Module org.apache.sis.storage

Package org.apache.sis.storage

Enum Class RasterLoadingStrategy

Object

Enum<RasterLoadingStrategy>

RasterLoadingStrategy

All Implemented Interfaces:

Serializable, Comparable<Raster­Loading­Strategy>, Constable

public enum RasterLoadingStrategy
extends Enum<RasterLoadingStrategy>

Time when the "physical" loading of raster data should happen. Some resource implementations may not load data immediately when the read method is invoked, but instead defer the actual loading until the image is rendered. This enumeration gives some control over the time when data loading happens. The different strategies are compromises between memory consumption, redundant loading of same data and early error detection.

Enumeration values are ordered from the most eager strategy to the laziest strategy. The eager strategy is fastest when all pixels are used, at the cost of largest memory consumption. The lazy strategy is more efficient when only a few tiles will be used and those tiles are not known in advance. The lazy strategy is also the only applicable one if the image is too large for holding in memory.

Since:

1.1

Nested Class Summary

Nested classes/interfaces inherited from class Enum

Enum.Enum­Desc<E extends Enum<E>>

Enum Constant Summary

Enum Constants

Enum Constant	Description
AT_GET_TILE_TIME	Raster data are loaded at Rendered­Image.get­Tile(int, int) invocation time.
AT_READ_TIME	Raster data are loaded at Grid­Coverage­Resource.read(Grid­Geometry, int...) invocation time.
AT_RENDER_TIME	Raster data are loaded at Grid­Coverage.render(Grid­Extent) invocation time.

Method Summary

Modifier and Type	Method	Description
static Raster­Loading­Strategy	value­Of(String name)	Returns the enum constant of this class with the specified name.
static Raster­Loading­Strategy[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class Enum

clone, compare­To, describe­Constable, equals, finalize, get­Declaring­Class, hash­Code, name, ordinal, to­String, value­Of

Methods inherited from class Object

get­Class, notify, notify­All, wait, wait, wait

Enum Constant Details

AT_READ_TIME

public static final RasterLoadingStrategy AT_READ_TIME

Raster data are loaded at Grid­Coverage­Resource.read(Grid­Geometry, int...) invocation time. This is the most eager loading strategy.

Advantages:

• Fastest loading strategy if all pixels in the returned Grid­Coverage will be used.
• No redundant data loading: all data stay in memory until the resource is garbage-collected.
• Immediate error notification with a checked Data­Store­Exception.

Disadvantages:

• Slower than other strategies if only a subset of the returned Grid­Coverage will be used.
• Consume memory for the full Grid­Coverage as long as the resource is referenced.

AT_RENDER_TIME

public static final RasterLoadingStrategy AT_RENDER_TIME

Raster data are loaded at Grid­Coverage.render(Grid­Extent) invocation time. Speed and memory usage are at an intermediate level between AT_READ_TIME and AT_GET_TILE_TIME.

Advantages:

• Faster than AT_GET_TILE_TIME if all pixels in the returned Rendered­Image will be used.
• Load less data than AT_READ_TIME if the Grid­Extent is a sub-region of the coverage.
• Memory is released sooner (when the Rendered­Image is garbage-collected) than above mode.

Disadvantages:

• Slower than AT_GET_TILE_TIME if only a few tiles will be used.
• Consume memory for the full Rendered­Image as long as the image is referenced.
• May reload the same data many times if images are discarded and recreated.
• Unchecked Cannot­Evaluate­Exception can happen relatively late (at render(…) invocation time) in a chain of coverage operations.

AT_GET_TILE_TIME

public static final RasterLoadingStrategy AT_GET_TILE_TIME

Raster data are loaded at Rendered­Image.get­Tile(int, int) invocation time. This is the laziest loading strategy. This is also the only strategy that can handle very large Rendered­Images.

Advantages:

• Only the tiles that are actually used are loaded.
• Memory can be released at any time (tiles are kept by soft references).

Disadvantages:

• Slower read operations (numerous seeks when tiles are read in random order).
• May reload the same data many times if tiles are discarded and recreated.
• Unchecked Imaging­Op­Exception can happen late (at get­Tile(…) invocation time) in a chain of image operations.

Method Details

values

public static RasterLoadingStrategy[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

an array containing the constants of this enum class, in the order they are declared

valueOf

public static RasterLoadingStrategy valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

Illegal­Argument­Exception - if this enum class has no constant with the specified name

Null­Pointer­Exception - if the argument is null