Chris Rosa, store manager at Meltdown Comics, feels that digital comics will not replace the demand for physical comics. The store was enjoying brisk sales ahead of Comic-Con being held over the weekend in San Diego.

Los Angeles ? It’s a book! It’s a cartoon! It’s … digital comics!

Technology, which has already upended the music, television and movie businesses, is now gripping the comic book world. Publishers are unleashing a torrent of digital comic books across smart phones, tablet devices, game consoles and digital book readers, portending major changes in how comics are made and marketed.

These new comics — many of which were showcased last week at Comic-Con International in San Diego — in some cases come with choreographed presentations that zoom or pan across panels, full-color animated characters, audio from professional voice actors, heart-thumping soundtracks and even the ability for readers to leave comments on the pages.

A growing market

With change comes its twin companions: angst and exhilaration.

Traditionalists argue that “experiments” with animation and sound effects threaten to undermine the aesthetic foundation of comics and wipe out comic book stores already struggling to stay afloat — in other words, to do what the iPod and iTunes did to record shops.

Enthusiasts dismiss such fears as nonsense. Digital distribution is not only bringing a desperately needed infusion of young comic readers but also giving birth to a renaissance of innovation in a medium that some say badly needs updating.

“Digital distribution is our new newsstand,” said Chip Mosher, the marketing director at Boom Studios, which is converting its entire library of several hundred comic titles for online reading. “It’s a way to get our product in front of a mass audience.”

The arguments aren’t new, as digital comics have been around for more than a decade. But the stakes are becoming much higher as sales of digital comics are poised to take off, with a proliferation of titles on mobile gadgets such as Google Inc.’s Android phones and Apple Inc.’s iPad tablets and iPhones.

“The industry is in a difficult spot,” said Scott McCloud, author of “Reinventing Comics” and several other books on comics as a medium. “It has to rethink its entire business model while it’s rethinking the art form.”

Marvel Entertainment, which has been offering unlimited access to more than 8,000 digital comic books via PCs for $10 a month, released an iPad application in April through which readers can browse more than 500 titles. DC Comics came out with its own iTunes app in June, starting with 200 titles and adding close to 50 titles a week.

Although digital sales are less than 5 percent of the roughly $1-billion U.S. market for comic books and Japanese manga, it’s rapidly growing.

“Comic book sales have seen flat to relatively modest growth in recent years, but digital sales for us have so far doubled, year over year,” said Ira Rubenstein, Marvel’s executive vice president of global digital media.

A generation battle

Traditional comic stores view the growth of online comics with some apprehension.

Some store owners believe digital sales will cannibalize print sales, especially if the digital version is priced at $1.99 while the print comic is typically $3.99. What’s more, the digital versions can be ordered and delivered within seconds.

Douglas Wolk, an avid collector and the author of “Reading Comics: How Graphic Novels Work and What They Mean,” says computer clicks can never duplicate the personal relationship between a reader and the person working the comic shop counter.

“Comic book stores have a very close relationship with their customers,” Wolk said. “But the old-school collectors are aging, and it may be that the print comic goes away eventually. There is an entire generation of readers who is not interested in physical copies.”

Rubenstein said Marvel’s digital sales largely come from lapsed comic book fans and new readers who may eventually venture into collecting print editions. A survey of more than 2,000 comic book readers conducted this spring by ComiXology, a New York-based startup that has its own app with 2,200 comics from about two dozen publishers, found that 1 in 5 who bought a digital comic book had never bought a comic before, according to the company’s chief executive, David Steinberger.

At least for now, stores can still count on comic book collectors who eagerly wait for new shipments to arrive every Wednesday.

One of those is Jeffrey Reddick, a lifelong comic book reader who took a break last week from his job as a screenwriter to hit Meltdown Comics in Hollywood.

“I’m old school. I like my comics printed,” the 41-year-old said as he prepared to pay for nine comic books, adding them to a prodigious collection that fills a walk-in closet in his Hollywood home. “Digital comics are good, but there’s not the magic of the book that makes me feel like that geeky kid.”

They might not have dampened Reddick’s enthusiasm, but digital comics also haven’t led a tidal wave of new buyers into Meltdown Comics, said store manager Chris Rosa. “The jury is still out on that one,” Rosa said.