Java Doc for HistogramDescriptor.java in  » 6.0-JDK-Modules » Java-Advanced-Imaging » javax » media » jai » operator » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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.

Resource List

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.

Parameter List

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}

Creates a ParameterBlockJAI from all supplied arguments except hints and invokes JAI.create(StringParameterBlockRenderingHints) .
See Also:   JAI
See Also:   ParameterBlockJAI
See Also:   RenderedOp
Parameters:
  source0 - RenderedImage source 0.
Parameters:
  roi - The region of the image to be scanned.May be null.
Parameters:
  xPeriod - The horizontal sampling rate; may not be less than 1.May be null.
Parameters:
  yPeriod - The vertical sampling rate; may not be less than 1.May be null.
Parameters:
  numBins - The number of bins for each band.May be null.
Parameters:
  lowValue - The lowest inclusive pixel value to be checked for each band.May be null.
Parameters:
  highValue - The highest exclusive pixel value to be checked for each band.May be null.
Parameters:
  hints - The RenderingHints to use.May be null.

Creates a ParameterBlockJAI from all supplied arguments except hints and invokes JAI.create(StringParameterBlockRenderingHints) .
See Also:   JAI
See Also:   ParameterBlockJAI
See Also:   RenderedOp
Parameters:
  source0 - RenderedImage source 0.
Parameters:
  roi - The region of the image to be scanned.May be null.
Parameters:
  xPeriod - The horizontal sampling rate; may not be less than 1.May be null.
Parameters:
  yPeriod - The vertical sampling rate; may not be less than 1.May be null.
Parameters:
  numBins - The number of bins for each band.May be null.
Parameters:
  lowValue - The lowest inclusive pixel value to be checked for each band.May be null.
Parameters:
  highValue - The highest exclusive pixel value to be checked for each band.May be null.
Parameters:
  hints - The RenderingHints to use.May be null. The RenderedOp destination.
throws:
  IllegalArgumentException - if source0 is null.

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.
throws:
  IllegalArgumentException - If args is null.
throws:
  IllegalArgumentException - If msg is nulland the validation fails.