diff options
| -rw-r--r-- | doc/lua-filters.md | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/doc/lua-filters.md b/doc/lua-filters.md index 518ee25c2..112a9bab2 100644 --- a/doc/lua-filters.md +++ b/doc/lua-filters.md @@ -479,6 +479,89 @@ function CodeBlock(block) end ``` +## Building images with tikz + +This filter converts raw LaTeX tikz environments into images. +It works with both PDF and HTML output. The tikz code is +compiled to an image using `pdflatex`, and the image is +converted (if necessary) from pdf to png format using +ImageMagick's `convert`, so both of these must be in the system +path. Converted images are cached in the working directory +and given filenames based on a hash of the source, so that +they need not be regenerated each time the document is built. +(A more sophisticated version of this might put these in a special +cache directory.) + +```lua +local function tikz2image(src, filetype, outfile) + local tmp = os.tmpname() + local tmpdir = string.match(tmp, "^(.*[\\/])") or "." + local f = io.open(tmp .. ".tex", 'w') + f:write("\\documentclass{standalone}\n\\usepackage{tikz}\n\\begin{document}\n") + f:write(src) + f:write("\n\\end{document}\n") + f:close() + os.execute("pdflatex -output-directory " .. tmpdir .. " " .. tmp) + if filetype == 'pdf' then + os.rename(tmp .. ".pdf", outfile) + else + os.execute("convert " .. tmp .. ".pdf " .. outfile) + end + os.remove(tmp .. ".tex") + os.remove(tmp .. ".pdf") + os.remove(tmp .. ".log") + os.remove(tmp .. ".aux") +end + +extension_for = { + html = 'png', + html4 = 'png', + html5 = 'png', + latex = 'pdf', + beamer = 'pdf' } + +local function file_exists(name) + local f = io.open(name, 'r') + if f ~= nil then + io.close(f) + return true + else + return false + end +end + +function RawBlock(el) + local filetype = extension_for[FORMAT] or "png" + local fname = pandoc.sha1(el.text) .. "." .. filetype + if not file_exists(fname) then + tikz2image(el.text, filetype, fname) + end + return pandoc.Para({pandoc.Image({}, fname)}) +end +``` + +Example of use: + +``` +pandoc --lua-filter tikz.lua -s -o cycle.html <<EOF +Here is a diagram of the cycle: + +\begin{tikzpicture} + +\def \n {5} +\def \radius {3cm} +\def \margin {8} % margin in angles, depends on the radius + +\foreach \s in {1,...,\n} +{ + \node[draw, circle] at ({360/\n * (\s - 1)}:\radius) {$\s$}; + \draw[->, >=latex] ({360/\n * (\s - 1)+\margin}:\radius) + arc ({360/\n * (\s - 1)+\margin}:{360/\n * (\s)-\margin}:\radius); +} +\end{tikzpicture} +EOF +``` + # Module text UTF-8 aware text manipulation functions, implemented in Haskell. |