Add lua filter for 'tikz' diagrams

.wiki/filters/tikz.lua

@@ -0,0 +1,63 @@
+local system = require 'pandoc.system'
+
+local tikz_doc_template = [[
+\documentclass{standalone}[border=0.2cm]
+\usepackage{tikz}
+\usetikzlibrary{automata, positioning, arrows.meta}
+\begin{document}
+%s
+\end{document}
+]]
+
+local function tikz2image(src, filetype, outfile)
+  system.with_temporary_directory('tikz2image', function (tmpdir)
+    system.with_working_directory(tmpdir, function()
+      local f = io.open('tikz.tex', 'w')
+      f:write(tikz_doc_template:format(src))
+      f:close()
+      os.execute('pdflatex tikz.tex')
+      if filetype == 'pdf' then
+        os.rename('tikz.pdf', outfile)
+      else
+        os.execute('pdf2svg tikz.pdf ' .. outfile)
+      end
+    end)
+  end)
+end
+
+extension_for = {
+  html = 'svg',
+  html4 = 'svg',
+  html5 = 'svg',
+  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
+
+local function starts_with(start, str)
+  return str:sub(1, #start) == start
+end
+
+function RawBlock(el)
+  if starts_with('\\begin{tikzpicture}', el.text) then
+    local filetype = extension_for[FORMAT] or 'svg'
+    local fbasename = pandoc.sha1(el.text) .. '.' .. filetype
+    -- Save to './img' if it does not exist yet
+    local fname = system.get_working_directory() .. '/img/' .. fbasename
+    if not file_exists(fname) then
+      tikz2image(el.text, filetype, fname)
+    end
+    -- Return `<img src="img/<file-name>" />` wrapped in a paragraph
+    return pandoc.Para({pandoc.Image({}, 'img/' .. fbasename)})
+  else
+   return el
+  end
+end