It is possible to delete optional content groups, but this will *not* delete the content that was associated with optional content group. Deleting text, image, etc, objects from PDF files is a messy business and so allowing users to delete all content associated with an OCG would result in broken PDF files.

What you will need to do is identify the particular image that you want to remove and then use the ClearImage function to basically delete that image. The image object is not actually deleted though, to prevent the corruption of existing links to the image it will not be deleted from the document. The image will be converted into a 24-bit RGB format consisting of a single transparent pixel.

I hope this helps.

In short: Acrobat uses the term layers, but we use the term optional content groups -- in QPL terminology layers refers to content streams.

The image that you are referring to is part of an optional content group. Despite the order that it is listed in the Acrobat Layers panel, this does not indicate that internally this image is stored in the last optional content group -- that is just a visual representation, but not an accurate representation of the order in which the OCGs are stored.

I will post more info shortly. Just running out of battery on my laptop.