javax.media.jai.operator
Class SubsampleAverageDescriptor

java.lang.Object
  javax.media.jai.OperationDescriptorImpl
      javax.media.jai.operator.SubsampleAverageDescriptor

All Implemented Interfaces:

OperationDescriptor, RegistryElementDescriptor, Serializable

public class SubsampleAverageDescriptor

extends OperationDescriptorImpl

An OperationDescriptor describing the "SubsampleAverage" operation. "SubsampleAverage" supports the rendered and renderable modes.

The "SubsampleAverage" operation subsamples an image by averaging over a moving window. The scale factors supplied to the operation are forward mapping coefficients representing the geometric transformation from source to destination image coordinates. For example, if both scale factors were equal to 0.5, the operation would produce an output image of half the size of the input image in both dimensions. Both scale factors must be in the range (0.0, 1.0] or an exception will be thrown when the operation is created. The default value of the vertical scale factor is the value of the horizontal scale factor. If both scale factors equal 1.0, the source image is returned directly.

The size of the moving window or block over which source pixels are averaged varies as a function of the scale factors and is defined as

     int blockX = (int)Math.ceil(1.0/scaleX);
     int blockY = (int)Math.ceil(1.0/scaleY);
 

For a given destination pixel (dstX, dstY), the upper left corner (srcX, srcY) of the source block over which averaging occurs is defined as

     int srcX = (int)Math.floor((dstX - dstMinX)/scaleX + 0.5) + srcMinX;
     int srcY = (int)Math.floor((dstY - dstMinY)/scaleY + 0.5) + srcMinY;
 

where (srcMinX, srcMinY) are the image coordinates of the upper left pixel of the source and (dstMinX, dstMinY) are the image coordinates of the upper left pixel of the destination.

The destination image bounds are defined as

    int dstMinX = (int)Math.floor(srcMinX*scaleX);
    int dstMinY = (int)Math.floor(srcMinY*scaleY);
    int dstWidth = (int)(srcWidth*scaleX);
    int dstHeight = (int)(srcHeight*scaleY);
 

where (srcWidth, srcHeight) and (dstWidth, dstHeight) are the source and destination image dimensions, respectively.

Resource List

Name	Value
GlobalName	SubsampleAverage
LocalName	SubsampleAverage
Vendor	com.sun.media.jai
Description	Subsamples an image by averaging over a moving window.
DocURL	http://java.sun.com/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/operator/SubsampleAverageDescriptor.html
Version	1.0
arg0Desc	The X scale factor.
arg1Desc	The Y scale factor.

Parameter List

Name	Class Type	Default Value
scaleX	java.lang.Double	0.5
scaleY	java.lang.Double	scaleX

Since:

JAI 1.1.2

See Also:

FilteredSubsampleDescriptor, SubsampleBinaryToGrayDescriptor, ScaleDescriptor, Serialized Form

Field Summary

Fields inherited from class javax.media.jai.OperationDescriptorImpl

sourceNames, supportedModes

Fields inherited from interface javax.media.jai.OperationDescriptor

NO_PARAMETER_DEFAULT

Constructor Summary

SubsampleAverageDescriptor()
Constructor.

Method Summary

static RenderedOp	create(RenderedImage source0, Double scaleX, Double scaleY, RenderingHints hints) Subsamples an image by averaging over a moving window.
static RenderableOp	createRenderable(RenderableImage source0, Double scaleX, Double scaleY, RenderingHints hints) Subsamples an image by averaging over a moving window.
PropertyGenerator[]	getPropertyGenerators(String modeName) Returns an array of PropertyGenerators implementing property inheritance for the "SubsampleAverage" operation.
protected boolean	validateParameters(String modeName, 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

SubsampleAverageDescriptor

public SubsampleAverageDescriptor()

Constructor.

Method Detail

getPropertyGenerators

public PropertyGenerator[] getPropertyGenerators(String modeName)

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

Specified by:

getPropertyGenerators in interface RegistryElementDescriptor

Overrides:

getPropertyGenerators in class OperationDescriptorImpl

Parameters:

modeName - the registry mode name

Returns:

An array of PropertyGenerators, or null if this operation does not have any of its own PropertyGenerators.

See Also:

RegistryElementDescriptor

validateParameters

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

Validates the input parameters.

In addition to the standard checks performed by the superclass method, this method sets "scaleX" to "scaleY" if the latter is not provided in args.

Overrides:

validateParameters in class OperationDescriptorImpl

See Also:

OperationDescriptorImpl.validateArguments(java.lang.String, java.awt.image.renderable.ParameterBlock, java.lang.StringBuffer), ParameterListDescriptorImpl.isParameterValueValid(java.lang.String, java.lang.Object)

create

public static RenderedOp create(RenderedImage source0,
                                Double scaleX,
                                Double scaleY,
                                RenderingHints hints)

Subsamples an image by averaging over a moving window.

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

Parameters:

source0 - RenderedImage source 0.

scaleX - The X scale factor. May be null.

scaleY - The Y scale factor. 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

createRenderable

public static RenderableOp createRenderable(RenderableImage source0,
                                            Double scaleX,
                                            Double scaleY,
                                            RenderingHints hints)

Subsamples an image by averaging over a moving window.

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

Parameters:

source0 - RenderableImage source 0.

scaleX - The X scale factor. May be null.

scaleY - The Y scale factor. May be null.

hints - The RenderingHints to use. May be null.

Returns:

The RenderableOp destination.

Throws:

IllegalArgumentException - if source0 is null.

See Also:

JAI, ParameterBlockJAI, RenderableOp