%D \module
%D   [       file=supp-mps,
%D        version=1997.07.05,
%D          title=\CONTEXT\ Support Macros,
%D       subtitle=\METAPOST\ Inclusion,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. Non||commercial use is
%C granted.

% E-tex   : a primitive that tells us that \write18 works
% E-tex   : \executeMetaPost filename
% ConTeXt : automatic flush at end of job

% The MP generation support is still experimental.

%D \METAPOST\ is John Hobbys alternative for \METAFONT\ and
%D produces superior \POSTSCRIPT\ code. In this module we
%D integrate \METAPOST\ support int \CONTEXT.  We offer two
%D tracks:
%D
%D \startopsomming
%D \som generating \METAPOST\ code, running this program from
%D      within \TEX\ using \type{\write18}, and importing the
%D      result
%D \som generating \METAPOST\ code, processing the code
%D      afterward, and importing the result in a second pass
%D \stopopsomming
%D
%D The first approach uses a non standard \TEX\ feature,
%D implemented in Web2c. I'm not going to discuss the pros and
%D cons of running programs from within others, but all
%D arguments against this can be overcome by implementing a
%D \TEX\ worthy primitive:
%D
%D \starttypen
%D \excuteMetaPost filename
%D \stoptypen
%D
%D Ok then, let's start:

\ifx \undefined \writestatus          \input supp-mis.tex \relax \fi
\ifx \undefined \startMPgraphic \else \expandafter \endinput     \fi

\writestatus{loading}{Context Support Macros / MetaPost Inclusion}

\unprotect

%D \macros
%D   {startMPgraphic}
%D
%D From within \TEX\ one can execute \METAPOST\ code by putting
%D it between the two commands
%D
%D \starttypen
%D \startMPgraphic
%D \stopMPgraphic
%D \stoptypen
%D
%D This is implemented as:

\long\def\startMPgraphic#1\stopMPgraphic%
  {\startwritingMPgraphic
   \writeMPgraphic{#1}%
   \stopwritingMPgraphic}

%D \macros
%D   {startMPrun}
%D
%D If we just wat to run \METAPOST\ code, that is, not to
%D explictly generate a figure in terms of \type{beginfig} and
%D \type{endfig}, we can use: 
%D
%D \starttypen
%D \startMPgraphic
%D \stopMPgraphic
%D \stoptypen
%D
%D \starttypen
%D \startMPrun
%D \stopMPrun
%D \stoptypen
%D
%D The next booleans are for internal purposes only.

% some day a bit more more clear:
%
% run directly/run afterwards/run external defined
% insert directly/insert whenever
% use object/don't use objects

\newif\ifMPgraphics \MPgraphicstrue
\newif\ifMPrun      \MPrunfalse

\ifCONTEXT

  \long\def\dostartMPrun#1#2\stopMPrun% 
    {\bgroup
     \MPruntrue
     \doifsomething{#1}{\def\MPgraphicfile{#1}}%
     \startwritingMPgraphic
     \writeMPgraphic{#2}%
     \stopwritingMPgraphic
     \egroup}
  
  \def\startMPrun%
    {\dosinglegroupempty\dostartMPrun}

\else

  \long\def\startMPrun#1\stopMPrun% 
    {\MPruntrue
     \startwritingMPgraphic
     \writeMPgraphic{#1}%
     \stopwritingMPgraphic
     \MPrunfalse}

\fi

%D \macros
%D   {startwritingMPgraphic,
%D    writeMPgraphic,
%D    stopwritingMPgraphic}
%D
%D If the writing process is divided into more steps, one can
%D use the components of this macro directly.
%D
%D \starttypen
%D \startwritingMPgraphic
%D ...
%D \writeMPgraphic{...}
%D ...
%D \writeMPgraphic{...}
%D ...
%D \stopwritingMPgraphic
%D \stoptypen

%D \macros
%D   {ifrunMPgraphics,ifinsertMPgraphics}
%D
%D These macros look a bit more complicated that one would
%D expect at first sight. This is due to the two ways of
%D processing these graphics, mentioned in a previous
%D paragraph. Which method is used, the direct or indirect
%D one, depends on a boolean.

\newif\ifrunMPgraphics    \runMPgraphicsfalse
\newif\ifinsertMPgraphics \insertMPgraphicstrue

%D If set to true, one can do with a single pass, else one must
%D process the \METAPOST\ file \type{mpgraph} between two
%D succesive \TEX\ runs.

\def\MPgraphicfile{mp\ifMPrun run\else graph\fi}

%D \macros
%D   {MPgraphic}
%D
%D When we run \METAPOST\ from within \TEX, each graphic is
%D processed at once, which means that we reuse this file many
%D times. When however the execution is delayed, all graphics
%D are saved in a separate figure. The current graphic is
%D characterized bij a \COUNTER. This counter is available 
%D in \type{\MPgraphic}.

\newcount\currentMPgraphic

\def\MPgraphic{0}

% %D \macros
% %D   {ifreuseMPgraphics}
% %D
% %D If one want to reuse grapics, one can save much redundant
% %D run time by setting the next switch to true.
% 
% \newif\ifreuseMPgraphics \reuseMPgraphicstrue

%D The three macros responsible for writing the graphic
%D implement both schemes.

%D \macros
%D   {MPinclusions, startMPinclusions}
%D
%D One can include for instance common input commands by
%D passing them to \type{\MPinclusions}: 
%D
%D \starttypen
%D \MPinclusions{input tools}
%D \stoptypen

\let\theMPinclusions=\empty

\long\def\startMPinclusions#1\stopMPinclusions%
  {\long\def\theMPinclusions{\writeMPgraphic{#1}}}

\long\def\MPinclusions#1%
  {\startMPinclusions#1\stopMPinclusions}

%D \macros
%D   {iflongMPlines}
%D
%D When grabbing a graphic deifnition, newlines are turned
%D into spaces. By default we split the graphic definition
%D at the colon, but long lines are still possible by
%D setting the next boolean to true.

\newwrite\MPwrite

\newif\iflongMPlines

\long\def\writeMPgraphic#1%
  {\bgroup
   \iflongMPlines
     \let\par=\empty
     \long\def\flush##1##2\par%
       {\ifx##1\relax \else
          \immediate\write\MPwrite{##1##2}%
          \expandafter\flush
        \fi}%
     \flush#1\empty\par\relax\par
   \else
     \long\def\flush##1##2;%
       {\ifx##1\relax \else
          \dowriteMPgraphicline##1##2btex\relax etex\MPend
          \expandafter\flush
        \fi}%
     \flush#1\empty;\relax;%
   \fi
   \egroup}

%D The \type{;} aware method (the \type{\else} branch) also 
%D takes care of \type{btex}||\type{etex} bound data. 

\def\dowriteMPgraphicline%
  {\futurelet\next\dodowriteMPgraphicline}

\long\def\dodowriteMPgraphicline#1btex#2#3etex#4\MPend%
  {\ifx\next\empty\else\ifx\next\relax\else
     \bgroup
     \let\par=\empty
     \ifx#2\relax
       \immediate\write\MPwrite{#1;}%
       \egroup
     \else
       \convertargument#2#3\to\ascii
       \immediate\write\MPwrite{#1btex \ascii etex;}%
       \egroup
       \dowriteMPgraphicline#4btex\relax etex\MPend
     \fi
   \fi\fi}

%D This stripper is suboptimal in the sense that more
%D \type{;}'s are output than feasible. Anyhow, \METAPOST\ 
%D can handle this and users may consider it being a sort 
%D of error prevention bonus. 

\def\writeMPgraph%
  {\immediate\write\MPwrite{mpgraph:=\the\currentMPgraphic;}}

\def\startwritingMPgraphic%
  {\ifMPrun \else 
     \global\advance\currentMPgraphic by 1 
   \fi
   \ifrunMPgraphics
     \xdef\MPgraphic{\the\currentMPgraphic}%
     \immediate\openout\MPwrite=\MPgraphicfile.mp
     \writeMPgraph
     \setMPrandomseed
     \theMPinclusions
   \else
     \xdef\MPgraphic{\the\currentMPgraphic}%
     \ifnum\currentMPgraphic=1
       \immediate\openout\MPwrite=\MPgraphicfile.mp
       \writeMPgraph
       \setMPrandomseed
       \theMPinclusions
     \fi
   \fi
   \ifMPrun \else
     \immediate\write\MPwrite{beginfig(\the\currentMPgraphic);}%
   \fi
   \global\let\flushMPgraphics\dodostopwritingMPgraphic
   \global\let\stopwritingMPgraphic=\dostopwritingMPgraphic}

\def\dostopwritingMPgraphic%
  {\ifMPrun \else 
     \immediate\write\MPwrite{endfig;}%
   \fi
   \ifrunMPgraphics
     \dodostopwritingMPgraphic
   \fi}

\def\dodostopwritingMPgraphic%
  {\ifnum\currentMPgraphic>0
     \donetrue
   \else\ifMPrun
     \donetrue
   \else
     \donefalse
   \fi\fi
   \ifdone
     \immediate\write\MPwrite{end.}%
     \immediate\closeout\MPwrite
     \runMPgraphic{\MPgraphicfile}%
   \fi
   \global\let\flushMPgraphics=\relax}

\let\stopwritingMPgraphic=\relax
\let\flushMPgraphics     =\relax

%D \macros
%D   {setMPrandomseed}
%D
%D Did you notice the random seed initialization? This is 
%D needed because \METAPOST\ has a rather poor initialization, 
%D which in some implementations depends on the time in 
%D minutes. So, in quick successive runs, random is not that 
%D random. 

\newif\ifsetMPrandomseed % false by default

\def\setMPrandomseed%
  {\ifsetMPrandomseed \ifx\getrandomnumber\undefined \else
     \getrandomnumber\localMPseed{0}{4095}%
     \writeMPgraphic{randomseed := \localMPseed ;}%
   \fi\fi}

%D This feature has become optional. Thanks to Fabrice Popineau, 
%D \METAPOST\ can now do a far better job! 

%D \macros
%D   {flushMPgraphics}
%D
%D When we use the indirect method, all graphics are saved in
%D one file. This means that we cannot close this file after
%D every \type{\stopMPgraphic}. Therefore we need to say:
%D
%D \starttypen
%D \flushMPgraphic
%D \stoptypen
%D
%D else the file is closed without writing the \METAPOST\ end
%D command. One will notice this fast enough when in indirect
%D mode. When using the direct mode this command is not
%D implicitly needed, but ommiting it makes files less
%D portable.

%D \macros
%D   {loadcurrentMPgraphic,
%D    placeMPgraphic}
%D
%D Once defined, we can call for this graphic by saying:
%D
%D \starttypen
%D \loadcurrentMPgraphic{setups}
%D \placeMPgraphic
%D \stoptypen
%D
%D This two stage insert permits some intermediate manipulations
%D of the graphic, which temporary saved in:

\newbox\MPgraphicbox

\def\doloadcurrentMPgraphic#1%
  {\loadMPgraphic{\MPgraphicfile.\the\currentMPgraphic}{#1}}

\ifCONTEXT
  \def\loadcurrentMPgraphic{\dosinglegroupempty\doloadcurrentMPgraphic}
\else
  \let\loadcurrentMPgraphic\doloadcurrentMPgraphic
\fi

\def\loadMPgraphic#1#2%
  {\setbox\MPgraphicbox=\hbox
     {\ifinsertMPgraphics\insertMPfile{#1}{#2}\fi}}

\def\placeMPgraphic%
  {\box\MPgraphicbox}

%D \macros
%D   {startreusableMPgraphic, reuseMPgraphic, useMPbox}
%D
%D One can use the next macro for defining graphics that are
%D to be reused. When the next switch is set, graphics are
%D cached.

\newif\ifuseMPbox  \useMPboxtrue 

\def\douseMPbox#1%
  {\setobject{MP}{#1}
     \vbox
       {\forgetall
        \loadMPgraphic{\MPgraphicfile.\the\currentMPgraphic}{}%
        \placeMPgraphic}%
   \setgvalue{#1}%
     {\getobject{MP}{#1}}}

\def\nouseMPbox#1%
  {\setxvalue{#1}%
     {\noexpand\forgetall
      \noexpand\loadMPgraphic{\MPgraphicfile.\the\currentMPgraphic}{}%
      \noexpand\placeMPgraphic}}

\ifCONTEXT \else \let\douseMPbox=\nouseMPbox          \fi
\ifCONTEXT \else \let\doifobjectssupportedelse=\relax \fi

% \long\def\startreusableMPgraphic#1#2\stopreusableMPgraphic%
%   {%\reuseMPgraphicstrue
%    \doifundefined{MP:#1}
%      {\startMPgraphic#2\stopMPgraphic
%       \doifobjectssupportedelse{}{\useMPboxfalse}% 
%       \ifuseMPbox
%         \douseMPbox{MP:#1}%
%       \else
%         \nouseMPbox{MP:#1}%
%       \fi}}

\long\def\startreusableMPgraphic#1#2\stopreusableMPgraphic%
  {\doifundefined{MP:#1}
     {\setgvalue{MP:#1}%
        {\startMPgraphic#2\stopMPgraphic
         \doifobjectssupportedelse{}{\useMPboxfalse}% 
         \ifuseMPbox
           \douseMPbox{MP:#1}%
         \else
           \nouseMPbox{MP:#1}%
         \fi
         \getvalue{MP:#1}}}}

\def\reuseMPgraphic#1%
  {\getvalue{MP:#1}}

%D \macros
%D   {startuseMPgraphic,useMPgraphic}
%D
%D The every||time||it's||used original one is defined below.
%D This one makes sense when the graphic uses random numbers.

\long\def\startuseMPgraphic#1#2\stopuseMPgraphic%
  {%\reuseMPgraphicstrue
   \long\setgvalue{MP:#1}%
     {\startMPgraphic#2\stopMPgraphic
      \loadcurrentMPgraphic{}%
      \placeMPgraphic}}

\let\useMPgraphic=\reuseMPgraphic

%D We didn't yet define the macro responsible for processing
%D the graphic from within \TEX.

\def\runMPgraphic#1%
  {\ifrunMPgraphics
     \executeMETAPOST{#1}%
   \else
     \message{[flush and process \MPgraphicfile.mp afterwards]}%
   \fi}

%D \macros
%D   {executeMetaPost, executeMETAPOST, executesystemcommand}
%D
%D With \type{\executeMETAPOST} being defined as:

\ifx\undefined\executeMetaPost
  \def\executeMETAPOST#1{\executesystemcommand{\executeMetaPost{#1}}}
\fi

%D There are two system dependant definitions:

\ifx\undefined\executesystemcommand
  \def\executesystemcommand#1{\immediate\write18{#1}}
\fi

\ifx\undefined\executeMetaPost
  \def\executeMetaPost#1{mpost #1}
\fi

%D \macros
%D   {insertMPfile}
%D
%D One can define this command in advance or redefine it after
%D loading this module. The same goes for the forward
%D reference to the figure loading macro:

\ifx\undefined\insertMPfile

  \def\insertMPfile#1#2%
    {\ifx\undefined\externalfigure
       \message{[insert file #1 here]}%
     \else
       \externalfigure[#1][\c!type=\c!mps,\c!object=\v!nee,#2]%
     \fi}

\fi

%D This macro takes {\em two} arguments, the second one can be
%D used to pass info to the inclusion macro. Some examples
%D of its use can be found in the modules \type{supp-tpi} and
%D \type{prag-log}.

%D This module can be used in \PLAIN\ \TEX too. When using 
%D \DVIPS, just try to process:
%D 
%D \starttypen
%D \input supp-mps
%D
%D \runMPgraphicstrue
%D 
%D \def\insertMPfile#1#2%
%D   {\special{psfile=#1}}
%D 
%D \startuseMPgraphic{1}
%D   prologues := 1;
%D   draw (0,0) withpen pencircle scaled 100;
%D \stopuseMPgraphic
%D 
%D \useMPgraphic{1}
%D \stoptypen
%D 
%D Don't forget to enable \type{\write18}. When does not say
%D \type{\runMPgraphicstrue}, the \METAPOST\ scratch file 
%D must be closed by saying
%D 
%D \starttypen
%D \flushMPgraphics
%D \stoptypen
%D
%D When using the indirect method, one has to process the file
%D \type{mpgraph.mp} between two successive \TEX\ runs. 

%D For some reason, \METAPOST\ needs the public domain \DVI\ to
%D \POSTSCRIPT\ converter \DVIPS. This symbiosis originates in
%D the need to include the fonts (glyphs) that \METAPOST\ uses
%D in the \POSTSCRIPT\ file. Driver independancy was one of my
%D prerequisites for using \METAPOST, so I decided to build
%D this kind of support myself. Personally I consider driver
%D dependancy a drawback for the dissemination of such a
%D package. The second part of this module more or less
%D decouples \METAPOST\ and \DVIPS.
%D
%D The macros hereafter are copied from the module
%D \type{m-metapost}. After writing module \type{supp-pdf} I
%D added this method to the module named and after a while
%D decided to hook it into module \type{spec-yy}. Therefore
%D they made it into a support module, but in a slightly
%D different way.

%D \macros
%D   {includeMPfonts, ifincludeMPfonts}
%D   {}
%D
%D The method we use is both robust and simple: one can do
%D with calling the next macro with the filename as argument:
%D
%D \starttypen
%D \includeMPfonts{filename}
%D \stoptypen
%D
%D We can turn of this mechanism with:
%D
%D \starttypen
%D \includeMPfontsfalse
%D \stoptypen

\newif\ifincludeMPfonts \includeMPfontstrue

\def\includeMPfonts#1%
  {\ifincludeMPfonts
     \bgroup
     \message{[MP fonts #1]}%
     %\uncatcodespecials
     \endlinechar=-1
     \setMPspecials
     \obeyMPspecials
     \setbox0=\hbox
       {\hskip-\maxdimen
        \doprocessfile\scratchread{#1}\handleMPfont}%
     \smashbox0
     \box0
     \egroup
   \fi}

\def\UseMetaPostGraphic      {\includeMPfonts}      % upward compatible
\def\DontUseMetaPostGraphics {\includeMPfontsfalse} % upward compatible

%D The characters are collected in a box and moved as far as
%D possible into the left margin. The resulting box has no
%D dimensions and can be prepended (appended) to the special
%D that handles the inclusion. The characters are in the file
%D but made invisible.

%D We scan the graphics file for the \type{fshow} operator,
%D that is, lines that start with \type{(}. If found it
%D interprets the line, which looks like:
%D
%D \starttypen
%D (string ... string) font size fshow
%D \stoptypen
%D
%D Font definitions specified in the preamble are simply
%D ignored. Only lines starting with \type{(} are interpreted.

\def\dohandleMPfont#1#2\relax%
  {\if#1(%
     \expandafter\includeMPcharacters\fileline\relax
   \fi}

\def\handleMPfont%
  {\expandafter\dohandleMPfont\fileline\relax}

%D Before we start scanning for data, we first change some
%D \CATCODES. The first set of macro's is copied from module
%D \type{supp-pdf}. This scheme is a bit overdone for this
%D module, but using the same macros saves us some memory.

\def\octalMPcharacter#1#2#3%
  {\char'#1#2#3\relax}

\bgroup
\catcode`\|=\@@comment
\catcode`\%=\@@active
\catcode`\[=\@@active
\catcode`\]=\@@active
\catcode`\{=\@@active
\catcode`\}=\@@active
\catcode`B=\@@begingroup
\catcode`E=\@@endgroup
\gdef\ignoreMPspecials|
  B\def%BE|
   \def[BE|
   \def]BE|
   \def{BE|
   \def}BEE
\gdef\obeyMPspecials|
  B\def%B\char 37\relax E|
   \def[B\char 91\relax E|
   \def]B\char 93\relax E|
   \def{B\char123\relax E|
   \def}B\char125\relax EE
\gdef\setMPspecials|
  B\setnaturalcatcodes
   \catcode`\%=\@@active
   \catcode`\[=\@@active
   \catcode`\]=\@@active
   \catcode`\{=\@@active
   \catcode`\}=\@@active
   \def\(B\char40\relax     E|
   \def\)B\char41\relax     E|
   \def\\B\char92\relax     E|
   \def\0B\octalMPcharacter0E|
   \def\1B\octalMPcharacter1E|
   \def\2B\octalMPcharacter2E|
   \def\3B\octalMPcharacter3E|
   \def\4B\octalMPcharacter4E|
   \def\5B\octalMPcharacter5E|
   \def\6B\octalMPcharacter6E|
   \def\7B\octalMPcharacter7E|
   \def\8B\octalMPcharacter8E|
   \def\9B\octalMPcharacter9EE
\egroup

%D The lines starting with \type{(} are interpreted and
%D handled by
%D
%D \starttypen
%D \def\includeMPcharacters(#1) #2 #3 #4\relax%
%D   {\font\temp=#2 at #3bp\temp#1}
%D \stoptypen
%D
%D While processing some \TUG~98 proceedings, I also had to 
%D deal with:
%D
%D \starttypen
%D /nfont {10 div dup scale 10} def
%D (T) ANTTB 7.13086 nfont fshow
%D \stoptypen
%D
%D which comes to rounding sizes. This is something 
%D experimental.

\def\PSnfont{nfont}

\def\includeMPcharacters(#1) #2 #3 #4#5#6#7#8#9\relax%
  {\edef\temp{#4#5#6#7#8}%
   \ifx\temp\PSnfont % round font size (to pt)
     \scratchdimen=#3pt
     \ifdim\scratchdimen<1pt
       \def\size{1pt}%
     \else
       \advance\scratchdimen by .5pt 
       \def\size##1.##2\relax{\def\size{##1pt}}% 
       \expandafter\size\the\scratchdimen\relax
     \fi
   \else
     \edef\size{#3bp}%
   \fi
   \font\temp=#2 at \size
   \temp\if#1 \char32\else#1\fi}

%D This method is both robust and reasonable fast. The only
%D disadvantage is that when not embedded properly in the
%D graphics inclusion macros, one has to load all graphics by
%D hand.

%D Now let's see if things work all right and show the example
%D files that are part of the \METAPOST\ distribution:
%D
%D \startregelcorrectie
%D \steluitlijnenin[midden]
%D \leavevmode
%D \startcombinatie[3*3]
%D   {\externfiguur[mp-exa-1][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-2][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-3][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-4][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-5][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-6][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-7][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-8][kader=aan,breedte=.2\hsize]} {}
%D   {\externfiguur[mp-exa-9][kader=aan,breedte=.2\hsize]} {}
%D \stopcombinatie
%D \stopregelcorrectie
%D
%D Here we used calls like:
%D
%D \starttypen
%D \externfiguur[mp-exa-1][methode-mps,kader=aan,breedte=.2\hsize]
%D \stoptypen

%D \macros
%D   {convertMPcolors,
%D    ifconvertMPcolors,ifreduceMPcolors,ifforceMPcolors}
%D
%D When I told the editors that I wanted to use colored
%D \METAPOST\ graphics in the color issue of the \MAPS, I was
%D asked to use the \kap{CMYK} colorspace instead of \kap{RGB}
%D one. However, \METAPOST\ only supports \kap{RGB} colors. I
%D decided to write a utility to convert the \type
%D {setrgbcolor} operators into \type {setcmykcolor} ones, and
%D some experiments showed me that I could best let \TEX\ do it
%D itself. Here it is:
%D
%D There are two booleans that control the conversion process.
%D These are false by default.

\newif\ifconvertMPcolors
\newif\ifreduceMPcolors
\newif\ifforcegrayMPcolors

%D The main macro is called as:
%D
%D \starttypen
%D \convertMPcolors{filename}
%D \stoptypen
%D
%D When active, this macro returns a message saying if indeed
%D conversion took place. The old file is overwritten! This
%D saves time in a succesive passes and can't harm, simply
%D because MP can generate them anew.

\def\convertMPcolorpath{} 
\def\convertMPcolorfile{metacmyk.eps}

\def\convertMPcolors#1%
  {\bgroup
   \ifforcegrayMPcolors
     \donetrue
   \else\ifconvertMPcolors
     \donetrue
   \else
     \donefalse
   \fi\fi
   \ifdone
     \message{[MP color conversion #1}%
     \endlinechar=-1
     \uncatcodespecials
     \donefalse
     \immediate\openout\scratchwrite=\convertMPcolorpath\convertMPcolorfile
     \doprocessfile\scratchread{#1}\handleMPcolor
     \immediate\closeout\scratchwrite
     \ifdone
       \immediate\openout\scratchwrite=\convertMPcolorpath#1
       \doprocessfile\scratchread{\convertMPcolorpath \convertMPcolorfile}\handleMPcopy
       \immediate\closeout\scratchwrite
       \message{done]}%
     \else
       \message{not needed]}%
     \fi
     \immediate\openout\scratchwrite=\convertMPcolorpath\convertMPcolorfile
     \immediate\closeout\scratchwrite
   \fi
   \egroup}

%D The process is rather simple: read a line, look for the
%D \type {setrgbcolor} operator, recalculate the components and
%D check for gray reduction or black removal, write the result
%D to a temporary file, and go on. Afterwards, the file is
%D copied back. We don't have to reduce to gray scales;
%D \METAPOST\ already takes care of that.

\def\handleMPcolor
  {\expandafter\dohandleMPcolor\fileline setrgbcolor*\\}

\def\dohandleMPcolor#1setrgbcolor#2#3\\%
  {\if#2*%
     \immediate\write\scratchwrite{#1}%
   \else
     \dodohandleMPcolor#1setrgbcolor#2#3\\%
   \fi}

\def\dodohandleMPcolor#1 #2 #3setrgbcolor#4setrgbcolor*\\%
  {\bgroup
   \ifforcegrayMPcolors
     \convertRGBtoGRAY{#1}{#2}{#3}%
     \immediate\write\scratchwrite
       {\@@cl@@s \space setgray #4}%
   \else
     \dimen0=1pt \advance\dimen0 by -#1pt
     \dimen2=1pt \advance\dimen2 by -#2pt
     \dimen4=1pt \advance\dimen4 by -#3pt
     \ifreduceMPcolors
       \dimen6=\dimen0
       \ifdim\dimen2<\dimen6 \dimen6=\dimen2 \fi
       \ifdim\dimen4<\dimen6 \dimen6=\dimen4 \fi
       \advance\dimen0 by -\dimen6
       \advance\dimen2 by -\dimen6
       \advance\dimen4 by -\dimen6
     \else
       \dimen6=\!!zeropoint
     \fi
     \immediate\write\scratchwrite
       {\withoutpt{\the\dimen0} \space
        \withoutpt{\the\dimen2} \space
        \withoutpt{\the\dimen4} \space
        \withoutpt{\the\dimen6} \space setcmykcolor #4}%
    \fi
    \egroup
    \donetrue} % needed for message

\def\handleMPcopy%
  {\immediate\write\scratchwrite{\fileline}}

%D The next macro is needed for forced conversion. This macro
%D is copied from \type{colo-ini}, just in case one uses this
%D module outside \CONTEXT.

\ifx\convertRGBtoGRAY\undefined

  \def\convertRGBtoGRAY#1#2#3%
    {\scratchdimen=#1\s!pt
     \scratchdimen=300\scratchdimen
     \scratchcounter=\scratchdimen
     \scratchdimen=#2\s!pt
     \scratchdimen=590\scratchdimen
     \advance\scratchcounter by \scratchdimen
     \scratchdimen=#3\s!pt
     \scratchdimen=110\scratchdimen
     \advance\scratchcounter by \scratchdimen
     \advance\scratchcounter by \!!medcard
     \divide\scratchcounter by \!!maxcard
     \edef\@@cl@@s{\realcolorvalue\scratchcounter}}

\fi

%D The next examples show the color conversion macros in
%D action. These examples also demonstrate in||text \METAPOST\
%D handling. As we will see, the conversion is hooked into the
%D \CONTEXT\ color mechanism.
%D
%D By setting both \type{rgb} and \type{cmyk} to off, we force
%D conversion to gray scales using:
%D
%D \plaatsformule[-]
%D   \startformule
%D   G = .30r + .59g + .11b
%D   \stopformule
%D
%D By using buffers, we keep the \ASCII\ layout clean:
%D
%D \startbuffer
%D \startbuffer[rgb]
%D   \stelkleurenin[rgb=ja,cmyk=nee,reductie=nee,conversie=nee]
%D   \useMPgraphic{hans}
%D \stopbuffer
%D
%D \startbuffer[cmyk]
%D   \stelkleurenin[rgb=nee,cmyk=ja,reductie=nee,conversie=nee]
%D   \useMPgraphic{hans}
%D \stopbuffer
%D
%D \startbuffer[cmy]
%D   \stelkleurenin[rgb=nee,cmyk=ja,reductie=ja,conversie=nee]
%D   \useMPgraphic{hans}
%D \stopbuffer
%D
%D \startbuffer[gray]
%D   \stelkleurenin[rgb=nee,cmyk=nee,reductie=nee,conversie=nee]
%D   \useMPgraphic{hans}
%D \stopbuffer
%D \stopbuffer
%D
%D \typebuffer
%D \haalbuffer
%D
%D The graphic is rather simple and is generated each time
%D it's called:
%D
%D \global\runMPgraphicstrue
%D
%D \startbuffer
%D \startbuffer[graphic]
%D   \startuseMPgraphic{hans}
%D     width  :=\the\tekstbreedte/5;
%D     height := width/4;
%D     fill fullcircle
%D       xscaled width
%D       yscaled height
%D       withcolor (\RedGreenBlue);
%D   \stopuseMPgraphic
%D \stopbuffer
%D \stopbuffer
%D
%D \typebuffer
%D \haalbuffer
%D
%D Next we combine the four alternative interpretations in a
%D combination:
%D
%D \startbuffer
%D \startbuffer[result]
%D   \startcombinatie[4]
%D     {\haalbuffer[rgb]}  {\tfxx original}
%D     {\haalbuffer[cmyk]} {\ttxx\string\convertMPcolorstrue}
%D     {\haalbuffer[cmy]}  {\ttxx\string\reduceMPcolorstrue}
%D     {\haalbuffer[gray]} {\ttxx\string\forcegrayMPcolorstrue}
%D   \stopcombinatie
%D \stopbuffer
%D \stopbuffer
%D
%D \typebuffer
%D \haalbuffer
%D
%D Finally we call the buffers, using different setting:
%D
%D \startbuffer
%D \plaatsfiguur
%D   {\METAPOST\ color conversions}
%D   {\def\RedGreenBlue{.1,.4,.6}\haalbuffer[graphic]\haalbuffer[result]\vskip6pt
%D    \def\RedGreenBlue{.1,.6,.4}\haalbuffer[graphic]\haalbuffer[result]\vskip6pt
%D    \def\RedGreenBlue{.4,.1,.6}\haalbuffer[graphic]\haalbuffer[result]\vskip6pt
%D    \def\RedGreenBlue{.4,.6,.1}\haalbuffer[graphic]\haalbuffer[result]\vskip6pt
%D    \def\RedGreenBlue{.6,.1,.4}\haalbuffer[graphic]\haalbuffer[result]\vskip6pt
%D    \def\RedGreenBlue{.6,.4,.1}\haalbuffer[graphic]\haalbuffer[result]}
%D \stopbuffer
%D
%D \typebuffer
%D \haalbuffer
%D
%D By the way, when the \POSTSCRIPT\ file resulting from
%D this input is converted into \PDF\ and viewed in Acrobat
%D Reader, one can quite different colors from those
%D displayed in \GHOSTSCRIPT, which view equals the
%D \POSTSCRIPT\ originals.

%D \macros
%D   {experimental}
%D
%D Some experimental macros:
%D 
%D \starttypen
%D \startMPdrawing
%D \stopMPdrawing
%D \pushMPdrawing
%D \popMPdrawing
%D \resetMPdrawing
%D \ifMPdrawingdone
%D \MPdivten[number]
%D \stoptypen
%D
%D These macros are used in \PPCHTEX. 

\let\MPdrawingdata\empty

\newif\ifMPdrawingdone  \MPdrawingdonefalse
\newif\ifMPshiftdrawing \MPshiftdrawingtrue

\def\resetMPdrawing%
  {\global\let\MPdrawingdata\empty
   \global\MPdrawingdonefalse}
 
\def\pushMPdrawing%
  {\pushmacro\MPdrawingdata
   \global\let\MPdrawingdata\empty}

\def\popMPdrawing%
  {\popmacro\MPdrawingdata}

\def\getMPdrawing%
  {\ifMPdrawingdone
     \bgroup
     \setbox0=\hbox
       {\expandafter\startMPgraphic\MPdrawingdata\stopMPgraphic
        \loadcurrentMPgraphic\empty
        \placeMPgraphic}%
     \ifMPshiftdrawing 
       \dimen0=\MPllx bp 
       \dimen2=\MPlly bp
       \hbox{\hskip\dimen0\raise\dimen2\box0}%
     \else
       \box0
     \fi
     \egroup
   \fi}

\long\def\startMPdrawing#1\stopMPdrawing%
  {\long\xdef\MPdrawingdata{\MPdrawingdata#1}}

\def\MPdivten[#1]%
  {\@EA\@EA\@EA\doMPdivten\@EA\@EA\@EA[\@EA#1]}

\def\doMPdivten[#1]%
  {\ifnum#1> 9999 \dodoMPdivtenB#1\else
   \ifnum#1>  999 \dodoMPdivtenC#1\else
   \ifnum#1>   99 \dodoMPdivtenD#1\else
   \ifnum#1>    9 \dodoMPdivtenE#1\else
   \ifnum#1>    0 \dodoMPdivtenF#1\else
   \ifnum#1<-9999 \dodoMPdivtenA#1\else
   \ifnum#1< -999 \dodoMPdivtenB#1\else
   \ifnum#1<  -99 \dodoMPdivtenC#1\else
   \ifnum#1<   -9 \dodoMPdivtenD#1\else
   \ifnum#1<    0 \dodoMPdivtenE#1\else
   0\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi}

\def\dodoMPdivtenA#1#2#3#4#5#6{#1#2#3#4#5.#6}
\def\dodoMPdivtenB  #1#2#3#4#5{#1#2#3#4.#5}
\def\dodoMPdivtenC    #1#2#3#4{#1#2#3.#4}
\def\dodoMPdivtenD      #1#2#3{#1#2.#3}
\def\dodoMPdivtenE        #1#2{#1.#2}
\def\dodoMPdivtenF          #1{.#1}

\protect

\endinput
