SVGtoPDF.lua

local PDF_DIR = ".converted-pdf"
os.execute("mkdir -p " .. PDF_DIR)

local function file_exists(fn)
  local f = io.open(fn,"r")
  if f then
    f:close()
    return true
  else
    return false
  end
end

function Image(elem)
  -- el.caption, src, title, attr
  local base = elem.src:match("^(.+)%.svg$")
  if base ~= nil then
    local infile = assert(io.open(elem.src,"r"))
    local svgContents = infile:read("*a")
    infile:close()
    local hash = pandoc.sha1(svgContents)
    local pdfPath = PDF_DIR .. "/" .. hash .. ".pdf"
    if not file_exists(pdfPath) then
      io.stderr:write("Running Inkscape: from " .. elem.src .. " to " .. pdfPath .. "\n")
      os.execute("inkscape --without-gui --export-pdf=" .. pdfPath .. " " .. elem.src)
    end
    return pandoc.Image(elem.caption, pdfPath, elem.title, elem.attr)
  else
    return elem
  end
end