HPR2771: Embedding hidden text in Djvu files

Hacker Public Radio

To embed text into a Djvu file, you must create a djvused script detailing the page and bitmap location of one of: character, word, line, paragraph, or region.

For good measure, you should first list the contents of your Djvu bundle:

$ djvused -e 'select; ls' test.djvu 1 P 177062 p0001.djvu 2 P 199144 p0002.djvu 3 P 12323 p0003.djvu 4 P 57059 p0004.djvu 5 P 96725 p0005.djvu 6 P 53868 p0006.djvu 

Then define the location of text in a file called, for instance, content.dsed. Assume that my page is 1000 px by 1000 px:

select; remove-ant; remove-txt select "p0004.djvu" # page 4 set-txt (page 0 0 1000 1000 (word 100 600 450 800 "Hello" ) (word 100 600 450 800 "world" )) . select "p0005.djvu" set-txt (page 0 0 1000 1000 (line 100 400 900 600 "Hacker Puppy Radio")) 

Apply this script to your Djvu file with dvjused:

djvused -f ./content.dsed -s test.djvu 

Converting from PDF to Djvu

You can convert PDF files to Djvu with the djvudigital command. Due to license incompatibility, it does require you to compile a Ghostscript plugin, but it's an easy build. Get the gsdjvu code, and then follow its README instructions.

Once you've built the Ghostscript driver, you can convert PDF to Djvu:

djvudigital --words foo.pdf foo.djvu