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(), XSLFRelation.CHART.getRelation(),
                XSLFRelation.DIAGRAM_DRAWING.getRelation()}) {
            try {
                for (PackageRelationship packageRelationship : slidePart
                        .getRelationshipsByType(relation)) {
                    if (packageRelationship.getTargetMode() == TargetMode.INTERNAL) {
                        PackagePartName relName = PackagingURIHelper
                                .createPartName(packageRelationship.getTargetURI());
                        parts.add(packageRelationship.getPackage().getPart(relName));
                    }
                }
            } catch (InvalidFormatException e) {
                //swallow
            }
        }
        //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/XSLFPowerPointExtractorDecorator.java