David Arnold wrote:
Hans et al,
Let me try to be more specific. Here is a file which is very typical
of the way I draw graphs for my mathematics classes. When you compile,
you will see the graph of the absolute value of x-1. That is, it draws
the graph of y=|x-1|, but only after clipping it to the cpath. What I
would like to do is draw the graph with the drawdblarrow command so
that the graph of the absolute value ends in arrowheads. So, I want to
clip the graph to the bounding box, save the picture, null the
picture, then somehow extract the path into the variable F in its
clipped form (not the original path F that extends outside the clip
path) so that I can replace the command draw pic with drawdblarrow F.
hm, this need some more brainpower than the previous solution,
in mp-tool there is a repathed macro that does most of the job so let's
extend that one a bit:
\starttext
\setupcolors[state=start]
\startMPpage
def restroke suffix p = p := repathed (21,p) enddef ; % keep attributes
def reprocess suffix p = p := repathed (22,p) enddef ; % no attributes
vardef repathed (expr mode, p) text t =
begingroup ;
if mode=0 : save withcolor ; remapcolors ; fi ;
save _p_, _pp_, _ppp_, _f_, _b_, _t_ ;
picture _p_, _pp_, _ppp_ ; color _f_ ; path _b_ ; transform _t_ ;
_b_ := boundingbox p ; _p_ := nullpicture ;
for i within p :
_f_ := (redpart i, greenpart i, bluepart i) ;
if bounded i :
_pp_ := repathed(mode,i) t ;
setbounds _pp_ to pathpart i ;
addto _p_ also _pp_ ;
elseif clipped i :
_pp_ := repathed(mode,i) t ;
clip _pp_ to pathpart i ;
addto _p_ also _pp_ ;
elseif stroked i :
if mode=21 :
_ppp_ := i ; % indirectness is needed
addto _p_ also image(scantokens(t & " pathpart _ppp_")
dashed dashpart i withpen penpart i
withcolor _f_ ; ) ;
elseif mode=22 :
_ppp_ := i ; % indirectness is needed
addto _p_ also image(scantokens(t & " pathpart _ppp_")) ;
else :
addto _p_ doublepath pathpart i
dashed dashpart i withpen penpart i
withcolor _f_ % (redpart i, greenpart i, bluepart i)
if mode=2 : t fi ;
fi ;
elseif filled i :
if mode=11 :
_ppp_ := i ; % indirectness is needed
addto _p_ also image(scantokens(t & " pathpart _ppp_")
withcolor _f_ ; ) ;
elseif mode=12 :
_ppp_ := i ; % indirectness is needed
addto _p_ also image(scantokens(t & " pathpart _ppp_")) ;
else :
addto _p_ contour pathpart i
withcolor _f_
if (mode=1) and (_f_<>refillbackground) : t fi ;
fi ;
elseif textual i : % textpart i <> "" :
if mode <> 4 :
addto _p_ also i if mode=3 : t fi ;
fi ;
else :
addto _p_ also i ;
fi ;
endfor ;
setbounds _p_ to _b_ ;
_p_
endgroup
enddef ;
picture pic; pic := image(
draw fullcircle scaled 5cm withpen pencircle scaled 5mm ;
draw fullsquare scaled 2cm withpen pencircle scaled 5mm ;
fill fullcircle scaled 1cm withpen pencircle scaled 5mm ;
) ;
redraw pic withpen pencircle scaled 1mm withcolor red ;
% restroke pic "drawdblarrow" ;
pic := repathed(21,pic) "drawdblarrow" ;
pic := repathed(11,pic) "drawdblarrow" ;
draw pic ;
\stopMPpage
\stoptext
the new restroke variant takes a macro name that itself takes one argument, i.e. a path, so in order to do more complex things, you need to define those
Hans
-----------------------------------------------------------------
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com
| www.pragma-pod.nl
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