The size of DjVu output is much larger than PDF input

[jwilk]

Issue reported by @jsbien:

What steps will reproduce the problem?

1. Download e.g. http://teksty.klf.uw.edu.pl/3/7/aaspzpE.pdf
2. Call pdf2djvu aaspzpE.pdf -o aaspzp.djvu

What is the expected output? What do you see instead?

I expect the DjVu file to be smaller.

-rw-r--r-- 1 jsbien jsbien 1.2M Oct 12 19:42 aaspzp.djvu
-rw-r--r-- 1 jsbien jsbien 625K Oct 12 19:40 aaspzpE.pdf

What version of the product are you using? On what operating system?

Package: pdf2djvu
Version: 0.7.17-4

Debian Release: jessie/sid

Please provide any additional information below.

The foreground/background separation seems perfect.

[jwilk]

That's 7KB/page, which is not that bad.

The djvu(1) manpage says that “a typical 300 dpi page in DjVuBitonal occupies 5 to 25 KB”.

I'm more intrigued how come the PDF is so small.

[jwilk]

Comment submitted by @jsbien:

Sorry, I've forgot the PDF is digitally born...