Problem with conversion

Hello everybody,

I am facing problem trying to convert pdf to txtz. I have few gb of pdf file to convert to txt in order to regexp from emacs. So I am implementing a shell script to do that. Problem is when it converts some pdf files I got a problem with image extraction. Command is

ebook-conevrt xyz.pdf xyz.txtz

This is the kind of image it extracts with some kind of pdf:

http://imgur.com/9kketiE