In putting together “Stripped,” a documentary exploring the art and evolution of newspaper comic strips, Dave Kellett and Fred Schroeder, the co-directors, interviewed more than 70 cartoonists. One of the biggest gets was Bill Watterson, the reclusive creator of “Calvin and Hobbes,” the beloved newspaper strip about a mischievous boy and his stuffed tiger, which ran from 1985 to 1995.

“In the right hands, a comic strip attains a beauty and an elegance that really I would put against any other art,” Mr. Watterson says in his interview. Mr. Schroeder said, “It seemed like he really wanted to express some thoughts about comics and cartooning, where they had been and where they are going.” The retired cartoonist was so pleased with the documentary that he also supplied the artwork for the poster of the film.

The film has evolved from its initial concept. “I started out wanting to make a documentary about artists in their studio spaces,” Mr. Schroeder said. But thanks to the access of Mr. Kellett, a cartoonist himself, the project grew into its current form: a musing on comic strips by many of their creators, how the medium has evolved and the migration to the Internet, some of it forced as the number of newspaper outlets for the strips has shrunk and some of it voluntary by a new generation of artists.

“Digital distribution changes everything,” Mr. Kellett said. “It’s kind of a magical time when everyone can do things themselves.” The co-directors are taking advantage of those opportunities themselves, with plans to release the film in various digital platforms as well as sales of a DVD, which will have extended footage of the interviews. “Stripped” will be available for advance ordering on iTunes at midnight Wednesday. On April 2 the DVD will go on sale.