LocalThreshold Filter class. More...

#include <LocalThresholdOp.h>

Inheritance diagram for icl::filter::LocalThresholdOp:

Public Types
enum	algorithm { regionMean, tiledNN, tiledLIN, global }
	Internally used algorithm. More...

Public Types inherited from icl::utils::Configurable
typedef Function< void, const Property & >	Callback
	Function type for changed properties. More...

Public Member Functions
	LocalThresholdOp (unsigned int maskSize=10, float globalThreshold=0, float gammaSlope=0)
	create a new LocalThreshold object with given mask-size and global threshold and RegionMean algorithm More...

	LocalThresholdOp (algorithm a, int maskSize=10, float globalThreshold=0, float gammaSlope=0)
	creates a LocalThresholdOp instance with given Algorithm-Type More...

	~LocalThresholdOp ()
	Destructor. More...

virtual void	apply (const core::ImgBase src, core::ImgBase *dst)
	virtual apply function More...

void	setMaskSize (unsigned int maskSize)
	set a new mask size (a new mask size image must be calculate in the next apply call) More...

void	setGlobalThreshold (float globalThreshold)
	sets a enw global threshold value to used More...

void	setGammaSlope (float gammaSlope)
	sets a new gamma slope to used (if gammaSlope is 0), the binary threshold is used More...

void	setup (unsigned int maskSize, float globalThreshold, algorithm a=regionMean, float gammaSlope=0)
	sets all parameters at once More...

unsigned int	getMaskSize () const
	returns the current mask size More...

float	getGlobalThreshold () const
	returns the current global threshold value More...

float	getGammaSlope () const
	returns the current gamma slope More...

algorithm	getAlgorithm () const
	returns currently used algorithm type More...

void	setAlgorithm (algorithm a)
	sets internally used algorithm More...

virtual void	apply (const core::ImgBase operand1, core::ImgBase *dst)=0
	Import unaryOps apply function without destination image. More...

virtual const core::ImgBase *	apply (const core::ImgBase *src)
	Import unaryOps apply function without destination image. More...

Public Member Functions inherited from icl::filter::UnaryOp
	UnaryOp ()
	Explicit empty constructor. More...

	UnaryOp (const UnaryOp &other)
	Explicit copy constructor. More...

UnaryOp &	operator= (const UnaryOp &other)
	Explicit declaration of the assignment operator. More...

virtual	~UnaryOp ()
	Destructor. More...

virtual ICL_DEPRECATED void	applyMT (const core::ImgBase operand1, core::ImgBase *dst, unsigned int nThreads)
	apply function for multithreaded filtering (currently even slower than using one thread) More...

virtual const core::ImgBase *	apply (const core::ImgBase *src)
	applys the filter usign an internal buffer as output image More...

void	operator() (const core::ImgBase src, core::ImgBase *dst)
	function operator (alternative for apply(src,dst) More...

const core::ImgBase *	operator() (const core::ImgBase *src)
	function operator for the implicit destination apply(src) call More...

const core::ImgBase &	operator() (const core::ImgBase &src)
	reference based function operator More...

void	setClipToROI (bool bClipToROI)
	sets if the image should be clip to ROI or not More...

void	setCheckOnly (bool bCheckOnly)
	sets if the destination image should be adapted to the source, or if it is only checked if it can be adapted. More...

bool	getClipToROI () const
	returns the ClipToROI status More...

bool	getCheckOnly () const
	returns the CheckOnly status More...

virtual void	setPropertyValue (const std::string &propertyName, const utils::Any &value)
	sets value of a property (always call call_callbacks(propertyName) or Configurable::setPropertyValue) More...

Public Member Functions inherited from icl::utils::Configurable
virtual	~Configurable ()
	virtual destructor More...

	Configurable (const Configurable &other)
	Copy constructor. More...

Configurable &	operator= (const Configurable &other)
	Assignment operator. More...

void	setConfigurableID (const std::string &ID)
	sets the ID of this configurable More...

const std::string &	getConfigurableID () const
	returns the configurables static ID More...

bool	isOrderedFlagSet () const
	returns whether the ordered flag is set More...

void	deactivateProperty (const std::string &pattern)
	adds an additional deativation pattern More...

void	deleteDeactivationPattern (const std::string &pattern)
	removed a formerly added deactivation pattern More...

std::vector< std::string >	getPropertyListWithoutDeactivated () const
	this returns a filtered list of properties (using all filters added by deactivateProperty) More...

virtual void	adaptProperty (const std::string &name, const std::string &newType, const std::string &newInfo, const std::string &newToolTip)
	this function can be used to adapt a specific property afterwards More...

void	registerCallback (const Callback &cb)
	add a callback for changed properties More...

void	removedCallback (const Callback &cb)
	removes a callback that was registered before More...

void	syncChangesTo (Configurable *others, int num=1)
	this can be used to let this instance also apply property changes to others More...

virtual std::vector< std::string >	getPropertyList () const
	returns a list of All properties, that can be set using setProperty More...

virtual bool	supportsProperty (const std::string &propertyName) const
	base implementation for property check (seaches in the property list) More...

virtual void	saveProperties (const std::string &filename, const std::vector< std::string > &propertiesToSkip=EMPTY_VEC) const
	writes all available properties into a file More...

virtual void	loadProperties (const std::string &filename, const std::vector< std::string > &propertiesToSkip=EMPTY_VEC)
	reads a camera config file from disc More...

virtual std::string	getPropertyType (const std::string &propertyName) const
	get type of property More...

virtual std::string	getPropertyInfo (const std::string &propertyName) const
	get information of a properties valid values More...

virtual Any	getPropertyValue (const std::string &propertyName) const
	returns the current value of a property or a parameter More...

virtual std::string	getPropertyToolTip (const std::string &propertyName) const
	returns the tooltip description for a given property More...

virtual int	getPropertyVolatileness (const std::string &propertyName) const
	Returns whether this property may be changed internally. More...

Private Member Functions
template<algorithm a>
void	apply_a (const core::ImgBase src, core::ImgBase *dst)
	internal algorithm function More...

Private Attributes
core::ImgBase *	m_roiBufSrc
	mask size More...

core::ImgBase *	m_roiBufDst
	output ROI buffer image for ROI support More...

IntegralImgOp *	m_iiOp
	IntegralImgOp for RegionMean algorithm. More...

BinaryCompareOp *	m_cmp
	BinaryCompareOp for tiledXXX algorithms. More...

core::ImgBase *	m_tiledBuf1
	first buffer for tiledXXX algorithsm More...

core::ImgBase *	m_tiledBuf2
	second buffer for tiledXXX algorithsm More...

Additional Inherited Members
Static Public Member Functions inherited from icl::filter::UnaryOp
static UnaryOp *	fromString (const std::string &definition)
	Creates a UnaryOp instance from given string definition. More...

static std::string	getFromStringSyntax (const std::string &opSpecifier)
	gives a string syntax description for given opSpecifier More...

static std::vector< std::string >	listFromStringOps ()
	returns a list of all supported OP_SPEC values for the fromString function More...

static void	applyFromString (const std::string &definition, const core::ImgBase src, core::ImgBase *dst)
	creates, applies and releases a UnaryOp defined by given definition string More...

Static Public Member Functions inherited from icl::utils::Configurable
static std::string	create_default_ID (const std::string &prefix)
	this function can be used in subclasses to create a default ID More...

static Configurable *	get (const std::string &id)
	returns configurable by given ID More...

static void	register_configurable_type (const std::string &classname, Function< Configurable * > creator)
	registers a configurable type More...

static std::vector< std::string >	get_registered_configurables ()
	returns a list of all registered configurable classnames More...

static Configurable *	create_configurable (const std::string &classname)
	creates a configurable by given name More...

Static Public Attributes inherited from icl::utils::Configurable
static const std::vector< std::string >	EMPTY_VEC
	used as shortcut – just an empty vector of std::strings More...

Protected Member Functions inherited from icl::filter::UnaryOp
bool	prepare (core::ImgBase **ppoDst, core::depth eDepth, const utils::Size &imgSize, core::format eFormat, int nChannels, const utils::Rect &roi, utils::Time timestamp=utils::Time::null)

virtual bool	prepare (core::ImgBase *ppoDst, const core::ImgBase poSrc)
	check+adapt destination image to properties of given source image More...

virtual bool	prepare (core::ImgBase *ppoDst, const core::ImgBase poSrc, core::depth eDepth)

Protected Member Functions inherited from icl::utils::Configurable
void	addProperty (const std::string &name, const std::string &type, const std::string &info, const Any &value=Any(), const int volatileness=0, const std::string &tooltip=std::string())
	This can be used by derived classes to store supported properties in the internal list. More...

void	addChildConfigurable (Configurable *configurable, const std::string &childPrefix="")
	This adds another configurable as child. More...

void	removeChildConfigurable (Configurable *configurable)
	removes the given child configurable More...

Property &	prop (const std::string &propertyName)
	this CAN be used e.g. to store a property value in internal property-list More...

const Property &	prop (const std::string &propertyName) const
	this CAN be used e.g. to store a property value in internal property-list More...

	Configurable (const std::string &ID="", bool ordered=true)
	create this configurable with given ID More...

void	call_callbacks (const std::string &propertyName, const Configurable *caller) const
	calls all registered callbacks More...

Protected Member Functions inherited from icl::utils::Uncopyable
	Uncopyable ()
	Empty base constructor. More...

Protected Attributes inherited from icl::filter::UnaryOp
utils::MultiThreader *	m_poMT

Protected Attributes inherited from icl::utils::Configurable
std::vector< Callback >	callbacks
	internally managed list of callbacks More...

Detailed Description

LocalThreshold Filter class.

The LocalThresholdOp implements a set of local threshold algorithms. Currently, three implementations are available:

regionMean: In this case the actual mean of a surrounding region of a pixel is used to determine its threshold
tiledNN: Here, a very simple tiled threshold is used. The image is split into square tiles with edge-size 2*maskSize. The threshold of all pixels within this tile is set relatively to the mean-value of the tile
tiledLIN: This is comparable with tiledNN, except, the actual threshold of a pixel is computed from a linear interpolation between its 4-nearest tiles mean-values

Result modes

This is the most sophisticated algorithms. Its implementation bases on the calculation of an integral image of the given input image (see icl::IntegralImgOp)
Once having access to the integral image data, it is possible to calculate the mean of an arbitrary rectangular image region in constant time. Consider the following ASCII example. A rectangular image region is always described by its four corner points A,B,C and D

.C....A...
..+++++...
..+++++...
..+++++...
..+++++...
.B++++D...
..........

The "mass" of pixels inside the rect can be obtained by calculating

$X = D - A - B + C$

in the integral image. The pixel count in the region is

$P = (A.x-C.x) * (B.y-C.y)$

, which directly leads to region-mean $X/P$ .

Threshold

A local image threshold at an image location $p=(px,py)$ must factor in the local image intensity, which can be approximated by the mean value $\mu_p$ of the square region centered at $p$ with a certain radius $r$ . To emphazise that $\mu_p$ depends also on $r$ we denote it by $\mu_r{p}$ . To have more influence on the actually used threshold at location $p$ , we used an additive global threshold variable $g$ .

Algorithm

Input: Input-Image i, region radius r, global threshold g, destination image d

1. I := integral image of i
2. (static) calculate region size image S
   This is nessesary because border regions do not have the expected region size
   (2*r+1)² due to the overlap with the image border. The calculation of S is not
   very complex, so it is not discussed here further.
3. I := extend (I). To avoid accessing invalid pixel locations of the integral image,
   it is enlarged to each edge by r. To garantee, that this optimization does not lead
   to incorrect results, the upper and the left border of the integral image is filled with
   zeros, and the lower and the right edge is filled with the value of the nearest non-
   border pixel.
4. Pixel Loop:
   For each pixel (x,y) of i
      4.1 Estimate the corresponding edge points A,B,C and D of the squared neighbourhood.
          (do not forget that the integral image has got a r-pixle border to each edge)
          C := (x-r,y-r)
          A := (x+r,y-r)
          B := (x-1,y+r)
          D := (x+r,y+r)
      4.2 Calculate the region mean with respect to the underlying region size
          M = (I(D) - I(A) - I(B) + I(C))/S(x,y)
      4.3 Calculate the theshold operation
          d(x,y) = 255 * (i(x,y) > (M+g) )
    endfor

Mutli channel images

This time, no special operation for multi channels images are implemneted, so each channel is process independently in this case.

Experimental feature gamma slope

By applying a small adaption, the procedure presented avoid can be used to apply a local gamma correction on a source image. We just have to exchange the "stair"-function above $ d(x,y) = 255 * (i(x,y) > (M+g) ) $ by a linear function:

using a linear function function f(x) = m*x + b    (with clipping to range [0,255])
with m = gammaSlope (new variable)
     k = M+g
     that f(k) = 128

   f(x) = m(x-k)+128     (clipped to [0,255])

Result

The RegionMean algorithm clearly provides the best results of the three algorithms. The nearest neighbour interpolation algorithm is not significantly faster than the linear version, however it's results are much worse. Here is a set of results images. All images use a tile size of 30 and a global threshold of 3

RegionMean

tiled-LIN

tiled-NN

Benchmarks

All threshold implementations are fast and highly optimized. In particular, we spend a lot of time for the optimization of the RegionMean algorithms, which provides the best results. Benchmarks were performed on a 2GHz Intel Core2Duo Machine with 2GB Ram. Compiler g++ 4.3, optimization flags -O4 -march=native.

MaskSize	tiledNN	tiledLIN	RegionMean
200	5	5	13ms
100	5	5	11ms
40	5	5	10ms
20	5	5	9ms
10	5	5	9ms
5	6	6	9ms
2	9	9	9ms

The experimental gamma-slope-computation is much more expensive: Here, the RegionMean algorithms needs about 25ms.

Member Enumeration Documentation

◆ algorithm

enum icl::filter::LocalThresholdOp::algorithm

Internally used algorithm.

Enumerator
regionMean	regionMean threshold calculation
tiledNN	tiled threshold with nearest neighbour interpolation
tiledLIN	tiled threshold with linear interpolation
global	simple global threshold

Constructor & Destructor Documentation

◆ LocalThresholdOp() [1/2]

icl::filter::LocalThresholdOp::LocalThresholdOp	(	unsigned int	maskSize = `10`,
		float	globalThreshold = `0`,
		float	gammaSlope = `0`
	)

create a new LocalThreshold object with given mask-size and global threshold and RegionMean algorithm

Parameters

maskSize	size of the mask to use for calculations, the image width and height must each be larger than 2*maskSize.
globalThreshold	additive Threshold to the calculated reagions mean
gammaSlope	gammaSlope (Default=0) (Experimental feature) if set to 0 (default) the binary threshold is used

◆ LocalThresholdOp() [2/2]

icl::filter::LocalThresholdOp::LocalThresholdOp	(	algorithm	a,
		int	maskSize = `10`,
		float	globalThreshold = `0`,
		float	gammaSlope = `0`
	)

creates a LocalThresholdOp instance with given Algorithm-Type

◆ ~LocalThresholdOp()

icl::filter::LocalThresholdOp::~LocalThresholdOp ( )

Destructor.

Member Function Documentation

◆ apply() [1/3]

virtual void icl::filter::LocalThresholdOp::apply	(	const core::ImgBase *	src,
		core::ImgBase **	dst
	)

virtual

virtual apply function

roi support is realized by copying the current input image ROI into a dedicate image buffer with no roi set

Implements icl::filter::UnaryOp.

◆ apply() [2/3]

virtual void icl::filter::UnaryOp::apply

Import unaryOps apply function without destination image.

◆ apply() [3/3]

virtual const core::ImgBase* icl::filter::UnaryOp::apply

Import unaryOps apply function without destination image.

◆ apply_a()

template<algorithm a>

void icl::filter::LocalThresholdOp::apply_a	(	const core::ImgBase *	src,
		core::ImgBase **	dst
	)

private

internal algorithm function

◆ getAlgorithm()

algorithm icl::filter::LocalThresholdOp::getAlgorithm ( ) const

returns currently used algorithm type

◆ getGammaSlope()

float icl::filter::LocalThresholdOp::getGammaSlope ( ) const

returns the current gamma slope

◆ getGlobalThreshold()

float icl::filter::LocalThresholdOp::getGlobalThreshold ( ) const

returns the current global threshold value

◆ getMaskSize()

unsigned int icl::filter::LocalThresholdOp::getMaskSize ( ) const

returns the current mask size

◆ setAlgorithm()

void icl::filter::LocalThresholdOp::setAlgorithm ( algorithm a )

sets internally used algorithm

◆ setGammaSlope()

void icl::filter::LocalThresholdOp::setGammaSlope ( float gammaSlope )

sets a new gamma slope to used (if gammaSlope is 0), the binary threshold is used

◆ setGlobalThreshold()

void icl::filter::LocalThresholdOp::setGlobalThreshold ( float globalThreshold )

sets a enw global threshold value to used

◆ setMaskSize()

void icl::filter::LocalThresholdOp::setMaskSize ( unsigned int maskSize )

set a new mask size (a new mask size image must be calculate in the next apply call)

◆ setup()

void icl::filter::LocalThresholdOp::setup	(	unsigned int	maskSize,
		float	globalThreshold,
		algorithm	a = `regionMean`,
		float	gammaSlope = `0`
	)

sets all parameters at once

Member Data Documentation

◆ m_cmp

BinaryCompareOp* icl::filter::LocalThresholdOp::m_cmp

private

BinaryCompareOp for tiledXXX algorithms.

currently used algorithm property algorithm m_algorithm;

◆ m_iiOp

IntegralImgOp* icl::filter::LocalThresholdOp::m_iiOp

private

IntegralImgOp for RegionMean algorithm.

◆ m_roiBufDst

core::ImgBase* icl::filter::LocalThresholdOp::m_roiBufDst

private

output ROI buffer image for ROI support

◆ m_roiBufSrc

core::ImgBase* icl::filter::LocalThresholdOp::m_roiBufSrc

private

mask size

global threshold gamma slope input ROI buffer image for ROI support

◆ m_tiledBuf1

core::ImgBase* icl::filter::LocalThresholdOp::m_tiledBuf1

private

first buffer for tiledXXX algorithsm

◆ m_tiledBuf2

core::ImgBase* icl::filter::LocalThresholdOp::m_tiledBuf2

private

second buffer for tiledXXX algorithsm

The documentation for this class was generated from the following file:

/Users/alneuman/vm/icl/ICLFilter/src/ICLFilter/LocalThresholdOp.h

Public Types

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Result modes

Threshold

Algorithm

Mutli channel images

Experimental feature gamma slope

Result

Benchmarks

Member Enumeration Documentation

◆ algorithm

Constructor & Destructor Documentation

◆ LocalThresholdOp() [1/2]

◆ LocalThresholdOp() [2/2]

◆ ~LocalThresholdOp()

Member Function Documentation

◆ apply() [1/3]

◆ apply() [2/3]

◆ apply() [3/3]

◆ apply_a()

◆ getAlgorithm()

◆ getGammaSlope()

◆ getGlobalThreshold()

◆ getMaskSize()

◆ setAlgorithm()

◆ setGammaSlope()

◆ setGlobalThreshold()

◆ setMaskSize()

◆ setup()

Member Data Documentation

◆ m_cmp

◆ m_iiOp

◆ m_roiBufDst

◆ m_roiBufSrc

◆ m_tiledBuf1

◆ m_tiledBuf2