LaTeX Filter

The AsciiDoc distribution includes a LaTeX filter that translates LaTeX source to PNG image which is automatically inserted into the AsciiDoc output document. Although it can accept any LaTeX source, the primary use is to render mathematical formulae (see the examples below). The filter implements the latex Listing block and Paragraph styles.

This LaTeX paragraph:


$y = \int_0^\infty \gamma^2 \cos(x) dx$

Renders:

latex-filter__1.png

This LaTeX block:

["latex","latex1.png",align="center"]
---------------------------------------------------------------------
$\displaystyle{ V_i = C_0 - C_3
\frac{C_1\cos(\theta_i+C_3)}{C_4+C_1\cos(\theta_i+C_2)} }$
---------------------------------------------------------------------

Renders:

latex1.png

This LaTeX block:

.LaTeX filter example

["latex","latex3.png"]
---------------------------------------------------------------------
\begin{equation}
\Re{z} =\frac{n\pi \dfrac{\theta +\psi}{2}}{
\left(\dfrac{\theta +\psi}{2}\right)^2 + \left( \dfrac{1}{2}
\log \left\lvert\dfrac{B}{A}\right\rvert\right)^2}.
\end{equation}

\begin{equation}
\boxed{\eta \leq C(\delta(\eta) +\Lambda_M(0,\delta))}
\end{equation}

\begin{equation}\label{first}
a=b+c
\end{equation}

\begin{subequations}\label{grp}
\begin{align}
a&=b+c\label{second}\\
d&=e+f+g\label{third}\\
h&=i+j\label{fourth}
\end{align}
\end{subequations}
---------------------------------------------------------------------

Renders:

latex-filter__2.png

Figure 1. LaTeX filter example

This LaTeX paragraph:

.A LaTeX table

\begin{tabular}{c r @{.} l}
Pi expression &
\multicolumn{2}{c}{Value} \\
\hline
$\pi$ & 3&1416 \\
$\pi^{\pi}$ & 36&46 \\
$(\pi^{\pi})^{\pi}$ & 80662&7 \\
\end{tabular}

Renders:

latex-filter__3.png

Figure 2. A LaTeX table


Using the Filter

  • The LaTeX filter is invoked by setting the Listing block or Paragraph style (the first positional block attribute) to latex.
  • The second positional attribute (named target is optional, it sets the name of the generated PNG image file. If this is not supplied a file name like {docname}__{target-number}.png is synthesised (where {docname} is the document file name and {target-number} is an integer number.
  • The third positional attribute, named dpi, is also optional; it is an integer number that sets the output resolution in dots per inch.

Because the LaTeX images are rendered using the image block templates you can also use the optional named image block attributes (see Image macro attributes in the AsciiDoc User Guide).

Tip

You can also change the image size using the following LaTeX commands:

\tiny
\scriptsize
\footnotesize
\small
\normalsize
\large
\Large
\LARGE
\huge

For example:


\Large $y = \int_0^\infty \gamma^2 \cos(x) dx$

Note

The \Large command is outside the $ math delimiters.

The filter (./filters/latex/latex2png.py) can be used outside AsciiDoc to convert LaTeX source to PNG images.

Execute the following command to see how to use it:

$ ./filters/latex/latex2png.py --help

Limitations

  • The asciidoc(1) input and output files cannot both be - (stdin and stdout), either the input or output files (or both) must be a named file.

Installation

In addition to AsciiDoc you will need to have latex(1) and dvipng(1) installed.

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