making books from a pdf

I needed to produce a book - or booklet more like from a PDF file I created. I wanted to print it on a duplex printer and fold the pages together (a signature). This is a common way of producing books.

I used pdftk (apt-get install pdftk) and pdfnup (apt-get install pdfjam).

The first thing to do was split my file into individual pages using:

 pdftk ./book.pdf burst

which produced a file for each page named 'pg_dddd.pdf' where d = digit.
Assuming my book has a page number which is a multiple of 4 (56 in the case below), I used the following script to concatenate these pages together in the correct order:

NOTE: This code will over write the file 'booksig.pdf' with a file of reorganised pages.

#!/usr/bin/perl -w

use strict;

my $totalPages = 56;

my $processedPages = 0;

my $pageOrderStr = "";
while ($processedPages < $totalPages/2) {     $pageOrderStr .= sprintf ("pg_%04d.pdf pg_%04d.pdf pg_%04d.pdf pg_%04d.pdf ",      $totalPages - $processedPages,     $processedPages + 1,      $processedPages + 2,      $totalPages - $processedPages - 1);     $processedPages += 2; }  my $catCMD = "pdftk $pageOrderStr cat output booksig.pdf"; print `$catCMD`; 

this resulted in a pdf call 'booksig.pdf'.
The final step was to use pdfnup to write these pages back to back:

pdfnup --nup 2x1 booksig.pdf

Which produced a file 'booksig-2x1.pdf' which I sent to my duplex printer and then bound together.

To it printed correctly, I chose 'Flip on Short Edge' two-sided printing. Which is non-standard. Apparently.

UPDATE: Julian spotted an error which is now fixed.

Java floats and doubles

I'm attempting to write some high performance Java. There is some limited evidence that you might expect a small performance improvement using floats over doubles.

There is a good case why memory usage will be reduced.

However, why is it such a pain to use floats? I am constantly finding methods, in the Graphics2D classes, which only support one or the other (generally better support for Doubles).

I think this post sums up reasons not to use floats, and makes a good point: why have floats at all?