net.sourceforge.javaocr.filter
Class SauvolaBinarisationFilter

java.lang.Object
  net.sourceforge.javaocr.filter.MedianFilter
      net.sourceforge.javaocr.filter.SauvolaBinarisationFilter

All Implemented Interfaces:

ImageFilter

public class SauvolaBinarisationFilter
extends MedianFilter

Performs local image threshloding with Sauvola algorithm. allocates integral images to achieve O(N) performance instead ow O(N2W2). This filter allocates working images and can be reused with destination image of same size. Please note, that window/2 pixels on borders of image are invalid. It is responsibility of caller to provide suitable padding.

Based on "Efficient Implementation of Local Adaptive Thresholding Techniques Using Integral Images" by Faisal Shafait , Daniel Keysers , Thomas M. Breuel from Image Understanding and Pattern Recognition (IUPR) Research Group German Research Center for Artificial Intelligence (DFKI) GmbH D-67663 Kaiserslautern, Germany and Thomas M. Breuel from Department of Computer Science, Technical University of Kaiserslautern D-67663 Kaiserslautern, Germany

Author:

Konstantin Pribluda

Field Summary

protected int	above
protected int	below
protected int	range
private SquaredIntergalImageFilter	squaredIntergalImageFilter
private Image	squaresImage
protected double	weight

Fields inherited from class net.sourceforge.javaocr.filter.MedianFilter

destination, halfWindow, integralImageFilter, squareWindow

Constructor Summary

SauvolaBinarisationFilter(int above, int below, Image destination, int maxValue, double weight, int window)

Method Summary

protected int	computePixel(Image image, int y, int x) compute median pixel value
int	getAbove()
int	getBelow()
int	getRange()
SquaredIntergalImageFilter	getSquaredIntergalImageFilter()
double	getWeight()
void	process(Image image) traversal will be done by median filter, actual processing delegated to derived method
protected int	retrievePixel(Image image, int y, int x)

Methods inherited from class net.sourceforge.javaocr.filter.MedianFilter

getHalfWindow, getIntegralImageFilter, getSquareWindow

Methods inherited from class java.lang.Object

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

Field Detail

above

protected final int above

below

protected final int below

range

protected final int range

weight

protected final double weight

squaredIntergalImageFilter

private SquaredIntergalImageFilter squaredIntergalImageFilter

squaresImage

private Image squaresImage

Constructor Detail

SauvolaBinarisationFilter

public SauvolaBinarisationFilter(int above,
                                 int below,
                                 Image destination,
                                 int maxValue,
                                 double weight,
                                 int window)

Parameters:

above - value to use for pixels above threshold

below - value to use for pixels below threshold

destination - destination image

maxValue - maxValue of intensity values

weight - weight of variance term (determines relation of threshold to local mean)

window - computing Window size

Method Detail

process

public void process(Image image)

traversal will be done by median filter, actual processing delegated to derived method

Specified by:

process in interface ImageFilter

Overrides:

process in class MedianFilter

Parameters:

image -

computePixel

protected int computePixel(Image image,
                           int y,
                           int x)

Description copied from class: MedianFilter

compute median pixel value

Overrides:

computePixel in class MedianFilter

retrievePixel

protected int retrievePixel(Image image,
                            int y,
                            int x)

getAbove

public int getAbove()

getBelow

public int getBelow()

getRange

public int getRange()

getWeight

public double getWeight()

getSquaredIntergalImageFilter

public SquaredIntergalImageFilter getSquaredIntergalImageFilter()