4.4BSD/usr/src/contrib/X11R5-lib/lib/X/CIELab.c
/* $XConsortium: CIELab.c,v 1.8 91/07/25 01:07:05 rws Exp $ */
/*
* Code and supporting documentation (c) Copyright 1990 1991 Tektronix, Inc.
* All Rights Reserved
*
* This file is a component of an X Window System-specific implementation
* of XCMS based on the TekColor Color Management System. Permission is
* hereby granted to use, copy, modify, sell, and otherwise distribute this
* software and its documentation for any purpose and without fee, provided
* that this copyright, permission, and disclaimer notice is reproduced in
* all copies of this software and in supporting documentation. TekColor
* is a trademark of Tektronix, Inc.
*
* Tektronix makes no representation about the suitability of this software
* for any purpose. It is provided "as is" and with all faults.
*
* TEKTRONIX DISCLAIMS ALL WARRANTIES APPLICABLE TO THIS SOFTWARE,
* INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE. IN NO EVENT SHALL TEKTRONIX BE LIABLE FOR ANY
* SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
* RESULTING FROM LOSS OF USE, DATA, OR PROFITS, WHETHER IN AN ACTION OF
* CONTRACT, NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR THE PERFORMANCE OF THIS SOFTWARE.
*
*
* NAME
* CIELab.c
*
* DESCRIPTION
* This file contains routines that support the CIE L*a*b*
* color space to include conversions to and from the CIE
* XYZ space. These conversions are from Principles of
* Color Technology Second Edition, Fred W. Billmeyer, Jr.
* and Max Saltzman, John Wiley & Sons, Inc., 1981.
*
* Note that the range for L* is 0 to 1.
*/
#include <X11/Xos.h>
#include "Xlibint.h"
#include "Xcmsint.h"
/*
* DEFINES
* Internal definitions that need NOT be exported to any package
* or program using this package.
*/
#ifdef DBL_EPSILON
# define XMY_DBL_EPSILON DBL_EPSILON
#else
# define XMY_DBL_EPSILON 0.00001
#endif
#define DIV16BY116 0.137931
/*
* EXTERNS
*/
extern char XcmsCIELab_prefix[];
/*
* FORWARD DECLARATIONS
*/
static int CIELab_ParseString();
Status XcmsCIELab_ValidSpec();
/*
* LOCAL VARIABLES
*/
/*
* NULL terminated list of functions applied to get from CIELab to CIEXYZ
*/
static XcmsConversionProc Fl_CIELab_to_CIEXYZ[] = {
XcmsCIELabToCIEXYZ,
NULL
};
/*
* NULL terminated list of functions applied to get from CIEXYZ to CIELab
*/
static XcmsConversionProc Fl_CIEXYZ_to_CIELab[] = {
XcmsCIEXYZToCIELab,
NULL
};
/*
* GLOBALS
*/
/*
* CIE Lab Color Space
*/
XcmsColorSpace XcmsCIELabColorSpace =
{
XcmsCIELab_prefix, /* prefix */
XcmsCIELabFormat, /* id */
CIELab_ParseString, /* parseString */
Fl_CIELab_to_CIEXYZ, /* to_CIEXYZ */
Fl_CIEXYZ_to_CIELab, /* from_CIEXYZ */
1
};
/************************************************************************
* *
* PRIVATE ROUTINES *
* *
************************************************************************/
/*
* NAME
* CIELab_ParseString
*
* SYNOPSIS
*/
static int
CIELab_ParseString(spec, pColor)
register char *spec;
XcmsColor *pColor;
/*
* DESCRIPTION
* This routines takes a string and attempts to convert
* it into a XcmsColor structure with XcmsCIELabFormat.
* The assumed CIELab string syntax is:
* CIELab:<L>/<a>/<b>
* Where L, a, and b are in string input format for floats
* consisting of:
* a. an optional sign
* b. a string of numbers possibly containing a decimal point,
* c. an optional exponent field containing an 'E' or 'e'
* followed by a possibly signed integer string.
*
* RETURNS
* 0 if failed, non-zero otherwise.
*/
{
int n;
char *pchar;
if ((pchar = strchr(spec, ':')) == NULL) {
return(XcmsFailure);
}
n = (int)(pchar - spec);
/*
* Check for proper prefix.
*/
if (strncmp(spec, XcmsCIELab_prefix, n) != 0) {
return(XcmsFailure);
}
/*
* Attempt to parse the value portion.
*/
if (sscanf(spec + n + 1, "%lf/%lf/%lf",
&pColor->spec.CIELab.L_star,
&pColor->spec.CIELab.a_star,
&pColor->spec.CIELab.b_star) != 3) {
return(XcmsFailure);
}
pColor->format = XcmsCIELabFormat;
pColor->pixel = 0;
return(XcmsCIELab_ValidSpec(pColor));
}
/************************************************************************
* *
* PUBLIC ROUTINES *
* *
************************************************************************/
/*
* NAME
* XcmsCIELab_ValidSpec
*
* SYNOPSIS
*/
Status
XcmsCIELab_ValidSpec(pColor)
XcmsColor *pColor;
/*
* DESCRIPTION
* Checks if color specification valid for CIE L*a*b*.
*
* RETURNS
* XcmsFailure if invalid,
* XcmsSuccess if valid.
*
*/
{
if (pColor->format != XcmsCIELabFormat
||
(pColor->spec.CIELab.L_star < 0.0 - XMY_DBL_EPSILON)
||
(pColor->spec.CIELab.L_star > 100.0 + XMY_DBL_EPSILON)) {
return(XcmsFailure);
}
return(XcmsSuccess);
}
/*
* NAME
* XcmsCIELabToCIEXYZ - convert CIELab to CIEXYZ
*
* SYNOPSIS
*/
Status
XcmsCIELabToCIEXYZ(ccc, pLab_WhitePt, pColors_in_out, nColors)
XcmsCCC ccc;
XcmsColor *pLab_WhitePt;
XcmsColor *pColors_in_out;
unsigned int nColors;
/*
* DESCRIPTION
* Converts color specifications in an array of XcmsColor
* structures from CIELab format to CIEXYZ format.
*
* WARNING: This routine assumes that Yn = 1.0;
*
* RETURNS
* XcmsFailure if failed,
* XcmsSuccess if succeeded.
*
*/
{
XcmsCIEXYZ XYZ_return;
XcmsFloat tmpFloat, tmpL;
XcmsColor whitePt;
int i;
XcmsColor *pColor = pColors_in_out;
/*
* Check arguments
*/
if (pLab_WhitePt == NULL || pColors_in_out == NULL) {
return(XcmsFailure);
}
/*
* Make sure white point is in CIEXYZ form, if not, convert it.
*/
if (pLab_WhitePt->format != XcmsCIEXYZFormat) {
/* Make a copy of the white point because we're going to modify it */
bcopy((char *)pLab_WhitePt, (char *)&whitePt, sizeof(XcmsColor));
if (!_XcmsDIConvertColors(ccc, &whitePt,
(XcmsColor *)NULL, 1, XcmsCIEXYZFormat)) {
return(XcmsFailure);
}
pLab_WhitePt = &whitePt;
}
/*
* Make sure it is a white point, i.e., Y == 1.0
*/
if (pLab_WhitePt->spec.CIEXYZ.Y != 1.0) {
return (0);
}
/*
* Now convert each XcmsColor structure to CIEXYZ form
*/
for (i = 0; i < nColors; i++, pColor++) {
/* Make sure original format is CIELab */
if (!XcmsCIELab_ValidSpec(pColor)) {
return(XcmsFailure);
}
/* Calculate Y: assume that Yn = 1.0 */
tmpL = (pColor->spec.CIELab.L_star + 16.0) / 116.0;
XYZ_return.Y = tmpL * tmpL * tmpL;
if (XYZ_return.Y < 0.008856) {
/* Calculate Y: assume that Yn = 1.0 */
tmpL = pColor->spec.CIELab.L_star / 9.03292;
/* Calculate X */
XYZ_return.X = pLab_WhitePt->spec.CIEXYZ.X *
((pColor->spec.CIELab.a_star / 3893.5) + tmpL);
/* Calculate Y */
XYZ_return.Y = tmpL;
/* Calculate Z */
XYZ_return.Z = pLab_WhitePt->spec.CIEXYZ.Z *
(tmpL - (pColor->spec.CIELab.b_star / 1557.4));
} else {
/* Calculate X */
tmpFloat = tmpL + (pColor->spec.CIELab.a_star / 5.0);
XYZ_return.X = pLab_WhitePt->spec.CIEXYZ.X * tmpFloat * tmpFloat * tmpFloat;
/* Calculate Z */
tmpFloat = tmpL - (pColor->spec.CIELab.b_star / 2.0);
XYZ_return.Z = pLab_WhitePt->spec.CIEXYZ.Z * tmpFloat * tmpFloat * tmpFloat;
}
bcopy((char *)&XYZ_return, (char *)&pColor->spec.CIEXYZ,
sizeof(XcmsCIEXYZ));
pColor->format = XcmsCIEXYZFormat;
}
return (1);
}
/*
* NAME
* XcmsCIEXYZToCIELab - convert CIEXYZ to CIELab
*
* SYNOPSIS
*/
Status
XcmsCIEXYZToCIELab(ccc, pLab_WhitePt, pColors_in_out, nColors)
XcmsCCC ccc;
XcmsColor *pLab_WhitePt;
XcmsColor *pColors_in_out;
unsigned int nColors;
/*
* DESCRIPTION
* Converts color specifications in an array of XcmsColor
* structures from CIEXYZ format to CIELab format.
*
* WARNING: This routine assumes that Yn = 1.0;
*
* RETURNS
* XcmsFailure if failed,
* XcmsSuccess if succeeded.
*
*/
{
XcmsCIELab Lab_return;
XcmsFloat fX_Xn, fY_Yn, fZ_Zn;
XcmsColor whitePt;
int i;
XcmsColor *pColor = pColors_in_out;
/*
* Check arguments
*/
if (pLab_WhitePt == NULL || pColors_in_out == NULL) {
return(XcmsFailure);
}
/*
* Make sure white point is in CIEXYZ form, if not, convert it.
*/
if (pLab_WhitePt->format != XcmsCIEXYZFormat) {
/* Make a copy of the white point because we're going to modify it */
bcopy((char *)pLab_WhitePt, (char *)&whitePt, sizeof(XcmsColor));
if (!_XcmsDIConvertColors(ccc, &whitePt, (XcmsColor *)NULL,
1, XcmsCIEXYZFormat)) {
return(XcmsFailure);
}
pLab_WhitePt = &whitePt;
}
/*
* Make sure it is a white point, i.e., Y == 1.0
*/
if (pLab_WhitePt->spec.CIEXYZ.Y != 1.0) {
return(XcmsFailure);
}
/*
* Now convert each XcmsColor structure to CIEXYZ form
*/
for (i = 0; i < nColors; i++, pColor++) {
/* Make sure original format is CIELab */
if (!XcmsCIEXYZ_ValidSpec(pColor)) {
return(XcmsFailure);
}
/* Calculate L*: assume Yn = 1.0 */
if (pColor->spec.CIEXYZ.Y < 0.008856) {
fY_Yn = (0.07787 * pColor->spec.CIEXYZ.Y) + DIV16BY116;
/* note fY_Yn used to compute Lab_return.a below */
Lab_return.L_star = 116.0 * (fY_Yn - DIV16BY116);
} else {
fY_Yn = (XcmsFloat)XCMS_CUBEROOT(pColor->spec.CIEXYZ.Y);
/* note fY_Yn used to compute Lab_return.a_star below */
Lab_return.L_star = (116.0 * fY_Yn) - 16.0;
}
/* Calculate f(X/Xn) */
if ((fX_Xn = pColor->spec.CIEXYZ.X / pLab_WhitePt->spec.CIEXYZ.X) < 0.008856) {
fX_Xn = (0.07787 * fX_Xn) + DIV16BY116;
} else {
fX_Xn = (XcmsFloat) XCMS_CUBEROOT(fX_Xn);
}
/* Calculate f(Z/Zn) */
if ((fZ_Zn = pColor->spec.CIEXYZ.Z / pLab_WhitePt->spec.CIEXYZ.Z) < 0.008856) {
fZ_Zn = (0.07787 * fZ_Zn) + DIV16BY116;
} else {
fZ_Zn = (XcmsFloat) XCMS_CUBEROOT(fZ_Zn);
}
Lab_return.a_star = 5.0 * (fX_Xn - fY_Yn);
Lab_return.b_star = 2.0 * (fY_Yn - fZ_Zn);
bcopy((char *)&Lab_return, (char *)&pColor->spec.CIELab,
sizeof(XcmsCIELab));
pColor->format = XcmsCIELabFormat;
}
return(XcmsSuccess);
}