Represents the "StructParent" entry of the image dictionary object.

It is defined as part of the PDF 1.3 specification.

It contains an integer representing a PDF numeric object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 89, page 208.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 4.39, page 27.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 87, page 257.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 146, page 349.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 144, page 418.

The StructParent integer links this image into the document's structure tree. It is a key into the parent tree that identifies which structure element is the parent of this XObject. This entry is required when the image is part of a tagged PDF structure.