boofcv.alg.filter.binary.impl

Class ThresholdSauvola

java.lang.Object

boofcv.alg.filter.binary.impl.ThresholdSauvola

public class ThresholdSauvola
extends java.lang.Object

Intended for use as a preprocessing step in OCR it computes a binary image from an input gray image. It's an adaptive algorithm and uses the local mean and standard deviation, as is shown in the equation below:
T(x,y) = m(x,y) * [ 1 + k * (s(x,y)/R - 1)]
where T(x,y) is the pixel's threshold, m(x,y) is the local mean, s(x,y) is the local deviation, R is dynamic range of standard deviation, and k is a user specified threshold.

There are two tuning parameters 'k' a positive number and the the 'radius' of the local region. Recommended values are k=0.3 and radius=15. These were found by tuning against a set of text.

Constructor Summary

Constructors

Constructor and Description
ThresholdSauvola(int radius, float k, boolean down) Configures the algorithm.

Method Summary

Modifier and Type	Method and Description
float	getK()
int	getRadius()
boolean	isDown()
void	process(GrayF32 input, GrayU8 output) Converts the input image into a binary image.
void	setDown(boolean down)
void	setK(float k)
void	setRadius(int radius)

Methods inherited from class java.lang.Object

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

Constructor Detail

ThresholdSauvola

public ThresholdSauvola(int radius,
                        float k,
                        boolean down)

Configures the algorithm.

Parameters:

radius - size of local radius. Try 15

k - User specified threshold adjustment factor. Must be positive. Try 0.3

down - Threshold down or up

Method Detail

process

public void process(GrayF32 input,
                    GrayU8 output)

Converts the input image into a binary image.

Parameters:

input - Input image. Not modified.

output - Output binary image. Modified.

getK

public float getK()

setK

public void setK(float k)

getRadius

public int getRadius()

setRadius

public void setRadius(int radius)

isDown

public boolean isDown()

setDown

public void setDown(boolean down)