🚀 go-pugleaf

> Newsgroups: comp.lang.postscript
> Date: 1 Oct 90 22:21:16 GMT
> Sender: dsmith@applga.aa.cad.slb.com (J. Daniel Smith)
> Reply-To: smithda@buster.cps.msu.edu
> 
> I'm trying to print 1 pixel wide lines on a 300dpi PS printer.
> Following the techniques on page 62-63 of _Real World PostScript_, 
> I have the code shown below.
> 
> The problem is that the top line of the box is thicker than the other
> sides.  I tried printing this file on two different Apple PS printers,
> and the result was the same on both of them.  I also tried different
> values for "setlinewidth" (0.24, 0.12 and 0.003).  And I tried putting
> the SnapToPixel before the "rmoveto".  None of this worked!  There
> must be a way to do this properly (i.e. *not* doing everything in
> 1/300 inch units).


The problem is that the endpoints for each line segment must be properly
alligned with the device pixels.  The Solution is to use SnapToPixel
on each corner of the box.  This requires a slight rewrite to the code because
SnapToPixel only works with absolute coordinates, not relative moves.



the solution is to change:
    0 boxy SnapToPixel moveto
    boxlength 0 rlineto
    0 logoheight rlineto
    boxlength neg 0 rlineto
  closepath

to:
    0 boxy SnapToPixel moveto
    boxlength boxy SnapToPixel lineto
    boxlength logoheight boxy add  SnapToPixel lineto
    0 logoheight boxy add SnapToPixel lineto
  closepath



Michael Fryd
President                           Voice: (412) 751-5557
MEFCO, Inc.                         Fax:   (412) 751-8403
2401 Coulter Road                   Email: Michael.Fryd@CS.CMU.EDU
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