How to split each page of a djvu file?

Question

In a djvu file, it has two book pages in one djvu page. I would like to split it so that one book page per djvu page. For example,

I was wondering if this can be done by some software, preferably command line utilities? Thanks and regards!

PS: This is a file that can be used for test.

Answer 1

http://en.wikisource.org/wiki/Help:DjVu_files#Splitting_DjVu_files

Hope you find your answer here.

Answer 2

The following is untested, but in principle it should work (I will test it if I have more time).

You could convert the djvu file for example to jpg's like this:

#!/bin/sh
# djvu -> jpgs converter

i=1

# number of pages (392)
while [ $i -ne 392 ]
do
ddjvu -page=$i -format=pnm 1.djvu $i.pnm
pnmtojpeg $i.pnm > $i.jpg
rm -f $i.pnm
echo "page $i done"
i=`expr $i + 1`
done

(from http://caree.livejournal.com/74639.html)

Then you could use scantailor to split the pages and produce a new output (consisting of tif files).

Apply in a third step djvubind to that folder and you get your desired djvu file.

Answer 3

There aren't so many tools that can operate directly on DjVu files, compared with other more common formats such as PDF or JPEG. With image manipulation programs, there's the added hurdle that most of these operate on a single image at a time, but the DjVu file contains multiple pages.

One possibility is to go via pdf. With ddjvu from DjVuLibre, a PDF un2up filter, and pdf2djvu:

ddjvu -format=pdf 2up.djvu 2up.pdf
un2up <2up.pdf | pdf2djvu /dev/stdin >1up.djvu

You might be able to cobble up an un2up for djvu inspired by my pdf version using python-djvulibre. I haven't checked how hard that API is to get into.