Path: utzoo!attcan!uunet!mcvax!ukc!eagle!icdoc!qmc-cs!liam From: liam@cs.qmc.ac.uk (William Roberts) Newsgroups: comp.lang.postscript Subject: Re: PostScript problems Summary: some answers, some no-you-can'ts Message-ID: <529@sequent.cs.qmc.ac.uk> Date: 4 Jul 88 17:46:39 GMT References: <5@phys0.anu.oz> Reply-To: liam@cs.qmc.ac.uk (William Roberts) Organization: Computer Science Dept, Queen Mary College, University of London, UK. Lines: 62 Expires: Sender: Followup-To: Distribution: Keywords: In article <5@phys0.anu.oz> bill@phys0.anu.oz writes: >both of which are probably PostScript design limitation problems A chisel can be used for opening tins of paint - are you using PostScript wrongly? >I would like to draw one diagram over the top of another diagram >and where the second diagram's blackened pixels intersect the blackened >pixels of the first diagram I would like to do an exclusive or of the pixels >(to produce a whitened pixel). > As an example of this, consider the following ... >gsave > diagram1 strokepath clip > gsave diagram 1 setgray stroke grestore >grestore Correct, the way to do this kind of thing is buy use of clipping. There is a gap in Adobe PostScript however; you can't ask for an "imagepath" and so you can't clip in/out using an image rather than an outline. >What I would like is use part of the frame buffer assembled so far >as input to the imagemask operator Not all PostScript devices have framebuffers, e.g. the big Linotronic machines. >The second problem is this: what I would like to be able to do is a proper >"solid shadowing" of a font with cross-connecting lines between the front >of the character and its shadow. This does have severe hidden-line problems and clipping is going to be an awkward way of dealing with it, especially since you can't get at the path descriptions for characters. I would give up on this one... >Another thing I would like to do with a font is draw a >proper outline of a character around an original black filled version of the >character (with white inbetween). I can do this! Use charpath to get outline of the character and then stroke it a) with a wide black line, then b) with a silghtly thinner white line, then draw the character itself. The stroke operator does exactly the "thick edging" you require, though unfortunately the results of "strokepath" isn't suitable for clipping. >I have always regarded the omission of a dotless j from the Adobe fonts >a serious omission. Has anybody ever properly overcome this omission? Clipping again. Experiment with big copies of ordinary j to find out a rough bounding rectangle for the j stem without the dot, then create a new character which first clips to that region and then draws an ordinary j. Hey presto, the clipping removes the unwanted dot. -- William Roberts ARPA: liam@cs.qmc.ac.uk (gw: cs.ucl.edu) Queen Mary College UUCP: liam@qmc-cs.UUCP LONDON, UK Tel: 01-975 5250