Extracting images

Pictures are p:pic shapes whose a:blip names an image part through a relationship. Embedded object previews count too.

for image in slide.images():
    image.shape_id, image.rel_id, image.part, image.content_type, image.external
    data = slide.image_bytes(image)        # bytes of the image part

for image in slide.images()? {
    let bytes = slide.image_bytes(&image)?;
}

Image bytes are read only when asked for, so a deck's media costs nothing until then. Linked images (r:link) resolve to an external target and have no bytes in the package. Embedded objects (p:oleObj) are listed by Slide::objects with their progId and part, and Slide::object_bytes reads them. Charts and diagrams are not rendered; Slide::charts and Slide::diagrams give their text and data.