lsst::afw::detection::Threshold Class Reference

A Threshold is used to pass a threshold value to detection algorithms. More...

#include <Threshold.h>

Public Types
enum	ThresholdType {   VALUE, BITMASK, STDEV, VARIANCE,   PIXEL_STDEV }
	Types of threshold: More...

Public Member Functions
	Threshold (double const value, ThresholdType const type=VALUE, bool const polarity=true, double const includeMultiplier=1.0)
ThresholdType	getType () const
	return type of threshold More...
double	getValue (const double param=-1) const
template<typename ImageT >
double	getValue (ImageT const &image) const
bool	getPolarity () const
	return Threshold's polarity More...
void	setPolarity (bool const polarity)
	set Threshold's polarity More...
double	getIncludeMultiplier () const
	return includeMultiplier More...
void	setIncludeMultiplier (double const includeMultiplier)
	set includeMultiplier More...

Static Public Member Functions
static ThresholdType	parseTypeString (std::string const &typeStr)
static std::string	getTypeString (ThresholdType const &type)

Private Attributes
double	_value
	value of threshold, to be interpreted via _type More...
ThresholdType	_type
	type of threshold More...
bool	_polarity
	true for positive polarity, false for negative More...
double	_includeMultiplier
	multiplier for threshold needed for inclusion in FootprintSet More...

Detailed Description

A Threshold is used to pass a threshold value to detection algorithms.

The threshold may be a simple value (type == VALUE), or in units of the image standard deviation. Alternatively you may specify that you'll provide the standard deviation (type == STDEV) or variance (type == VARIANCE)

Note that the constructor is not declared explicit, so you may pass a bare threshold, and it'll be interpreted as a VALUE.

Examples:

spatialCellExample.cc.

Definition at line 44 of file Threshold.h.

Member Enumeration Documentation

enum lsst::afw::detection::Threshold::ThresholdType

Types of threshold:

Enumerator
VALUE	Use pixel value.
BITMASK	Use (pixels & (given mask))
STDEV	Use number of sigma given s.d.
VARIANCE	Use number of sigma given variance.
PIXEL_STDEV	Use number of sigma given per-pixel s.d.

Definition at line 47 of file Threshold.h.

                       {
        VALUE,               
        BITMASK,             
        STDEV,               
        VARIANCE,            
        PIXEL_STDEV          
    }; 

Constructor & Destructor Documentation

lsst::afw::detection::Threshold::Threshold ( double const  value, ThresholdType const  type = VALUE, bool const  polarity = true, double const  includeMultiplier = 1.0  )

inline

Threshold constructor

Parameters

value	desired threshold value
type	interpretation of type
polarity	search pixel above threshold? (useful for -ve thresholds)
includeMultiplier	threshold multiplier for inclusion in FootprintSet

Definition at line 58 of file Threshold.h.

               : _value(value), _type(type), _polarity(polarity),
                 _includeMultiplier(includeMultiplier) {}

Member Function Documentation

double lsst::afw::detection::Threshold::getIncludeMultiplier ( ) const

inline

return includeMultiplier

Definition at line 94 of file Threshold.h.

{ return _includeMultiplier; }

bool lsst::afw::detection::Threshold::getPolarity ( ) const

inline

return Threshold's polarity

Definition at line 88 of file Threshold.h.

{ return _polarity; }

ThresholdType lsst::afw::detection::Threshold::getType ( ) const

inline

return type of threshold

Definition at line 67 of file Threshold.h.

{ return _type; }

std::string lsst::afw::detection::Threshold::getTypeString ( ThresholdType const &  type )

static

Definition at line 59 of file Threshold.cc.

                                                             {
    if (type == VALUE) {
        return "value";
    } else if (type == STDEV) {
        return "stdev";
    } else if (type == VARIANCE) {
        return "variance";
    } else {
        throw LSST_EXCEPT(
            lsst::pex::exceptions::InvalidParameterError,
            (boost::format("Unsopported Threshold type: %d") % type).str()
        );
    }
}

double lsst::afw::detection::Threshold::getValue

(

const double

param = -1

)

const

return value of threshold, to be interpreted via type

Parameters

param

value of variance/stdev if needed

Returns

value of threshold

Definition at line 79 of file Threshold.cc.

                                                   {
    switch (_type) {
      case STDEV:
        if (param <= 0) {
            throw LSST_EXCEPT(
                lsst::pex::exceptions::InvalidParameterError,
                (boost::format("St. dev. must be > 0: %g") % param).str()
            );
        }
        return _value*param;
      case VALUE:
      case BITMASK:
      case PIXEL_STDEV:
        return _value;
      case VARIANCE:
        if (param <= 0) {
            throw LSST_EXCEPT(
                lsst::pex::exceptions::InvalidParameterError,
                (boost::format("Variance must be > 0: %g") % param).str()
            );
        }
        return _value*std::sqrt(param);
      default:
        throw LSST_EXCEPT(
            lsst::pex::exceptions::InvalidParameterError,
            (boost::format("Unsupported type: %d") % _type).str()
        );
    }
}

template<typename ImageT >

double lsst::afw::detection::Threshold::getValue

(

ImageT const &

image

)

const

return value of threshold by interrogating the image, if required

Parameters

image

Image to interrogate, if threshold type demands

Returns

value of threshold

Definition at line 110 of file Threshold.cc.

                                                    {
    double param = -1;                  // Parameter for getValue()
    if (_type == STDEV || 
        _type == VARIANCE) {
        math::Statistics stats = math::makeStatistics(image, math::STDEVCLIP);
        double const sd = stats.getValue(math::STDEVCLIP);

        pexLogging::TTrace<3>("afw.detection", "St. Dev = %g", sd);
        
        if (_type == VARIANCE) {
            param = sd*sd;
        } else {
            param = sd;
        }
    }
    return getValue(param);
}

Threshold::ThresholdType lsst::afw::detection::Threshold::parseTypeString ( std::string const &  typeStr )

static

Definition at line 40 of file Threshold.cc.

                                                                           {
    if (typeStr.compare("bitmask") == 0) {
        return Threshold::BITMASK;           
    } else if (typeStr.compare("value") == 0) {
        return Threshold::VALUE;           
    } else if (typeStr.compare("stdev") == 0) {
        return Threshold::STDEV;
    } else if (typeStr.compare("variance") == 0) {
        return Threshold::VARIANCE;
    } else if (typeStr.compare("pixel_stdev") == 0) {
        return Threshold::PIXEL_STDEV;
    } else {
        throw LSST_EXCEPT(
            lsst::pex::exceptions::InvalidParameterError,
            (boost::format("Unsupported Threshold type: %s") % typeStr).str()
        );
    }    
}

void lsst::afw::detection::Threshold::setIncludeMultiplier ( double const  includeMultiplier )

inline

set includeMultiplier

Parameters

includeMultiplier

desired multiplier

Definition at line 96 of file Threshold.h.

                               { _includeMultiplier = includeMultiplier; }

void lsst::afw::detection::Threshold::setPolarity ( bool const  polarity )

inline

set Threshold's polarity

Parameters

polarity

desired polarity

Definition at line 90 of file Threshold.h.

                      { _polarity = polarity; }

Member Data Documentation

double lsst::afw::detection::Threshold::_includeMultiplier

private

multiplier for threshold needed for inclusion in FootprintSet

Definition at line 103 of file Threshold.h.

bool lsst::afw::detection::Threshold::_polarity

private

true for positive polarity, false for negative

Definition at line 102 of file Threshold.h.

ThresholdType lsst::afw::detection::Threshold::_type

private

type of threshold

Definition at line 101 of file Threshold.h.

double lsst::afw::detection::Threshold::_value

private

value of threshold, to be interpreted via _type

Definition at line 100 of file Threshold.h.

---

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

• /home/lsstsw/stack/Linux64/afw/11.0-2-g04d2804/include/lsst/afw/detection/Threshold.h
• /home/lsstsw/stack/Linux64/afw/11.0-2-g04d2804/src/detection/Threshold.cc