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+
+/*
+ * 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
+ * CIELabMnL.c
+ *
+ * DESCRIPTION
+ * Source for the XcmsCIELabQueryMinL() gamut boundary
+ * querying routine.
+ *
+ */
+
+#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_L_STAR (XcmsFloat)40.0
+
+
+/************************************************************************
+ * *
+ * PUBLIC ROUTINES *
+ * *
+ ************************************************************************/
+
+/*
+ * NAME
+ * XcmsCIELabQueryMinL - Compute max Lstar for a hue and chroma
+ *
+ * SYNOPSIS
+ */
+Status
+XcmsCIELabQueryMinL(
+ XcmsCCC ccc,
+ XcmsFloat hue_angle, /* hue angle in degrees */
+ XcmsFloat chroma,
+ XcmsColor *pColor_return)
+/*
+ * DESCRIPTION
+ * Return the maximum Lstar for a specified hue_angle and chroma.
+ *
+ * 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 with no modifications
+ *
+ */
+{
+ XcmsCCCRec myCCC;
+ XcmsColor max_lc, tmp, prev;
+ XcmsFloat max_chroma, tmp_chroma;
+ XcmsFloat hue, nT, nChroma, lastChroma, prevChroma;
+ XcmsFloat rFactor;
+ XcmsRGBi rgb_saved;
+ int nCount, nMaxCount;
+
+ /*
+ * Check Arguments
+ */
+ if (ccc == NULL || pColor_return == NULL) {
+ return(XcmsFailure);
+ }
+
+ /* setup the CCC to use for the conversions. */
+ memcpy ((char *) &myCCC, (char *) ccc, sizeof(XcmsCCCRec));
+ myCCC.clientWhitePt.format = XcmsUndefinedFormat;
+ myCCC.gamutCompProc = (XcmsCompressionProc) NULL;
+
+ 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 = START_L_STAR;
+ tmp.spec.CIELab.a_star = XCMS_CIEASTAROFHUE(hue, chroma);
+ tmp.spec.CIELab.b_star = XCMS_CIEBSTAROFHUE(hue, chroma);
+ tmp.pixel = pColor_return->pixel;
+ tmp.format = XcmsCIELabFormat;
+
+ /* Step 1: Obtain the maximum L_star and chroma for this hue. */
+ if (_XcmsCIELabQueryMaxLCRGB(&myCCC, hue, &max_lc, &rgb_saved)
+ == XcmsFailure) {
+ return(XcmsFailure);
+ }
+
+ max_chroma = XCMS_CIELAB_PMETRIC_CHROMA(max_lc.spec.CIELab.a_star,
+ max_lc.spec.CIELab.b_star);
+
+ if (max_chroma <= chroma) {
+ /*
+ * If the chroma is greater than the chroma for the
+ * maximum L/chroma point then the L_star is the
+ * the L_star for the maximum L_star/chroma point.
+ * This is an error but I return the best approximation I can.
+ * Thus the inconsistency.
+ */
+ memcpy ((char *) pColor_return, (char *) &max_lc, sizeof (XcmsColor));
+ return(XcmsSuccess);
+ }
+
+ /*
+ * If the chroma is equal to the chroma for the
+ * maximum L_star/chroma point then the L_star is the
+ * the L_star for the maximum L* and chroma point.
+ */
+ /* if (max_chroma == chroma) {
+ * memcpy ((char *) pColor_return, (char *) &max_lc, sizeof (XcmsColor));
+ * return(XcmsSuccess);
+ * }
+ */
+
+ /* must do a bisection here to compute the maximum L* */
+ /* save the structure input so that any elements that */
+ /* are not touched are recopied later in the routine. */
+ nChroma = chroma;
+ tmp_chroma = max_chroma;
+ lastChroma = -1.0;
+ nMaxCount = MAXBISECTCOUNT;
+ rFactor = 1.0;
+
+ for (nCount = 0; nCount < nMaxCount; nCount++) {
+ prevChroma = lastChroma;
+ lastChroma = tmp_chroma;
+ nT = (nChroma - max_chroma) / max_chroma * rFactor;
+ memcpy ((char *)&prev, (char *)&tmp, sizeof(XcmsColor));
+ 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 the return against what is expected */
+ tmp_chroma = XCMS_CIELAB_PMETRIC_CHROMA(tmp.spec.CIELab.a_star,
+ tmp.spec.CIELab.b_star);
+ if (tmp_chroma <= chroma + EPS && tmp_chroma >= chroma - EPS) {
+ /* Found It! */
+ memcpy ((char *) pColor_return, (char *) &tmp, sizeof (XcmsColor));
+ return(XcmsSuccess);
+ }
+ nChroma += chroma - tmp_chroma;
+ if (nChroma > max_chroma) {
+ nChroma = max_chroma;
+ rFactor *= 0.5; /* selective relaxation employed */
+ } else if (nChroma < 0.0) {
+ if (XCMS_FABS(lastChroma - chroma) <
+ XCMS_FABS(tmp_chroma - chroma)) {
+ memcpy ((char *)pColor_return, (char *)&prev,
+ sizeof(XcmsColor));
+ } else {
+ memcpy ((char *)pColor_return, (char *)&tmp,
+ sizeof(XcmsColor));
+ }
+ return(XcmsSuccess);
+ } else if (tmp_chroma <= prevChroma + EPS &&
+ tmp_chroma >= prevChroma - EPS) {
+ rFactor *= 0.5; /* selective relaxation employed */
+ }
+ }
+
+ if (nCount >= nMaxCount) {
+ if (XCMS_FABS(lastChroma - chroma) <
+ XCMS_FABS(tmp_chroma - chroma)) {
+ memcpy ((char *)pColor_return, (char *)&prev,
+ sizeof(XcmsColor));
+ } else {
+ memcpy ((char *)pColor_return, (char *)&tmp,
+ sizeof(XcmsColor));
+ }
+ }
+ memcpy ((char *) pColor_return, (char *) &tmp, sizeof (XcmsColor));
+ return(XcmsSuccess);
+}