Given the popularity of the iPhone, this was bound to happen sometime, and here it is: Microsoft Live Labs today becomes the first group inside the Redmond company to release an application for Apple's mobile phone.

Seadragon Mobile, published to the App Store this afternoon, is a free demonstration program meant to test the viability of the high-tech Seadragon photo-display technology on mobile platforms.

Seadragon is best known as a core technology behind Microsoft's Photosynth photo-browsing program. It's designed for zooming smoothly in, out and around photos over the Internet, regardless of bandwidth constraints or image size. Seadragon's technological trick is to store images in multiple resolutions and deliver only the bits needed to present the view a user wants at any given moment.

So why release an iPhone version? Alex Daley, group product manager for Microsoft Live Labs, said the Seadragon team wants to make sure the technology works well on everything from a wall-sized display to a mobile device.

"The iPhone is the most widely distributed phone with a (graphics processing unit)," Daley explained. "Most phones out today don’t have accelerated graphics in them The iPhone does and so it enabled us to do something that has been previously difficult to do. I couldn’t just pick up a Blackberry or a Nokia off the shelf and build Seadragon for it without GPU support."

The iPhone presents a dilemma for Microsoft more broadly, because it competes with the mobile phones that use the company's Windows Mobile operating system.

Previously, the speculation had been that Microsoft's Tellme voice-recognition service would be the first technology from the Redmond company to be offered for the iPhone, but that app isn't expected until next year.

There are signs that more Microsoft groups may also be interested in iPhone app development, with David Geller of Eyejot commenting yesterday on TechFlash about the "large number" of Microsofties attending a recent Seattle-area iPhone developers group meeting.

Seadragon Mobile for the iPhone comes with a collection of about 50 sample images, ranging as high as 10 gigapixels, including satellite imagery, art and pictures of space. Seadragon Mobile also will let people zoom around the 2D images that make up Photosynth collections, although not the full 3D Photosynth "synths" themselves. In addition, people who create and upload Seadragon "Deep Zoom" images online will be able to use the Seadragon technology to view them.

People will use their fingers on the iPhone's touch screen to zoom around, in and out of the high-resolution photos in the Seadragon application.

"It should give you an idea about the power of multi-resolution image formats when you combine them with an inherently multi-resolution interface," Daley said. "The iPhone uses the zoom as one of its core interaction metaphors, and when you couple that with inherently zoomable content, it’s very a pleasing experience."

[Note: As of 5 p.m. Pacific time Saturday, the Seadragon Mobile app was available for download and transfer to the iPhone through the App Store in iTunes, but it didn't yet show up when I searched for Seadragon in the App Store on the iPhone itself.]

Seattle-based Seadragon Software was acquired by Microsoft in early 2006. Seadragon is part of Live Labs, a group formed nearly three years ago to bridge the company's research initiatives and product groups to make Microsoft more nimble on the Internet. Earlier this week, Live Labs separately released a new Web collections tool called Thumbtack.

The Seadragon team recently released a Seadragon Ajax version, for viewing Deep Zoom photos using standard Web technologies. Earlier the group had released Deep Zoom technology for Microsoft's Silverlight interactive technology.

The iPhone app represents the next step.

The goal "is to test whether this is really viable on the mobile platform in a way that we haven’t been able to test before," Daley said. "The fact that we can give it away and share it with other people so they can validate that for us is great."

Follow-up: Wild idea: Zune app for iPhone.