I know I get alot of requests on how to convert an image to halftones for printing without a rip program...so here is a video that shows the steps to convert a one color image to halftones with 45 lpi at 22.5 screen angle...the output resolution is 600.
hope this helps !
Halftone_Movie.mp3.avi - YouTube
The same general process can be used to create 4/C process as well, without a RIP. Just use the data from each of the 4 data channels, then convert to halftone screens.