shovelhead posted a link to something i think was called a "halftone generator'" some time in the last year. I downloaded it & messed around with it a bit. I believe it can do what you want, with a great deal of flexibility & control. Mosh's (say that 3 times real fast) ..Mosh's idea would work too, and might be quicker then searching an old post & downloading a software.. but the halftone gererator was pretty cool... so if you like messing with cool freeware on your holiday break... it will probably offer you a faster way, once you find it & install it... plus it can do gradient adjustments of the dot pattern & different dot shapes etc...