//---------------------------------------------------------------------------------

//

//  Little Color Management System

//  Copyright (c) 1998-2026 Marti Maria Saguer

//

// 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 "lcms2_internal.h"

#define cmsmin(a, b) (((a) < (b)) ? (a) : (b))

#define cmsmax(a, b) (((a) > (b)) ? (a) : (b))

// This file contains routines for resampling and LUT optimization, black point detection

// and black preservation.

// Black point detection -------------------------------------------------------------------------

// PCS -> PCS round trip transform, always uses relative intent on the device -> pcs

static

cmsHTRANSFORM CreateRoundtripXForm(cmsHPROFILE hProfile, cmsUInt32Number nIntent)

{

    cmsContext ContextID = cmsGetProfileContextID(hProfile);

    cmsHPROFILE hLab = cmsCreateLab4ProfileTHR(ContextID, NULL);

    cmsHTRANSFORM xform;

    cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE };

    cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 };

    cmsHPROFILE hProfiles[4];

    cmsUInt32Number Intents[4];

    hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab;

    Intents[0]   = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC;

    xform =  cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents,

        States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE);

    cmsCloseProfile(hLab);

    return xform;

}

// Use darker colorants to obtain black point. This works in the relative colorimetric intent and

// assumes more ink results in darker colors. No ink limit is assumed.

static

cmsBool  BlackPointAsDarkerColorant(cmsHPROFILE    hInput,

                                    cmsUInt32Number Intent,

                                    cmsCIEXYZ* BlackPoint,

                                    cmsUInt32Number dwFlags)

{

    cmsUInt16Number *Black;

    cmsHTRANSFORM xform;

    cmsColorSpaceSignature Space;

    cmsUInt32Number nChannels;

    cmsUInt32Number dwFormat;

    cmsHPROFILE hLab;

    cmsCIELab  Lab;

    cmsCIEXYZ  BlackXYZ;    

    cmsContext ContextID = cmsGetProfileContextID(hInput);

    // If the profile does not support input direction, assume Black point 0

    if (!cmsIsIntentSupported(hInput, Intent, LCMS_USED_AS_INPUT)) {

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    // Create a formatter which has n channels and no floating point

    dwFormat = cmsFormatterForColorspaceOfProfile(hInput, 2, FALSE);

    // Try to get black by using black colorant

    Space = cmsGetColorSpace(hInput);

    // This function returns darker colorant in 16 bits for several spaces

    if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    if (nChannels != T_CHANNELS(dwFormat)) {

       BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

       return FALSE;

    }

    // Lab will be used as the output space, but lab2 will avoid recursion

    hLab = cmsCreateLab2ProfileTHR(ContextID, NULL);

    if (hLab == NULL) {

       BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

       return FALSE;

    }

    // Create the transform

    xform = cmsCreateTransformTHR(ContextID, hInput, dwFormat,

                                hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE);

    cmsCloseProfile(hLab);

    if (xform == NULL) {

        // Something went wrong. Get rid of open resources and return zero as black

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    // Convert black to Lab

    cmsDoTransform(xform, Black, &Lab, 1);

    if (Lab.L > 95)

        Lab.L = 0;  // for synthetical negative profiles

    else if (Lab.L < 0)

        Lab.L = 0;

    else if (Lab.L > 50)

        Lab.L = 50;

    // Free the resources

    cmsDeleteTransform(xform);

    // Convert from Lab (which is now clipped) to XYZ.

    cmsLab2XYZ(NULL, &BlackXYZ, &Lab);

    if (BlackPoint != NULL)

        *BlackPoint = BlackXYZ;

    return TRUE;

    cmsUNUSED_PARAMETER(dwFlags);

}

// Get a black point of output CMYK profile, discounting any ink-limiting embedded

// in the profile. For doing that, we use perceptual intent in input direction:

// Lab (0, 0, 0) -> [Perceptual] Profile -> CMYK -> [Rel. colorimetric] Profile -> Lab

static

cmsBool BlackPointUsingPerceptualBlack(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile)

{

    cmsHTRANSFORM hRoundTrip;

    cmsCIELab LabIn, LabOut;

    cmsCIEXYZ  BlackXYZ;

     // Is the intent supported by the profile?

    if (!cmsIsIntentSupported(hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) {

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return TRUE;

    }

    hRoundTrip = CreateRoundtripXForm(hProfile, INTENT_PERCEPTUAL);

    if (hRoundTrip == NULL) {

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    LabIn.L = LabIn.a = LabIn.b = 0;

    cmsDoTransform(hRoundTrip, &LabIn, &LabOut, 1);

    // Clip Lab to reasonable limits

    if (LabOut.L > 50) LabOut.L = 50;

    LabOut.a = LabOut.b = 0;

    cmsDeleteTransform(hRoundTrip);

    // Convert it to XYZ

    cmsLab2XYZ(NULL, &BlackXYZ, &LabOut);

    if (BlackPoint != NULL)

        *BlackPoint = BlackXYZ;

    return TRUE;

}

static

cmsBool isInkColorspace(cmsColorSpaceSignature c)

{

    switch(c)

    {

    case cmsSigCmykData:

    case cmsSigCmyData:

    case cmsSigMCH1Data:

    case cmsSigMCH2Data:

    case cmsSigMCH3Data:

    case cmsSigMCH4Data:

    case cmsSigMCH5Data:

    case cmsSigMCH6Data:

    case cmsSigMCH7Data:

    case cmsSigMCH8Data:

    case cmsSigMCH9Data:

    case cmsSigMCHAData:

    case cmsSigMCHBData:

    case cmsSigMCHCData:

    case cmsSigMCHDData:

    case cmsSigMCHEData:

    case cmsSigMCHFData:    

    case cmsSig1colorData:

    case cmsSig2colorData:

    case cmsSig3colorData:

    case cmsSig4colorData:

    case cmsSig5colorData:

    case cmsSig6colorData:

    case cmsSig7colorData:

    case cmsSig8colorData:

    case cmsSig9colorData:

    case cmsSig10colorData:

    case cmsSig11colorData:

    case cmsSig12colorData:

    case cmsSig13colorData:

    case cmsSig14colorData:

    case cmsSig15colorData:

            return TRUE;

    default:

        return FALSE;

    }

}

// This function shouldn't exist at all -- there is such quantity of broken

// profiles on black point tag, that we must somehow fix chromaticity to

// avoid huge tint when doing Black point compensation. This function does

// just that. There is a special flag for using black point tag, but turned

// off by default because it is bogus on most profiles. The detection algorithm

// involves to turn BP to neutral and to use only L component.

cmsBool CMSEXPORT cmsDetectBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)

{

    cmsProfileClassSignature devClass;

    // Make sure the device class is adequate

    devClass = cmsGetDeviceClass(hProfile);

    if (devClass == cmsSigLinkClass ||

        devClass == cmsSigAbstractClass ||

        devClass == cmsSigNamedColorClass) {

            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

            return FALSE;

    }

    // Make sure intent is adequate

    if (Intent != INTENT_PERCEPTUAL &&

        Intent != INTENT_RELATIVE_COLORIMETRIC &&

        Intent != INTENT_SATURATION) {

            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

            return FALSE;

    }

    // v4 + perceptual & saturation intents does have its own black point, and it is

    // well specified enough to use it. Black point tag is deprecated in V4.

    if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&

        (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {

            // Matrix shaper share MRC & perceptual intents

            if (cmsIsMatrixShaper(hProfile))

                return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);

            // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents

            BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;

            BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;

            BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;

            return TRUE;

    }

#ifdef CMS_USE_PROFILE_BLACK_POINT_TAG

    // v2, v4 rel/abs colorimetric

    if (cmsIsTag(hProfile, cmsSigMediaBlackPointTag) &&

        Intent == INTENT_RELATIVE_COLORIMETRIC) {

            cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite;

            cmsCIELab Lab;

            // If black point is specified, then use it,

            BlackPtr = cmsReadTag(hProfile, cmsSigMediaBlackPointTag);

            if (BlackPtr != NULL) {

                BlackXYZ = *BlackPtr;

                _cmsReadMediaWhitePoint(&MediaWhite, hProfile);

                // Black point is absolute XYZ, so adapt to D50 to get PCS value

                cmsAdaptToIlluminant(&UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(), &BlackXYZ);

                // Force a=b=0 to get rid of any chroma

                cmsXYZ2Lab(NULL, &Lab, &UntrustedBlackPoint);

                Lab.a = Lab.b = 0;

                if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50

                cmsLab2XYZ(NULL, &TrustedBlackPoint, &Lab);

                if (BlackPoint != NULL)

                    *BlackPoint = TrustedBlackPoint;

                return TRUE;

            }

    }

#endif

    // That is about v2 profiles.

    // If output profile, discount ink-limiting and that's all

    if (Intent == INTENT_RELATIVE_COLORIMETRIC &&

        (cmsGetDeviceClass(hProfile) == cmsSigOutputClass) &&

        (isInkColorspace(cmsGetColorSpace(hProfile))))

        return BlackPointUsingPerceptualBlack(BlackPoint, hProfile);

    // Nope, compute BP using current intent.

    return BlackPointAsDarkerColorant(hProfile, Intent, BlackPoint, dwFlags);

}

// ---------------------------------------------------------------------------------------------------------

// Least Squares Fit of a Quadratic Curve to Data

// http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html

static

cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(int n, cmsFloat64Number x[], cmsFloat64Number y[])

{

    double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;

    double sum_y = 0, sum_yx = 0, sum_yx2 = 0;

    double d, a, b, c;

    int i;

    cmsMAT3 m;

    cmsVEC3 v, res;

    if (n < 4) return 0;

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

        double xn = x[i];

        double yn = y[i];

        sum_x  += xn;

        sum_x2 += xn*xn;

        sum_x3 += xn*xn*xn;

        sum_x4 += xn*xn*xn*xn;

        sum_y += yn;

        sum_yx += yn*xn;

        sum_yx2 += yn*xn*xn;

    }

    _cmsVEC3init(&m.v[0], n,      sum_x,  sum_x2);

    _cmsVEC3init(&m.v[1], sum_x,  sum_x2, sum_x3);

    _cmsVEC3init(&m.v[2], sum_x2, sum_x3, sum_x4);

    _cmsVEC3init(&v, sum_y, sum_yx, sum_yx2);

    if (!_cmsMAT3solve(&res, &m, &v)) return 0;

    a = res.n[2];

    b = res.n[1];

    c = res.n[0];

    if (fabs(a) < 1.0E-10) {

        if (fabs(b) < 1.0E-10) return 0;

        return cmsmax(0, cmsmin(50, -c/b ));

    }

    else {

         d = b*b - 4.0 * a * c;

         if (d <= 0) {

             return 0;

         }

         else {

             double rt;

             if (fabs(a) < 1.0E-10) return 0;

             rt = (-b + sqrt(d)) / (2.0 * a);

             return cmsmax(0, cmsmin(50, rt));

         }

   }

}

// Calculates the black point of a destination profile.

// This algorithm comes from the Adobe paper disclosing its black point compensation method.

cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)

{

    cmsColorSpaceSignature ColorSpace;

    cmsHTRANSFORM hRoundTrip = NULL;

    cmsCIELab InitialLab, destLab, Lab;

    cmsFloat64Number inRamp[256], outRamp[256];

    cmsFloat64Number MinL, MaxL;

    cmsBool NearlyStraightMidrange = TRUE;  

    cmsFloat64Number yRamp[256];

    cmsFloat64Number x[256], y[256];

    cmsFloat64Number lo, hi;

    int n, l;

    cmsProfileClassSignature devClass;

    // Make sure the device class is adequate

    devClass = cmsGetDeviceClass(hProfile);

    if (devClass == cmsSigLinkClass ||

        devClass == cmsSigAbstractClass ||

        devClass == cmsSigNamedColorClass) {

            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

            return FALSE;

    }

    // Make sure intent is adequate

    if (Intent != INTENT_PERCEPTUAL &&

        Intent != INTENT_RELATIVE_COLORIMETRIC &&

        Intent != INTENT_SATURATION) {

            BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

            return FALSE;

    }

    // v4 + perceptual & saturation intents does have its own black point, and it is

    // well specified enough to use it. Black point tag is deprecated in V4.

    if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&

        (Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {

            // Matrix shaper share MRC & perceptual intents

            if (cmsIsMatrixShaper(hProfile))

                return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);

            // Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents

            BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;

            BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;

            BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;

            return TRUE;

    }

    // Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document)

    ColorSpace = cmsGetColorSpace(hProfile);

    if (!cmsIsCLUT(hProfile, Intent, LCMS_USED_AS_OUTPUT ) ||

        (ColorSpace != cmsSigGrayData &&

         ColorSpace != cmsSigRgbData  &&

         !isInkColorspace(ColorSpace))) {

        // In this case, handle as input case

        return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags);

    }

    // It is one of the valid cases!, use Adobe algorithm

    // Set a first guess, that should work on good profiles.

    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {

        cmsCIEXYZ IniXYZ;

        // calculate initial Lab as source black point

        if (!cmsDetectBlackPoint(&IniXYZ, hProfile, Intent, dwFlags)) {

            return FALSE;

        }

        // convert the XYZ to lab

        cmsXYZ2Lab(NULL, &InitialLab, &IniXYZ);

    } else {

        // set the initial Lab to zero, that should be the black point for perceptual and saturation

        InitialLab.L = 0;

        InitialLab.a = 0;

        InitialLab.b = 0;

    }

    // Step 2

    // ======

    // Create a roundtrip. Define a Transform BT for all x in L*a*b*

    hRoundTrip = CreateRoundtripXForm(hProfile, Intent);

    if (hRoundTrip == NULL)  return FALSE;

    // Compute ramps

    for (l=0; l < 256; l++) {

        Lab.L = (cmsFloat64Number) (l * 100.0) / 255.0;

        Lab.a = cmsmin(50, cmsmax(-50, InitialLab.a));

        Lab.b = cmsmin(50, cmsmax(-50, InitialLab.b));

        cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);

        inRamp[l]  = Lab.L;

        outRamp[l] = destLab.L;

    }

    // Make monotonic

    for (l = 254; l > 0; --l) {

        outRamp[l] = cmsmin(outRamp[l], outRamp[l+1]);

    }

    // Check

    if (! (outRamp[0] < outRamp[255])) {

        cmsDeleteTransform(hRoundTrip);

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    // Test for mid range straight (only on relative colorimetric)

    NearlyStraightMidrange = TRUE;

    MinL = outRamp[0]; MaxL = outRamp[255];

    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {

        for (l=0; l < 256; l++) {

            if (! ((inRamp[l] <= MinL + 0.2 * (MaxL - MinL) ) ||   

                (fabs(inRamp[l] - outRamp[l]) < 4.0 )))

                NearlyStraightMidrange = FALSE;

        }

        // If the mid range is straight (as determined above) then the 

        // DestinationBlackPoint shall be the same as initialLab. 

        // Otherwise, the DestinationBlackPoint shall be determined 

        // using curve fitting.

        if (NearlyStraightMidrange) {

            cmsLab2XYZ(NULL, BlackPoint, &InitialLab);

            cmsDeleteTransform(hRoundTrip);

            return TRUE;

        }

    }

    // curve fitting: The round-trip curve normally looks like a nearly constant section at the black point,

    // with a corner and a nearly straight line to the white point.  

    for (l=0; l < 256; l++) {

        yRamp[l] = (outRamp[l] - MinL) / (MaxL - MinL);

    }

    // find the black point using the least squares error quadratic curve fitting

    if (Intent == INTENT_RELATIVE_COLORIMETRIC) {

        lo = 0.1;

        hi = 0.5;

    }

    else {

        // Perceptual and saturation

        lo = 0.03;

        hi = 0.25;

    }

    // Capture shadow points for the fitting.

    n = 0;

    for (l=0; l < 256; l++) {

        cmsFloat64Number ff = yRamp[l];

        if (ff >= lo && ff < hi) {

            x[n] = inRamp[l];

            y[n] = yRamp[l];

            n++;

        }    

    }

    // No suitable points

    if (n < 3 ) {

        cmsDeleteTransform(hRoundTrip);

        BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;

        return FALSE;

    }

    // fit and get the vertex of quadratic curve

    Lab.L = RootOfLeastSquaresFitQuadraticCurve(n, x, y);

    if (Lab.L < 0.0) { // clip to zero L* if the vertex is negative

        Lab.L = 0;

    }

    Lab.a = InitialLab.a;

    Lab.b = InitialLab.b;

    cmsLab2XYZ(NULL, BlackPoint, &Lab);

    cmsDeleteTransform(hRoundTrip);

    return TRUE;

}