Current PowerPointExtractor constructor can take only HSLFSlideShowImpl but not HSLFSlideShow. If one need to extract text and images from the .ppt file, he for she now needs to analyse say InputStream twice: once for text and once for images. Could be much easier to create an extractor from HSLFSlideShow as ExcelExtractor does — has the constructor with HSSFWorkbook.
I think HSLFSlideShow is a wrapper around HSLFSlideShowImpl. Does this work? PowerPointExtractor(new HSLFSlideShow(myHSLFSlideShowImpl))
In the future 4.0.0 release, there's a org.apache.poi.sl.extractor.SlideShowExtractor class which takes a SlideShow in the constructor. So this issue seems to be obsolete.