usr/src/contrib/X11R5-lib/lib/X/CIELabMxC.c

/* $XConsortium: CIELabMxC.c,v 1.2 91/07/25 01:07:18 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
 *              CIELabMxC.c
 *
 *      DESCRIPTION
 *              Source for the XcmsCIELabQueryMaxC() gamut boundary
 *              querying routine.
 *
 */

#include "Xlibint.h"
#include "Xcmsint.h"
#include <math.h>

/*
 *      DEFINES
 */
#define MAXBISECTCOUNT  100
#define EPS             (XcmsFloat)0.001
#define START_CHROMA    (XcmsFloat)3.6
#define TOPL            (XcmsFloat)100.0

/*
 *      EXTERNS
 */
extern Status _XcmsCIELabQueryMaxLCRGB();

\f
/************************************************************************
 *                                                                      *
 *                       PUBLIC ROUTINES                                *
 *                                                                      *
 ************************************************************************/

/*
 *      NAME
 *              XcmsCIELabQueryMaxC - max chroma for a hue_angle and L_star
 *
 *      SYNOPSIS
 */
Status
XcmsCIELabQueryMaxC(ccc, hue_angle, L_star, pColor_return)
    XcmsCCC ccc;
    XcmsFloat hue_angle;            /* hue angle in degrees */
    XcmsFloat L_star;
    XcmsColor *pColor_return;
/*
 *      DESCRIPTION
 *              Return the maximum chroma for a specific hue_angle and L_star.
 *              The returned format is in XcmsCIELabFormat.
 *
 *
 *      ASSUMPTIONS
 *              This routine assumes that the white point associated with
 *              the color specification is the Screen White Point.  The
 *              Screen White Point will also be associated with the
 *              returned color specification.
 *
 *      RETURNS
 *              XcmsFailure - Failure
 *              XcmsSuccess - Succeeded
 *
 */
{
    XcmsCCCRec  myCCC;
    XcmsColor  tmp;
    XcmsColor  max_lc;
    XcmsFloat n_L_star, last_L_star, prev_L_star;
    XcmsFloat hue, lastaStar, lastbStar, /*lastChroma,*/ maxDist, nT, rFactor;
    XcmsRGBi   rgb_saved;
    int nCount, nMaxCount;

    /*
     * Check Arguments
     */
    if (ccc == NULL || pColor_return == NULL) {
        return(XcmsFailure);
    }

    /* Use my own CCC and inherit screen white Pt */
    bcopy ((char *)ccc, (char *)&myCCC, sizeof(XcmsCCCRec));
    myCCC.clientWhitePt.format = XcmsUndefinedFormat;
    myCCC.gamutCompProc = (XcmsCompressionProc)NULL;/* no gamut comp func */

    while (hue_angle < 0.0) {
        hue_angle += 360.0;
    }
    while (hue_angle >= 360.0) {
        hue_angle -= 360.0;
    }

    hue = radians(hue_angle);
    tmp.spec.CIELab.L_star = L_star;
    tmp.spec.CIELab.a_star = XCMS_CIEASTAROFHUE(hue, START_CHROMA);
    tmp.spec.CIELab.b_star = XCMS_CIEBSTAROFHUE(hue, START_CHROMA);
    tmp.pixel = pColor_return->pixel;
    tmp.format = XcmsCIELabFormat;

    /* Step 1: compute the maximum L_star and chroma for this hue. */
    bcopy((char *)&tmp, (char *)&max_lc, sizeof(XcmsColor));
    if (_XcmsCIELabQueryMaxLCRGB(&myCCC, hue, &max_lc, &rgb_saved)
        == XcmsFailure) {
            return(XcmsFailure);
    }

    /*
     * Step 2:  Do a bisection here to compute the maximum chroma
     *          Note the differences between when the point to be found
     *          is above the maximum LC point and when it is below.
     */
    if (L_star <= max_lc.spec.CIELab.L_star) {
        maxDist = max_lc.spec.CIELab.L_star;
    } else {
        maxDist = TOPL - max_lc.spec.CIELab.L_star;
    }

    n_L_star = L_star;
    last_L_star = -1.0;
    nMaxCount = MAXBISECTCOUNT;
    rFactor = 1.0;

    for (nCount = 0; nCount < nMaxCount; nCount++) {
        prev_L_star =  last_L_star;
        last_L_star =  tmp.spec.CIELab.L_star;
/*      lastChroma = XCMS_CIELAB_PMETRIC_CHROMA(tmp.spec.CIELab.a_star,  */
/*                                              tmp.spec.CIELab.b_star); */
        lastaStar = tmp.spec.CIELab.a_star;
        lastbStar = tmp.spec.CIELab.b_star;
        nT = (n_L_star - max_lc.spec.CIELab.L_star) / maxDist * rFactor;
        if (nT > 0) {
            tmp.spec.RGBi.red = rgb_saved.red * (1.0 - nT) + nT;
            tmp.spec.RGBi.green = rgb_saved.green * (1.0 - nT) + nT;
            tmp.spec.RGBi.blue  = rgb_saved.blue * (1.0 - nT) + nT;
        } else {
            tmp.spec.RGBi.red = rgb_saved.red + (rgb_saved.red * nT);
            tmp.spec.RGBi.green = rgb_saved.green + (rgb_saved.green * nT);
            tmp.spec.RGBi.blue = rgb_saved.blue + (rgb_saved.blue * nT);
        }
        tmp.format = XcmsRGBiFormat;

        /* convert from RGB to CIELab */
        if (_XcmsConvertColorsWithWhitePt(&myCCC, &tmp,
                            ScreenWhitePointOfCCC(&myCCC), 1, XcmsCIELabFormat,
                            (Bool *) NULL) == XcmsFailure) {
            return(XcmsFailure);
        }

        /*
         * Now check if we've reached the target L_star
         */
        /* printf("result Lstar = %lf\n", tmp.spec.CIELab.L_star); */
        if (tmp.spec.CIELab.L_star <= L_star + EPS &&
            tmp.spec.CIELab.L_star >= L_star - EPS) {
                bcopy((char *)&tmp, (char *)pColor_return, sizeof(XcmsColor));
                return(XcmsSuccess);
        }
        if (nT > 0) {
            n_L_star += ((TOPL - n_L_star) *
                         (L_star - tmp.spec.CIELab.L_star)) / (TOPL - L_star);
        } else {
            n_L_star *= L_star / tmp.spec.CIELuv.L_star;
        }
        if (tmp.spec.CIELab.L_star <= prev_L_star + EPS &&
            tmp.spec.CIELab.L_star >= prev_L_star - EPS) {
                rFactor *= 0.5;  /* selective relaxation employed */
                /* printf("rFactor = %lf\n", rFactor); */
        }
    }
    if (XCMS_FABS(last_L_star - L_star) <
        XCMS_FABS(tmp.spec.CIELab.L_star - L_star)) {
            tmp.spec.CIELab.a_star = lastaStar;
            tmp.spec.CIELab.b_star = lastbStar;
/*          tmp.spec.CIELab.a_star = XCMS_CIEASTAROFHUE(hue, lastChroma); */
/*          tmp.spec.CIELab.b_star = XCMS_CIEBSTAROFHUE(hue, lastChroma); */
    }
    tmp.spec.CIELab.L_star = L_star;
    bcopy((char *)&tmp, (char *)pColor_return, sizeof(XcmsColor));
    return(XcmsSuccess);
}