Editing MetaPost

{{short description|Programming language}}
{{multiple issues|
{{how-to|date=January 2016}}
{{more footnotes needed|date=January 2016}}
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{{Infobox programming language
| name = MetaPost
| logo = MPlogo.svg
| paradigm = [[Imperative programming|imperative]], [[typesetting]]
| released = {{Start date|1994}}
| designer = John D. Hobby
| developer = Taco Hoekwater, Luigi Scarso
| latest_release_version = 1.8
| latest_release_date = {{start date and age|2013|06|17|df=yes}}
| latest_preview_version = 2.0rc2
| latest_preview_date = {{start date and age|2018|02|19|df=yes}}
| typing = [[duck typing|duck]], [[dynamic typing|dynamic]], [[strong typing|strong]]
| implementations = 
| dialects = 
| influenced by = [[Metafont]]
| influenced = 
| operating_system = [[Cross-platform]]
| license = [[LGPL]]
| website = {{URL|http://tug.org/metapost}}
| file_ext = 
}}

'''MetaPost''' refers to both a [[programming language]] and the [[interpreter (computer software)|interpreter]] of the MetaPost programming language. Both are derived from [[Donald Knuth]]'s [[Metafont]] language and interpreter. MetaPost produces vector graphic diagrams from a geometric/algebraic description. The language shares Metafont's declarative syntax for manipulating lines, curves, points and geometric transformations. However,

* Metafont is set up to produce fonts, in the form of image files (in .gf format) with associated font metric files (in .tfm format), whereas MetaPost produces [[encapsulated PostScript|EPS]], [[Scalable Vector Graphics|SVG]], or [[Portable Network Graphics|PNG]] files
* The output of Metafont consists of the fonts at a fixed resolution in a raster-based format, whereas MetaPost's output is vector-based graphics (lines, [[Bézier curve]]s)
* Metafont output is monochrome, whereas MetaPost uses [[RGB]] or [[CMYK]] colors.
* The MetaPost language can include text labels on the diagrams, either strings from a specified font, or anything else that can be typeset with [[TeX]].
* Starting with version 1.8, Metapost allows floating-point arithmetic with 64 bits (default: 32 bit fixed-point arithmetic)

Many of the limitations of MetaPost derive from features of Metafont. For instance, MetaPost does not support all features of [[PostScript]]. Most notably, paths can have only one segment (so that regions are [[simply connected]]), and regions can be filled only with uniform colours. PostScript level 1 supports tiled patterns and PostScript 3 supports [[Gouraud shading]].

==Availability and usage==
MetaPost is distributed with many distributions of the [[TeX]] and Metafont framework, for example, it is included in the [[MiKTeX]] and the [[TeX Live]] distributions.

The encapsulated postscript produced by Metapost can be included in [[LaTeX]], [[ConTeXt]], and [[TeX]] documents via standard graphics inclusion commands. The encapsulated postscript output can also be used with the [[PDFTeX]] engine, thus directly giving [[Portable Document Format|PDF]]. This ability is implemented in ConTeXt and in the LaTeX graphics package, and can be used from plain TeX via the supp-pdf.tex macro file.

ConTeXt and [[LuaTeX]] supports the inclusion of MetaPost code within the input file. Inclusion of MetaPost code in LaTeX is also possible by using LaTeX-packages, for example <code>gmp</code> or <code>mpgraphics</code>.

==Examples==
This is a single file <samp>example.mp</samp> which when processed by the MetaPost interpreter (via the command <code>mpost</code> on [[Linux]]) produces three eps files <samp>example.1</samp>, <samp>example.2</samp>, <samp>example.3</samp>. These are pictured on the right.
[[Image:Metapost ex.svg|thumb|198px|right|example outputs]]
<syntaxhighlight lang="octave">
transform pagecoords;
pagecoords:=identity scaled 10mm shifted (100mm,150mm);
beginfig (1)
    fill ((0,0)--(2,0)--(2,1)--(1,1)--(1,2)--(0,2)--cycle)
        transformed pagecoords withcolor green;
    draw ((2,0)..(2,1)..(1,1)..(1,2)..(0,2))
        transformed pagecoords;
    drawarrow ((0,0)--(2,2)) transformed pagecoords;
endfig;
beginfig (2)
    draw (for i=0 upto 7: dir (135i)-- endfor cycle)
        transformed pagecoords;
endfig;
pagecoords:=identity scaled 15mm shifted (100mm,150mm);
beginfig (3);
    % declare paths to be used
    path p[],p[]t;
    % set up points by defining relationships
    z1=(0,0);   z2=z1+2up;
    z3=z1+whatever*dir (60)=z2+whatever*dir (-50);
    z4=z3+(-1.5,-.5);
    z5=z1+dir (135);
    z0=whatever[z1,z2]=whatever[z3,z4];
    % set up paths
    p0=fullcircle yscaled .5 rotated 45 shifted z0 ;
    p1=z2---z4..z0..z3---z1;
    p2=p1 cutbefore p0 cutafter p0;
    p3=p0 cutbefore p1 cutafter p1;
    p4=p2---p3---cycle;
    % define transformed versions of paths and points
    for i=0 upto 4: p[i]t=p[i] transformed pagecoords; endfor
    for i=0 upto 5: z[i]t=z[i] transformed pagecoords; endfor
    % do some drawing
    fill p4t withcolor (1,1,0.2);
    draw z1t---z2t withcolor .5white;
    draw z3t---z4t withcolor .5white;
    pickup pencircle;
    draw p0t dashed withdots scaled .3;
    draw p1t dashed evenly;
    draw p2t withcolor blue;
    draw p3t withcolor red;
    label.lrt (btex $z_0$ etex, z0t);
    label.llft (btex $z_1$ etex, z1t);
    label.top (btex $z_2$ etex, z2t);
    label.rt (btex $z_3$ etex, z3t);
    label.llft (btex $z_4$ etex, z4t);
    for i=0 upto 4:
        drawdot z[i]t withpen pencircle scaled 2;
    endfor
endfig;
bye
</syntaxhighlight>

The resulting three eps files can be used in [[TeX]] via [[LaTeX]]'s <code>\includegraphics</code> command, [[ConTeXt]]'s <code>\externalfigure</code>, Plain TeX's <code>\epsfbox</code> command, or (in Plain pdftex) the <code>\convertMPtoPDF</code> command from <samp>supp-pdf.tex</samp>. To view or print the third diagram, this inclusion is necessary, as the TeX fonts ([[Computer Modern]]) are not included in the eps files produced by MetaPost by default.

==See also==
{{Portal|Free and open-source software}}
* [[PSTricks]]
* [[PGF/TikZ]]
* [[METATYPE1]]
* [[Asymptote (vector graphics language)|Asymptote]]

==References==
{{Refbegin}}
* {{cite web|url=http://wiki.contextgarden.net/MetaFun|title=MetaFun|type=modules for Metapost|last=Hagen|first=Hans}}
* {{cite book|last=Knuth|first=Donald|author-link=Donald Knuth|title=The [[METAFONT]]book|series=[[Computers and Typesetting]]|volume=C|publisher=[[Addison-Wesley]]|year=1986|isbn=0-201-13444-6}}
* {{cite web|title=Comprehensive T<sub>E</sub>X Archive Network|type=[[CTAN]]|url=http://www.ctan.org/|publisher=Repository of the T<sub>E</sub>X source and hundreds of add-ons and style files}}
* {{cite web|title=(La)TeX Navigator provides 305 simple MetaPost examples|url=http://tex.loria.fr/prod-graph/zoonekynd/metapost/metapost.html|access-date=2006-11-17|archive-url=https://web.archive.org/web/20130727021112/http://tex.loria.fr/prod-graph/zoonekynd/metapost/metapost.html|archive-date=2013-07-27|url-status=dead}}
* {{cite journal|last=Hoekwater|first=Taco|url=http://www.tug.org/TUGboat/Articles/tb27-1/tb86hoekwater-metapost.pdf|title=MetaPost developments—autumn 2006|journal=TUGboat|volume=27|issue=1|year=2006}}
{{Refend}}

==External links==
* The TeX Users Group ([[TeX Users Group|TUG]]) http://www.tug.org/ has a page devoted to MetaPost: http://www.tug.org/metapost.html
{{Vector graphics markup languages}}
{{Free and open-source typography}}

{{DEFAULTSORT:Metapost}}
[[Category:Programming languages created in 1994]]
[[Category:Declarative programming languages]]
[[Category:Domain-specific programming languages]]
[[Category:Free TeX software]]
[[Category:PostScript]]
[[Category:Public-domain software]]
[[Category:Vector graphics markup languages]]