jpx_metanode::get_numlist_info

Use this function to determine whether or not the node is represented by a number list. A number list is a list of image entities: codestreams; compositing layers; or the complete "rendered result". In many cases, the number list information is derived from a JPX number list ( nlst) box. However, it can also be derived by the containment of metadata within a JPX codestream header box or compositing layer header box. The ensuing discussion assumes that the function returns true, meaning that the node is represented by a number list.

If this is an intermediate node, the number list is at least notionally the first sub-box of an association box, and all of the node's descendants (both immediate and indirect descendants) are deemed to be associated with each and every one of the image entities in the number list.

As mentioned above, it is also possible that an intermediate node is represented by a number list, without the appearance of an actual number list box within the JPX data source. This happens if relevant metadata is encountered while parsing a JPX codestream header box or a JPX compositing layer header box. In this case, a "virtual" number list is created, to refer to exactly one image entity — the codestream or compositing layer, whose header generated the node. The node's descendants then represent the metadata sub-boxes found within the relevant header. It is important to realize that this kind of "virtual" number list can always be written into a JPX file as a real number list box within an association box, and indeed the JPX file writer always writes metadata in this way, rather than encapsulating it within header boxes.

If this node is a leaf, the number list corresponds to an isolated number list ( nlst) box, all by itself. This is semantically less useful, of course, but still legal.

In addition to identifying whether or not the node is represented by a number list, this function also provides information concerning the number of codestreams and compositing layers which are referenced by the number list, and whether or not the number list references the complete "rendered result".

True only if the box is represented by a number list.

num_codestreams [int &]

num_layers [int &]

applies_to_rendered_result [bool &]