colorspace/colorspace.c File Reference

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include "colorspace.h"

Include dependency graph for colorspace.c:

Defines
#define	MIN(A, B) (((A) <= (B)) ? (A) : (B))
	Min of A and B.
#define	MAX(A, B) (((A) >= (B)) ? (A) : (B))
	Max of A and B.
#define	MIN3(A, B, C) (((A) <= (B)) ? MIN(A,C) : MIN(B,C))
	Min of A, B, and C.
#define	MAX3(A, B, C) (((A) >= (B)) ? MAX(A,C) : MAX(B,C))
	Max of A, B, and C.
#define	M_PI 3.14159265358979323846264338327950288
	The constant pi.
#define	GAMMACORRECTION(t)
	sRGB gamma correction, transforms R to R' http://en.wikipedia.org/wiki/SRGB
#define	INVGAMMACORRECTION(t)
	Inverse sRGB gamma correction, transforms R' to R.
#define	LABF(t)
	CIE Lab* f function (used to convert XYZ to Lab*) http://en.wikipedia.org/wiki/Lab_color_space.
#define	LABINVF(t)
	CIE Lab* inverse f function http://en.wikipedia.org/wiki/Lab_color_space.
#define	WHITEPOINT_U
	u'v' coordinates of the white point for CIE Luv
#define	WHITEPOINT_V
#define	UNKNOWN_SPACE 0
	Enumeration of the supported color spaces.
#define	RGB_SPACE 1
#define	YUV_SPACE 2
#define	YCBCR_SPACE 3
#define	JPEGYCBCR_SPACE 4
#define	YPBPR_SPACE 5
#define	YDBDR_SPACE 6
#define	YIQ_SPACE 7
#define	HSV_SPACE 8
#define	HSL_SPACE 9
#define	HSI_SPACE 10
#define	XYZ_SPACE 11
#define	LAB_SPACE 12
#define	LUV_SPACE 13
#define	LCH_SPACE 14
#define	CAT02LMS_SPACE 15
#define	NUM_TRANSFORM_PAIRS 18
Functions
void	Rgb2Yuv (num Y, num U, num *V, num R, num G, num B)
	Convert sRGB to NTSC/PAL Y'UV Luma + Chroma.
void	Yuv2Rgb (num R, num G, num *B, num Y, num U, num V)
	Convert NTSC/PAL Y'UV to sRGB.
void	Rgb2Ycbcr (num Y, num Cb, num *Cr, num R, num G, num B)
	sRGB to Y'CbCr Luma + Chroma
void	Ycbcr2Rgb (num R, num G, num *B, num Y, num Cr, num Cb)
	Y'CbCr to sRGB.
void	Rgb2Jpegycbcr (num Y, num Cb, num *Cr, num R, num G, num B)
	sRGB to JPEG-Y'CbCr Luma + Chroma
void	Jpegycbcr2Rgb (num R, num G, num *B, num Y, num Cb, num Cr)
	JPEG-Y'CbCr to sRGB.
void	Rgb2Ypbpr (num Y, num Pb, num *Pr, num R, num G, num B)
	sRGB to Y'PbPr Luma (ITU-R BT.601) + Chroma
void	Ypbpr2Rgb (num R, num G, num *B, num Y, num Pb, num Pr)
	Y'PbPr to sRGB.
void	Rgb2Ydbdr (num Y, num Db, num *Dr, num R, num G, num B)
	sRGB to SECAM Y'DbDr Luma + Chroma
void	Ydbdr2Rgb (num R, num G, num *B, num Y, num Db, num Dr)
	SECAM Y'DbDr to sRGB.
void	Rgb2Yiq (num Y, num I, num *Q, num R, num G, num B)
	sRGB to NTSC YIQ
void	Yiq2Rgb (num R, num G, num *B, num Y, num I, num Q)
	Convert NTSC YIQ to sRGB.
void	Rgb2Hsv (num H, num S, num *V, num R, num G, num B)
	Convert an sRGB color to Hue-Saturation-Value (HSV).
void	Hsv2Rgb (num R, num G, num *B, num H, num S, num V)
	Convert a Hue-Saturation-Value (HSV) color to sRGB.
void	Rgb2Hsl (num H, num S, num *L, num R, num G, num B)
	Convert an sRGB color to Hue-Saturation-Lightness (HSL).
void	Hsl2Rgb (num R, num G, num *B, num H, num S, num L)
	Convert a Hue-Saturation-Lightness (HSL) color to sRGB.
void	Rgb2Hsi (num H, num S, num *I, num R, num G, num B)
	Convert an sRGB color to Hue-Saturation-Intensity (HSI).
void	Hsi2Rgb (num R, num G, num *B, num H, num S, num I)
	Convert a Hue-Saturation-Intesity (HSI) color to sRGB.
void	Rgb2Xyz (num X, num Y, num *Z, num R, num G, num B)
	Transform sRGB to CIE XYZ with the D65 white point.
void	Xyz2Rgb (num R, num G, num *B, num X, num Y, num Z)
	Transform CIE XYZ to sRGB with the D65 white point.
void	Xyz2Lab (num L, num a, num *b, num X, num Y, num Z)
void	Lab2Xyz (num X, num Y, num *Z, num L, num a, num b)
void	Xyz2Luv (num L, num u, num *v, num X, num Y, num Z)
void	Luv2Xyz (num X, num Y, num *Z, num L, num u, num v)
void	Xyz2Lch (num L, num C, num *H, num X, num Y, num Z)
void	Lch2Xyz (num X, num Y, num *Z, num L, num C, num H)
void	Xyz2Cat02lms (num L, num M, num *S, num X, num Y, num Z)
	XYZ to CAT02 LMS.
void	Cat02lms2Xyz (num X, num Y, num *Z, num L, num M, num S)
	CAT02 LMS to XYZ.
void	Rgb2Lab (num L, num a, num *b, num R, num G, num B)
void	Lab2Rgb (num R, num G, num *B, num L, num a, num b)
void	Rgb2Luv (num L, num u, num *v, num R, num G, num B)
void	Luv2Rgb (num R, num G, num *B, num L, num u, num v)
void	Rgb2Lch (num L, num C, num *H, num R, num G, num B)
void	Lch2Rgb (num R, num G, num *B, num L, num C, num H)
void	Rgb2Cat02lms (num L, num M, num *S, num R, num G, num B)
void	Cat02lms2Rgb (num R, num G, num *B, num L, num M, num S)
static int	IdFromName (const char *Name)
	Convert a color space name to an integer ID.
int	GetColorTransform (colortransform Trans, const char TransformString)
	Given a transform string, returns a colortransform struct.
void	ApplyColorTransform (colortransform Trans, num D0, num D1, num *D2, num S0, num S1, num S2)
	Apply a colortransform.
Variables
struct {
int Space [2]
void(* Fun [2])(num , num , num *, num, num, num)
}	TransformPair [NUM_TRANSFORM_PAIRS]
	Table representing all transformations in this file.

Detailed Description

Author:: Pascal Getreuer 2005-2010 <getreuer@gmail.com>

== Summary == This file implements routines for color transformations between the spaces sRGB, Y'UV, Y'CbCr, Y'PbPr, Y'DbDr, Y'IQ, HSV, HSL, HSI, CIEXYZ, CIELAB, CIELUV, CIELCH, and CIECAT02 LMS.

== Usage == First call GetColorTransform, specifying the source and destination color spaces as "dest<-src" or "src->dest". Then call ApplyColorTransform to perform the transform:

       num S[3] = {173, 0.8, 0.5};
       num D[3];
       colortransform Trans;
       
       if(!(GetColorTransform(&Trans, "HSI -> Lab")))
       {
           printf("Invalid syntax or unknown color space\n");
           return;
       }   
       
       ApplyColorTransform(Trans, &D[0], &D[1], &D[2], S[0], S[1], S[2]);

"num" is a typedef defined at the beginning of colorspace.h that may be set to either double or float, depending on the application.

Specific transformation routines can also be called directly. The following converts an sRGB color to CIELAB and then back to sRGB:

     num R = 0.85, G = 0.32, B = 0.5;
     num L, a, b;
     Rgb2Lab(&L, &a, &b, R, G, B);
     Lab2Rgb(&R, &G, &B, L, a, b);

Generally, the calling syntax is

     Foo2Bar(&B0, &B1, &B2, F0, F1, F2);

where (F0,F1,F2) are the coordinates of a color in space "Foo" and (B0,B1,B2) are the transformed coordinates in space "Bar." For any transformation routine, its inverse has the sytax

     Bar2Foo(&F0, &F1, &F2, B0, B1, B2);

The conversion routines are consistently named with the first letter of a color space capitalized with following letters in lower case and omitting prime symbols. For example, "Rgb2Ydbdr" converts sRGB to Y'DbDr. For any transformation routine Foo2Bar, its inverse is Bar2Foo.

All transformations assume a two degree observer angle and a D65 illuminant. The white point can be changed by modifying the WHITEPOINT_X, WHITEPOINT_Y, WHITEPOINT_Z definitions at the beginning of colorspace.h.

== List of transformation routines ==

It is possible to transform between two arbitrary color spaces by first transforming from the source space to sRGB and then transforming from sRGB to the desired destination space. For transformations between CIE color spaces, it is convenient to use XYZ as the intermediate space. This is the strategy used by GetColorTransform and ApplyColorTransform.

== References == The definitions of these spaces and the many of the transformation formulas can be found in

Poynton, "Frequently Asked Questions About Gamma" http://www.poynton.com/notes/colour_and_gamma/GammaFAQ.html

Poynton, "Frequently Asked Questions About Color" http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html

and Wikipedia articles http://en.wikipedia.org/wiki/SRGB http://en.wikipedia.org/wiki/YUV http://en.wikipedia.org/wiki/YCbCr http://en.wikipedia.org/wiki/YPbPr http://en.wikipedia.org/wiki/YDbDr http://en.wikipedia.org/wiki/YIQ http://en.wikipedia.org/wiki/HSL_and_HSV http://en.wikipedia.org/wiki/CIE_1931_color_space http://en.wikipedia.org/wiki/Lab_color_space http://en.wikipedia.org/wiki/CIELUV_color_space http://en.wikipedia.org/wiki/LMS_color_space

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Definition in file colorspace.c.

Define Documentation

#define CAT02LMS_SPACE 15

Definition at line 213 of file colorspace.c.

#define GAMMACORRECTION ( t )

Value:

(((t) <= 0.0031306684425005883) ? \
        (12.92*(t)) : (1.055*pow((t), 0.416666666666666667) - 0.055))

sRGB gamma correction, transforms R to R' http://en.wikipedia.org/wiki/SRGB

Definition at line 164 of file colorspace.c.

#define HSI_SPACE 10

Definition at line 208 of file colorspace.c.

#define HSL_SPACE 9

Definition at line 207 of file colorspace.c.

#define HSV_SPACE 8

Definition at line 206 of file colorspace.c.

#define INVGAMMACORRECTION ( t )

Value:

(((t) <= 0.0404482362771076) ? \
        ((t)/12.92) : pow(((t) + 0.055)/1.055, 2.4))

Inverse sRGB gamma correction, transforms R' to R.

Definition at line 171 of file colorspace.c.

#define JPEGYCBCR_SPACE 4

Definition at line 202 of file colorspace.c.

#define LAB_SPACE 12

Definition at line 210 of file colorspace.c.

#define LABF ( t )

Value:

((t >= 8.85645167903563082e-3) ? \
        pow(t,0.333333333333333) : (841.0/108.0)*(t) + (4.0/29.0))

CIE L*a*b* f function (used to convert XYZ to L*a*b*) http://en.wikipedia.org/wiki/Lab_color_space.

Definition at line 179 of file colorspace.c.

#define LABINVF ( t )

Value:

((t >= 0.206896551724137931) ? \
        ((t)*(t)*(t)) : (108.0/841.0)*((t) - (4.0/29.0)))

CIE L*a*b* inverse f function http://en.wikipedia.org/wiki/Lab_color_space.

Definition at line 187 of file colorspace.c.

#define LCH_SPACE 14

Definition at line 212 of file colorspace.c.

#define LUV_SPACE 13

Definition at line 211 of file colorspace.c.

#define M_PI 3.14159265358979323846264338327950288

The constant pi.

Definition at line 157 of file colorspace.c.

#define MAX	(	A,
		B		)	(((A) >= (B)) ? (A) : (B))

Max of A and B.

Definition at line 147 of file colorspace.c.

#define MAX3	(	A,
		B,
		C	)	(((A) >= (B)) ? MAX(A,C) : MAX(B,C))

Max of A, B, and C.

Definition at line 153 of file colorspace.c.

#define MIN	(	A,
		B		)	(((A) <= (B)) ? (A) : (B))

Min of A and B.

Definition at line 144 of file colorspace.c.

#define MIN3	(	A,
		B,
		C	)	(((A) <= (B)) ? MIN(A,C) : MIN(B,C))

Min of A, B, and C.

Definition at line 150 of file colorspace.c.

#define NUM_TRANSFORM_PAIRS 18

Definition at line 215 of file colorspace.c.

#define RGB_SPACE 1

Definition at line 199 of file colorspace.c.

#define UNKNOWN_SPACE 0

Enumeration of the supported color spaces.

Definition at line 198 of file colorspace.c.

#define WHITEPOINT_U

Value:

((4*WHITEPOINT_X) \
        /(WHITEPOINT_X + 15*WHITEPOINT_Y + 3*WHITEPOINT_Z))

u'v' coordinates of the white point for CIE Lu*v*

Definition at line 192 of file colorspace.c.

#define WHITEPOINT_V

Value:

((9*WHITEPOINT_Y) \
        /(WHITEPOINT_X + 15*WHITEPOINT_Y + 3*WHITEPOINT_Z))

Definition at line 194 of file colorspace.c.

#define XYZ_SPACE 11

Definition at line 209 of file colorspace.c.

#define YCBCR_SPACE 3

Definition at line 201 of file colorspace.c.

#define YDBDR_SPACE 6

Definition at line 204 of file colorspace.c.

#define YIQ_SPACE 7

Definition at line 205 of file colorspace.c.

#define YPBPR_SPACE 5

Definition at line 203 of file colorspace.c.

#define YUV_SPACE 2

Definition at line 200 of file colorspace.c.

Function Documentation

void ApplyColorTransform	(	colortransform	Trans,
		num *	D0,
		num *	D1,
		num *	D2,
		num	S0,
		num	S1,
		num	S2
	)

Apply a colortransform.

Parameters:

	Trans	colortransform struct created by GetColorTransform
	D0,D1,D2	pointers to hold the result
	S0,S1,S2	the input values

Definition at line 1191 of file colorspace.c.

void Cat02lms2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	L,
		num	M,
		num	S
	)

Definition at line 964 of file colorspace.c.

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void Cat02lms2Xyz	(	num *	X,
		num *	Y,
		num *	Z,
		num	L,
		num	M,
		num	S
	)

CAT02 LMS to XYZ.

Definition at line 897 of file colorspace.c.

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int GetColorTransform	(	colortransform *	Trans,
		const char *	TransformString
	)

Given a transform string, returns a colortransform struct.

Parameters:

	Trans	a colortransform pointer to hold the transform
	TransformString	string specifying the transformations

Returns:: 1 on success, 0 on failure

This function provides a convenient interface to the collection of transform functions in this file. TransformString specifies the source and destination color spaces, TransformString = "dest<-src" or alternatively, TransformString = "src->dest".

Supported color spaces are "RGB" sRGB Red Green Blue (ITU-R BT.709 gamma-corrected), "YPbPr" Luma (ITU-R BT.601) + Chroma, "YCbCr" Luma + Chroma ("digitized" version of Y'PbPr), "JPEG-YCbCr" Luma + Chroma space used in JFIF JPEG, "YUV" NTSC PAL Y'UV Luma + Chroma, "YIQ" NTSC Y'IQ Luma + Chroma, "YDbDr" SECAM Y'DbDr Luma + Chroma, "HSV" or "HSB" Hue Saturation Value/Brightness, "HSL" or "HLS" Hue Saturation Luminance, "HSI" Hue Saturation Intensity, "XYZ" CIE XYZ, "Lab" CIE L*a*b* (CIELAB), "Luv" CIE L*u*v* (CIELUV), "LCH" CIE L*C*H* (CIELCH), "CAT02 LMS" CIE CAT02 LMS. Color space names are case-insensitive and spaces are ignored. When sRGB is the source or destination, it can be omitted. For example "yuv<-" is short for "yuv<-rgb".

The routine returns a colortransform structure representing the transform. The transform is performed by calling GetColorTransform. For example,

       num S[3] = {173, 0.8, 0.5};
       num D[3];
       colortransform Trans;
       
       if(!(GetColorTransform(&Trans, "HSI -> Lab")))
       {
           printf("Invalid syntax or unknown color space\n");
           return;
       }   
       
       ApplyColorTransform(Trans, &D[0], &D[1], &D[2], S[0], S[1], S[2]);

Definition at line 1067 of file colorspace.c.

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void Hsi2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	H,
		num	S,
		num	I
	)

Convert a Hue-Saturation-Intesity (HSI) color to sRGB.

Parameters:

	R,G,B	pointers to hold the result
	H,S,I	the input HSI values

The input values are assumed to be scaled as 0 <= H < 360, 0 <= S <= 1, 0 <= I <= 1. The output sRGB values are scaled between 0 and 1. This is the inverse transformation of Rgb2Hsi.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 658 of file colorspace.c.

void Hsl2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	H,
		num	S,
		num	L
	)

Convert a Hue-Saturation-Lightness (HSL) color to sRGB.

Parameters:

	R,G,B	pointers to hold the result
	H,S,L	the input HSL values

The input values are assumed to be scaled as 0 <= H < 360, 0 <= S <= 1, 0 <= L <= 1. The output sRGB values are scaled between 0 and 1. This is the inverse transformation of Rgb2Hsl.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 558 of file colorspace.c.

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void Hsv2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	H,
		num	S,
		num	V
	)

Convert a Hue-Saturation-Value (HSV) color to sRGB.

Parameters:

	R,G,B	pointers to hold the result
	H,S,V	the input HSV values

The input values are assumed to be scaled as 0 <= H < 360, 0 <= S <= 1, 0 <= V <= 1. The output sRGB values are scaled between 0 and 1. This is the inverse transformation of Rgb2Hsv.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 446 of file colorspace.c.

static int IdFromName ( const char * Name ) [static]

Convert a color space name to an integer ID.

Definition at line 980 of file colorspace.c.

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void Jpegycbcr2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	Cb,
		num	Cr
	)

JPEG-Y'CbCr to sRGB.

Definition at line 313 of file colorspace.c.

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void Lab2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	L,
		num	a,
		num	b
	)

Definition at line 917 of file colorspace.c.

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void Lab2Xyz	(	num *	X,
		num *	Y,
		num *	Z,
		num	L,
		num	a,
		num	b
	)

Convert CIE L*a*b* (CIELAB) to CIE XYZ with the D65 white point

Parameters:

	X,Y,Z	pointers to hold the result
	L,a,b	the input Lab* values

Wikipedia: http://en.wikipedia.org/wiki/Lab_color_space

Definition at line 782 of file colorspace.c.

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void Lch2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	L,
		num	C,
		num	H
	)

Definition at line 948 of file colorspace.c.

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void Lch2Xyz	(	num *	X,
		num *	Y,
		num *	Z,
		num	L,
		num	C,
		num	H
	)

Convert CIE L*C*H* to CIE XYZ with the D65 white point

Parameters:

	X,Y,Z	pointers to hold the result
	L,C,H	the input LCH* values

Definition at line 877 of file colorspace.c.

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void Luv2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	L,
		num	u,
		num	v
	)

Definition at line 933 of file colorspace.c.

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void Luv2Xyz	(	num *	X,
		num *	Y,
		num *	Z,
		num	L,
		num	u,
		num	v
	)

Convert CIE L*u*v* (CIELUV) to CIE XYZ with the D65 white point

Parameters:

	X,Y,Z	pointers to hold the result
	L,u,v	the input Luv* values

Wikipedia: http://en.wikipedia.org/wiki/CIELUV_color_space

Definition at line 830 of file colorspace.c.

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void Rgb2Cat02lms	(	num *	L,
		num *	M,
		num *	S,
		num	R,
		num	G,
		num	B
	)

Definition at line 956 of file colorspace.c.

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void Rgb2Hsi	(	num *	H,
		num *	S,
		num *	I,
		num	R,
		num	G,
		num	B
	)

Convert an sRGB color to Hue-Saturation-Intensity (HSI).

Parameters:

	H,S,I	pointers to hold the result
	R,G,B	the input sRGB values scaled in [0,1]

This routine transforms from sRGB to the cylindrical HSI color space. The sRGB values are assumed to be between 0 and 1. The output values are H = polar hue angle (0 <= H < 360), S = 1 - min(R',G',B')/I (0 <= S <= 1), I = (R'+G'+B')/3 (0 <= I <= 1). The inverse color transformation is given by Hsi2Rgb.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 622 of file colorspace.c.

void Rgb2Hsl	(	num *	H,
		num *	S,
		num *	L,
		num	R,
		num	G,
		num	B
	)

Convert an sRGB color to Hue-Saturation-Lightness (HSL).

Parameters:

	H,S,L	pointers to hold the result
	R,G,B	the input sRGB values scaled in [0,1]

This routine transforms from sRGB to the double hexcone HSL color space The sRGB values are assumed to be between 0 and 1. The outputs are H = hexagonal hue angle (0 <= H < 360), S = { C/(2L) if L <= 1/2 (0 <= S <= 1), { C/(2 - 2L) if L > 1/2 L = (max(R',G',B') + min(R',G',B'))/2 (0 <= L <= 1), where C = max(R',G',B') - min(R',G',B'). The inverse color transformation is given by Hsl2Rgb.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 512 of file colorspace.c.

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void Rgb2Hsv	(	num *	H,
		num *	S,
		num *	V,
		num	R,
		num	G,
		num	B
	)

Convert an sRGB color to Hue-Saturation-Value (HSV).

Parameters:

	H,S,V	pointers to hold the result
	R,G,B	the input sRGB values scaled in [0,1]

This routine transforms from sRGB to the hexcone HSV color space. The sRGB values are assumed to be between 0 and 1. The output values are H = hexagonal hue angle (0 <= H < 360), S = C/V (0 <= S <= 1), V = max(R',G',B') (0 <= V <= 1), where C = max(R',G',B') - min(R',G',B'). The inverse color transformation is given by Hsv2Rgb.

Wikipedia: http://en.wikipedia.org/wiki/HSL_and_HSV

Definition at line 400 of file colorspace.c.

void Rgb2Jpegycbcr	(	num *	Y,
		num *	Cb,
		num *	Cr,
		num	R,
		num	G,
		num	B
	)

sRGB to JPEG-Y'CbCr Luma + Chroma

Definition at line 305 of file colorspace.c.

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void Rgb2Lab	(	num *	L,
		num *	a,
		num *	b,
		num	R,
		num	G,
		num	B
	)

Definition at line 909 of file colorspace.c.

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void Rgb2Lch	(	num *	L,
		num *	C,
		num *	H,
		num	R,
		num	G,
		num	B
	)

Definition at line 940 of file colorspace.c.

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void Rgb2Luv	(	num *	L,
		num *	u,
		num *	v,
		num	R,
		num	G,
		num	B
	)

Definition at line 925 of file colorspace.c.

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void Rgb2Xyz	(	num *	X,
		num *	Y,
		num *	Z,
		num	R,
		num	G,
		num	B
	)

Transform sRGB to CIE XYZ with the D65 white point.

Parameters:

	X,Y,Z	pointers to hold the result
	R,G,B	the input sRGB values

Poynton, "Frequently Asked Questions About Color," page 10 Wikipedia: http://en.wikipedia.org/wiki/SRGB Wikipedia: http://en.wikipedia.org/wiki/CIE_1931_color_space

Definition at line 704 of file colorspace.c.

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void Rgb2Ycbcr	(	num *	Y,
		num *	Cb,
		num *	Cr,
		num	R,
		num	G,
		num	B
	)

sRGB to Y'CbCr Luma + Chroma

Definition at line 284 of file colorspace.c.

void Rgb2Ydbdr	(	num *	Y,
		num *	Db,
		num *	Dr,
		num	R,
		num	G,
		num	B
	)

sRGB to SECAM Y'DbDr Luma + Chroma

Definition at line 340 of file colorspace.c.

void Rgb2Yiq	(	num *	Y,
		num *	I,
		num *	Q,
		num	R,
		num	G,
		num	B
	)

sRGB to NTSC YIQ

Definition at line 358 of file colorspace.c.

void Rgb2Ypbpr	(	num *	Y,
		num *	Pb,
		num *	Pr,
		num	R,
		num	G,
		num	B
	)

sRGB to Y'PbPr Luma (ITU-R BT.601) + Chroma

Definition at line 322 of file colorspace.c.

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void Rgb2Yuv	(	num *	Y,
		num *	U,
		num *	V,
		num	R,
		num	G,
		num	B
	)

Convert sRGB to NTSC/PAL Y'UV Luma + Chroma.

Parameters:

	Y,U,V	pointers to hold the result
	R,G,B	the input sRGB values

Wikipedia: http://en.wikipedia.org/wiki/YUV

Definition at line 261 of file colorspace.c.

void Xyz2Cat02lms	(	num *	L,
		num *	M,
		num *	S,
		num	X,
		num	Y,
		num	Z
	)

XYZ to CAT02 LMS.

Definition at line 888 of file colorspace.c.

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void Xyz2Lab	(	num *	L,
		num *	a,
		num *	b,
		num	X,
		num	Y,
		num	Z
	)

Convert CIE XYZ to CIE L*a*b* (CIELAB) with the D65 white point

Parameters:

	L,a,b	pointers to hold the result
	X,Y,Z	the input XYZ values

Wikipedia: http://en.wikipedia.org/wiki/Lab_color_space

Definition at line 760 of file colorspace.c.

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void Xyz2Lch	(	num *	L,
		num *	C,
		num *	H,
		num	X,
		num	Y,
		num	Z
	)

Convert CIE XYZ to CIE L*C*H* with the D65 white point

Parameters:

	L,C,H	pointers to hold the result
	X,Y,Z	the input XYZ values

CIE L*C*H* is related to CIE L*a*b* by a* = C* cos(H* pi/180), b* = C* sin(H* pi/180).

Definition at line 858 of file colorspace.c.

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void Xyz2Luv	(	num *	L,
		num *	u,
		num *	v,
		num	X,
		num	Y,
		num	Z
	)

Convert CIE XYZ to CIE L*u*v* (CIELUV) with the D65 white point

Parameters:

	L,u,v	pointers to hold the result
	X,Y,Z	the input XYZ values

Wikipedia: http://en.wikipedia.org/wiki/CIELUV_color_space

Definition at line 801 of file colorspace.c.

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void Xyz2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	X,
		num	Y,
		num	Z
	)

Transform CIE XYZ to sRGB with the D65 white point.

Parameters:

	R,G,B	pointers to hold the result
	X,Y,Z	the input XYZ values

Official sRGB specification (IEC 61966-2-1:1999) Poynton, "Frequently Asked Questions About Color," page 10 Wikipedia: http://en.wikipedia.org/wiki/SRGB Wikipedia: http://en.wikipedia.org/wiki/CIE_1931_color_space

Definition at line 726 of file colorspace.c.

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void Ycbcr2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	Cr,
		num	Cb
	)

Y'CbCr to sRGB.

Definition at line 293 of file colorspace.c.

void Ydbdr2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	Db,
		num	Dr
	)

SECAM Y'DbDr to sRGB.

Definition at line 349 of file colorspace.c.

void Yiq2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	I,
		num	Q
	)

Convert NTSC YIQ to sRGB.

Definition at line 367 of file colorspace.c.

void Ypbpr2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	Pb,
		num	Pr
	)

Y'PbPr to sRGB.

Definition at line 331 of file colorspace.c.

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void Yuv2Rgb	(	num *	R,
		num *	G,
		num *	B,
		num	Y,
		num	U,
		num	V
	)

Convert NTSC/PAL Y'UV to sRGB.

Parameters:

	R,G,B	pointers to hold the result
	Y,U,V	the input YUV values

Definition at line 275 of file colorspace.c.

Variable Documentation

void(* Fun[2])(num *, num *, num *, num, num, num)

Definition at line 222 of file colorspace.c.

int Space[2]

Definition at line 221 of file colorspace.c.

struct { ... } TransformPair[NUM_TRANSFORM_PAIRS] [static]

Table representing all transformations in this file.

colorspace/colorspace.c File Reference

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Functions

Variables

Detailed Description

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Variable Documentation