'I didn't see how a program without vision might be able to handle color until about 20 years ago," says Harold Cohen, professor emeritus of visual arts at the University of California, San Diego. Cohen is the creator of AARON, an artificial-intelligence computer program that creates original works of art. "In the artificial intelligence trade it's known as an 'expert system,' which means that the expert's knowledge is expressed as a long list of rules," Cohen explains. "The rule is really a statement saying, 'If such and such, do the following.'" Beginning Wednesday, May 23, "paintings" produced by Cohen's creation will be on display at the Earl and Birdie Taylor Library in Pacific Beach.

About five years ago, Cohen replaced a painting machine that used velvet pads to distribute fabric dye on canvas with a modern printer. Cohen commands the program to create work overnight. In the morning, he finds between 100 and 150 images on his computer, a Dell Workstation, from which he culls about a dozen to print on his large-format Roland Hi-Fi Jet Pro. This high-end inkjet printer, often used for fine-art applications, produces output at a resolution of 1440x1440 dots per inch. This resolution is so fine that the dots cannot be seen by the unaided eye. According to one of its vendors, the printer's "variable dot technology uses three different dot sizes, which allow the nozzle to vary the droplet size."

"Think about how human experts behave," says Cohen, describing how his robotic artist works. "By the time somebody gets to be an expert in anything, all of the rules have all been internalized. A world-class chess master, at any point in the game, has thousands of possible moves that can be made, and he only ever sees three of them. There's some algorithm going on there [that makes him] go straight to those three. In an expert system, it has all been internalized and encapsulated in this small procedure that does everything the big thing had done and a great deal more. It took me 20 years of programming with respect to color and another 30 or 40 years of painting before that to get to the point where I could encapsulate a lifetime of experience in coloring into a few lines of code that I don't even really understand."

Cohen adds that the program is now "a better colorist than I ever was." Within the past year, Cohen came up with a new algorithm, a set of instructions that works like a recipe as a block of code that tells the machine how to accomplish a specific task. "The whole coloring program now is not more than about 4 percent of the amount of code that it had been."

The current body of work that the program is outputting is comprised of brightly colored abstractions of organic forms based on plant life. "All of the material in all of the images is in fact derived from plant growth, not plant forms, but plant growth, because when [the program] goes about drawing a leaf, it has to generate a leaf from scratch from the way it knows how things grow," says Cohen. The program only "knows" what Cohen has written into the code and makes "decisions" based on this knowledge.

"Starting with the organic source of the material imposes a kind of order. You don't have to think in terms of 'It would be nice to have a blue blob there and a green blob there' -- it's actually representing plants." In the program's earlier stages it was assigned the task of producing figures of people in a landscape setting. "Gradually, the landscape settings took over, until there were a couple of people, Adam and Eve figures so to speak, in front of a big tree. And then there were a number of portraits with sort of potted plants in the background, and eventually the potted plants took over, then the pots disappeared and the only thing left was foliage."

Cohen guides his computer program in the direction he wants the artwork to go. "What I do for a living is work on the program, almost all day, almost every day; so obviously the program has changed a good deal over time."

Cohen is not willing to sell his creation, though futurist-author Ray Kurzweil (whose inventions include the flatbed scanner and the first natural-sounding electric piano) was licensed to distribute a desktop screensaver version of AARON. The license expired five years ago and has not yet been renewed because, according to Cohen, Kurzweil is "too busy being famous."

When it comes to how he selects which of his program's images to print, Cohen says, "If I knew how to answer that question, I'd know how to tell the machine to do the choosing for me." -- Barbarella

Harold Cohen: AARON's Garden New Digital Images May 23 through July 8 Opening reception: Sunday, May 27 1 p.m. to 4 p.m. Earl and Birdie Taylor Library 4275 Cass Street Pacific Beach Cost: Free Info: 858-581-9934 or www.sandiego.gov/public-library