Fierce and scary geometry algorithm for ‘ParallelPath’

Newsgroups	comp.lang.postscript
Date	2019-04-17 13:37 -0700
Message-ID	<e7dba0a9-68e6-4dfe-90ba-6e9b00e7d3d3@googlegroups.com> (permalink)
Subject	Fierce and scary geometry algorithm for ‘ParallelPath’
From	jdawiseman.bloomberg@gmail.com

Show all headers | View raw

Algorithm question, the problem being illustrated by:
http://www.jdawiseman.com/2019/20190400_ParallelPath.ps
http://www.jdawiseman.com/2019/20190400_ParallelPath.pdf
http://www.jdawiseman.com/2019/20190400_ParallelPath.png

I want a decorative effect like that in the linked ps, pdf, and png.

That is currently being achieved by starting with the target path, and clipping to it. Then setlinewidth thick and setgray black, stroke; setlinewidth a bit thinner and setgray white, stroke; setlinewidth a bit thinner and setgray black, stroke; etc.

Done that way the on-screen the PDF looks good, and if converted to a bitmap with GraphicConverter, still looks good. Happiness!

But if printed on some actual printers, the outermost black line seems thicker than the others. Not happy. This is likely to be a printer artefact, the printer being more aggressive about spreading white than about spreading black. That would affect one side of the outermost line, but two sides of the others — making the outermost seem thicker. (Though the cause might be different: I don’t know.)

One way to fix this would be to trace and stroke directly the parallel lines, rather than as the gap between a black stroke and a white stroke. That would require a routine, perhaps called ParallelPath, which would take two parameters: a distance in points; and a boolean = left|right. ParallelPath would walk round the currentpath, replacing it with a new path the parameters’s distance to the left|right, as if holding out a left|right arm that far away from the body.

Seems like a fierce and scary algorithm to write. If you have already written such an algorithm, or something like it, please share.

Back to comp.lang.postscript | Previous | Next — Next in thread | Find similar

Thread

Fierce and scary geometry algorithm for ‘ParallelPath’ jdawiseman.bloomberg@gmail.com - 2019-04-17 13:37 -0700
  Re: Fierce and scary geometry algorithm for ‘ParallelPath’ edspikechapman@gmail.com - 2019-04-19 08:55 -0700
    Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdawiseman.bloomberg@gmail.com - 2019-04-20 02:44 -0700
      Re: Fierce and scary geometry algorithm for ‘ParallelPath’ Carlos <carlos@cvkm.cz> - 2019-04-29 02:41 +0200
        Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdaw1 <jdawiseman@gmail.com> - 2019-06-19 15:04 -0700
          Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-22 13:33 -0700
            Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-22 14:54 -0700
              Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-22 15:37 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-23 15:59 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-27 06:59 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-27 07:48 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-27 08:30 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-06-28 12:10 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-07-19 14:00 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-07-20 09:33 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-07-20 13:20 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdaw1 <jdawiseman@gmail.com> - 2021-03-14 10:25 -0700
  Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdawiseman.bloomberg@gmail.com - 2019-04-20 06:54 -0700
    Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-04-20 10:44 -0700
      Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdawiseman.bloomberg@gmail.com - 2019-04-20 11:01 -0700
        Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-04-20 11:33 -0700
          Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-04-20 11:50 -0700
            Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-04-20 13:01 -0700
              Re: Fierce and scary geometry algorithm for ‘ParallelPath’ jdawiseman.bloomberg@gmail.com - 2019-04-21 03:29 -0700
                Re: Fierce and scary geometry algorithm for ‘ParallelPath’ luser droog <luser.droog@gmail.com> - 2019-04-28 13:33 -0700

csiph-web