for Mac adds another area of potential tension between Google and Apple because it could be seen as a competitor to Apple's iPhoto. While Google's presence on Apple's iPhone and on Apple's board of directors suggests a cordial relationship between the two companies, the search company's interest in Android phones could strain that rapport.

But Google appears to be downplaying that possibility by suggesting Picasa and iPhoto can co-exist peacefully. Axe insists that Picasa for Mac "plays nice" with iPhoto by duplicating iPhoto files and leaving the originals untouched.

Apple, however, may return the favor, perhaps as soon as Tuesday, when the company is expected to announce new products at the Macworld Conference. Rumor has it that Apple wants to extend its consumer applications to the Web, to Google's territory.

Though Apple struggled with the launch of its MobileMe online service, the company almost certainly wants to continue to develop the online capabilities of its desktop applications, just as Adobe and Microsoft have been doing. The problem it faces is convincing customers to keep paying the fees it charges for software and services -- $99 annually for MobileMe, $79 for iLife '08 -- that aren't all that different from what Google offers for free.