org.jaitools.media.jai.contour

Class ContourDescriptor

java.lang.Object

javax.media.jai.OperationDescriptorImpl

org.jaitools.media.jai.contour.ContourDescriptor

All Implemented Interfaces:

Serializable, javax.media.jai.OperationDescriptor, javax.media.jai.RegistryElementDescriptor

public class ContourDescriptor
extends javax.media.jai.OperationDescriptorImpl

Describes the "Contour" operation in which contour lines are interpolated from values in a source image band. The desired contour values can be specified either by supplying a Collection of values via the "levels" parameter, or a single value via the "interval" parameter. In the interval case, the resulting contour values will be integer multiples of the interval. If both parameters are supplied the "levels" parameter takes preference.

Contours are returned as a destination image property in the form of a Collection of LineString objects. The source image value associated with each contour can be retrieved with the Geometry.getUserData() method.

Source image pixels are passed through to the destination image unchanged.

Three boolean parameters control the form of the generated contours:

1. simplify: if true (the default) colinear vertices are removed to reduce contour memory requirements.
2. mergeTiles: if true (the default) contour lines are merged into LineStrings across image tile boundaries; if false mergine is skipped for faster processing.
3. smooth: if true contours are smoothed using Bezier interpolation before being returned; if false (the default) no smoothing is done. This option will probably have little effect on the form of contours unless the source image resolution is coarse.

Example of use:

 RenderedImage src = ...
 ParameterBlockJAI pb = new ParameterBlockJAI("Contour");
 pb.setSource("source0", src);
 
 // For contours at specific levels set the levels parameter
 List<Double> levels = Arrays.asList(new double[]{1.0, 5.0, 10.0, 20.0, 50.0, 100.0});
 pb.setParameter("levels", levels);
 
 // Alternatively, set a constant interval between contours
 pb.setParameter("interval", 10.0);
 
 RenderedOp dest = JAI.create("Contour", pb);
 Collection<LineString> contours = (Collection<LineString>) 
         dest.getProperty(ContourDescriptor.CONTOUR_PROPERTY_NAME);
 
 for (LineString contour : contours) {
   // get this contour's value
   Double contourValue = (Double) contour.getUserData();
   ...
 }
 

The interpolation algorithm used is that of Paul Bourke: originally published in Byte magazine (1987) as the CONREC contouring subroutine written in FORTRAN. The implementation here was adapted from Paul Bourke's C code for the algorithm available at: http://local.wasp.uwa.edu.au/~pbourke/papers/conrec/

Summary of parameters:

Summary of parameters

Name	Class	Default	Description
roi	ROI	null	An optional ROI defining the area to contour.
band	Integer	0	Source image band to process.
levels	Collection	null	The values for which to generate contours.
interval	Number	null	The interval between contour values. This parameter is ignored if the levels parameter has been supplied. With interval contouring the minimum and maximum contour values will be integer multiples of the interval parameter value.
nodata	Collection	The set: {Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, Double.MAX_VALUE}	Values to be treated as NO_DATA. A value can be either a Number or a Range (mixtures of both are permitted).
strictNodata	Boolean	Boolean.TRUE	If true, any NODATA values in the 2x2 cell moving window used by the contouring algorithm will cause that part of the image to be skipped. If false, a single NODATA value will be permitted in the window. This probably only makes a noticeable difference with small images.
simplify	Boolean	Boolean.TRUE	Whether to simplify contour lines by removing collinear vertices.
smooth	Boolean	Boolean.FALSE	Whether to smooth contour lines using Bezier interpolation. This probably only makes a noticeable difference with small images.

Since:

1.1

Version:

$Id$

Author:

Michael Bedward

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	CONTOUR_PROPERTY_NAME Constant identifying the image property that will hold the generated contours.

Fields inherited from class javax.media.jai.OperationDescriptorImpl

resources, sourceNames, supportedModes

Fields inherited from interface javax.media.jai.OperationDescriptor

NO_PARAMETER_DEFAULT

Constructor Summary

Constructors

Constructor and Description
ContourDescriptor() Creates a new instance.

Method Summary

Modifier and Type	Method and Description
protected boolean	validateParameters(String modeName, ParameterBlock pb, StringBuffer msg) Validates supplied parameters.

Methods inherited from class javax.media.jai.OperationDescriptorImpl

arePropertiesSupported, getDefaultSourceClass, getDestClass, getDestClass, getInvalidRegion, getName, getNumParameters, getNumSources, getParamClasses, getParamDefaults, getParamDefaultValue, getParameterListDescriptor, getParamMaxValue, getParamMinValue, getParamNames, getPropertyGenerators, getPropertyGenerators, getRenderableDestClass, getRenderableSourceClasses, getResourceBundle, getResources, getSourceClasses, getSourceClasses, getSourceNames, getSupportedModes, isImmediate, isModeSupported, isRenderableSupported, isRenderedSupported, makeDefaultSourceClassList, validateArguments, validateArguments, validateParameters, validateRenderableArguments, validateRenderableSources, validateSources, validateSources

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONTOUR_PROPERTY_NAME

public static final String CONTOUR_PROPERTY_NAME

Constant identifying the image property that will hold the generated contours.

See Also:

Constant Field Values

Constructor Detail

ContourDescriptor

public ContourDescriptor()

Creates a new instance.

Method Detail

validateParameters

protected boolean validateParameters(String modeName,
                                     ParameterBlock pb,
                                     StringBuffer msg)

Validates supplied parameters.

Overrides:

validateParameters in class javax.media.jai.OperationDescriptorImpl

Parameters:

modeName - the rendering mode

pb - the parameter block

msg - a StringBuffer to receive error messages

Returns:

true if parameters are valid; false otherwise