I am trying to make an editor and need to parse slide content into an HTML canvas and I am unable to extract CSS for the same.
PowerPoint files are OOXML. Styles are saved in several places. slideMaster1.xml contains titleStyle, bodyStyle and otherStyle for titles, placeholders and tables, respectively.
If layouts and/or slides have had their outline list levels modified instead of inheriting them from the slide master, then there will be lstStyle overrides in them.
Default text box styling is most often found in theme1.xml in the txDef section of objectDefaults. This section also stores the default line and default autoshape settings. More rarely, text box styling can be stored in the defaultTextStyle section of presentation.xml.
Finally, if the notes master outline levels have been modified, notesMaster1.xml will contains a notesStyle section.
Fortunately, all style sections have an identical syntax. Here's my article on otherStyle that explains some of the structure: Default Table Text