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
    };

\f
/************************************************************************
 *                                                                      *
 *                       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));
}


\f
/************************************************************************
 *                                                                      *
 *                       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);
}

\f
/*
 *      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);
}

\f
/*
 *      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);
}