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

[Otared Kavian <otared@gmail.com>]

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 <garulfo@azules.eu> 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 <garulfo@azules.eu> 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
>> ___________________________________________________________________________________
> ___________________________________________________________________________________
> 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
> ___________________________________________________________________________________

___________________________________________________________________________________
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
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