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java.lang.Object javax.media.jai.OperationDescriptorImpl javax.media.jai.operator.HistogramDescriptor
This OperationDescriptor
defines the "Histogram"
operation.
A histogram of an image is represented by a list of "bins"
where each bin is the total number of pixel samples of the image
whose values lie within a given range. This data are encapulated
in the javax.media.jai.Histogram
object, and may be
retrieved by calling the getProperty
method on this
operator with "histogram" as the property name.
At a request for the histogram property, this operator scans
the specific region of the source image, generates the pixel count
data, and returns an instance of the Histogram
class
where the data are stored. The source image's pixels are unchanged
by this operator.
The region-of-interest (ROI), within which the pixels are counted,
does not have to be a rectangle. It may be null
, in
which case the entire image is scanned to accumulate the histogram.
The set of pixels scanned may be further reduced by specifying the "xPeriod" and "yPeriod" parameters that represent the sampling rate along the two axis. These variables may not be less than 1. If they are not set, the default value of 1 is used so that every pixel within the ROI is counted.
The three arguments, numBins
, lowValue
,
and highValue
, define the type of the histogram to be
generated. Please see the Histogram
specification for
their detailed descriptions. The three arrays must either have an
array length of 1, in which case the same value is applied to all
bands of the source image, or an array length that equals to the
number of bands of the source image, in which case each value is
applied to its corresponding band. The numBins
must
all be greater than 0, and each lowValue
must be less
than its corresponding highValue
. Note that the default
values of these three parameters are specific to the case wherein
the image data are of type byte
. For other image data
types the values of these parameters should be supplied explicitely.
Name | Value |
---|---|
GlobalName | Histogram |
LocalName | Histogram |
Vendor | com.sun.media.jai |
Description | Generates a histogram based on the pixel values within a specific region of an image. |
DocURL | http://java.sun.com/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/operator/HistogramDescriptor.html |
Version | 1.1 |
arg0Desc | The region of the image to be scanned. |
arg1Desc | The horizontal sampling rate; may not be less than 1. |
arg2Desc | The vertical sampling rate; may not be less than 1. |
arg3Desc | The number of bins for each band. |
arg4Desc | The lowest inclusive pixel value to be checked for each band. |
arg5Desc | The highest exclusive pixel value to be checked for each band. |
Name | Class Type | Default Value |
---|---|---|
roi | javax.media.jai.ROI | null |
xPeriod | java.lang.Integer | 1 |
yPeriod | java.lang.Integer | 1 |
numBins | int[] | {256} |
lowValue | double[] | {0.0} |
highValue | double[] | {256.0} |
Histogram
,
ROI
,
OperationDescriptor
,
Serialized FormField Summary |
Fields inherited from class javax.media.jai.OperationDescriptorImpl |
sourceNames, supportedModes |
Fields inherited from interface javax.media.jai.OperationDescriptor |
NO_PARAMETER_DEFAULT |
Constructor Summary | |
HistogramDescriptor()
Constructor. |
Method Summary | |
static RenderedOp |
create(RenderedImage source0,
ROI roi,
Integer xPeriod,
Integer yPeriod,
int[] numBins,
double[] lowValue,
double[] highValue,
RenderingHints hints)
Generates a histogram based on the pixel values within a specific region of an image. |
Number |
getParamMinValue(int index)
Returns the minimum legal value of a specified numeric parameter for this operation. |
protected boolean |
validateParameters(ParameterBlock args,
StringBuffer msg)
Returns true if this operation is capable of handling
the input parameters. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public HistogramDescriptor()
Method Detail |
public Number getParamMinValue(int index)
getParamMinValue
in interface OperationDescriptor
getParamMinValue
in class OperationDescriptorImpl
index
- The index of the parameter to be queried.
Number
representing the minimum legal value,
or null
if the specified parameter is not
numeric.ParameterListDescriptor.getParamValueRange(java.lang.String)
,
ParameterListDescriptor.getEnumeratedParameterValues(java.lang.String)
,
ParameterListDescriptor.isParameterValueValid(java.lang.String, java.lang.Object)
protected boolean validateParameters(ParameterBlock args, StringBuffer msg)
true
if this operation is capable of handling
the input parameters.
In addition to the default validations done in the super class,
this method verifies that each element of numBins
is
greater than 0, and each lowValue
is less than its
corresponding highValue
.
validateParameters
in class OperationDescriptorImpl
IllegalArgumentException
- If args
is null
.
IllegalArgumentException
- If msg
is null
and the validation fails.OperationDescriptorImpl.validateParameters(java.lang.String, java.awt.image.renderable.ParameterBlock, java.lang.StringBuffer)
public static RenderedOp create(RenderedImage source0, ROI roi, Integer xPeriod, Integer yPeriod, int[] numBins, double[] lowValue, double[] highValue, RenderingHints hints)
Creates a ParameterBlockJAI
from all
supplied arguments except hints
and invokes
JAI.create(String,ParameterBlock,RenderingHints)
.
source0
- RenderedImage
source 0.roi
- The region of the image to be scanned.
May be null
.xPeriod
- The horizontal sampling rate; may not be less than 1.
May be null
.yPeriod
- The vertical sampling rate; may not be less than 1.
May be null
.numBins
- The number of bins for each band.
May be null
.lowValue
- The lowest inclusive pixel value to be checked for each band.
May be null
.highValue
- The highest exclusive pixel value to be checked for each band.
May be null
.hints
- The RenderingHints
to use.
May be null
.
RenderedOp
destination.
IllegalArgumentException
- if source0
is null
.JAI
,
ParameterBlockJAI
,
RenderedOp
|
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