org.geotools.coverage.processing
Class FilterOperation

java.lang.Object
  org.geotools.coverage.processing.AbstractOperation
      org.geotools.coverage.processing.Operation2D
          org.geotools.coverage.processing.OperationJAI
              org.geotools.coverage.processing.FilterOperation

All Implemented Interfaces:

org.opengis.coverage.processing.Operation, java.io.Serializable

Direct Known Subclasses:

NodataFilter

public class FilterOperation

extends OperationJAI

Common super-class for filter operation. The following is adapted from OpenGIS specification:

Filtering is an enhancement operation that alters the grid values on the basis of the neighborhood grid values. For this reason, filtering is considered to be a spatial or area opeartion. There are many different filters that can be applied to a grid coverage but the general concept of filtering is the same. A filter window or kernel is defined, its dimension being an odd number in the x and y dimensions. Each cell in this window contains a co-efficient or weighting factor representative of some mathmetical relationship. A filtered grid coverage is generated by multipling each coefficient in the window by the grid value in the original grid coverage corresponding to the window?s current location and assigning the result to the central pixel location of the window in the filtered grid coverage. The window is moved thoughout the grid coverage on pixel at a time. This window multiplication process is known as convolution. A grid coverage contains both low and high spatial information. High frequencies describe rapid change from one grid cell to another such as roads or other boundary conditions. Low frequencies describe gradual change over a large number of cells such as water bodies. High pass filters allow only high frequency information to be generated in the new grid coverage Grid coverages generated with high pass filters will show edge conditions. Low pass filters allow low frequency information to be generated in the new grid coverage. The grid coverage produced from a filtering operation will have the same dimension as the source grid coverage. To produce filtered values around the edges of the source grid coverage, edge rows and columns will be duplicated to fill a complete kernel.

Since:

2.2

Version:

$Id: FilterOperation.java 17672 2006-01-19 00:25:55Z desruisseaux $

Author:

Martin Desruisseaux

See Also:

Serialized Form

Nested Class Summary

Nested classes inherited from class org.geotools.coverage.processing.OperationJAI

OperationJAI.Parameters

Field Summary

Fields inherited from class org.geotools.coverage.processing.OperationJAI

operation

Fields inherited from class org.geotools.coverage.processing.Operation2D

SOURCE_0

Fields inherited from class org.geotools.coverage.processing.AbstractOperation

descriptor

Constructor Summary

FilterOperation(java.lang.String name)
Constructs a new filter operation.

Method Summary

protected GridSampleDimension[]

deriveSampleDimension(GridSampleDimension[][] bandLists, OperationJAI.Parameters parameters) Returns the target sample dimensions.

Methods inherited from class org.geotools.coverage.processing.OperationJAI

computeOnGeophysicsValues, createRenderedImage, deriveCategory, deriveGridCoverage, deriveName, deriveRange, deriveUnit, doOperation, equals, getJAI, resampleToCommonGeometry

Methods inherited from class org.geotools.coverage.processing.Operation2D

getFactory, getGridCoverageProcessor

Methods inherited from class org.geotools.coverage.processing.AbstractOperation

ensureNonNull, getDescription, getDocURL, getName, getNumSources, getParameters, getProcessor, getVendor, getVersion, hashCode, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

FilterOperation

public FilterOperation(java.lang.String name)
                throws org.opengis.coverage.processing.OperationNotFoundException

Constructs a new filter operation.

Parameters:

name - The JAI operation name.

Throws:

org.opengis.coverage.processing.OperationNotFoundException - if no JAI descriptor was found for the given name.

Method Detail

deriveSampleDimension

protected GridSampleDimension[] deriveSampleDimension(GridSampleDimension[][] bandLists,
                                                      OperationJAI.Parameters parameters)

Returns the target sample dimensions. Since filter operation do not change the range of values, this method returns the same sample dimension than the first source.

Overrides:

deriveSampleDimension in class OperationJAI

Parameters:

bandLists - The set of sample dimensions for each source GridCoverage2Ds.

parameters - Parameters, rendering hints and coordinate reference system to use.

Returns:

The sample dimensions for each band in the destination image, or if unknow.

See Also:

OperationJAI.deriveCategory(org.geotools.coverage.Category[], org.geotools.coverage.processing.OperationJAI.Parameters), OperationJAI.deriveUnit(javax.units.Unit[], org.geotools.coverage.processing.OperationJAI.Parameters)