modules/lcms/src/cmsgmt.c
author Benjamin Smedberg <benjamin@smedbergs.us>
Tue, 27 May 2008 13:51:53 -0400
changeset 15145 f68cd87e0d10de19925227af59a343d7787167d3
parent 4506 0f1b7da7647bda9d9249298ab0c44d4f4cd22f02
permissions -rw-r--r--
Back out JS-as-C++, because it's a suspect in the Linux performance regression.

//
//  Little cms
//  Copyright (C) 1998-2007 Marti Maria
//
// Permission is hereby granted, free of charge, to any person obtaining 
// a copy of this software and associated documentation files (the "Software"), 
// to deal in the Software without restriction, including without limitation 
// the rights to use, copy, modify, merge, publish, distribute, sublicense, 
// and/or sell copies of the Software, and to permit persons to whom the Software 
// is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO 
// THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


#include "lcms.h"

/*
Gamut check by default is a catching of 0xFFFF/0xFFFF/0xFFFF PCS values, used
internally by lcms to hold invalid values. Matrix LUT's, operates in a way that
unencodeable values are marked as this combination, if PCS is XYZ, this is a very
high value since encoding is a 1.15 fixed point, something like 1.9997, 1.9997, 1.9997
not a very common color after all. Lab PCS is not to be a problem, since L>100 are truely
undefined. There is a posibility than ICC comitee defines L>100 as a valid means
to use highlights, then it will be lost.

(1.10 - Actually ICC did it, so this should be checked for full ICC 4.0 support)

*/


LCMSBOOL _cmsEndPointsBySpace(icColorSpaceSignature Space, WORD **White, WORD **Black,
                            int *nOutputs)
{
       // Only most common spaces

       static WORD RGBblack[4]  = { 0, 0, 0 };
       static WORD RGBwhite[4]  = { 0xffff, 0xffff, 0xffff };
       static WORD CMYKblack[4] = { 0xffff, 0xffff, 0xffff, 0xffff };   // 400% of ink
       static WORD CMYKwhite[4] = { 0, 0, 0, 0 };
       static WORD LABblack[4]  = { 0, 0x8000, 0x8000 };
       static WORD LABwhite[4]  = { 0xFF00, 0x8000, 0x8000 };
       static WORD CMYblack[4]  = { 0xffff, 0xffff, 0xffff };
       static WORD CMYwhite[4]  = { 0, 0, 0 };
       static WORD Grayblack[4] = { 0 };
       static WORD GrayWhite[4] = { 0xffff };

       switch (Space) {

       case icSigGrayData: if (White)    *White = GrayWhite;
                           if (Black)    *Black = Grayblack;
                           if (nOutputs) *nOutputs = 1;
                           return TRUE;
                        
       case icSigRgbData:  if (White)    *White = RGBwhite;
                           if (Black)    *Black = RGBblack;
                           if (nOutputs) *nOutputs = 3;
                           return TRUE;

       case icSigLabData:  if (White)    *White = LABwhite;
                           if (Black)    *Black = LABblack;
                           if (nOutputs) *nOutputs = 3;
                           return TRUE;

       case icSigCmykData: if (White)    *White = CMYKwhite;
                           if (Black)    *Black = CMYKblack;
                           if (nOutputs) *nOutputs = 4;
                           return TRUE;

       case icSigCmyData:  if (White)    *White = CMYwhite;
                           if (Black)    *Black = CMYblack;
                           if (nOutputs) *nOutputs = 3;
                           return TRUE;

       default:;
       }

  return FALSE;
}


WORD *_cmsWhiteBySpace(icColorSpaceSignature Space)
{
       WORD *White= NULL, *Black = NULL;
       int Dummy;
       static WORD Default[MAXCHANNELS];

       if (_cmsEndPointsBySpace(Space, &White, &Black, &Dummy))
              return White;

       return Default;

}




WORD Clamp_L(Fixed32 in)
{
       if (in == 0xFFFF) return 0xFFFFU;  // Marker

       if (in > 0xFF00) return 0xFF00U;  // L* = 100.0
       return (WORD) in;
}


#define ENCODE_AB(x) (WORD) (((x) + 128.0) * 256.0 + 0.5)

WORD Clamp_ab(Fixed32 in)
{
       if (in == 0xFFFF) return 0xFFFFU;             // Marker

       if (in < 0) return ENCODE_AB(-128.0);         // Max negative number
       if (in > 0xFFFF) return ENCODE_AB(+127.9961); // Max positive number
       return (WORD) in;
}



// Returns dE on two Lab values

double LCMSEXPORT cmsDeltaE(LPcmsCIELab Lab1, LPcmsCIELab Lab2)
{
        double dL, da, db;
        
        if (Lab1 -> L < 0 ||
            Lab2 -> L < 0) return 65536.;

        if (Lab1 -> a < -200 || Lab1 -> a > 200) return 65536.;
        if (Lab1 -> b < -200 || Lab1 -> b > 200) return 65536.;

        if (Lab2 -> a < -200 || Lab2 -> a > 200) return 65536.;
        if (Lab2 -> b < -200 || Lab2 -> b > 200) return 65536.;

        if (Lab1 ->L == 0 && Lab2 ->L == 0) return 0;
        
        dL = fabs(Lab1 -> L - Lab2 -> L);
        da = fabs(Lab1 -> a - Lab2 -> a);
        db = fabs(Lab1 -> b - Lab2 -> b);

        return pow(dL*dL + da * da + db * db, 0.5);

}


// Square
static
double Sqr(double v)
{
    return v *  v; 
}

// Return the CIE94 Delta E 
double LCMSEXPORT cmsCIE94DeltaE(LPcmsCIELab Lab1, LPcmsCIELab Lab2)
{
    cmsCIELCh LCh1, LCh2;
    double dE, dL, dC, dh, dhsq;
    double c12, sc, sh;

    if (Lab1 ->L == 0 && Lab2 ->L == 0) return 0;

    dL = fabs(Lab1 ->L - Lab2 ->L);

    cmsLab2LCh(&LCh1, Lab1);
    cmsLab2LCh(&LCh2, Lab2);

    dC  = fabs(LCh1.C - LCh2.C);
    dE  = cmsDeltaE(Lab1, Lab2);
    
    dhsq = Sqr(dE) - Sqr(dL) - Sqr(dC);
    if (dhsq < 0)
        dh = 0;
    else
        dh = pow(dhsq, 0.5);

    c12 = sqrt(LCh1.C * LCh2.C);

    sc = 1.0 + (0.048 * c12);
    sh = 1.0 + (0.014 * c12);
            
    return sqrt(Sqr(dL)  + Sqr(dC) / Sqr(sc) + Sqr(dh) / Sqr(sh));
}


// Auxiliary

static
double ComputeLBFD(LPcmsCIELab Lab)
{
  double yt;

  if (Lab->L > 7.996969)
        yt = (Sqr((Lab->L+16)/116)*((Lab->L+16)/116))*100;
  else
        yt = 100 * (Lab->L / 903.3);

  return (54.6 * (LOGE * (log(yt + 1.5))) - 9.6);
}



// bfd - gets BFD(1:1) difference between Lab1, Lab2
double LCMSEXPORT cmsBFDdeltaE(LPcmsCIELab Lab1, LPcmsCIELab Lab2)
{
    double lbfd1,lbfd2,AveC,Aveh,dE,deltaL,
        deltaC,deltah,dc,t,g,dh,rh,rc,rt,bfd;
    cmsCIELCh LCh1, LCh2;
    
    
    if (Lab1 ->L == 0 && Lab2 ->L == 0) return 0;
    
    lbfd1 = ComputeLBFD(Lab1);
    lbfd2 = ComputeLBFD(Lab2);
    deltaL = lbfd2 - lbfd1;
    
    cmsLab2LCh(&LCh1, Lab1);
    cmsLab2LCh(&LCh2, Lab2);
    
    deltaC = LCh2.C - LCh1.C;
    AveC = (LCh1.C+LCh2.C)/2;
    Aveh = (LCh1.h+LCh2.h)/2;
    
    dE = cmsDeltaE(Lab1, Lab2);
    
    if (Sqr(dE)>(Sqr(Lab2->L-Lab1->L)+Sqr(deltaC)))
        deltah = sqrt(Sqr(dE)-Sqr(Lab2->L-Lab1->L)-Sqr(deltaC));
    else
        deltah =0;
    
    
    dc   = 0.035 * AveC / (1 + 0.00365 * AveC)+0.521;
    g    = sqrt(Sqr(Sqr(AveC))/(Sqr(Sqr(AveC))+14000));
    t    = 0.627+(0.055*cos((Aveh-254)/(180/M_PI))-       
        0.040*cos((2*Aveh-136)/(180/M_PI))+
        0.070*cos((3*Aveh-31)/(180/M_PI))+
        0.049*cos((4*Aveh+114)/(180/M_PI))-
        0.015*cos((5*Aveh-103)/(180/M_PI)));
    
    dh    = dc*(g*t+1-g);
    rh    = -0.260*cos((Aveh-308)/(180/M_PI))-
        0.379*cos((2*Aveh-160)/(180/M_PI))-
        0.636*cos((3*Aveh+254)/(180/M_PI))+
        0.226*cos((4*Aveh+140)/(180/M_PI))-
        0.194*cos((5*Aveh+280)/(180/M_PI));
    
    rc = sqrt((AveC*AveC*AveC*AveC*AveC*AveC)/((AveC*AveC*AveC*AveC*AveC*AveC)+70000000));
    rt = rh*rc;
    
    bfd = sqrt(Sqr(deltaL)+Sqr(deltaC/dc)+Sqr(deltah/dh)+(rt*(deltaC/dc)*(deltah/dh)));
    
    return bfd;
}


//  cmc - CMC(1:1) difference between Lab1, Lab2
double LCMSEXPORT cmsCMCdeltaE(LPcmsCIELab Lab1, LPcmsCIELab Lab2)
{
  double dE,dL,dC,dh,sl,sc,sh,t,f,cmc;
  cmsCIELCh LCh1, LCh2;

  if (Lab1 ->L == 0 && Lab2 ->L == 0) return 0;

  cmsLab2LCh(&LCh1, Lab1);
  cmsLab2LCh(&LCh2, Lab2);

  
  dL = Lab2->L-Lab1->L;
  dC = LCh2.C-LCh1.C;

  dE = cmsDeltaE(Lab1, Lab2);
  if (Sqr(dE)>(Sqr(dL)+Sqr(dC))) 
            dh = sqrt(Sqr(dE)-Sqr(dL)-Sqr(dC));
  else
            dh =0;

  if ((LCh1.h > 164) && (LCh1.h<345)) 
      t = 0.56 + fabs(0.2 * cos(((LCh1.h + 168)/(180/M_PI))));
  else 
      t = 0.36 + fabs(0.4 * cos(((LCh1.h + 35 )/(180/M_PI))));

   sc  = 0.0638   * LCh1.C / (1 + 0.0131  * LCh1.C) + 0.638;
   sl  = 0.040975 * Lab1->L /(1 + 0.01765 * Lab1->L);
   
   if (Lab1->L<16)
         sl = 0.511; 

   f   = sqrt((LCh1.C * LCh1.C * LCh1.C * LCh1.C)/((LCh1.C * LCh1.C * LCh1.C * LCh1.C)+1900));
   sh  = sc*(t*f+1-f);
   cmc = sqrt(Sqr(dL/sl)+Sqr(dC/sc)+Sqr(dh/sh));

   return cmc;
}



static
double atan2deg(double b, double a)
{
   double h;

   if (a == 0 && b == 0)
            h   = 0;
    else
            h = atan2(a, b);
   
    h *= (180. / M_PI);
    
    while (h > 360.)         
        h -= 360.;
    
    while ( h < 0)
        h += 360.;
    
    return h;

}


static
double RADIANES(double deg)
{
    return (deg * M_PI) / 180.;
}


// dE2000 The weightings KL, KC and KH can be modified to reflect the relative 
// importance of lightness, chroma and hue in different industrial applications

double LCMSEXPORT cmsCIE2000DeltaE(LPcmsCIELab Lab1, LPcmsCIELab Lab2,
                                  double Kl, double Kc, double Kh)
{
    double L1  = Lab1->L;
    double a1  = Lab1->a;
    double b1  = Lab1->b;
    double C   = sqrt( Sqr(a1) + Sqr(b1) );

    double Ls = Lab2 ->L;
    double as = Lab2 ->a;
    double bs = Lab2 ->b;
    double Cs = sqrt( Sqr(as) + Sqr(bs) );

    double G = 0.5 * ( 1 - sqrt(pow((C + Cs) / 2 , 7.0) / (pow((C + Cs) / 2, 7.0) + pow(25.0, 7.0) ) ));

    double a_p = (1 + G ) * a1;
    double b_p = b1;
    double C_p = sqrt( Sqr(a_p) + Sqr(b_p));
    double h_p = atan2deg(a_p, b_p); 
                

    double a_ps = (1 + G) * as;
    double b_ps = bs;
    double C_ps = sqrt(Sqr(a_ps) + Sqr(b_ps));
    double h_ps = atan2deg(a_ps, b_ps);
              
    double meanC_p =(C_p + C_ps) / 2;

    double hps_plus_hp  = h_ps + h_p;
    double hps_minus_hp = h_ps - h_p;

    double meanh_p = fabs(hps_minus_hp) <= 180.000001 ? (hps_plus_hp)/2 : 
                            (hps_plus_hp) < 360 ? (hps_plus_hp + 360)/2 : 
                                                 (hps_plus_hp - 360)/2;

    double delta_h = (hps_minus_hp) <= -180.000001 ?  (hps_minus_hp + 360) :
                            (hps_minus_hp) > 180 ? (hps_minus_hp - 360) : 
                                                    (hps_minus_hp);
    double delta_L = (Ls - L1);
    double delta_C = (C_ps - C_p );


    double delta_H =2 * sqrt(C_ps*C_p) * sin(RADIANES(delta_h) / 2);

    double T = 1 - 0.17 * cos(RADIANES(meanh_p-30)) 
                 + 0.24 * cos(RADIANES(2*meanh_p))  
                 + 0.32 * cos(RADIANES(3*meanh_p + 6)) 
                 - 0.2  * cos(RADIANES(4*meanh_p - 63));

    double Sl = 1 + (0.015 * Sqr((Ls + L1) /2- 50) )/ sqrt(20 + Sqr( (Ls+L1)/2 - 50) );

    double Sc = 1 + 0.045 * (C_p + C_ps)/2;
    double Sh = 1 + 0.015 * ((C_ps + C_p)/2) * T;

    double delta_ro = 30 * exp( -Sqr(((meanh_p - 275 ) / 25)));

    double Rc = 2 * sqrt(( pow(meanC_p, 7.0) )/( pow(meanC_p, 7.0) + pow(25.0, 7.0)));

    double Rt = -sin(2 * RADIANES(delta_ro)) * Rc;

    double deltaE00 = sqrt( Sqr(delta_L /(Sl * Kl)) + 
                            Sqr(delta_C/(Sc * Kc))  + 
                            Sqr(delta_H/(Sh * Kh))  + 
                            Rt*(delta_C/(Sc * Kc)) * (delta_H / (Sh * Kh)));

    return deltaE00;
}

   

// Carefully,  clamp on CIELab space.

void LCMSEXPORT cmsClampLab(LPcmsCIELab Lab, double amax, double amin,
                                   double bmax, double bmin)
{

            // Whole Luma surface to zero

        if (Lab -> L < 0) {

                Lab-> L = Lab->a = Lab-> b = 0.0;
                return;
            }

            // Clamp white, DISCARD HIGHLIGHTS. This is done
            // in such way because icc spec doesn't allow the
            // use of L>100 as a highlight means.

            if (Lab->L > 100)
                        Lab -> L = 100;

            // Check out gamut prism, on a, b faces

            if (Lab -> a < amin || Lab->a > amax||
                Lab -> b < bmin || Lab->b > bmax) {

                 cmsCIELCh LCh;
                 double h, slope;

                 // Falls outside a, b limits. Transports to LCh space,
                 // and then do the clipping


                 if (Lab -> a == 0.0) { // Is hue exactly 90?

                        // atan will not work, so clamp here
                        Lab -> b = Lab->b < 0 ? bmin : bmax;
                        return;
                 }

                 cmsLab2LCh(&LCh, Lab);

                 slope = Lab -> b / Lab -> a;
                 h = LCh.h;

                 // There are 4 zones

                 if ((h >= 0. && h < 45.) ||
                     (h >= 315 && h <= 360.)) {

                     // clip by amax
                     Lab -> a = amax;
                     Lab -> b = amax * slope;
                 }
                 else
                 if (h >= 45. && h < 135)
                 {
                        // clip by bmax
                        Lab -> b = bmax;
                        Lab -> a = bmax / slope;
                 }
                 else
                 if (h >= 135 && h < 225) {
                        // clip by amin
                        Lab -> a = amin;
                        Lab -> b = amin * slope;

                 }
                 else
                 if (h >= 225 && h < 315) {
                        // clip by bmin
                        Lab -> b = bmin;
                        Lab -> a = bmin / slope;
                 }
                 else
                        cmsSignalError(LCMS_ERRC_ABORTED, "Invalid angle");

        }
}

// Several utilities -------------------------------------------------------

// Translate from our colorspace to ICC representation

icColorSpaceSignature LCMSEXPORT _cmsICCcolorSpace(int OurNotation)
{
       switch (OurNotation) {

       case 1:
       case PT_GRAY: return  icSigGrayData;

       case 2:
       case PT_RGB:  return  icSigRgbData;

       case PT_CMY:  return  icSigCmyData;
       case PT_CMYK: return  icSigCmykData;
       case PT_YCbCr:return  icSigYCbCrData;
       case PT_YUV:  return  icSigLuvData;
       case PT_XYZ:  return  icSigXYZData;
       case PT_Lab:  return  icSigLabData;
       case PT_YUVK: return  icSigLuvKData;
       case PT_HSV:  return  icSigHsvData;
       case PT_HLS:  return  icSigHlsData;
       case PT_Yxy:  return  icSigYxyData;
       case PT_HiFi: return  icSigHexachromeData;
       case PT_HiFi7: return icSigHeptachromeData;
       case PT_HiFi8: return icSigOctachromeData;

       case PT_HiFi9:  return icSigMCH9Data;
       case PT_HiFi10: return icSigMCHAData;
       case PT_HiFi11: return icSigMCHBData;
       case PT_HiFi12: return icSigMCHCData;
       case PT_HiFi13: return icSigMCHDData;
       case PT_HiFi14: return icSigMCHEData;
       case PT_HiFi15: return icSigMCHFData;

       default:  return icMaxEnumData;
       }
}


int LCMSEXPORT _cmsLCMScolorSpace(icColorSpaceSignature ProfileSpace)
{    
    switch (ProfileSpace) {
        
    case icSigGrayData: return  PT_GRAY;
    case icSigRgbData:  return  PT_RGB;
    case icSigCmyData:  return  PT_CMY;
    case icSigCmykData: return  PT_CMYK;
    case icSigYCbCrData:return  PT_YCbCr;
    case icSigLuvData:  return  PT_YUV;
    case icSigXYZData:  return  PT_XYZ;
    case icSigLabData:  return  PT_Lab;
    case icSigLuvKData: return  PT_YUVK;
    case icSigHsvData:  return  PT_HSV;
    case icSigHlsData:  return  PT_HLS;
    case icSigYxyData:  return  PT_Yxy;
        
    case icSig6colorData:
    case icSigHexachromeData: return PT_HiFi;
        
    case icSigHeptachromeData:
    case icSig7colorData:     return PT_HiFi7;
        
    case icSigOctachromeData:
    case icSig8colorData:     return PT_HiFi8;
        
    case icSigMCH9Data:
    case icSig9colorData:     return PT_HiFi9;
        
    case icSigMCHAData:
    case icSig10colorData:     return PT_HiFi10;
        
    case icSigMCHBData:
    case icSig11colorData:     return PT_HiFi11;
        
    case icSigMCHCData:
    case icSig12colorData:     return PT_HiFi12;
        
    case icSigMCHDData:
    case icSig13colorData:     return PT_HiFi13;
        
    case icSigMCHEData:
    case icSig14colorData:     return PT_HiFi14;
        
    case icSigMCHFData:
    case icSig15colorData:     return PT_HiFi15;
                
    default:  return icMaxEnumData;
    }
}


int LCMSEXPORT _cmsChannelsOf(icColorSpaceSignature ColorSpace)
{

    switch (ColorSpace) {

    case icSigGrayData: return 1;

    case icSig2colorData:  return 2;
        
    case icSigXYZData:
    case icSigLabData:
    case icSigLuvData:
    case icSigYCbCrData:
    case icSigYxyData:
    case icSigRgbData:   
    case icSigHsvData:
    case icSigHlsData:
    case icSigCmyData: 
    case icSig3colorData:  return 3;
                   
    case icSigLuvKData:
    case icSigCmykData:
    case icSig4colorData:  return 4;

    case icSigMCH5Data:
    case icSig5colorData:  return 5;  

    case icSigHexachromeData:   
    case icSig6colorData:  return 6;
        
    case icSigHeptachromeData:
    case icSig7colorData:  return  7;

    case icSigOctachromeData:
    case icSig8colorData:  return  8;

    case icSigMCH9Data:
    case icSig9colorData:  return  9;

    case icSigMCHAData:
    case icSig10colorData: return 10;

    case icSigMCHBData:
    case icSig11colorData: return 11;
    
    case icSigMCHCData:
    case icSig12colorData: return 12;

    case icSigMCHDData:
    case icSig13colorData: return 13;

    case icSigMCHEData:
    case icSig14colorData: return 14;

    case icSigMCHFData:
    case icSig15colorData: return 15;

    default: return 3;
    }

}


// v2 L=100 is supposed to be placed on 0xFF00. There is no reasonable 
// number of gridpoints that would make exact match. However, a 
// prelinearization of 258 entries, would map 0xFF00 on entry 257. 
// This is almost what we need, unfortunately, the rest of entries 
// should be scaled by (255*257/256) and this is not exact.
// 
// An intermediate solution would be to use 257 entries. This does not
// map 0xFF00 exactly on a node, but so close that the dE induced is
// negligible. AND the rest of curve is exact.

static
void CreateLabPrelinearization(LPGAMMATABLE LabTable[])
{
    int i;

    LabTable[0] = cmsAllocGamma(257);
    LabTable[1] = cmsBuildGamma(257, 1.0);
    LabTable[2] = cmsBuildGamma(257, 1.0);

    // L* uses 257 entries. Entry 256 holds 0xFFFF, so, the effective range
    // is 0..0xFF00. Last entry (257) is also collapsed to 0xFFFF

    // From 0 to 0xFF00
    for (i=0; i < 256; i++) 
        LabTable[0]->GammaTable[i] = RGB_8_TO_16(i);

    // Repeat last for 0xFFFF
    LabTable[0] ->GammaTable[256] = 0xFFFF;        
}


// Used by gamut & softproofing

typedef struct {

    cmsHTRANSFORM hInput;               // From whatever input color space. NULL for Lab
    cmsHTRANSFORM hForward, hReverse;   // Transforms going from Lab to colorant and back
    double Thereshold;                  // The thereshold after which is considered out of gamut
    
    } GAMUTCHAIN,FAR* LPGAMUTCHAIN;

// This sampler does compute gamut boundaries by comparing original
// values with a transform going back and forth. Values above ERR_THERESHOLD 
// of maximum are considered out of gamut.


#define ERR_THERESHOLD      5 


static
int GamutSampler(register WORD In[], register WORD Out[], register LPVOID Cargo)
{
    LPGAMUTCHAIN t = (LPGAMUTCHAIN) Cargo;
    WORD Proof[MAXCHANNELS], Check[MAXCHANNELS];
    WORD Proof2[MAXCHANNELS], Check2[MAXCHANNELS];
    cmsCIELab LabIn1, LabOut1;  
    cmsCIELab LabIn2, LabOut2;  
    double dE1, dE2, ErrorRatio;
    
    // Assume in-gamut by default.
    dE1 = 0.;
    dE2 = 0;
    ErrorRatio = 1.0;
    

    // Any input space? I can use In[] no matter channels 
    // because is just one pixel

    if (t -> hInput != NULL) cmsDoTransform(t -> hInput, In, In, 1);

    // converts from PCS to colorant. This always
    // does return in-gamut values, 
    cmsDoTransform(t -> hForward, In, Proof, 1);
    
    // Now, do the inverse, from colorant to PCS.
    cmsDoTransform(t -> hReverse, Proof, Check, 1);
    
    
    // Try again, but this time taking Check as input
    cmsDoTransform(t -> hForward, Check, Proof2,  1);
    cmsDoTransform(t -> hReverse, Proof2, Check2, 1);
    
    
    
    // Does the transform returns out-of-gamut?
    if (Check[0] == 0xFFFF && 
        Check[1] == 0xFFFF && 
        Check[2] == 0xFFFF) 
        
        Out[0] = 0xFF00;            // Out of gamut!
    else {
        
        // Transport encoded values
        cmsLabEncoded2Float(&LabIn1,  In);
        cmsLabEncoded2Float(&LabOut1, Check);
        
        // Take difference of direct value
        dE1 = cmsDeltaE(&LabIn1, &LabOut1);        
                
        cmsLabEncoded2Float(&LabIn2,  Check);
        cmsLabEncoded2Float(&LabOut2, Check2);
        
        // Take difference of converted value
        dE2 = cmsDeltaE(&LabIn2, &LabOut2);                 
               
        
        // if dE1 is small and dE2 is small, value is likely to be in gamut
        if (dE1 < t->Thereshold && dE2 < t->Thereshold) 
            Out[0] = 0;
        else
            // if dE1 is small and dE2 is big, undefined. Assume in gamut
            if (dE1 < t->Thereshold && dE2 > t->Thereshold)
                Out[0] = 0;
            else
                // dE1 is big and dE2 is small, clearly out of gamut
                if (dE1 > t->Thereshold && dE2 < t->Thereshold)
                    Out[0] = (WORD) _cmsQuickFloor((dE1 - t->Thereshold) + .5);
                else  {
                    
                    // dE1 is big and dE2 is also big, could be due to perceptual mapping
                    // so take error ratio
                    if (dE2 == 0.0)
                        ErrorRatio = dE1;
                    else
                        ErrorRatio = dE1 / dE2;
                    
                    if (ErrorRatio > t->Thereshold) 
                        Out[0] = (WORD)  _cmsQuickFloor((ErrorRatio - t->Thereshold) + .5);
                    else
                        Out[0] = 0;
                }
            
    }    
    
    return TRUE;
}


// Does compute a gamut LUT going back and forth across 
// pcs -> relativ. colorimetric intent -> pcs
// the dE obtained is then annotated on the LUT.
// values truely out of gamut, are clipped to dE = 0xFFFE
// and values changed are supposed to be handled by
// any gamut remapping, so, are out of gamut as well.
//
// **WARNING: This algorithm does assume that gamut
// remapping algorithms does NOT move in-gamut colors,
// of course, many perceptual and saturation intents does
// not work in such way, but relativ. ones should.

static
LPLUT ComputeGamutWithInput(cmsHPROFILE hInput, cmsHPROFILE hProfile, int Intent)
{
    cmsHPROFILE hLab;
    LPLUT Gamut;
    DWORD dwFormat;
    GAMUTCHAIN Chain;
    int nErrState, nChannels, nGridpoints;
    LPGAMMATABLE Trans[3];
    icColorSpaceSignature ColorSpace;
            
    
    ZeroMemory(&Chain, sizeof(GAMUTCHAIN)); 
       
    hLab = cmsCreateLabProfile(NULL);
    
    // Safeguard against early abortion
    nErrState = cmsErrorAction(LCMS_ERROR_IGNORE);

    // The figure of merit. On matrix-shaper profiles, should be almost zero as
    // the conversion is pretty exact. On LUT based profiles, different resolutions
    // of input and output CLUT may result in differences. 

    if (!cmsIsIntentSupported(hProfile, Intent, LCMS_USED_AS_INPUT) &&
        !cmsIsIntentSupported(hProfile, Intent, LCMS_USED_AS_OUTPUT))

        Chain.Thereshold = 1.0;
    else
        Chain.Thereshold = ERR_THERESHOLD;
   
    ColorSpace  = cmsGetColorSpace(hProfile);  

    // If input profile specified, create a transform from such profile to Lab
    if (hInput != NULL) {
          
        nChannels   = _cmsChannelsOf(ColorSpace);     
        nGridpoints = _cmsReasonableGridpointsByColorspace(ColorSpace, cmsFLAGS_HIGHRESPRECALC);
        dwFormat    = (CHANNELS_SH(nChannels)|BYTES_SH(2));

        Chain.hInput = cmsCreateTransform(hInput, dwFormat, 
                                          hLab,   TYPE_Lab_16, 
                                          Intent, 
                                          cmsFLAGS_NOTPRECALC);
    }
    else  {
        // Input transform=NULL (Lab) Used to compute the gamut tag
        // This table will take 53 points to give some accurancy, 
        // 53 * 53 * 53 * 2 = 291K

        nChannels    = 3;      // For Lab
        nGridpoints  = 53;
        Chain.hInput = NULL;
        dwFormat = (CHANNELS_SH(_cmsChannelsOf(ColorSpace))|BYTES_SH(2)); 
    }

   
    // Does create the forward step
    Chain.hForward = cmsCreateTransform(hLab, TYPE_Lab_16, 
                                        hProfile, dwFormat, 
                                        INTENT_RELATIVE_COLORIMETRIC,
                                        cmsFLAGS_NOTPRECALC);

    // Does create the backwards step
    Chain.hReverse = cmsCreateTransform(hProfile, dwFormat, 
                                        hLab, TYPE_Lab_16,                                      
                                        INTENT_RELATIVE_COLORIMETRIC,
                                        cmsFLAGS_NOTPRECALC);

    // Restores error handler previous state
    cmsErrorAction(nErrState);

   
    // All ok?
    if (Chain.hForward && Chain.hReverse) {
           
    // Go on, try to compute gamut LUT from PCS.
    // This consist on a single channel containing 
    // dE when doing a transform back and forth on
    // the colorimetric intent. 

    Gamut = cmsAllocLUT();
    Gamut = cmsAlloc3DGrid(Gamut, nGridpoints, nChannels, 1);
     
    // If no input, then this is a gamut tag operated by Lab,
    // so include pertinent prelinearization
    if (hInput == NULL) {
       
        CreateLabPrelinearization(Trans);               
        cmsAllocLinearTable(Gamut, Trans, 1);              
        cmsFreeGammaTriple(Trans);
    }

   
    cmsSample3DGrid(Gamut, GamutSampler, (LPVOID) &Chain, Gamut ->wFlags);          
    }
    else 
        Gamut = NULL;   // Didn't work...

    // Free all needed stuff.
    if (Chain.hInput)   cmsDeleteTransform(Chain.hInput);
    if (Chain.hForward) cmsDeleteTransform(Chain.hForward);
    if (Chain.hReverse) cmsDeleteTransform(Chain.hReverse);

    cmsCloseProfile(hLab);
    
    // And return computed hull
    return Gamut;
}


// Wrapper

LPLUT _cmsComputeGamutLUT(cmsHPROFILE hProfile, int Intent)
{    
    return ComputeGamutWithInput(NULL, hProfile, Intent);
}


// This routine does compute the gamut check CLUT. This CLUT goes from whatever 
// input space to the 0 or != 0 gamut check.

LPLUT _cmsPrecalculateGamutCheck(cmsHTRANSFORM h)
{
       _LPcmsTRANSFORM p = (_LPcmsTRANSFORM) h;
       
       return ComputeGamutWithInput(p->InputProfile, p ->PreviewProfile, p->Intent);
}


// SoftProofing. Convert from Lab to device, then back to Lab, 
// any gamut remapping is applied

static
int SoftProofSampler(register WORD In[], register WORD Out[], register LPVOID Cargo)
{
        LPGAMUTCHAIN t = (LPGAMUTCHAIN) Cargo;
        WORD Colorant[MAXCHANNELS];
                
        // From pcs to colorant
        cmsDoTransform(t -> hForward, In, Colorant, 1);

        // Now, do the inverse, from colorant to pcs.
        cmsDoTransform(t -> hReverse, Colorant, Out, 1);
                
        return TRUE;
}

// Does return Softproofing LUT on desired intent

LPLUT _cmsComputeSoftProofLUT(cmsHPROFILE hProfile, int nIntent)
{
    cmsHPROFILE hLab;
    LPLUT SoftProof;
    DWORD dwFormat;
    GAMUTCHAIN Chain;
    int nErrState;
    LPGAMMATABLE Trans[3];
        

    // LUTs are never abs. colorimetric, is the transform who
    // is responsible of generating white point displacement
    if (nIntent == INTENT_ABSOLUTE_COLORIMETRIC)
        nIntent = INTENT_RELATIVE_COLORIMETRIC;

    ZeroMemory(&Chain, sizeof(GAMUTCHAIN));

    hLab = cmsCreateLabProfile(NULL);

    // ONLY 4 channels  
    dwFormat = (CHANNELS_SH(4)|BYTES_SH(2));
    
    // Safeguard against early abortion
    nErrState = cmsErrorAction(LCMS_ERROR_IGNORE);

    // Does create the first step
    Chain.hForward = cmsCreateTransform(hLab, TYPE_Lab_16, 
                                        hProfile, dwFormat, 
                                        nIntent,
                                        cmsFLAGS_NOTPRECALC);

    // Does create the last step
    Chain.hReverse = cmsCreateTransform(hProfile, dwFormat, 
                                        hLab, TYPE_Lab_16,                                      
                                        INTENT_RELATIVE_COLORIMETRIC, 
                                        cmsFLAGS_NOTPRECALC);

    // Restores error handler previous state
    cmsErrorAction(nErrState);

    // All ok?
    if (Chain.hForward && Chain.hReverse) {
                
    // This is Lab -> Lab, so 33 point should hold anything
    SoftProof = cmsAllocLUT();
    SoftProof = cmsAlloc3DGrid(SoftProof, 33, 3, 3);

    CreateLabPrelinearization(Trans);
    cmsAllocLinearTable(SoftProof, Trans, 1);
    cmsFreeGammaTriple(Trans);

    cmsSample3DGrid(SoftProof, SoftProofSampler, (LPVOID) &Chain, SoftProof->wFlags);
    }
    else 
        SoftProof = NULL;   // Didn't work...

    // Free all needed stuff.
    if (Chain.hForward) cmsDeleteTransform(Chain.hForward);
    if (Chain.hReverse) cmsDeleteTransform(Chain.hReverse);

    cmsCloseProfile(hLab);

    return SoftProof;
}


static
int MostlyLinear(WORD Table[], int nEntries)
{
       register int i;
       int diff;

       for (i=5; i < nEntries; i++) {

           diff = abs((int) Table[i] - (int) _cmsQuantizeVal(i, nEntries));              
           if (diff > 0x0300)
                     return 0;
       }

       return 1;
}


static
void SlopeLimiting(WORD Table[], int nEntries)
{
    int At = (int) floor((double) nEntries * 0.02 + 0.5);   // Cutoff at 2%
    double Val, Slope;
    int i;

    Val   = Table[At];
    Slope = Val / At;

    for (i=0; i < At; i++)
        Table[i] = (WORD) floor(i * Slope + 0.5);

}


// Check for monotonicity.

static
LCMSBOOL IsMonotonic(LPGAMMATABLE t)
{
    int n = t -> nEntries;
    int i, last;

    last = t ->GammaTable[n-1];

    for (i = n-2; i >= 0; --i) {
        
        if (t ->GammaTable[i] > last)

               return FALSE;
        else
                last = t ->GammaTable[i];

    }

    return TRUE;
}

// Check for endpoints

static
LCMSBOOL HasProperEndpoints(LPGAMMATABLE t)
{
    if (t ->GammaTable[0] != 0) return FALSE;
    if (t ->GammaTable[t ->nEntries-1] != 0xFFFF) return FALSE;

    return TRUE;
}



#define PRELINEARIZATION_POINTS 4096

// Fixes the gamma balancing of transform. Thanks to Mike Chaney
// for pointing this subtle bug.

void _cmsComputePrelinearizationTablesFromXFORM(cmsHTRANSFORM h[], int nTransforms, LPLUT Grid)
{
    LPGAMMATABLE Trans[MAXCHANNELS];
    unsigned int t, i, v;  
    int j;
    WORD In[MAXCHANNELS], Out[MAXCHANNELS];
    LCMSBOOL lIsSuitable;
    _LPcmsTRANSFORM InputXForm   = (_LPcmsTRANSFORM) h[0];   
    _LPcmsTRANSFORM OutputXForm  = (_LPcmsTRANSFORM) h[nTransforms-1];   

    
    // First space is *Lab, use our specialized curves for v2 Lab
    
    if (InputXForm ->EntryColorSpace == icSigLabData && 
        OutputXForm->ExitColorSpace != icSigLabData) {
    
                CreateLabPrelinearization(Trans);
                cmsAllocLinearTable(Grid, Trans, 1);
                cmsFreeGammaTriple(Trans);
                return;
    }
              

    // Do nothing on all but Gray/RGB to Gray/RGB transforms

    if (((InputXForm ->EntryColorSpace != icSigRgbData) && (InputXForm ->EntryColorSpace != icSigGrayData)) || 
        ((OutputXForm->ExitColorSpace  != icSigRgbData) && (OutputXForm->ExitColorSpace  != icSigGrayData))) return;
    

    for (t = 0; t < Grid -> InputChan; t++) 
            Trans[t] = cmsAllocGamma(PRELINEARIZATION_POINTS);

    for (i=0; i < PRELINEARIZATION_POINTS; i++) {

                v = _cmsQuantizeVal(i, PRELINEARIZATION_POINTS);

                for (t=0; t < Grid -> InputChan; t++)
                        In[t] = (WORD) v;

                cmsDoTransform(h[0], In, Out, 1);
                for (j=1; j < nTransforms; j++)
                        cmsDoTransform(h[j], Out, Out, 1);

                for (t=0; t < Grid -> InputChan; t++)
                        Trans[t] ->GammaTable[i] = Out[t];

    }
    

    // Check transfer curves
    lIsSuitable = TRUE;
    for (t=0; (lIsSuitable && (t < Grid->InputChan)); t++) {

    
        // Exclude if already linear
        if (MostlyLinear(Trans[t]->GammaTable, PRELINEARIZATION_POINTS))
                    lIsSuitable = FALSE;

        // Exclude if non-monotonic
        if (!IsMonotonic(Trans[t]))
                    lIsSuitable = FALSE;        
        
        // Exclude if weird endpoints
        if (!HasProperEndpoints(Trans[t]))
                    lIsSuitable = FALSE;

        /*
        // Exclude if transfer function is not smooth enough
        // to be modelled as a gamma function, or the gamma is reversed
        
        if (cmsEstimateGamma(Trans[t]) < 1.0)
                    lIsSuitable = FALSE;
        */
              
    }

    if (lIsSuitable) {
    
            for (t = 0; t < Grid ->InputChan; t++) 
                SlopeLimiting(Trans[t]->GammaTable, Trans[t]->nEntries);
    }
      
    if (lIsSuitable) cmsAllocLinearTable(Grid, Trans, 1);


    for (t = 0; t < Grid ->InputChan; t++) 
                        cmsFreeGamma(Trans[t]);

    
}


// Compute K -> L* relationship. Flags may include black point compensation. In this case, 
// the relationship is assumed from the profile with BPC to a black point zero.
static
LPGAMMATABLE ComputeKToLstar(cmsHPROFILE hProfile, int nPoints, int Intent, DWORD dwFlags)
{
    LPGAMMATABLE out;   
    int i;
    WORD cmyk[4], wLab[3];
    cmsHPROFILE   hLab  = cmsCreateLabProfile(NULL);
    cmsHTRANSFORM xform = cmsCreateTransform(hProfile, TYPE_CMYK_16,
                                             hLab, TYPE_Lab_16, 
                                             Intent, (dwFlags|cmsFLAGS_NOTPRECALC));


    out = cmsAllocGamma(nPoints);
    for (i=0; i < nPoints; i++) {

        cmyk[0] = 0;
        cmyk[1] = 0;
        cmyk[2] = 0;
        cmyk[3] = _cmsQuantizeVal(i, nPoints);

        cmsDoTransform(xform, cmyk, wLab, 1);
        out->GammaTable[i] = (WORD) (0xFFFF - wLab[0]);
    }

    cmsDeleteTransform(xform);
    cmsCloseProfile(hLab);

    return out;
}



// Compute Black tone curve on a CMYK -> CMYK transform. This is done by
// using the proof direction on both profiles to find K->L* relationship
// then joining both curves. dwFlags may include black point compensation.

LPGAMMATABLE _cmsBuildKToneCurve(cmsHTRANSFORM hCMYK2CMYK, int nPoints)
{
    LPGAMMATABLE in, out;   
    LPGAMMATABLE KTone; 
    _LPcmsTRANSFORM p = (_LPcmsTRANSFORM) hCMYK2CMYK;


    // Make sure CMYK -> CMYK
    if (p -> EntryColorSpace != icSigCmykData ||
        p -> ExitColorSpace  != icSigCmykData) return NULL;

    // Create individual curves. BPC works also as each K to L* is
    // computed as a BPC to zero black point in case of L*
    in  = ComputeKToLstar(p ->InputProfile,  nPoints, p->Intent, p -> dwOriginalFlags);
    out = ComputeKToLstar(p ->OutputProfile, nPoints, p->Intent, p -> dwOriginalFlags);

    // Build the relationship
    KTone = cmsJoinGamma(in, out);
            
    cmsFreeGamma(in); cmsFreeGamma(out);

    // Make sure it is monotonic
    
    if (!IsMonotonic(KTone)) {

        cmsFreeGamma(KTone);
        return NULL;
    }
    

    return KTone;
}