private void addSlideParts(PackagePart slidePart, List<PackagePart> parts) {

        for (String relation : new String[]{XSLFRelation.VML_DRAWING.getRelation(),
                XSLFRelation.SLIDE_LAYOUT.getRelation(), XSLFRelation.NOTES_MASTER.getRelation(),
                XSLFRelation.NOTES.getRelation()}) {
            PackageRelationshipCollection prc = null;
            try {
                prc = slidePart.getRelationshipsByType(relation);
            } catch (InvalidFormatException e) {
                metadata.add(TikaCoreProperties.TIKA_META_EXCEPTION_WARNING,
                        ExceptionUtils.getStackTrace(e));
            }
            if (prc != null) {
                for (PackageRelationship packageRelationship : prc) {
                    if (packageRelationship.getTargetMode() == TargetMode.INTERNAL) {
                        PackagePartName relName = null;
                        try {
                            relName = PackagingURIHelper
                                    .createPartName(packageRelationship.getTargetURI());
                        } catch (InvalidFormatException e) {
                            metadata.add(TikaCoreProperties.TIKA_META_EXCEPTION_WARNING,
                                    ExceptionUtils.getStackTrace(e));
                        }
                        if (relName != null) {
                            parts.add(packageRelationship.getPackage().getPart(relName));
                        }
                    }
                }
            }
        }
        //and slide of course
        parts.add(slidePart);

    }
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/SXSLFPowerPointExtractorDecorator.java