Package boofcv.alg.filter.binary

Class ThresholdBlock<T extends ImageGray<T>,S extends ImageBase<S>>

java.lang.Object

boofcv.alg.filter.binary.ThresholdBlock<T,S>

All Implemented Interfaces:

InputToBinary<T>

Direct Known Subclasses:

ThresholdBlock_MT

public class ThresholdBlock<T extends ImageGray<T>,S extends ImageBase<S>>
extends Object
implements InputToBinary<T>

Computes image statistics in regularly spaced blocks across the image. Then computes an average of the statistics in a block within a local 3x3 grid region. The average statistics in a local 3x3 grid region is used to reduce the adverse affects of using a grid. Ideally a local region around each pixel would be used, but this is expensive to compute. Since a grid is used instead of a pixel local region boundary conditions can be an issue. For example, consider a black square in the image, if the grid just happens to lie on this black square perfectly then if you look at only a single grid element it will be considered textureless and the edge lost. This problem isn't an issue if you consder a local 3x3 region of blocks.

The size each block in the grid in pixels is adjusted depending on image size. This is done to minimize "squares" in the upper image boundaries from having many more pixels than other blocks.

The block based approach used here was inspired by a high level description found in AprilTags.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	ThresholdBlock.BlockProcessor<T extends ImageGray<T>,S extends ImageBase<S>>

Field Summary

Fields

Modifier and Type	Field	Description
protected int	blockHeight
protected int	blockWidth
protected ThresholdBlock.BlockProcessor<T,S>	original
protected RecycleStack<ThresholdBlock.BlockProcessor<T,S>>	processors
protected ConfigLength	requestedBlockWidth
protected S	stats
protected boolean	thresholdFromLocalBlocks

Constructor Summary

Constructors

Constructor	Description
ThresholdBlock(ThresholdBlock.BlockProcessor<T,S> processor, ConfigLength requestedBlockWidth, boolean thresholdFromLocalBlocks, Class<T> imageClass)	Configures the detector

Method Summary

Modifier and Type	Method	Description
protected void	applyThreshold(T input, GrayU8 output)	Applies the dynamically computed threshold to each pixel in the image, one block at a time
protected void	computeStatistics(T input, int innerWidth, int innerHeight)	Computes the min-max value for each block in the image
ImageType<T>	getInputType()
boolean	isThresholdFromLocalBlocks()
void	process(T input, GrayU8 output)	Converts the gray scale input image into a binary image
void	setThresholdFromLocalBlocks(boolean thresholdFromLocalBlocks)

Methods inherited from class java.lang.Object

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

Field Details

stats

protected S extends ImageBase<S> stats

requestedBlockWidth

protected ConfigLength requestedBlockWidth

blockWidth

protected int blockWidth

blockHeight

protected int blockHeight

thresholdFromLocalBlocks

protected boolean thresholdFromLocalBlocks

original

protected ThresholdBlock.BlockProcessor<T extends ImageGray<T>,S extends ImageBase<S>> original

processors

protected RecycleStack<ThresholdBlock.BlockProcessor<T extends ImageGray<T>,S extends ImageBase<S>>> processors

Constructor Details

ThresholdBlock

public ThresholdBlock(ThresholdBlock.BlockProcessor<T,S> processor,
 ConfigLength requestedBlockWidth,
 boolean thresholdFromLocalBlocks,
 Class<T> imageClass)

Configures the detector

Parameters:

requestedBlockWidth - About how wide and tall you wish a block to be in pixels.

Method Details

process

public void process(T input,
 GrayU8 output)

Converts the gray scale input image into a binary image

Specified by:

process in interface InputToBinary<T extends ImageGray<T>>

Parameters:

input - Input image

output - Output binary image

applyThreshold

protected void applyThreshold(T input,
 GrayU8 output)

Applies the dynamically computed threshold to each pixel in the image, one block at a time

computeStatistics

protected void computeStatistics(T input,
 int innerWidth,
 int innerHeight)

Computes the min-max value for each block in the image

isThresholdFromLocalBlocks

public boolean isThresholdFromLocalBlocks()

setThresholdFromLocalBlocks

public void setThresholdFromLocalBlocks(boolean thresholdFromLocalBlocks)

getInputType

public ImageType<T> getInputType()

Specified by:

getInputType in interface InputToBinary<T extends ImageGray<T>>