@Override
    protected List<PackagePart> getMainDocumentParts() throws TikaException {
        List<PackagePart> parts = new ArrayList<>();
        XSLFSlideShow document = null;
        try {
            document = new XSLFSlideShow(extractor.getPackage());
        } catch (Exception e) {
            throw new TikaException(e.getMessage()); // Shouldn't happen
        }

        CTSlideIdList ctSlideIdList = document.getSlideReferences();
        if (ctSlideIdList != null) {
            for (int i = 0; i < ctSlideIdList.sizeOfSldIdArray(); i++) {
                CTSlideIdListEntry ctSlide = ctSlideIdList.getSldIdArray(i);
                // Add the slide
                PackagePart slidePart;
                try {
                    slidePart = document.getSlidePart(ctSlide);
                } catch (IOException | XmlException e) {
                    throw new TikaException("Broken OOXML file", e);
                }
                addSlideParts(slidePart, parts);
            }
        }
        //add full document to include macros
        parts.add(document.getPackagePart());

        for (String rel : new String[]{XSLFRelation.SLIDE_MASTER.getRelation(), HANDOUT_MASTER}) {
            try {
                PackageRelationshipCollection prc =
                        document.getPackagePart().getRelationshipsByType(rel);
                for (int i = 0; i < prc.size(); i++) {
                    PackagePart pp =
                            document.getPackagePart().getRelatedPart(prc.getRelationship(i));
                    if (pp != null) {
                        parts.add(pp);
                    }
                }

            } catch (InvalidFormatException e) {
                //log
            }
        }

        return parts;
    }
In PowerPoint files, slides have things embedded in them,
and slide drawings which have the images
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-microsoft-module/src/main/java/org/apache/tika/parser/microsoft/ooxml/XSLFPowerPointExtractorDecorator.java