ISO/IEC 18023-1:200x(E) — Table 6.112 DRM_Image

Table 6.112 — DRM_Image_Anchor

Property

Description

Class

<DRM Image Anchor>

Superclass

<DRM SEDRIS Abstract Base>

Subclass

None.

Definition

An instance of this DRM class specifies where the given <DRM Image> is located in the specified spatial reference frame.

<DRM Image Anchor> is used in 2 ways:

As a component of an <DRM Image> in an <DRM Image Library>.
In this case, the <DRM Image> is not tied to a particular <DRM Feature> or <DRM Geometry>, and the <DRM Image Anchor>'s <DRM Location> components merely specify the positions of the corners of the <DRM Image> in the specified spatial reference frame.
Please note that if 2 geo-referenced <DRM Image> instances are to be placed exactly next to each other by means of <DRM Image Anchor> components, the <DRM Location> components of those <DRM Image Anchor> instances would be exactly the same along the common edge.
As a component of an <DRM Image Mapping Function> instance.
In this case, the <DRM Image Anchor> defines how the associated <DRM Image> is to be applied to the object having the <DRM Image Mapping Function> instance as a component, and the spatial reference frame parameters of the <DRM Image Anchor> shall match those of the context in which the <DRM Image Mapping Function> is being applied.
<DRM Image Anchor> instances are used to support spherical and cylindrical image projections for <DRM Image Mapping Function> instances. By specifying anchor points that are not in the same plane, non-orthogonal projection becomes possible.
Note that when an image mapping is applied to many <DRM Polygon> instances using a single <DRM Image Mapping Function>, a “continuous” image should result when displayed.

Class diagram

Figure 6.131 — DRM_Image_Anchor

Inherited field elements

Field name	Range	Field data type
None

Field elements

Field name	Range	Field data type
srf_info		SRF_Info

Associated to (one-way) (inherited)

None.

Associated to (one-way)

None.

Associated by (one-way) (inherited)

None.

Associated by (one-way)

None.

Associated with (two-way) (inherited)

None.

Associated with (two-way)

None.

Composed of (two-way) (inherited)

None.

Composed of (two-way)

exactly 3 {ordered} <DRM Location> instances¹

Composed of (two-way metadata) (inherited)

None.

Composed of (two-way metadata)

None.

Component of (two-way) (inherited)

None.

Component of (two-way)

zero or more <DRM Image> instances
zero or more <DRM Image Mapping Function> instances

Constraints

Clarifications

¹ The three <DRM Location> components of an <DRM Image Anchor> instance are interpreted as the locations of corners of the given <DRM Image> instance, NOT those of the centre of the texels in the corners of the <DRM Image>.

When an <DRM Image Anchor> is interpreted as a component of an <DRM Image>, or as a component of an <DRM Image Mapping Function> specifying a planar projection, the <DRM Location> components of the <DRM Image Anchor> are interpreted as follows.

The first <DRM Location> component specifies the location to which the lower left corner of the <DRM Image> is mapped.
The second <DRM Location> component specifies the location to which the upper left corner of the <DRM Image> is mapped.
The third <DRM Location> component specifies the location to which the upper right corner of the <DRM Image> is mapped.

When an <DRM Image Anchor> is interpreted as a component of an <DRM Image Mapping Function> that specifies a non-planar projection, the <DRM Location> components of the <DRM Image Anchor> are interpreted as follows.

For a cylindrical projection, the first <DRM Location> specifies the centre of the cylinder. The second specifies a point at the centre of the top of the cylinder, thus indicating direction. The third <DRM Location> specifies the alignment of the cylinder by specifying a point on the surface of the cylinder.
For a spherical projection, the first <DRM Location> specifies the centre of the sphere. The second specifies the point at the “north pole” of the sphere, thus indicating direction. The third <DRM Location> specifies a point on the “equator” of the sphere.

Example(s)

A producer has a geo-specific “global” texture that has been derived from overhead photography and rectified. It might, for example, be used to “drape” over a terrain surface. This would typically be represented as an <DRM Image> (in an <DRM Image Library>) with an <DRM Image Anchor> component.
If a producer has a geo-referenced <DRM Image> data that is to be explicitly applied to one or more terrain <DRM Polygon> instances, the mapping of the image data to the <DRM Polygon> instances would be defined by an <DRM Image Mapping Function> (component of each <DRM Polygon>) that has an <DRM Image Anchor> and an association to the appropriate <DRM Image>.