Re: [NTG-context] MetaFun - "remove the paths of text" from a rectangle to let the background visible

23 Dec 2020

      Hi Garulfo,

Thank you for sharing your nice example: it typesets correctly with mkiv, but it seems to me that with LMTX the text does not appear (at least on my installation of the latest LMTX).

Best regards: Otared
...
On 24 Dec 2020, at 00:14, Garulfo  wrote:
Thanks Taco,
I made some progress :
https://wiki.contextgarden.net/Talk:Cover_Pages
I now have two additional questions ... ;-)
- How can I deal with "space" characters (because current solution
 requires to explicitly add the ~ character)
- What would be the work to do in order to make this mechanism directly
 usable in metapost / metafun, within \startMPpage \stopMPpage,
 - to avoid switching between \start\stopMPdrawing and TeX
 - to have something like "draw followtext" in mp-blob.mpiv ?
%------------------------------------------------------------------------------
\setuppapersize  [A4]
%------------------------------------------------------------------------------
\def\MyFont{\definedfont[name:%
texgyrepagellabold%
%exo2black%
%agaramondprobold%
*default at 55pt]}
%------------------------------------------------------------------------------
\startluacode
function document.outlinepaths(character)
   local chardata  = fonts.hashes.characters[true] -- by unicode
   local shapedata = fonts.hashes.shapes[true] -- by index
   local c         = chardata[character]
   if c and c.index and shapedata then
       local shapeglyphs = shapedata.glyphs or { }
       local glyph       = shapeglyphs[c.index]
       if glyph and (glyph.segments or glyph.sequence) then
           local units  = shapedata.units or 1000
           local factor = 100/units
           return fonts.metapost.paths(glyph,factor)
       end
   end
   return { }
end
function document.defineoutline(char,target)
   local outlines = document.outlinepaths(char)
   local nofpaths = #outlines
   context("\\startMPdrawing")                             -- ADDED by garulfo
   context("path %s[] ;",target)
   context("numeric %sn ; %sn := %s ;",target,target,nofpaths)
   for i=1,nofpaths do
       context("%s[%i] := %s ; ",target,i,outlines[i])
   end
   context("\\stopMPdrawing")                              -- ADDED by garulfo
end
\stopluacode
%------------------------------------------------------------------------------
\def\mpdefineoutlines#1#2{\ctxlua{document.defineoutline(\number`#1,"#2")}}
%------------------------------------------------------------------------------
\def\EmptyLetters#1%
{%
\resetMPdrawing
\MPtoks={}
%
\startMPdrawing
 picture pic[], pictA ;
 numeric wid[], len[], pos[], n ;
 wid[0] := len[0] := pos[0] := n := 0 ;
 numeric scaling;
 path pictB , frame ;
 pair shiftB ;
 picture monImageA; monImageA := nullpicture;
 picture monImageB; monImageB := nullpicture;
 color colorframe;  colorframe := 0.6white;
%
\stopMPdrawing
%
\MyFont\handletokens#1\with\whatever
%
\startMPdrawing
 frame :=  unitsquare
         xscaled ( (xpart urcorner monImageB - xpart llcorner monImageB) + 5mm )
         yscaled ( (ypart urcorner monImageB - ypart llcorner monImageB) + 5mm );
 frame := frame shifted (center monImageB - center frame);
 addto monImageB contour
       frame
       withpostscript "evenodd"
       withcolor transparent (1,1.,colorframe);
 draw monImageB ;
 draw monImageA ;
\stopMPdrawing
%
\MPdrawingdonetrue
\getMPdrawing}
%------------------------------------------------------------------------------
\def\whatever#1%
 {\appendtoks#1\to\MPtoks
  \setbox\MPbox=\hbox{\MyFont\the\MPtoks}%
  %
  \startMPdrawing
    n := n + 1 ; len[n] := \the\wd\MPbox ;
  \stopMPdrawing
  %
  \mpdefineoutlines{M}{MaLettre}
  %
  \startMPdrawing
  pictA := textext.drt("\MyFont M") ;
  pictB := MaLettre[1];
  scaling := bbheight pictA / bbheight pictB;
  \stopMPdrawing
  %
  \doifinstringelse{~}{#1}{}{%                HOW TO PROPERLY COPE WITH SPACES ?
  \mpdefineoutlines{#1}{MyGlyph}
  %
  \startMPdrawing
    string sb; sb := "i";
    pic[n] := textext.drt("\MyFont\setstrut\strut#1") ;
    %
    shiftB := - llcorner pic[n];
    pic[n] := pic[n] shifted shiftB ;
    %
    wid[n] := abs(xpart urcorner pic[n] - xpart llcorner pic[n]) ;
    pos[n] := len[n]-wid[n] ;
    %
    addto monImageB contour
          ((MyGlyph[1] scaled scaling)
          shifted ( (pos[n],0) +  shiftB))
          withpostscript "collect";
    %
    if MyGlyphn > 1 :
       for ind=2 upto MyGlyphn :
           if (((xpart llcorner MyGlyph[ind]) > (xpart llcorner MyGlyph[1])) and
               ((ypart llcorner MyGlyph[ind]) > (ypart llcorner MyGlyph[1])) and
               ((xpart urcorner MyGlyph[ind]) < (xpart urcorner MyGlyph[1])) and
               ((ypart urcorner MyGlyph[ind]) < (ypart urcorner MyGlyph[1]))) :
               %
               addto monImageA contour
                     (MyGlyph[ind] scaled scaling)
                     shifted ( (pos[n],0) +  shiftB)
                     withcolor transparent (1,1.,colorframe);
           else :
               addto monImageB contour
                     (MyGlyph[ind] scaled scaling)
                     shifted ( (pos[n],0) +  shiftB)
                     withpostscript "collect";
           fi;
        endfor;
     fi;
  \stopMPdrawing}}
%==============================================================================
%==============================================================================
\starttext
%------------------------------------------------------------------------------
\startuseMPgraphic{MyBackgroundGraphic}
 path pathbackground ;
 numeric dimA ; dimA := \the\paperwidth;
 numeric dimB ; dimB := \the\paperheight;
 pathbackground :=  unitsquare xscaled dimA yscaled dimB ;
 fill pathbackground
      withshademethod "linear"
      withshadedirection(0,1)
      withshadecolors (red,blue);
\stopuseMPgraphic
%------------------------------------------------------------------------------
\definelayer[MyBackgroundLayer]
\setlayer[MyBackgroundLayer]{\useMPgraphic{MyBackgroundGraphic}}
\setupbackgrounds[page][background={MyBackgroundLayer}]
%------------------------------------------------------------------------------
\EmptyLetters{MetaPost~is~fun!}
\EmptyLetters{ABCDEFGHIJ}
\EmptyLetters{KLMNOPQRST}
\EmptyLetters{UVWXYZ!?\&*}
\EmptyLetters{abcdefghij}
\EmptyLetters{klmnopqrst}
\EmptyLetters{uvwxyz<>;:@}
\EmptyLetters{0123456789}
%------------------------------------------------------------------------------
\stoptext
Le 21/12/2020 à 16:29, Taco Hoekwater a écrit :
...
...
On 21 Dec 2020, at 16:09, Garulfo  wrote:
Hi,
* I try to "remove the paths of text" from a metapost pictures to let
 the background visible.
* Using
 https://mailman.ntg.nl/pipermail/ntg-context/2018/thread.html#92725
* I was able to get the following with one glyph (MVE code below)
https://wiki.contextgarden.net/images/d/d2/test_extract_glyphs.pdf
2 questions:
1/ for some fonts (e.g. dejavu vs latin modern) the "encompassing" path
  of the B glyph can switch from B[1] to B[Bn]. Is there a trick to
  identify which id match with "the encompassing" path ?
What you get is the order of the paths as defined in the font, which is arbitrary, as you discovered.
A quick trick (that will not always work, but should work quite well for font variations of alphabetics) is to check the actual arclength of the paths. The longest one will typically be the outer one.
But much depends on the font, so a generic solution is likely quite complicated. Consider an outline font’s colon glyph ;)
2/ now, I would like to do the same, but for text... a kind of
  derivative of "textext" or "outlinetext".
  Would you please give me some guidelines ?
  does it already exist ?
  should I use something like \handletokens, \scantokens ?
  do you have examples where I can get inspiration ?
Thanks again for your help,
Garulfo
%==============================================================================
\starttext
%------------------------------------------------------------------------------
\startluacode
function document.outlinepaths(character)
   local chardata  = fonts.hashes.characters[true] -- by unicode
   local shapedata = fonts.hashes.shapes[true] -- by index
   local c         = chardata[character]
   if c and c.index and shapedata then
       local shapeglyphs = shapedata.glyphs or { }
       local glyph       = shapeglyphs[c.index]
       if glyph and (glyph.segments or glyph.sequence) then
           local units  = shapedata.units or 1000
           local factor = 100/units
           return fonts.metapost.paths(glyph,factor)
       end
   end
   return { }
end
function document.defineoutline(char,target)
   local outlines = document.outlinepaths(char)
   local nofpaths = #outlines
   context("path %s[] ;",target)
   context("numeric %sn ; %sn := %s ;",target,target,nofpaths)
   for i=1,nofpaths do
       context("%s[%i] := %s ; ",target,i,outlines[i])
   end
end
\stopluacode
%------------------------------------------------------------------------------
\def\mpdefineoutlines#1#2{\ctxlua{document.defineoutline(\number`#1,"#2")}}
%------------------------------------------------------------------------------
\startMPpage
numeric dimA ; dimA := 20cm;
path pathbackground ;
pathbackground :=  unitsquare scaled dimA ;
fill pathbackground withshademethod "linear" withshadedirection(0,1) withshadecolors (red,blue);
%--------------------------------------
\mpdefineoutlines{B}{B}
%--------------------------------------
numeric dimB  ; dimB := 2cm;
numeric vratio ; vratio := 2;
path frame ;
frame :=  unitsquare
         xscaled (dimA - 2 * dimB)
         yscaled (dimA / vratio)
         shifted (dimB , (dimA - (dimA / vratio))/2 );
%--------------------------------------
pair shift ; shift := center frame;
numeric scal ; scal := (0.9) * (10cm / (bbheight B[1])) ;
picture monImageB; monImageB := nullpicture;
addto monImageB contour
     (B[1] shifted (- center B[1]) scaled scal)
     shifted shift
     withpostscript "collect";
addto monImageB contour
     frame
     withpostscript "evenodd";
for i=2 upto Bn :
 addto monImageB contour
       (B[i] shifted (- center B[1]) scaled scal)
       shifted shift;
endfor ;
%--------------------------------------
draw monImageB withcolor white;
\stopMPpage
\stoptext
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________
Taco Hoekwater
Elvenkind BV

If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: [NTG-context] MetaFun - "remove the paths of text" from a rectangle to let the background visible

Otared Kavian