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/* $XConsortium: LabMxL.c /main/4 1995/10/24 11:18:46 gildea $ */
/*
* 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
* CIELabMxL.c
*
* DESCRIPTION
* Source for the XcmsCIELabQueryMaxL() gamut boundary
* querying routine.
*
*/
/* $XFree86: xc/lib/X11/LabMxL.c,v 1.2 1999/05/09 10:49:43 dawes Exp $ */
#include "Xlibint.h"
#include "Xcmsint.h"
#include <math.h>
/*
* DEFINES
*/
#define MAXBISECTCOUNT 100
#define EPS (XcmsFloat)0.001
#define START_L_STAR (XcmsFloat)40
/*
* EXTERNS
*/
extern Status _XcmsCIELabQueryMaxLCRGB();
/* CvColW.c */
extern Status _XcmsConvertColorsWithWhitePt();
/************************************************************************
* *
* PUBLIC ROUTINES *
* *
************************************************************************/
/*
* NAME
* XcmsCIELabQueryMaxL - Compute max Lstar for a hue and chroma
*
* SYNOPSIS
*/
Status
XcmsCIELabQueryMaxL(ccc, hue_angle, chroma, pColor_return)
XcmsCCC ccc;
XcmsFloat hue_angle; /* hue 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 = (1.0 - (nChroma / max_chroma)) * rFactor;
memcpy ((char *)&prev, (char *)&tmp, sizeof(XcmsColor));
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;
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);
}
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