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Create article. Not too stubbish.
[[MetaPost]] only supports the RGB color space, although with the help of [[MetaFun]] you can face transparency and CMYK colors. This article describes the use of colors in MetaPost and MetaFun.
== The basics ==
Colors are defined as vectors with three components: a red, green and blue one. Like pens, colors have their {{code|with}} command:
withcolor (.4,.5.,6)
You can define color variables like so:
color darkred ; darkred := (.625,0.0) ;
% use the color
withcolor darkred
% actually, red is already defined, so this works:
withcolor .625red
Because for MetaPost colors are just vectors, you can manipulate them like you would manipulate points. This is a color halfway between red and green:
withcolor .5[red,green]
== Using colors defined in TeX ==
In ConTeXt you define colors with {{cmd|definecolor}}. Instead of defining a color a second time in MetaPost, you can use the {{code|\MPcolor{colorname}|}} command.
<context source=yes>
\definecolor[darkred] [r=.625] % a RGB color
\definecolor[darkgray][s=.625] % a gray scale
\startuseMPgraphic{color demo}
pickup pencircle scaled 1mm ;
path p ; p := fullcircle xscaled 5cm yscaled 0.5cm ;
fill p withcolor \MPcolor{darkgray} ;
draw p withcolor \MPcolor{darkred} ;
\stopuseMPgraphic
\bold{\color[darkgray]{This} is an \color[darkred]{ellipse}:}
\useMPgraphic{color demo}
</context>
== Transparent colors ==
You can use transparent colors with the {{code|transparent(method, factor, color)}} function. For example:
<context source=yes>
\runMPgraphicstrue
\setupcolors[state=start]
\starttext
\startreusableMPgraphic{a}
fill unitsquare scaled 1cm withcolor yellow;
fill unitsquare shifted (0.5,0.5)
% method 1 = normal
scaled 1cm withcolor transparent(1,0.5,red);
\stopreusableMPgraphic
\placefigure[force,none]{}{\reuseMPgraphic{a}}
\stoptext
</context>
The available transparency methods are the twelve methods supported by PDF specification:
* 1. normal
* 2. multiply
* 3. screen
* 4. overlay
* 5. softlight
* 6. hardlight
* 7. colordodge
* 8. colorburn
* 9. darken
* 10. lighten
* 11. difference
* 12. exclusion
=== Troubleshooting transparency ===
If you see black colors rather than transparent ones, then you probably hit the 'missing specials' problem. This problem was around in 2006; people may not encounter it anymore, but the solution is mentioned here anyway. From the mailing list:
<pre>
This all sounds like the 'missing specials' problem that is caused
by conflicting -progname= arguments when using the web2c version
of MetaPost.
Make sure you do not have conflicting memory settings for both
main_memory.mpost
as well as
main_memory.metafun
The best is to remove all trace of '.mpost' and '.metafun' memory
settings from your texmf.cnf, but at least make sure all the
'.mpost' and 'metafun' values are the same .
Then regenerate metafun using texexec --make, and all should be
well again.
</pre>
If you are using ConTeXt from the Debian/Ubuntu distribution of TeX, instead of via the recommended [[ConTeXt Standalone]], you need to edit ''/etc/texmf/texmf.d/95NonPath.cnf'':
<pre>
main_memory = 1000000 % words of inimemory available; also applies to inimf&mp
main_memory.context = 1500000
main_memory.mpost = 1500000
</pre>
* Comment out the .mpost line (MetaFun uses the main_memory value of 1000000; the difference in values is the cause of the problem).
* Regenerate {{code|/etc/texmf/texmf.cnf}} with {{code|sudo update-texmf}};
* then regenerate the MetaFun format with {{code|texexec --make metafun}}
* transparency should work now.
== The basics ==
Colors are defined as vectors with three components: a red, green and blue one. Like pens, colors have their {{code|with}} command:
withcolor (.4,.5.,6)
You can define color variables like so:
color darkred ; darkred := (.625,0.0) ;
% use the color
withcolor darkred
% actually, red is already defined, so this works:
withcolor .625red
Because for MetaPost colors are just vectors, you can manipulate them like you would manipulate points. This is a color halfway between red and green:
withcolor .5[red,green]
== Using colors defined in TeX ==
In ConTeXt you define colors with {{cmd|definecolor}}. Instead of defining a color a second time in MetaPost, you can use the {{code|\MPcolor{colorname}|}} command.
<context source=yes>
\definecolor[darkred] [r=.625] % a RGB color
\definecolor[darkgray][s=.625] % a gray scale
\startuseMPgraphic{color demo}
pickup pencircle scaled 1mm ;
path p ; p := fullcircle xscaled 5cm yscaled 0.5cm ;
fill p withcolor \MPcolor{darkgray} ;
draw p withcolor \MPcolor{darkred} ;
\stopuseMPgraphic
\bold{\color[darkgray]{This} is an \color[darkred]{ellipse}:}
\useMPgraphic{color demo}
</context>
== Transparent colors ==
You can use transparent colors with the {{code|transparent(method, factor, color)}} function. For example:
<context source=yes>
\runMPgraphicstrue
\setupcolors[state=start]
\starttext
\startreusableMPgraphic{a}
fill unitsquare scaled 1cm withcolor yellow;
fill unitsquare shifted (0.5,0.5)
% method 1 = normal
scaled 1cm withcolor transparent(1,0.5,red);
\stopreusableMPgraphic
\placefigure[force,none]{}{\reuseMPgraphic{a}}
\stoptext
</context>
The available transparency methods are the twelve methods supported by PDF specification:
* 1. normal
* 2. multiply
* 3. screen
* 4. overlay
* 5. softlight
* 6. hardlight
* 7. colordodge
* 8. colorburn
* 9. darken
* 10. lighten
* 11. difference
* 12. exclusion
=== Troubleshooting transparency ===
If you see black colors rather than transparent ones, then you probably hit the 'missing specials' problem. This problem was around in 2006; people may not encounter it anymore, but the solution is mentioned here anyway. From the mailing list:
<pre>
This all sounds like the 'missing specials' problem that is caused
by conflicting -progname= arguments when using the web2c version
of MetaPost.
Make sure you do not have conflicting memory settings for both
main_memory.mpost
as well as
main_memory.metafun
The best is to remove all trace of '.mpost' and '.metafun' memory
settings from your texmf.cnf, but at least make sure all the
'.mpost' and 'metafun' values are the same .
Then regenerate metafun using texexec --make, and all should be
well again.
</pre>
If you are using ConTeXt from the Debian/Ubuntu distribution of TeX, instead of via the recommended [[ConTeXt Standalone]], you need to edit ''/etc/texmf/texmf.d/95NonPath.cnf'':
<pre>
main_memory = 1000000 % words of inimemory available; also applies to inimf&mp
main_memory.context = 1500000
main_memory.mpost = 1500000
</pre>
* Comment out the .mpost line (MetaFun uses the main_memory value of 1000000; the difference in values is the cause of the problem).
* Regenerate {{code|/etc/texmf/texmf.cnf}} with {{code|sudo update-texmf}};
* then regenerate the MetaFun format with {{code|texexec --make metafun}}
* transparency should work now.
