camcta@tasu11.UUCP (Amnon Cohen ) (05/16/91)
>Is there an easy way to cause the setgray operator to use a finer screen >i.e. smaller dots in its shading? Please mail replies to me. I will >post a summary if there is any demand. Thanks to SNOW@DRYCAS.CLUB.CC.CMU.EDU (ken) for the following reply: ------------------------------------------------------------------- The operator that controls the halftone screen is "setscreen"... <freq> <angle> <spot-fcn> setscreen It takes 3 parameters: frequency (in cells per inch), angle, and the "spot function" (a procedure defining the order to fill the halftone cell pixels). Since you only want to change the frequency, you can do... currentscreen 3 -1 roll pop <newfreq> 3 1 roll setscreen ...which will change only the frequency of the default screen, leaving the rest the same. This operator is device-specific; that is, the actual settings that can be achieved depend on device characteristics (PostScript will try to get as close as it can to the parameters you request), and different devices may give different results with the same setscreen call. It is particularly sensitve to device resolution. Also, be aware that as you increase the halftone cell frequency you decrease its size, so it can represent fewer levels of gray. ======================================================================== Email: amnonb@taux01.nsc.com Smail: Amnon Baron Cohen National Semiconductor