Comment 41 for bug 384553

(In reply to comment #5)
> Hi guys,
>
> I'm interested in working in this bug.
>
> I know we need to understand how OOXML handles this, but there is some
> documents and code pointers where we can touch this?

Hi, you might find this useful: http://www.osb-alliance.de/fileadmin/Working_Groups/OfficeInteroperability/Project1/suse-ooxml-tender-use-case-5.1-report.pdf

Or this:
http://www.officeopenxml.com/prSlide-background.php
http://officeopenxml.com/drwSp-PattFill.php
http://www.officeopenxml.com/prSlideMaster.php

I also uploaded another pptx test file with transparent background, which is still not detected by LibreOffice.