javax.media.jai.operator
Class ScaleDescriptor

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

All Implemented Interfaces:

OperationDescriptor, RegistryElementDescriptor, Serializable

public class ScaleDescriptor

extends OperationDescriptorImpl

An OperationDescriptor describing the "Scale" operation.

The "Scale" operation translates and resizes an image. For each pixel (x, y) of the destination, the source value at the fractional subpixel position ((x - xTrans)/xScale, (y - yTrans)/yScale) is constructed by means of an Interpolation object and written to the destination.

When applying scale factors of scale_x, scale_y to a source image with width of src_width and height of src_height, the resulting image is defined to have the following dimensions: dst_width = src_width * scale_x dst_height = src_height * scale_y

When interpolations which require padding the source such as Bilinear or Bicubic interpolation are specified, the source needs to be extended such that it has the extra pixels needed to compute all the destination pixels. This extension is performed via the BorderExtender class. The type of Border Extension can be specified as a RenderingHint to the JAI.create method.

If no Border Extension is specified, the source will not be extended. The scaled image size is still calculated according to the formula specified above. However since there isn't enough source to compute all the destination pixels, only that subset of the destination image's pixels, which can be computed, will be written in the destination. The rest of the destination will not be written.

Specifying a scale factor of greater than 1 increases the size of the image, specifying a scale factor between 0 and 1 (non-inclusive) decreases the size of an image. An IllegalArgumentException will be thrown if the specified scale factors are negative or equal to zero.

It may be noted that the minX, minY, width and height hints as specified through the JAI.KEY_IMAGE_LAYOUT hint in the RenderingHints object are not honored, as this operator calculates the destination image bounds itself. The other ImageLayout hints, like tileWidth and tileHeight, however are honored.

"Scale" defines a PropertyGenerator that performs an identical transformation on the "ROI" property of the source image, which can be retrieved by calling the getProperty method with "ROI" as the property name.

Resource List

Name	Value
GlobalName	Scale
LocalName	Scale
Vendor	com.sun.media.jai
Description	Resizes an image.
DocURL	http://java.sun.com/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/operator/ScaleDescriptor.html
Version	1.0
arg0Desc	The X scale factor.
arg1Desc	The Y scale factor.
arg2Desc	The X translation.
arg3Desc	The Y translation.
arg4Desc	The interpolation method for resampling.

Parameter List

Name	Class Type	Default Value
xScale	java.lang.Float	1.0F
yScale	java.lang.Float	1.0F
xTrans	java.lang.Float	0.0F
yTrans	java.lang.Float	0.0F
interpolation	javax.media.jai.Interpolation	InterpolationNearest

See Also:

Interpolation, BorderExtender, OperationDescriptor, Serialized Form

Fields inherited from class javax.media.jai.OperationDescriptorImpl

resources, sourceNames, supportedModes

Constructor Summary

ScaleDescriptor()
Constructor.

Method Summary

Number	getParamMinValue(int index) Returns the minimum legal value of a specified numeric parameter for this operation.
PropertyGenerator[]	getPropertyGenerators() Returns an array of PropertyGenerators implementing property inheritance for the "Scale" operation.
boolean	isRenderableSupported() Returns true since renderable operation is supported.
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, getParamNames, getPropertyGenerators, getRenderableDestClass, getRenderableSourceClasses, getResourceBundle, getResources, getSourceClasses, getSourceClasses, getSourceNames, getSupportedModes, isImmediate, isModeSupported, 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

ScaleDescriptor

public ScaleDescriptor()

Constructor.

Method Detail

isRenderableSupported

public boolean isRenderableSupported()

Returns true since renderable operation is supported.

Overrides:

isRenderableSupported in class OperationDescriptorImpl

Tags copied from class: OperationDescriptorImpl

See Also:

OperationDescriptorImpl.isModeSupported(java.lang.String)

getPropertyGenerators

public PropertyGenerator[] getPropertyGenerators()

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

Overrides:

getPropertyGenerators in class OperationDescriptorImpl

Returns:

An array of property generators.

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 "xScale" and "yScale" are both greater than 0.

Overrides:

validateParameters in class OperationDescriptorImpl

Tags copied from class: 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)

getParamMinValue

public Number getParamMinValue(int index)

Returns the minimum legal value of a specified numeric parameter for this operation.

For the minimum value of "xScale" and "yScale", this method returns 0. However, the scale factors must be a positive floating number and can not be 0.

Overrides:

getParamMinValue in class OperationDescriptorImpl

Tags copied from class: OperationDescriptorImpl

Parameters:

index - The index of the parameter to be queried.

Returns:

A Number representing the minimum legal value, or null if the specified parameter is not numeric.

Throws:

IllegalArgumentException - if this operation has no parameters.

ArrayIndexOutOfBoundsException - if there is no parameter corresponding to the specified index.

See Also:

ParameterListDescriptor.getParamValueRange(java.lang.String), ParameterListDescriptor.getEnumeratedParameterValues(java.lang.String), ParameterListDescriptor.isParameterValueValid(java.lang.String, java.lang.Object)