Table 6.109 — DRM_Image_Anchor

Property

Description

Class

  • <DRM Image Anchor>

Superclass

Subclass

  • None.

Definition

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

A <DRM Image Anchor> instance is used in one of two ways:

  1. As a component of a <DRM Image> component of a <DRM Image Library> instance.

    In this case, the <DRM Image> instance is not tied to a particular <DRM Feature Representation> instance or <DRM Geometry Representation> instance. The <DRM Location> components of the <DRM Image Anchor> instance specify the positions of the corners of the <DRM Image> instance in the specified SRF.

    NOTE 1  If two georeferenced <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 are exactly the same along the common edge.

  2. As a component of a <DRM Image Mapping Function> instance.

    In this case, the <DRM Image Anchor> instance defines how the associated <DRM Image> instance is to be applied to the DRM object having the <DRM Image Mapping Function> instance as a component. The srf_context_info of the <DRM Image Anchor> instance shall match that of the context in which the <DRM Image Mapping Function> instance 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 2  When an image mapping is applied to many <DRM Polygon> instances using a single <DRM Image Mapping Function> instance, a continuous image results when displayed.

The srf_context_info field specifies the SRF within which the <DRM Image Anchor> instance is defined.

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_context_info

 

SRF_Context_Info

Default field values

Default field values for DRM_Image_Anchor

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)

Composed of (two-way metadata) (inherited)

  • None.

Composed of (two-way metadata)

  • None.

Component of (two-way) (inherited)

  • None.

Component of (two-way)

Constraints

Clarifications

1The three <DRM Location> components of a <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> instance.

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

  1. The first <DRM Location> component specifies the location to which the lower left corner of the <DRM Image> instance is mapped.

  2. The second <DRM Location> component specifies the location to which the upper left corner of the <DRM Image> instance is mapped.

  3. The third <DRM Location> component specifies the location to which the upper right corner of the <DRM Image> instance is mapped.

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

  1. For a cylindrical projection, the first <DRM Location> component 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> component specifies the alignment of the cylinder by specifying a point on the surface of the cylinder.

  2. For a spherical projection, the first <DRM Location> component 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> component specifies a point on the equator of the sphere.

Example(s)