Unfortunately, the way DEDA works is working, from my understanding, is
by calibrating itself on "known bad" documents, meaning that it doesn't
provide a generic solution.
A better solution would be to render the documents in black and white,
since the yellow marks will likely be rounded to white, but this will
make non-textual documents barely usable/readable. Like pdf-redact-tool
(
https://github.com/firstlookmedia/pdf-redact-tools ) is doing.
Maybe I should add such option to mat2, behind a `--paranoid` flag?
