The SEDRIS Data Representation Model
APPENDIX A - Classes
Colour

Abstract Class Name: Colour

Superclass - <SEDRIS Abstract Base>

Subclasses

Definition

An instance of a concrete class derived from this DRM class is either an instance of <Inline Colour> (which will be directly attached to representations of coloured objects) or an instance of <Colour Index> (referring to colours stored in a <Colour Table> instance).

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

See concrete subclasses for examples.

FAQs

Where can one find more information on colour in SEDRIS?

See Part 4, Volume 8 Images and Colour Models Technical Guide of the SEDRIS Documentation Set for further information.

Where do RGB values go in all this? How is a single, simple colour represented?

The actual colour values are represented by a single <Primitive Colour> for each <Colour> instance. The location of this <Primitive Colour> depends on whether the <Colour> in question is an <Inline Colour> or a <Colour Index>. See those classes for details.

A single, simple colour is represented as an <Inline Colour>, the colour_mapping of which is set to some variation of PRIMARY_COLOUR, and the <Primitive Colour> of which has only an <Ambient Colour> component specified.

See <Primitive Colour> for further discussion.

How can a data provider represent a colour (such as RGB) that has a coefficient (such as K)?

The data provider in this example has two options.

  1. The coefficient can be factored into the colour to create an <Inline Colour> instance.

  2. The colour can be placed in a <Colour Table> instance, then referenced by a <Colour Index> instance, the intensity of which is set to the value of the coefficient.

How does one determine how to apply a <Colour> instance to the object using it? What is the colour_mapping field for?

The colour_mapping field indicates how to apply a <Colour> instance to the object using it -- which side of the object it applies to, whether it is used for the primary colour, for distance or image blending, or something else. (See SE_Colour_Mapping for the details of specific colour mappings).

Incidentally, the colour_mapping field is a set, rather than a simple enumeration, in order to simplify the consumer's task of identifying what a colour applies to. Its members are taken from the SE_Colour_Mapping enumeration.

Is a <Primitive Geometry> instance required to have a PRIMARY_COLOUR as a component (whether direct or inherited)?

No. Some texture mapping techniques don't require colour to be present on <Polygon> instances, so some data providers have no PRIMARY_COLOUR to supply. If a consumer cannot handle the texture mapping technique used in a transmittal, then the consumer will have to choose some appropriate default colour.

Are all combinations of PRIMARY_COLOUR, DISTANCE_BLEND_COLOUR, and IMAGE_BLEND_COLOUR colour mapping valid for a single polygon's OTW front face?

Yes.

Constraints

Composed of (two-way)

Component of (two-way)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Colour_Mapping colour_mapping; (notes)

Notes

Composed of Notes


Presentation_Domain

 If present, this component identifies the type of sensor for which
 the given <Colour> instance is applicable.

Fields Notes


colour_mapping

 The colour_mapping field specifies the set of SE_Colour_Mapping
 tokens applicable to the given <Colour> instance.
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Last updated: July 16, 2004 Copyright © 2004 SEDRIS™