lti::splitImageToYPbPr Class Reference
[Color Analysis]

Computes the YPbPr values from a given RGB color representation (rgbPixel). More...

#include <ltiSplitImageToYPbPr.h>

Inheritance diagram for lti::splitImageToYPbPr:

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Collaboration diagram for lti::splitImageToYPbPr:

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List of all members.

Public Member Functions
	splitImageToYPbPr ()
	splitImageToYPbPr (const splitImageToYPbPr &other)
virtual	~splitImageToYPbPr ()
virtual const char *	getTypeName () const
splitImageToYPbPr &	copy (const splitImageToYPbPr &other)
splitImageToYPbPr &	operator= (const splitImageToYPbPr &other)
virtual functor *	clone () const
virtual bool	apply (const rgbPixel &pixel, float &c1, float &c2, float &c3) const
virtual bool	apply (const rgbPixel &pixel, ubyte &c1, ubyte &c2, ubyte &c3) const
virtual bool	apply (const image &img, channel &c1, channel &c2, channel &c3) const
virtual bool	apply (const image &img, channel8 &c1, channel8 &c2, channel8 &c3) const

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Detailed Description

Computes the YPbPr values from a given RGB color representation (rgbPixel).

In the literature, technical and scientific, there is often confusion among the color spaces YUV, YCbCr and YPbPr. Poynton in http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html explains that YUV is usually never correctly meant, because the color space normally used for component digital video is the YCbCr (ITU-RS601 or CCIR-601). Other devices use the YPbPr, but the "real" YUV is rarely employed.

The LTI-Lib provides all three spaces:

• YCbCr: lti::splitImageToYCbCr used by IEEE 1394 FireWire cameras
• YPbPr: lti::splitImageToYPbPr used by some WebCams
• YUV: lti::splitImageToYUV did they really meant to use this?

This functor splits an RGB images into the color space YPbPr using the conversion equations given by the above mentioned reference:

In the formula above, RGB have been assumed to be in the intervall [0,1]. With it, the Y values will have also be in [0,1], while Pb and Pr will lie between [-0.5 and 0.5]. For the ubyte types an offset of 128 is added to the Pb and Pr values, which are previously scaled by 255.

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Constructor & Destructor Documentation

lti::splitImageToYPbPr::splitImageToYPbPr

(

)

default constructor

lti::splitImageToYPbPr::splitImageToYPbPr

(

const splitImageToYPbPr &

other

)

copy constructor

Parameters:

other

the object to be copied

virtual lti::splitImageToYPbPr::~splitImageToYPbPr

(

)

[virtual]

destructor

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Member Function Documentation

virtual bool lti::splitImageToYPbPr::apply	(	const image &	img,
		channel8 &	c1,
		channel8 &	c2,
		channel8 &	c3
	)			const [virtual]

Split image into 8-bit channels.

N.B.: when casting the transformation result to unsigned shorts (8-bit channel) major rounding errors will occur.

As a result, the merging operation might produce negative values or values > 1, which are truncated subsequently. When accurate Y, U and V values are required, prefer float values.

Implements lti::splitImage.

virtual bool lti::splitImageToYPbPr::apply	(	const image &	img,
		channel &	c1,
		channel &	c2,
		channel &	c3
	)			const [virtual]

split pixel into float channels

Implements lti::splitImage.

bool lti::splitImageToYPbPr::apply	(	const rgbPixel &	pixel,
		ubyte &	c1,
		ubyte &	c2,
		ubyte &	c3
	)			const [inline, virtual]

Split pixel into 8-bit values (between 0 and 255).

N.B.: when casting the transformation result to unsigned shorts (8-bit channel) major rounding errors will occur.

As a result, the merging operation might produce negative values or values > 1, which are truncated subsequently.

When accurate Y, U and V values are required, prefer float values

Implements lti::splitImage.

References lti::rgbPixel::getBlue(), lti::rgbPixel::getGreen(), and lti::rgbPixel::getRed().

bool lti::splitImageToYPbPr::apply	(	const rgbPixel &	pixel,
		float &	c1,
		float &	c2,
		float &	c3
	)			const [inline, virtual]

split pixel into float values (between 0 and 1)

Implements lti::splitImage.

References lti::rgbPixel::getBlue(), lti::rgbPixel::getGreen(), and lti::rgbPixel::getRed().

virtual functor* lti::splitImageToYPbPr::clone

(

)

const [virtual]

returns a pointer to a clone of this functor.

Implements lti::functor.

splitImageToYPbPr& lti::splitImageToYPbPr::copy

(

const splitImageToYPbPr &

other

)

copy data of "other" functor.

Parameters:

other

the functor to be copied

Returns:

a reference to this functor object

Reimplemented from lti::splitImage.

virtual const char* lti::splitImageToYPbPr::getTypeName

(

)

const [virtual]

returns the name of this type ("splitImageToYPbPr")

Reimplemented from lti::splitImage.

splitImageToYPbPr& lti::splitImageToYPbPr::operator=

(

const splitImageToYPbPr &

other

)

alias for copy member

Parameters:

other

the functor to be copied

Returns:

a reference to this functor object

Reimplemented from lti::splitImage.

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

• ltiSplitImageToYPbPr.h