DcmQuantColorTable Class Reference

this class implements a color table that can either be a look-up table or an image color histogram. More...

List of all members.

Public Member Functions
	DcmQuantColorTable ()
	constructor
	~DcmQuantColorTable ()
	destructor
void	clear ()
	resets the object to default-constructed state
unsigned long	getColors () const
	returns the number of colors in the color table
void	setDescriptionString (OFString &str) const
	creates a description string suitable for use as Derivation Description.
OFCondition	computeHistogram (DicomImage &image, unsigned long maxcolors)
	creates a color table containing a histogram of the given image.
unsigned long	getMaxVal () const
	after a call to computeHistogram(), this method returns the maximum pixel value to which all color samples were down-sampled during computation of the histogram.
const DcmQuantPixel &	getPixel (unsigned long idx) const
	returns the color at index idx.
DcmQuantComponent	getRed (unsigned long idx) const
	returns the red color component at index idx
DcmQuantComponent	getGreen (unsigned long idx) const
	returns the green color component at index idx
DcmQuantComponent	getBlue (unsigned long idx) const
	returns the blue color component at index idx
OFCondition	medianCut (DcmQuantColorTable &histogram, unsigned long sum, unsigned long theMaxval, unsigned long numberOfColors, DcmLargestDimensionType largeType, DcmRepresentativeColorType repType)
	computes a color LUT for the given image histogram.
int	computeIndex (const DcmQuantPixel &px) const
	determines for a given color the closest match in the color LUT.
OFCondition	write (DcmItem &target, OFBool writeAsOW, OFBool write16BitEntries)
	writes the current color table into a DICOM object, encoded as Red/Green/Blue Palette Color Lookup Table and Data.
Private Member Functions
void	computeClusters ()
	after a call to medianCut(), this method computes for each entry in the color map the minimum of the euclidean distances to any other of the entries.
	DcmQuantColorTable (const DcmQuantColorTable &src)
	private undefined copy constructor
DcmQuantColorTable &	operator= (const DcmQuantColorTable &src)
	private undefined copy assignment operator
Private Attributes
DcmQuantHistogramItemPointer *	array
	color table data
unsigned long	numColors
	number of entries in color table
unsigned long	maxval
	maximum pixel value to which all color samples were down-sampled during computation of the histogram.

---

Detailed Description

this class implements a color table that can either be a look-up table or an image color histogram.

---

Member Function Documentation

void DcmQuantColorTable::computeClusters

(

)

[private]

after a call to medianCut(), this method computes for each entry in the color map the minimum of the euclidean distances to any other of the entries.

Any color which has an euclidean distance of less than half of this distance is necessarily mapped to this entry. This data is used by computeIndex()

OFCondition DcmQuantColorTable::computeHistogram	(	DicomImage &	image,
		unsigned long	maxcolors
	)

creates a color table containing a histogram of the given image.

Pixel sample values are downsampled if necessary to make sure the histogram fits into the given size limit.

Parameters:

image	color image for which a histogram is computed
maxcolors	maximum number of colors allowed in histogram. If necessary, pixel sample values are down-sampled to enforce this maximum.

Returns:

EC_Normal if successful, an error code otherwise.

int DcmQuantColorTable::computeIndex

(

const DcmQuantPixel &

px

)

const [inline]

determines for a given color the closest match in the color LUT.

Parameters:

px	color to look up in LUT

Returns:

index of closest match in LUT, -1 if look-up table empty

DcmQuantComponent DcmQuantColorTable::getBlue

(

unsigned long

idx

)

const [inline]

returns the blue color component at index idx

Parameters:

idx	index, must be < getColors()

Returns:

blue color component

unsigned long DcmQuantColorTable::getColors

(

)

const [inline]

returns the number of colors in the color table

Returns:

number of colors in color table

DcmQuantComponent DcmQuantColorTable::getGreen

(

unsigned long

idx

)

const [inline]

returns the green color component at index idx

Parameters:

idx	index, must be < getColors()

Returns:

green color component

const DcmQuantPixel& DcmQuantColorTable::getPixel

(

unsigned long

idx

)

const [inline]

returns the color at index idx.

Parameters:

idx	index, must be < getColors()

Returns:

const reference to color

DcmQuantComponent DcmQuantColorTable::getRed

(

unsigned long

idx

)

const [inline]

returns the red color component at index idx

Parameters:

idx	index, must be < getColors()

Returns:

red color component

OFCondition DcmQuantColorTable::medianCut	(	DcmQuantColorTable &	histogram,
		unsigned long	sum,
		unsigned long	theMaxval,
		unsigned long	numberOfColors,
		DcmLargestDimensionType	largeType,
		DcmRepresentativeColorType	repType
	)

computes a color LUT for the given image histogram.

This median-cut colormap generator is based on Paul Heckbert's paper "Color Image Quantization for Frame Buffer Display", SIGGRAPH '82 Proceedings, page 297.

Parameters:

histogram	image color histogram
sum	number of pixels in image (colums * rows * frames)
theMaxval	maximum value to which pixels were downsampled for histogram computation
numberOfColors	desired number of colors in color LUT
largeType	algorithm used for determining the largest dimension in the Median Cut algorithm
repType	algorithm for choosing a representative color for each box in the Median Cut algorithm

Returns:

EC_Normal if successful, an error code otherwise.

void DcmQuantColorTable::setDescriptionString

(

OFString &

str

)

const

creates a description string suitable for use as Derivation Description.

Parameters:

str	description string returned in this parameter

OFCondition DcmQuantColorTable::write	(	DcmItem &	target,
		OFBool	writeAsOW,
		OFBool	write16BitEntries
	)

writes the current color table into a DICOM object, encoded as Red/Green/Blue Palette Color Lookup Table and Data.

Parameters:

target	DICOM dataset to write to
writeAsOW	if true, LUT data is encoded as OW, otherwise LUT data is encoded as US. A LUT with 64k entries is always encoded as OW since a US data element with 64k entries cannot be written in explicit VR.
write16BitEntries	if true, LUT data is encoded with 16 bits per entry

Returns:

EC_Normal if successful, an error code otherwise.

---

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

• dcmimage/include/dcmtk/dcmimage/diqtctab.h