filtering pages from /PrintPageRange

[Pablo Rodriguez <oinos@gmx.es>]

Dear list,

this is a new experience deep inside LuaMetaTeX (for me).

I need to compose a new document from selected pages (which are marked
automatically and stored in /PrintPageRange) in a PDF document
containing 1000 pages.

It has to be one of the worst coding snippets ever written, but it
works. It reads the array from /PrintPageRange, deploying it in
context.filterpages.

  \startluacode
  function document.printrange_from_file(filename)
      range_array =
pdfe.open(filename).Catalog.ViewerPreferences.PrintPageRange
      for i=1,#range_array do
          file_page = range_array[i]
          if file_pagerange == nil then
              file_pagerange = file_page
          else
              file_pagerange = file_pagerange .. " " .. file_page
          end
      end
      for str in file_pagerange:gmatch("([^%s]+)") do
          add_one = str + 1
          if right_range == nil then
              right_range =  add_one
          else
              right_range = right_range .. " " .. add_one
          end
      end
      spaces_in_pagerange = right_range:find(' ')
      local _, spaces_in_pagerange = right_range:gsub(" ", "")
          for actualspace=1,spaces_in_pagerange do
              if (actualspace % 2 == 0) then
                  right_range = right_range:gsub(' ',',', 1)
              else
                  right_range = right_range:gsub(' ',':', 1)
              end
          end

      context.filterpages( { filename }, { right_range },
		{ width = Opt } )
  end
  \stopluacode

  \def\filterfrompagerange[#1]{%
      \ctxlua{document.printrange_from_file("#1")}}

  \setuplayout[page]
  \setupinteractionscreen[option={portrait, paper}]

  \starttext
  \filterfrompagerange[huge-book.pdf]
  \stoptext

I copied and adapted all from Stackoverflow snippets.

It is useful for me, since it file will be changing, page marking is
automatic and filtering marked pages will be automatic too.

But I wonder whether this may be useful to others. I wonder whether it
makes sense to add it to the wiki.

Let me know what you think about

--
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