javax.media.jai.operator
Class GradientMagnitudeDescriptor

java.lang.Object
  |
  +--javax.media.jai.OperationDescriptorImpl
        |
        +--javax.media.jai.operator.GradientMagnitudeDescriptor

All Implemented Interfaces:

OperationDescriptor, RegistryElementDescriptor, Serializable

public class GradientMagnitudeDescriptor

extends OperationDescriptorImpl

An OperationDescriptor describing the "GradientMagnitude" operation.

The "GradientMagnitude" operation is an edge detector which computes the magnitude of the image gradient vector in two orthogonal directions.

The result of the "GradientMagnitude" operation may be defined as:

 dst[x][y][b] = ((SH(x,y,b))^2 + (SV(x,y,b))^2 )^0.5
 

where SH(x,y,b) and SV(x,y,b) are the horizontal and vertical gradient images generated from band b of the source image by correlating it with the supplied orthogonal (horizontal and vertical) gradient masks. Origins set on the kernels will be ignored. The origins are assumed to be width/2 & height/2. It should be noted that this operation automatically adds a value of Boolean.TRUE for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL to the given configuration so that the operation is performed on the pixel values instead of being performed on the indices into the color map if the source(s) have an IndexColorModel. This addition will take place only if a value for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL has not already been provided by the user. Note that the configuration Map is cloned before the new hint is added to it. The operation can be smart about the value of the JAI.KEY_REPLACE_INDEX_COLOR_MODEL RenderingHints, i.e. while the default value for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL is Boolean.TRUE, in some cases the operator could set the default.

Resource List

Name	Value
GlobalName	GradientMagnitude
LocallName	GradientMagnitude
Vendor	com.sun.media.jai
Description	Performs gradient magnitude edge detection on an image.
DocURL	http://java.sun.com/products/java-media/jai/forDevelopers/jaiapi/javax.media.jai.operator.GradientMagnitudeDescriptor.html
Version	1.0
arg0Desc	A gradient mask
arg1Desc	A gradient mask orthogonal to the first one.

Parameter List

Name	Class Type	Default Value
mask1	javax.media.jai.KernelJAI	KernalJAI.GRADIENT_MASK_SOBEL_HORIZONTAL
mask2	javax.media.jai.KernelJAI	KernalJAI.GRADIENT_MASK_SOBEL_VERTICAL

See Also:

OperationDescriptor, KernelJAI, Serialized Form

Fields inherited from class javax.media.jai.OperationDescriptorImpl

resources, sourceNames, supportedModes

Fields inherited from interface javax.media.jai.OperationDescriptor

NO_PARAMETER_DEFAULT

Constructor Summary

GradientMagnitudeDescriptor()
Constructor for the GradientMagnitudeDescriptor.

Method Summary

static RenderedOp	create(RenderedImage source0, KernelJAI mask1, KernelJAI mask2, RenderingHints hints) Computes the gradient of an image
PropertyGenerator[]	getPropertyGenerators() Returns an array of PropertyGenerators implementing property inheritance for the "GradientMagnitude" operation.
protected boolean	validateParameters(ParameterBlock args, StringBuffer msg) Validates the input 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, 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

Constructor Detail

GradientMagnitudeDescriptor

public GradientMagnitudeDescriptor()

Constructor for the GradientMagnitudeDescriptor.

Method Detail

validateParameters

protected boolean validateParameters(ParameterBlock args,
                                     StringBuffer msg)

Validates the input parameters.

In addition to the standard checks performed by the superclass method, this method checks that "mask1" and "mask2" have the same dimensions.

Overrides:

validateParameters in class OperationDescriptorImpl

Following copied from class: javax.media.jai.OperationDescriptorImpl

Throws:

IllegalArgumentException - if args is null.

IllegalArgumentException - if msg is null and the validation fails.

See Also:

OperationDescriptorImpl.validateParameters(java.lang.String, java.awt.image.renderable.ParameterBlock, java.lang.StringBuffer)

getPropertyGenerators

public PropertyGenerator[] getPropertyGenerators()

Returns an array of PropertyGenerators implementing property inheritance for the "GradientMagnitude" operation.

Overrides:

getPropertyGenerators in class OperationDescriptorImpl

Returns:

An array of property generators.

create

public static RenderedOp create(RenderedImage source0,
                                KernelJAI mask1,
                                KernelJAI mask2,
                                RenderingHints hints)

Computes the gradient of an image

Creates a ParameterBlockJAI from all supplied arguments except hints and invokes JAI.create(String,ParameterBlock,RenderingHints).

Parameters:

source0 - RenderedImage source 0.

mask1 - A gradient mask. May be null.

mask2 - A gradient mask orthogonal to the first one. May be null.

hints - The RenderingHints to use. May be null.

Returns:

The RenderedOp destination.

Throws:

IllegalArgumentException - if source0 is null.

See Also:

JAI, ParameterBlockJAI, RenderedOp