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+/* $Xorg: LabMxC.c,v 1.3 2000/08/17 19:44:40 cpqbld 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.
+ *
+ */
+/* $XFree86: xc/lib/X11/LabMxC.c,v 1.3 2001/01/17 19:41:39 dawes Exp $ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include "Xlibint.h"
+#include "Xcmsint.h"
+#include <math.h>
+#include "Cv.h"
+
+/*
+ * DEFINES
+ */
+#define MAXBISECTCOUNT 100
+#define EPS (XcmsFloat)0.001
+#define START_CHROMA (XcmsFloat)3.6
+#define TOPL (XcmsFloat)100.0
+
+
+/************************************************************************
+ * *
+ * 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 */
+ memcpy ((char *)&myCCC, (char *)ccc, 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. */
+ memcpy((char *)&max_lc, (char *)&tmp, 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) {
+ memcpy((char *)pColor_return, (char *)&tmp, 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;
+ memcpy((char *)pColor_return, (char *)&tmp, sizeof(XcmsColor));
+ return(XcmsSuccess);
+}
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