[NTG-context] \setuparranging values for perfect bound A5 on A3?

[Max Chernoff]

Hi Bruce,

> I have a book to be perfect bound[1] and I'm trying to work out what
> imposition to use.
> 
> The printer would like 4 A5 pages laid out on A3 e.g.
> 
> +---+---+
> |   |   |
> | a | b |
> |   |   |
> +---+---+
> |   |   |
> | c | d |
> |   |   |
> +---+---+
> 
> so that he can cut the paper and simply stack a, b, c, & d on top of
> each other and then put them in the binding machine[2].
> 
> If the book is 40 pages long, say, then stack 'a' has page 1 on the
> top, page 2 on the reverse, then the next sheet has page 3 and 4, and
> so on down to the last sheet which has page 9 on the front and page 10
> on the back. Stack 'b' would have page 11 on the front, 12 on the back
> and so on, so that each stack has a quarter of the book.
> 
> Is this something LMTX can do and if so what combination of
> \setuplayout and \setuppaper do I need to use? If they can be printed
> in reverse order then great but I assume the printer can do that
> fairly easily.

I don't think that there's any way to do this from within a document
run, so I think that you'll need to use an external program.

> If not, is there a recommended external program that can do it?

But, you can use ConTeXt as the external program here. 

Save as "imposition.cld":

   local filename = document.getargument("filename")
   local pdf = lpdf.epdf.image.open(filename)
   local pages = pdf.nofpages
   local max = math.ceil(pages / 4)
   
   context.setuppapersize({ "A5" }, { "A3" })
   context.setuppaper { nx = 2, ny = 2 }
   context.setuparranging { "XY" }
   
   local function insert_page(n)
       context.startpagemakeup()
       context.filterpages({ filename }, { n })
       context.stoppagemakeup()
   end
   
   context.starttext()
   for i = 1, max do
       if i % 2 == 1 then
           insert_page(i + 0 * max)
           insert_page(i + 1 * max)
           insert_page(i + 2 * max)
           insert_page(i + 3 * max)
       else
           insert_page(i + 1 * max)
           insert_page(i + 0 * max)
           insert_page(i + 3 * max)
           insert_page(i + 2 * max)
       end
   end
   context.stoptext()
   
Then run:

   context imposition.cld --filename=document.pdf
   
where "document.pdf" is replaced by your document name.

I'm not sure if I got your desired output quite right here, but
hopefully you can easily modify the script if something isn't quite
right.

Thanks,
-- Max