Eine Schnittstelle zur Latex-Compiler um Bilder aus Latex Code zu generieren.

Quick-check System

  • ❏ convert --version soll die Version von ImageMagick ausgeben.

  • ❏ xelatex --version soll die Version von TexLive ausgeben.

  • ❏ TexLive ist so eingestellet, dass \write18 partial erlaubt ist.

  • ❏ Das Latex-Paket circdia ist installiert.

  • ❏ Einstellung in Tomcat um Java AWT auch in Server Modus zu nutzen.

Installation von TexLive

  • TL soll mit schema-full installiert werden.

  • Quickcheck: Kopieren den unterstehenden Code in texmf.conf

% Enable system commands via \write18{...}.  When enabled fully (set to
% t), obviously insecure.  When enabled partially (set to p), only the
% commands listed in shell_escape_commands are allowed.  Although this
% is not fully secure either, it is much better, and so useful that we
% enable it for everything but bare tex.
shell_escape = p

% No spaces in this command list.
%
% The programs listed here are as safe as any we know: they either do
% not write any output files, respect openout_any, or have hard-coded
% restrictions similar to or higher than openout_any=p.  They also have
% no features to invoke arbitrary other programs, and no known
% exploitable bugs.  All to the best of our knowledge.  They also have
% practical use for being called from TeX.
%
shell_escape_commands = \
bibtex,bibtex8,biber,\
extractbb,\
gregorio,\
kpsewhich,\
makeindex,xindy\
repstopdf,\
texosquery-jre8,\
convert,convert-im6,\
uname

Installation von Latex-Paket circdia

  • Kopieren den Ordner circdia aus dem Ordner src/main/latex in ${HOME}/texmf/tex/latex wobei ${HOME} das Home-Verzeichnis von dem Nutzer, unter dessen Name die MathCoach-Web Anwendung läuft.

    cd src/main/latex
cp -r circdia ${HOME}/texmf/tex/latex

  • Den Befehl texhash ${HOME}/texmf/ aufrufen

Installation von Image Magick

Unter Ubuntu soll das Paket bereits installiert sein. Wenn nicht kann man mit

sudo apt install imagemagick

das Paket installieren.

Java AWT Einstellung

Füget in $CATALINA_BASE/setenv.sh folgenden Code hinzu:

export CATALINA_OPTS="$CATALINA_OPTS -Djava.awt.headless=true"

Anhang

Configure latex

Determine texmf.cnf

$ kpsewhich -a texmf.cnf
/opt/texlive/2017/texmf.cnf
/opt/texlive/2017/texmf-dist/web2c/texmf.cnf

Configure

  • Open the first output entry, eg. /opt/texlive/2018/texmf.cnf, you should see something like

% (Public domain.)
% This texmf.cnf file should contain only your personal changes from the
% original texmf.cnf (for example, as chosen in the installer).
%
% That is, if you need to make changes to texmf.cnf, put your custom
% settings in this file, which is .../texlive/YYYY/texmf.cnf, rather than
% the distributed file (which is .../texlive/YYYY/texmf-dist/web2c/texmf.cnf).
% And include *only* your changed values, not a copy of the whole thing!
%

  • Extend the opened file with the following code:

% Enable system commands via \write18{...}.  When enabled fully (set to
% t), obviously insecure.  When enabled partially (set to p), only the
% commands listed in shell_escape_commands are allowed.  Although this
% is not fully secure either, it is much better, and so useful that we
% enable it for everything but bare tex.
shell_escape = p

% No spaces in this command list.
%
% The programs listed here are as safe as any we know: they either do
% not write any output files, respect openout_any, or have hard-coded
% restrictions similar to or higher than openout_any=p.  They also have
% no features to invoke arbitrary other programs, and no known
% exploitable bugs.  All to the best of our knowledge.  They also have
% practical use for being called from TeX.
%
shell_escape_commands = \
bibtex,bibtex8,biber,\
extractbb,\
gregorio,\
kpsewhich,\
makeindex,xindy\
repstopdf,\
texosquery-jre8,\
convert,convert-im6,\
uname

Affect: All Tex-Compiler (tex, xetex, pdflatex, xelatex, ect.) are permitted to call all commands above.

  • Save the above file and try to compile the file tex/standalone-tikz.tex with

cd tex
xelatex standalone-tikz.tex

You should see a generated file standalone-tikz.png and a Warning in console like

Class standalone Warning: Conversion failed! Please ensure that shell escape
(standalone)              is enabled (e.g. use '-shell-escape').

Compile the file again. The PNG File standalone-tikz.png must be generated.

In some case ImageMagick is configured, that it does not have authority to access PDF / PS files. You will get error like:

convert: not authorized `TexPicture-D1DCB88201027DC556E52715EB3E16820C6E0F39095242863F234B9FD3CD66F2.pdf' @ error/constitute.c/ReadImage/412.
convert: no images defined `TexPicture-D1DCB88201027DC556E52715EB3E16820C6E0F39095242863F234B9FD3CD66F2.png' @ error/convert.c/ConvertImageCommand/3210.
system returned with code 256

In such situation one can change the Policy of ImageMagick in the file /etc/ImageMagick-6/policy.xml. Change the line

<policy domain="coder" rights="none" pattern="PDF" />

to

<policy domain="coder" rights="read|write" pattern="PDF" />

should allow ImageMagick to access PDF files.