de.unihalle.informatik.MiToBo.segmentation.thresholds

Class CalcGlobalThreshOtsu

java.lang.Object

de.unihalle.informatik.Alida.operator.ALDOperator

de.unihalle.informatik.MiToBo.core.operator.MTBOperator

de.unihalle.informatik.MiToBo.segmentation.thresholds.CalcGlobalThreshOtsu

All Implemented Interfaces:

de.unihalle.informatik.Alida.datatypes.ALDConfigurationValidator, de.unihalle.informatik.Alida.operator.events.ALDOperatorExecutionProgressEventListener, EventListener

@ALDAOperator(genericExecutionMode=ALL,
              shortDescription="Otsu\'s method for calculating global thresholds for image binarization.")
public class CalcGlobalThreshOtsu
extends MTBOperator

This class implements Otsu's method for calculating an optimal threshold for a given grayscale images.

Basically, the optimal threshold is defined as the threshold which best separates the image histogram in two classes, more or less equal in size and well-separated in terms of their average intensities.

The threshold calculation is based on the following goal function,

\begin{eqnarray*} J(T) &=& \pi_{fg}(T) \cdot \pi_{bg}(T) \cdot ( \mu_{fg}(T) - \mu_{bg}(T) )^2, \\ \pi_{fg}(T) &=& \text{a-priori probability of a pixel for belonging to the foreground}\\ \pi_{bg}(T) &=& \text{a-priori probability of a pixel for belonging to the background}\\ \mu_{fg}(T) &=& \text{average intensity in foreground class}\\ \mu_{bg}(T) &=& \text{average intensity in background class} \end{eqnarray*}

which is to be maximized with regard to threshold T. Maximization is done by explicitly calculating the value of the goal function for all possible thresholds T and searching for the maximum value.

Since the number of possible thresholds is directly linked to the number of histogram bins and, hence, to the computation time the maximum number of possible bins is restricted to 1024 in this implementation to keep the computational effort acceptable.

Reference: Nobuyuki Otsu, "A threshold selection method from gray-level histograms", IEEE Trans. Sys., Man., Cyber. 9 (1): 62–66, 1979.

Author:

Birgit Moeller

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CalcGlobalThreshOtsu.InputType Type of input to work on.

Nested classes/interfaces inherited from class de.unihalle.informatik.Alida.operator.ALDOperator

de.unihalle.informatik.Alida.operator.ALDOperator.HidingMode, de.unihalle.informatik.Alida.operator.ALDOperator.HistoryConstructionMode

Field Summary

Fields

Modifier and Type	Field and Description
private MTBImageHistogram	inHisto Input histogram.
private MTBImage	inImg Input image.
private CalcGlobalThreshOtsu.InputType	inType Input type.
private MTBDoubleData	threshold Result threshold.

Fields inherited from class de.unihalle.informatik.Alida.operator.ALDOperator

completeDAG, name, operatorExecutionEventlistenerList, portHashAccess, verbose, versionProvider

Constructor Summary

Constructors

Constructor and Description
CalcGlobalThreshOtsu() Default constructor.
CalcGlobalThreshOtsu(MTBImage img) Default constructor with input image as argument.
CalcGlobalThreshOtsu(MTBImageHistogram histo) Default constructor with input histogram as argument.

Method Summary

Modifier and Type	Method and Description
private MTBDoubleData	calcThreshold(MTBImage image) Calculate Otsu threshold on given image.
private MTBDoubleData	calcThreshold(MTBImageHistogram histo) Calculate Otsu threshold on given histogram.
String	getDocumentation()
MTBDoubleData	getOtsuThreshold() Get the resulting threshold.
private void	inputTypeChanged() Callback routine to change parameters on change of input type.
protected void	operate()
void	validateCustom()

Methods inherited from class de.unihalle.informatik.MiToBo.core.operator.MTBOperator

readResolve

Methods inherited from class de.unihalle.informatik.Alida.operator.ALDOperator

addOperatorExecutionProgressEventListener, addParameter, addParameter, addParameterUnconditioned, fieldContained, fireOperatorExecutionProgressEvent, getALDPortHashAccessKey, getConstructionMode, getHidingMode, getInactiveParameterNames, getInInoutNames, getInInoutNames, getInNames, getInOutNames, getMissingRequiredInputs, getName, getNumParameters, getOutInoutNames, getOutNames, getParameter, getParameterDescriptor, getParameterDescriptorUnconditioned, getParameterNames, getParameterUnconditioned, getSupplementalNames, getVerbose, getVersion, handleOperatorExecutionProgressEvent, hasInOutParameters, hasParameter, isAnnotatedParameter, isConfigured, print, print, print, printInterface, printInterface, readHistory, reinitializeParameterDescriptors, removeOperatorExecutionProgressEventListener, removeParameter, runOp, runOp, runOp, setConstructionMode, setConstructionMode, setConstructionMode, setHidingMode, setName, setParameter, setParameterUnconditioned, setVerbose, toStringVerbose, unconfiguredItems, validate, validateGeneric, writeHistory, writeHistory, writeHistory

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

inType

@Parameter(label="Input Type",
           required=true,
           dataIOOrder=0,
           supplemental=false,
           callback="inputTypeChanged",
           direction=IN,
           description="Type of input data.",
           paramModificationMode=MODIFIES_INTERFACE)
private CalcGlobalThreshOtsu.InputType inType

Input type.

inImg

@Parameter(label="Input Image",
           required=true,
           supplemental=false,
           dataIOOrder=1,
           direction=IN,
           description="Input image.")
private transient MTBImage inImg

Input image.

inHisto

@Parameter(label="Input Histogram",
           required=true,
           supplemental=false,
           dataIOOrder=1,
           direction=IN,
           description="Input histogram")
private transient MTBImageHistogram inHisto

Input histogram.

threshold

@Parameter(label="Threshold",
           supplemental=false,
           direction=OUT,
           description="Result threshold")
private MTBDoubleData threshold

Result threshold.

Constructor Detail

CalcGlobalThreshOtsu

public CalcGlobalThreshOtsu()
                     throws de.unihalle.informatik.Alida.exceptions.ALDOperatorException

Default constructor.

Throws:

de.unihalle.informatik.Alida.exceptions.ALDOperatorException - Thrown if construction fails.

CalcGlobalThreshOtsu

public CalcGlobalThreshOtsu(MTBImage img)
                     throws de.unihalle.informatik.Alida.exceptions.ALDOperatorException

Default constructor with input image as argument.

Parameters:

img - Input image.

Throws:

de.unihalle.informatik.Alida.exceptions.ALDOperatorException - Thrown if construction fails.

CalcGlobalThreshOtsu

public CalcGlobalThreshOtsu(MTBImageHistogram histo)
                     throws de.unihalle.informatik.Alida.exceptions.ALDOperatorException

Default constructor with input histogram as argument.

Parameters:

histo - Input histogram.

Throws:

de.unihalle.informatik.Alida.exceptions.ALDOperatorException - Thrown if construction fails.

Method Detail

validateCustom

public void validateCustom()
                    throws de.unihalle.informatik.Alida.exceptions.ALDOperatorException

Overrides:

validateCustom in class de.unihalle.informatik.Alida.operator.ALDOperator

Throws:

de.unihalle.informatik.Alida.exceptions.ALDOperatorException

getOtsuThreshold

public MTBDoubleData getOtsuThreshold()

Get the resulting threshold.

Returns:

Otsu threshold.

operate

protected void operate()

Specified by:

operate in class de.unihalle.informatik.Alida.operator.ALDOperator

calcThreshold

private MTBDoubleData calcThreshold(MTBImage image)

Calculate Otsu threshold on given image.

Parameters:

image - MiToBo image.

Returns:

Calculated Otsu threshold.

calcThreshold

private MTBDoubleData calcThreshold(MTBImageHistogram histo)

Calculate Otsu threshold on given histogram.

Parameters:

histo - Histogram.

Returns:

Calculated Otsu threshold.

inputTypeChanged

private void inputTypeChanged()

Callback routine to change parameters on change of input type.

getDocumentation

public String getDocumentation()

Overrides:

getDocumentation in class de.unihalle.informatik.Alida.operator.ALDOperator