Implement PDF compression

luametalatex-back-pdf.lua

@@ -1,4 +1,5 @@
 local pdf = pdf
+local pdfvariable = pdf.variable
 local writer = require'luametalatex-nodewriter'
 local newpdf = require'luametalatex-pdf'
 local nametree = require'luametalatex-pdf-nametree'
@@ -35,9 +36,9 @@ local properties = node.direct.properties
 token.luacmd("shipout", function()
   local pfile = get_pfile()
   local voff = node.new'kern'
-  voff.kern = tex.voffset + pdf.variable.vorigin
+  voff.kern = tex.voffset + pdfvariable.vorigin
   voff.next = token.scan_list()
-  voff.next.shift = tex.hoffset + pdf.variable.horigin
+  voff.next.shift = tex.hoffset + pdfvariable.horigin
   local list = node.direct.tonode(node.direct.vpack(node.direct.todirect(voff)))
   list.height = tex.pageheight
   list.width = tex.pagewidth
@@ -94,7 +95,7 @@ callback.register("stop_run", function()
     pfile:indirect(id, require'luametalatex-pdf-font'(pfile, f, sorted))
   end
   pfile.root = pfile:getobj()
-  pfile.version = string.format("%i.%i", pdf.variable.majorversion, pdf.variable.minorversion)
+  pfile.version = string.format("%i.%i", pdfvariable.majorversion, pdfvariable.minorversion)
   local destnames = {}
   for k,obj in next, dests do
     if pfile:written(obj) then
@@ -235,7 +236,7 @@ local function write_link(p, link)
 end
 local function addlinkpoint(p, link, x, y, list, kind)
   local quads = link.quads
-  local off = pdf.variable.linkmargin
+  local off = pdfvariable.linkmargin
   x = kind == 'start' and x-off or x+off
   if link.annots and link.annots ~= p.annots then -- We started on another page, let's finish that before starting the new page
     write_link(p, link)

luametalatex-baseregisters.tex

@@ -46,7 +46,7 @@
   end
   local pdf_params = {}
   pdf.variable_tokens = pdf_params
-  pdf.variable = setmetatable({}, {
+  setmetatable(pdf.variable, {
     __index = function(t, k)
       local v = pdf_params[k]
       if v then
@@ -99,8 +99,8 @@
 \pdfAlloc{dimen}{linkmargin}{0pt}
 \pdfAlloc{count}{majorversion}{1}
 \pdfAlloc{count}{minorversion}{7}
-\pdfAlloc{count}{compresslevel}{0} % 0 is actually the only supported value right now, so this is basically ignored
-\pdfAlloc{count}{objcompresslevel}{0} % see above
+\pdfAlloc{count}{compresslevel}{0}
+\pdfAlloc{count}{objcompresslevel}{0} % 0 is actually the only supported value right now, so this is basically ignored
 \pdfAlloc{toks}{pageresources}{{}}
 
 \texAlloc{count}{bodydirection}{0}

luametalatex-init.lua

@@ -45,6 +45,7 @@ pdf = {
   getfontname = function(id) -- No font sharing
     return id
   end,
+  variable = {},
 }
 local olddefinefont = font.define
 function font.define(f)

luametalatex-pdf.lua

@@ -7,6 +7,8 @@ local pairs = pairs
 local setmetatable = setmetatable
 local assigned = {}
 local delayed = {}
+local compress = xzip.compress
+local pdfvariable = pdf.variable
 -- slightly tricky interface: No/nil return means that the objects content
 -- isn't known yet, while false indicates a delayed object.
 local function written(pdf, num)
@@ -26,7 +28,16 @@ local function stream(pdf, num, dict, content, isfile, raw)
     content = f:read'a'
     f:close()
   end
-  pdf.file:write(format('%i 0 obj\n<<%s/Length %i>>stream\n', num, dict, #content))
+  local level = not raw and pdfvariable.compresslevel or 0
+  local filter = ''
+  if level > 0 then
+    local compressed = compress(content, level)
+    if #compressed < #content + 19 then -- Filter has some overhead
+      filter = "/Filter/FlateDecode"
+      content = compressed
+    end
+  end
+  pdf.file:write(format('%i 0 obj\n<<%s%s/Length %i>>stream\n', num, dict, filter, #content))
   pdf.file:write(content)
   pdf.file:write'\nendstream\nendobj\n'
   return num