Each image node, e.g. /images2D/0/, contains a raster. These images may be stored as one of four representations: visualReferenceRepresentation, pinholeRepresentation, sphericalRepresentation, or cylindricalRepresentation. The representation type controls which additional properties are stored (see the Feature Representation section for more details).
One image node may actually contain two rasters: one of the set { pinholeRepresentation, sphericalRepresentation, or cylindricalRepresentation}, and one visualReferenceRepresentation node. In this case, the reader will produce an aggregate geometry that holds both rasters. Similarly, the writer can ingest aggregates of two rasters.
Raster data is stored within an E57 file as PNG or JPEG blobs.
An image mask may optionally be stored separately from the image data. When reading, FME will combine the image mask and data into a single raster.
Additional Notes
E57 elements that that are not part of the set (i.e. user attributes, traits, or components not in the table above) should be stored in "Extensions." Each extension in a file shall be defined by a prefix and namespace. Extensions are controlled in FME through the e57_extensions{}.prefix and e57_extensions{}.uri format attributes. On reading, these attributes specify the extensions in the source dataset. On writing, these attributes may be used to define extensions. User attributes, traits, and components should be stored in extensions to ensure compatibility with other E57 readers. So for example, instead of writing a user attribute called "myAttr", one might would write a user attribute called "ext:myAttr", and define the "ext" extension through the e57_extensions{}.prefix and e57_extensions{}.uri format attributes.