Package org.opengis.coverage

Coverages (generate a value for any point).

See:
Description

Interface Summary

Coverage	Provides access to a coverage.
SampleDimension	Contains information for an individual sample dimension of coverage.

Class Summary

ColorInterpretation	Specifies the mapping of a band to a color model component.
PaletteInterpretation	Describes the color entry in a color table.
SampleDimensionType	Specifies the various dimension types for coverage values.

Exception Summary

CannotEvaluateException	The base class for exceptions thrown when a quantity can't be evaluated.
MetadataNameNotFoundException	Thrown when a requested metadata is not found.
PointOutsideCoverageException	Thrown when a evaluate(…) method is invoked with a point outside coverage.

Package org.opengis.coverage Description

Coverages (generate a value for any point). The following is adapted from OpenGIS® Grid Coverages Implementation Specification.

The architecture of the grid coverage specification is composed of three packages. The specification includes a package for the general coverage specification, a package specifically for grid coverages and a package for grid coverage processing. The processing package is optional and not required for an OGC compliant implementation.

The essential property of coverage is to be able to generate a value for any point within its domain. How coverage is represented internally is not a concern. For example consider the following different internal representations of coverage:

1. A coverage may be represented by a set of polygons which exhaustively tile a plane (that is each point on the plane falls in precisely one polygon). The value returned by the coverage for a point is the value of an attribute of the polygon that contains the point.
   
2. A coverage may be represented by a grid of values. The value returned by the coverage for a point is that of the grid value whose location is nearest the point.
   
3. Coverage may be represented by a mathematical function. The value returned by the coverage for a point is just the return value of the function when supplied the coordinates of the point as arguments.
   
4. Coverage may be represented by combination of these. For example, coverage may be represented by a combination of mathematical functions valid over a set of polynomials.

Color Palettes

A coverage can have a color palette. A color palette is valid for only coverages which are integer values (usually bytes). Color palettes supported include gray scale, RGB, HLS and CMYK. The coverage dimension information maps the grid sample dimensions to a color palette or to color model components. For example 8-bit pseudo color TIFF image would be represented as a grid with one sample dimension and a color palette with 256 RGB entries. A 24-bit RGB TIFF file would be represented as a grid with three bands and no color palette. The dimension information would indicate which bands to use for the RGB color components. The following illustrates example values for different color components:

Gray Scale	Vector contains one entry which a shade of gray. 0 is black and 255 is white.
RGB	Vector contains three values: Red Green Blue. Each value ranges from 0 to 255 where 0 is no intensity and 255 is maximum intensity.
RGBA	Vector contains four values RGBA: Red Green Blue Alpha. The alpha value is the level of transparency of the color. Alpha of 0 is transparent and 255 is opaque.
HLS	Vector contains three values: Hue Saturation Lightness. Hue is a value from 0 to 360. Saturation is a value from 0 to 100 where 0 is no color intensity and 100 is full color intensity. Lightness is a value from 0 to 100 where 0 is no lightness and 100 is full lightness.
CMYK	Vector contains four values: Cyan Magenta Yellow Black. Each value ranges from 0 to 255 where 0 is no intensity and 255 is maximum intensity.

WARNING: THIS PACKAGE WILL CHANGE. Current API is derived from OGC Grid Coverages Implementation specification 1.0. We plan to replace it by new interfaces derived from ISO 19123 (Schema for coverage geometry and functions). Current interfaces should be considered as legacy and are included in this distribution only because they were part of GeoAPI 1.0 release. We will try to preserve as much compatibility as possible, but no migration plan has been determined yet.