Image

The SEDRIS Data Representation Model APPENDIX A - Classes Image

Class Name: Image

Superclass - <SEDRIS Abstract Base>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies one or more MIP levels of texels, and can have three dimensions. Each texel consists of the set of components identified by the image_signature field.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

A brick <Image> instance that is repeated over the surface of a <Polygon> instance to represent a brick wall.
An <Image> instance of a tree that when applied to a <Polygon> instance and combined with a <Translucency> instance creates a flat version of a tree.
The sequence of <Image> instance(s) mapped to a <Polygon> instance to represent a television.
Consider an <Image> instance that has three <Property Table Reference> components:
1. a reference to a <Property Table> instance for infrared properties,
2. a reference to a <Property Table> instance for night vision goggles properties, and
3. a reference to a <Property Table> instance for surface material category properties (see Figure 23).
Figure 23 — <DRM Image> example

Consider the case of one material. A given texel contains a single integer, which is used in place of the index_on_axis field for all the <Property Table Reference> components of the <Image> instance.
Consider the case of two materials. A given texel contains three integers, two of which are used in place of the index_on_axis field for all the <Property Table Reference> components of the <Image> instance, and a third integer, which specifies the percentage of the second material. For a given texel, say the numbers are 7 6 50. The material at that texel is something that is 50% glass and 50% concrete.
Consider the case of three materials. A given texel contains five integers, three of which are used in place of the index_on_axis field for all the <Property Table Reference> components of the <Image> instance, and two of which specify the percentages of material two and three. For a given texel, say the numbers are 4 6 7 20 30. The material at that texel is something that is 50% wood, 20% concrete, and 30% glass.

FAQs

Where can users go for further information about <Image> instances and texture mapping?

See Part 4 Volume 8, Images and Colour Models Technical Guide, of the SEDRIS Documentation Set for detailed information on <Data Table> manipulation.

The <Image> class does not appear to have a field for storing the texels of an <Image> instance. Where are the texels, and how can a data provider get at them?

The actual texels of an <Image> instance are hidden by the API implementation being used to provide the <Image> instance. See the SE_PutImageData() function in the level 0 API.

The <Image> class does not appear to have a field for storing the texels of an <Image> instance. Where are the texels, and how can a data consumer get at them?

The actual texels of an <Image> instance are hidden by the API implementation being used to provide the <Image> instance, so they are accessed via the SE_GetImageData() (in level 0) and SE_GetRearrangedImageData() (in level 1) API functions.

How are the bits_of_xxx, min_value_of_xxx, and max_value_of_xxx fields used?

See the comments for the individual image signatures in SE_Image_Signature for details on which values are present for which signature.

The mininum / maximum fields are used to specify the minimum and maximum values that a component may have on the producer's system, and do not relate to whatever values may actually be present in the transmittal.

EXAMPLES:

If the image components are floating point 32 bits, a minimum value of -1.0 and a maximum value of 1.0 means that all values in an image on the producer's system shall be represented within the range [-1.0, 1.0].
An image with unsigned integer components of 8 bits may specify its range to be [0, 99], indicating that even though the maximum value that can be specified with 8 bits is 255, the value 99 should be treated as the maximum value for this image.

What is the maximum size of an image that the DRM can represent?

There is no known size limitation for images in a transmittal. (Well, 1.8 x 10^19 texels by the depth of the texel.) However, there may be size limitations in either the media that is used in the transmission or in computer hardware that interprets the transmittal. To alleviate some of the problems associated with large images, the DRM has "hidden" the actual image data behind a function call that allows for the consumer to specify the size of the data that is to be handed off to the consumer. This function call is documented in P4V17 of the SEDRIS Documentation Set.

A data provider has an image that does not correspond to any registered SE_Image_Signature in the DRM. What can be done with it?

There are two possibilities.

Decompose this image into component images which do correspond to various registered image signatures, if possible. In addition to complex image signatures, individual image components are also supported as an SE_Image_Signature. After the decomposition, add an <Identification> component to the resulting <Image> instances to convey to consumers how the component images are to be reassembled into the complete image.
If one of the components of the image does not correspond to any registered SE_Image_Signature, submit a SEDRIS Change Request requesting that the desired signature be registered as an addition to SE_Image_Signature.

Why doesn't the DRM support JPEG (and other compressed formats)?

It is not currently deemed appropriate to directly support "lossy" imagery within the DRM.

What kind of image data ordering does the DRM support?

Currently the DRM only supports texel (pixel) data ordering. Scan line (All the red values on the first scan line, then all the green values ...) and image plane ordering (all the values of red within the image, then all the values of green...) are not supported.

The <Classification Data> component of a <Geometry Representation> instance G classifies G as a wall, but an <Image> instance referenced by the <Image Mapping Function> component of G has a <Classification Data> component specifying railway track. Which is it?

The <Image> instance was created for use as a railway track, but when it is creatively reused by a <Geometry Representation> instance that is not classified as a railway track, the classification of the <Geometry Representation> instance overrides.

Constraints

Associated by (one-way)

zero or more <Camera Point> instances
zero or more <Image Mapping Function> instances

Composed of (two-way)

zero or one <Classification Data> instance¹
zero or one <Image Anchor> instance
zero or one <Lineage> instance²
zero or one <Presentation Domain> instance³
zero or more <Property Table Reference> instances
zero or one <Spatial Extent> instance

Composed of (two-way metadata)

zero or one <Identification> instance⁴
zero or one <Time Constraints Data> instance

Component of (two-way)

one <Image Library> instance

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_String	name;	⁵
SE_Colour_Model	colour_model;	⁶
SE_Short_Integer_Positive	level_count;	⁷
SE_Image_MIP_Extents	mip_extents_array[];	⁸
SE_Image_Signature	image_signature;	⁹
SE_Image_Scan_Direction	scan_direction;	¹⁰
SE_Image_Scan_Direction_Z	scan_direction_z;	¹¹
SE_Image_Component_Type	component_data_type;	¹²
SE_Boolean	data_is_little_endian;	¹³
SE_Boolean	data_is_3D;	¹⁴
SE_Short_Integer_Unsigned	bits_of_alpha;	¹⁵
SE_Short_Integer_Unsigned	bits_of_luminance;	¹⁶
SE_Short_Integer_Unsigned	bits_of_colour_coordinate_1;	¹⁷
SE_Short_Integer_Unsigned	bits_of_colour_coordinate_2;	¹⁸
SE_Short_Integer_Unsigned	bits_of_colour_coordinate_3;	¹⁹
SE_Short_Integer_Unsigned	bits_of_bump_map_height;	²⁰
SE_Short_Integer_Unsigned	bits_of_material_1;	²¹
SE_Short_Integer_Unsigned	bits_of_material_2;	²²
SE_Short_Integer_Unsigned	bits_of_material_3;	²³
SE_Short_Integer_Unsigned	bits_of_material_2_percentage;	²⁴
SE_Short_Integer_Unsigned	bits_of_material_3_percentage;	²⁵
SE_Short_Integer_Unsigned	bits_of_image_index;	²⁶
SE_Short_Integer_Unsigned	bits_of_bump_map_u;	²⁷
SE_Short_Integer_Unsigned	bits_of_bump_map_v;	²⁸
SE_Float	min_value_of_alpha;	²⁹
SE_Float	max_value_of_alpha;	³⁰
SE_Float	min_value_of_luminance;	³¹
SE_Float	max_value_of_luminance;	³²
SE_Float	min_value_of_colour_coordinate_1;	³³
SE_Float	max_value_of_colour_coordinate_1;	³⁴
SE_Float	min_value_of_colour_coordinate_2;	³⁵
SE_Float	max_value_of_colour_coordinate_2;	³⁶
SE_Float	min_value_of_colour_coordinate_3;	³⁷
SE_Float	max_value_of_colour_coordinate_3;	³⁸
SE_Float	min_value_of_bump_map_height;	³⁹
SE_Float	max_value_of_bump_map_height;	⁴⁰
SE_Float	min_value_of_bump_map_u;	⁴¹
SE_Float	max_value_of_bump_map_u;	⁴²
SE_Float	min_value_of_bump_map_v;	⁴³
SE_Float	max_value_of_bump_map_v;	⁴⁴

Notes

Composed of Notes

Classification_Data

If provided, the <Classification Data> component identifies the content of the imagery.

Identification

If provided, the <Identification> component may be used to provide a more detailed description than that specified by the name field.

Lineage

If provided, the <Lineage> component specifies either information about the events and/or source data used in constructing the <Image> instance or lack of knowledge about lineage.

Presentation_Domain

The <Presentation Domain> component is intended to support geospecific <Image> instances that are not referenced by any <Image Mapping Function> instance since an <Image> instance may be significant only for a particular domain, such as radar, thermal, or OTW.

Fields Notes

name

The name field specifies a meaningful short name.

colour_model

The colour_model field specifies the colour model used throughout the <Image> instance. Only one colour model is allowed per <Image> instance.

level_count

The level_count field specifies the number of levels of detail defined for the <Image> instance (for mipmaps). If the given instance is not a MIP-mapped image, only one level is specified (level_count = 1).

NOTE 1 Many end-user applications require that <Image> instances having MIP levels specify both the horizontal and vertical dimensions as a power of two. However, some applications can handle <Image> instances for which the horizontal and vertical dimensions are a multiple of two rather than a power of two. For example, 96 texels in a direction is a multiple of two but not a power of two. The DRM places no restriction on either the dimensional size of an <Image> instance, nor makes any statement as to whether the use of MIP information within the <Image> instance will be valid on a given consuming application.

mip_extents_array

There are level_count entries in the mip_extents_array. Each entry defines the number of horizontal, vertical, and z texels for a single MIP level of the <Image> instance. The first map shall contain the highest level of detail; that is, mip_extents_array[0] corresponds to the level containing the most texels.

image_signature

The image_signature field specifies how texels are represented within the <Image> instance (see SE_Image_Signature for details).

NOTE 2 For an <Image> instance with an image_signature of SE_IMAGSIG_EDCS_CLASSIFICATION_CODE, the bit size is a constant that represents the number of bits needed to represent an ECC.

scan_direction

The scan_direction field specifies the origin and direction of the horizontal and vertical components of the <Image> instance.

scan_direction_z

The scan_direction_z field specifies the direction in which the z components of the <Image> instance are ordered.

component_data_type

The component_data_type field specifies the data type of each component of the raw texel data. If signed or unsigned integer is specified, the "minimum_value" and "maximum_value" fields apply. If floating point is specified, the component values are in the range [0.0, 1.0], and the applicable "minimum_value" and "maximum_value" fields shall be set to the applicable value of either 0.0 or 1.0. In addition, if floating point is specified, the applicable "bits_of" fields shall be set to either 32 or 64.

data_is_little_endian

The data_is_little_endian field specifies the endianess of the raw image data.

data_is_3D

The data_is_3D field specifies whether the image data has three dimensions.

bits_of_alpha

The bits_of_alpha field specifies how many bits of a texel within the image data specify alpha information. It is zero if alpha is not used.

bits_of_luminance

The bits_of_luminance field specifies how many bits of a texel within the image data specify luminance information. It is zero if luminance is not used.

bits_of_colour_coordinate_1

The bits_of_colour_coordinate_1 field specifies how many bits of a texel within the image data specify colour coordinate 1 information. It is zero if colour coordinate 1 is not used.

bits_of_colour_coordinate_2

The bits_of_colour_coordinate_2 field specifies how many bits of a texel within the image data specify colour coordinate 2 information. It is zero if colour coordinate 2 is not used.

bits_of_colour_coordinate_3

The bits_of_colour_coordinate_3 field specifies how many bits of a texel within the image data specify colour coordinate 3 information. It is zero if colour coordinate 3 is not used.

bits_of_bump_map_height

The bits_of_bump_map_height field specifies how many bits of a texel within the image data specify bump map height information. It is zero if bump map height is not used.

bits_of_material_1

If the value of the bits_of_material_1 field is non-zero, the <Image> instance has at least one <Property Table Reference> component, and the bits in the image data corresponding to material 1 specify indexes into the <Property Table> instance(s) that are referenced by the <Property Table Reference> component(s) of the <Image> instance. If the value of the bits_of_material_1 field is zero, the image data does not contain material 1 index information.

NOTE 3 With no material 2 or material 3 percentages, material 1 is at 100%.

bits_of_material_2

If the value of the bits_of_material_2 field is non-zero, the <Image> instance has at least one <Property Table Reference> component, and the bits in the image data corresponding to material 2 specify indexes into the <Property Table> instance(s) referenced by the <Property Table Reference> component(s) of the <Image> instance. However, if bits_of_material_2 = 0, the texel data of the <Image> instance does not contain material 2 index information.

bits_of_material_3

If the bits_of_material_3 field specifies non-zero, the <Image> instance has at least one <Property Table Reference> component, and the bits in the image data corresponding to material 3 specify indexes into the <Property Table> instance(s) referenced by the <Property Table Reference> component(s) of the <Image> instance. However, if bits_of_material_3 = 0, the texel data of the <Image> instance does not contain material 3 index information.

Last updated: July 1, 2011