LcmsColorProfileContainer.cpp

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/*
 * This file is part of the KDE project
 *  SPDX-FileCopyrightText: 2000 Matthias Elter <elter@kde.org>
 *  SPDX-FileCopyrightText: 2001 John Califf
 *  SPDX-FileCopyrightText: 2004 Boudewijn Rempt <boud@valdyas.org>
 *  SPDX-FileCopyrightText: 2007 Thomas Zander <zander@kde.org>
 *  SPDX-FileCopyrightText: 2007 Adrian Page <adrian@pagenet.plus.com>
 *
 * SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
#include "LcmsColorProfileContainer.h"
 
#include <QGenericMatrix>
#include <QTransform>
#include <array>
#include <cfloat>
#include <cmath>
 
#include <QDebug>
 
#include "kis_debug.h"
 
#include <KisLazyStorage.h>
#include <KisLazyValueWrapper.h>
 
namespace {
struct ReverseCurveWrapper
{
    ReverseCurveWrapper() : reverseCurve(0) {}
 
    explicit ReverseCurveWrapper(cmsToneCurve *curve) {
        reverseCurve = cmsReverseToneCurve(curve);
    }
 
    ~ReverseCurveWrapper() {
        if (reverseCurve) {
            cmsFreeToneCurve(reverseCurve);
        }
    }
 
    operator cmsToneCurve*() const {
        return reverseCurve;
    }
 
    operator cmsToneCurve*() {
        return reverseCurve;
    }
 
    ReverseCurveWrapper(const ReverseCurveWrapper&rhs) = delete;
    ReverseCurveWrapper& operator=(const ReverseCurveWrapper&rhs) = delete;
 
    ReverseCurveWrapper(ReverseCurveWrapper&&rhs) = default;
    ReverseCurveWrapper& operator=(ReverseCurveWrapper&&rhs) = default;
 
    cmsToneCurve *reverseCurve {0};
};
} // namespace
 
class LcmsColorProfileContainer::Private
{
public:
    cmsHPROFILE profile;
    cmsColorSpaceSignature colorSpaceSignature;
    cmsProfileClassSignature deviceClass;
    QString productDescription;
    QString manufacturer;
    QString copyright;
    QString name;
    float version;
    IccColorProfile::Data *data {0};
    bool valid {false};
    bool suitableForOutput {false};
    bool hasColorants;
 
    using LazyBool = KisLazyStorage<KisLazyValueWrapper<bool>, std::function<bool()>>;
 
    LazyBool hasTRC = LazyBool(LazyBool::init_value_tag{}, {});
    LazyBool isLinear = LazyBool(LazyBool::init_value_tag{}, {});
 
    bool adaptedFromD50;
    cmsCIEXYZ mediaWhitePoint;
    cmsCIExyY whitePoint;
    cmsCIEXYZTRIPLE colorants;
    cmsToneCurve *redTRC {0};
    cmsToneCurve *greenTRC {0};
    cmsToneCurve *blueTRC {0};
    cmsToneCurve *grayTRC {0};
 
    using LazyReverseCurve = KisLazyStorage<ReverseCurveWrapper, cmsToneCurve*>;
 
    LazyReverseCurve redTRCReverse = LazyReverseCurve(LazyReverseCurve::init_value_tag{}, {});
    LazyReverseCurve greenTRCReverse = LazyReverseCurve(LazyReverseCurve::init_value_tag{}, {});
    LazyReverseCurve blueTRCReverse = LazyReverseCurve(LazyReverseCurve::init_value_tag{}, {});
    LazyReverseCurve grayTRCReverse = LazyReverseCurve(LazyReverseCurve::init_value_tag{}, {});
 
    cmsUInt32Number defaultIntent;
    bool isPerceptualCLUT;
    bool isRelativeCLUT;
    bool isAbsoluteCLUT;
    bool isSaturationCLUT;
    bool isMatrixShaper;
 
    QByteArray uniqueId;
};
 
LcmsColorProfileContainer::LcmsColorProfileContainer()
    : d(new Private())
{
    d->profile = 0;
}
 
LcmsColorProfileContainer::LcmsColorProfileContainer(IccColorProfile::Data *data)
    : d(new Private())
{
    d->data = data;
    d->profile = 0;
    init();
}
 
QByteArray LcmsColorProfileContainer::lcmsProfileToByteArray(const cmsHPROFILE profile)
{
    cmsUInt32Number  bytesNeeded = 0;
    // Make a raw data image ready for saving
    cmsSaveProfileToMem(profile, 0, &bytesNeeded); // calc size
    QByteArray rawData;
    rawData.resize(bytesNeeded);
    if (rawData.size() >= (int)bytesNeeded) {
        cmsSaveProfileToMem(profile, rawData.data(), &bytesNeeded); // fill buffer
    } else {
        qWarning() << "Couldn't resize the profile buffer, system is probably running out of memory.";
        rawData.resize(0);
    }
    return rawData;
}
 
IccColorProfile *LcmsColorProfileContainer::createFromLcmsProfile(const cmsHPROFILE profile)
{
    IccColorProfile *iccprofile = new IccColorProfile(lcmsProfileToByteArray(profile));
    cmsCloseProfile(profile);
    return iccprofile;
}
 
LcmsColorProfileContainer::~LcmsColorProfileContainer()
{
    cmsCloseProfile(d->profile);
    delete d;
}
 
#define _BUFFER_SIZE_ 1000
 
bool LcmsColorProfileContainer::init()
{
    if (d->profile) {
        cmsCloseProfile(d->profile);
    }
 
    d->profile = cmsOpenProfileFromMem((void *)d->data->rawData().constData(), d->data->rawData().size());
 
 
#ifndef NDEBUG
    if (d->data->rawData().size() == 4096) {
        qWarning() << "Profile has a size of 4096, which is suspicious and indicates a possible misuse of QIODevice::read(int), check your code.";
    }
#endif
 
    if (d->profile) {
        wchar_t buffer[_BUFFER_SIZE_];
        d->colorSpaceSignature = cmsGetColorSpace(d->profile);
        d->deviceClass = cmsGetDeviceClass(d->profile);
        cmsGetProfileInfo(d->profile, cmsInfoDescription, cmsNoLanguage, cmsNoCountry, buffer, _BUFFER_SIZE_);
        d->name = QString::fromWCharArray(buffer);
 
        //apparently this should give us a localised string??? Not sure about this.
        cmsGetProfileInfo(d->profile, cmsInfoModel, cmsNoLanguage, cmsNoCountry, buffer, _BUFFER_SIZE_);
        d->productDescription = QString::fromWCharArray(buffer);
 
        cmsGetProfileInfo(d->profile, cmsInfoManufacturer, cmsNoLanguage, cmsNoCountry, buffer, _BUFFER_SIZE_);
        d->manufacturer = QString::fromWCharArray(buffer);
 
        cmsGetProfileInfo(d->profile, cmsInfoCopyright, cmsNoLanguage, cmsNoCountry, buffer, _BUFFER_SIZE_);
        d->copyright = QString::fromWCharArray(buffer);
 
        cmsProfileClassSignature profile_class;
        profile_class = cmsGetDeviceClass(d->profile);
        d->valid = (   profile_class != cmsSigNamedColorClass
                    && profile_class != cmsSigLinkClass);
 
        //This is where obtain the whitepoint, and convert it to the actual white point of the profile in the case a Chromatic adaption tag is
        //present. This is necessary for profiles following the v4 spec.
        cmsCIEXYZ baseMediaWhitePoint;//dummy to hold copy of mediawhitepoint if this is modified by chromatic adaption.
        cmsCIEXYZ *mediaWhitePointPtr;
        bool whiteComp[3];
        bool whiteIsD50;
        // Possible bug in profiles: there are in fact some that says they contain that tag
        //    but in fact the pointer is null.
        //    Let's not crash on it anyway, and assume there is no white point instead.
        //    BUG:423685
        if (cmsIsTag(d->profile, cmsSigMediaWhitePointTag)
                && (mediaWhitePointPtr = (cmsCIEXYZ *)cmsReadTag(d->profile, cmsSigMediaWhitePointTag))) {
 
            d->mediaWhitePoint = *(mediaWhitePointPtr);
            baseMediaWhitePoint = d->mediaWhitePoint;
 
            whiteComp[0] = std::fabs(baseMediaWhitePoint.X - cmsD50_XYZ()->X) < 0.00001;
            whiteComp[1] = std::fabs(baseMediaWhitePoint.Y - cmsD50_XYZ()->Y) < 0.00001;
            whiteComp[2] = std::fabs(baseMediaWhitePoint.Z - cmsD50_XYZ()->Z) < 0.00001;
            whiteIsD50 = std::all_of(std::begin(whiteComp), std::end(whiteComp), [](bool b) {return b;});
 
            cmsXYZ2xyY(&d->whitePoint, &d->mediaWhitePoint);
            cmsCIEXYZ *CAM1;
            if (cmsIsTag(d->profile, cmsSigChromaticAdaptationTag)
                    && (CAM1 = (cmsCIEXYZ *)cmsReadTag(d->profile, cmsSigChromaticAdaptationTag))
                    && whiteIsD50) {
                //the chromatic adaption tag represent a matrix from the actual white point of the profile to D50.
 
                //We first put all our data into structures we can manipulate.
                double d3dummy [3] = {d->mediaWhitePoint.X, d->mediaWhitePoint.Y, d->mediaWhitePoint.Z};
                QGenericMatrix<1, 3, double> whitePointMatrix(d3dummy);
                QTransform invertDummy(CAM1[0].X, CAM1[0].Y, CAM1[0].Z, CAM1[1].X, CAM1[1].Y, CAM1[1].Z, CAM1[2].X, CAM1[2].Y, CAM1[2].Z);
                //we then abuse QTransform's invert function because it probably does matrix inversion 20 times better than I can program.
                //if the matrix is uninvertable, invertedDummy will be an identity matrix, which for us means that it won't give any noticeable
                //effect when we start multiplying.
                QTransform invertedDummy = invertDummy.inverted();
                //we then put the QTransform into a generic 3x3 matrix.
                double d9dummy [9] = {invertedDummy.m11(), invertedDummy.m12(), invertedDummy.m13(),
                                      invertedDummy.m21(), invertedDummy.m22(), invertedDummy.m23(),
                                      invertedDummy.m31(), invertedDummy.m32(), invertedDummy.m33()
                                     };
                QGenericMatrix<3, 3, double> chromaticAdaptionMatrix(d9dummy);
                //multiplying our inverted adaption matrix with the whitepoint gives us the right whitepoint.
                QGenericMatrix<1, 3, double> result = chromaticAdaptionMatrix * whitePointMatrix;
                //and then we pour the matrix into the whitepoint variable. Generic matrix does row/column for indices even though it
                //uses column/row for initialising.
                d->mediaWhitePoint.X = result(0, 0);
                d->mediaWhitePoint.Y = result(1, 0);
                d->mediaWhitePoint.Z = result(2, 0);
                cmsXYZ2xyY(&d->whitePoint, &d->mediaWhitePoint);
            }
        }
        //This is for RGB profiles, but it only works for matrix profiles. Need to design it to work with non-matrix profiles.
        cmsCIEXYZ *tempColorantsRed, *tempColorantsGreen, *tempColorantsBlue;
        // Note: don't assume that cmsIsTag is enough to check for errors; check the pointers, too
        // BUG:423685
        if (cmsIsTag(d->profile, cmsSigRedColorantTag) && cmsIsTag(d->profile, cmsSigRedColorantTag) && cmsIsTag(d->profile, cmsSigRedColorantTag)
                && (tempColorantsRed = (cmsCIEXYZ *)cmsReadTag(d->profile, cmsSigRedColorantTag))
                && (tempColorantsGreen = (cmsCIEXYZ *)cmsReadTag(d->profile, cmsSigGreenColorantTag))
                && (tempColorantsBlue = (cmsCIEXYZ *)cmsReadTag(d->profile, cmsSigBlueColorantTag))) {
            cmsCIEXYZTRIPLE tempColorants;
            tempColorants.Red = *tempColorantsRed;
            tempColorants.Green = *tempColorantsGreen;
            tempColorants.Blue = *tempColorantsBlue;
            //convert to d65, this is useless.
            cmsAdaptToIlluminant(&d->colorants.Red, cmsD50_XYZ(), &d->mediaWhitePoint, &tempColorants.Red);
            cmsAdaptToIlluminant(&d->colorants.Green, cmsD50_XYZ(), &d->mediaWhitePoint, &tempColorants.Green);
            cmsAdaptToIlluminant(&d->colorants.Blue, cmsD50_XYZ(), &d->mediaWhitePoint, &tempColorants.Blue);
            //d->colorants = tempColorants;
            d->hasColorants = true;
        } else {
            //qDebug()<<d->name<<": has no colorants";
            d->hasColorants = false;
        }
        //retrieve TRC.
        if (cmsIsTag(d->profile, cmsSigRedTRCTag) && cmsIsTag(d->profile, cmsSigBlueTRCTag) && cmsIsTag(d->profile, cmsSigGreenTRCTag)) {
 
            d->redTRC = ((cmsToneCurve *)cmsReadTag (d->profile, cmsSigRedTRCTag));
            d->greenTRC = ((cmsToneCurve *)cmsReadTag (d->profile, cmsSigGreenTRCTag));
            d->blueTRC = ((cmsToneCurve *)cmsReadTag (d->profile, cmsSigBlueTRCTag));
            if (d->redTRC) d->redTRCReverse = Private::LazyReverseCurve(d->redTRC);
            if (d->greenTRC) d->greenTRCReverse = Private::LazyReverseCurve(d->greenTRC);
            if (d->blueTRC) d->blueTRCReverse = Private::LazyReverseCurve(d->blueTRC);
 
            d->hasTRC = Private::LazyBool([d = d] () {
                return d->redTRC && d->greenTRC && d->blueTRC && *d->redTRCReverse && *d->greenTRCReverse && *d->blueTRCReverse;
            });
 
            d->isLinear = Private::LazyBool([d = d] () {
                return *d->hasTRC
                    && cmsIsToneCurveLinear(d->redTRC)
                    && cmsIsToneCurveLinear(d->greenTRC)
                    && cmsIsToneCurveLinear(d->blueTRC);
            });
 
        } else if (cmsIsTag(d->profile, cmsSigGrayTRCTag)) {
            d->grayTRC = ((cmsToneCurve *)cmsReadTag (d->profile, cmsSigGrayTRCTag));
            if (d->grayTRC) d->grayTRCReverse = Private::LazyReverseCurve(d->grayTRC);
 
            d->hasTRC = Private::LazyBool([d = d] () {
                return d->grayTRC && *d->grayTRCReverse;
            });
 
            d->isLinear = Private::LazyBool([d = d] () {
                return *d->hasTRC && cmsIsToneCurveLinear(d->grayTRC);
            });
        } else {
            d->hasTRC = Private::LazyBool(Private::LazyBool::init_value_tag{}, {});
        }
 
        // Check if the profile can convert (something->this)
        d->suitableForOutput = cmsIsIntentSupported(d->profile,
                                                    INTENT_PERCEPTUAL,
                                                    LCMS_USED_AS_OUTPUT);
 
        d->version = cmsGetProfileVersion(d->profile);
        d->defaultIntent = cmsGetHeaderRenderingIntent(d->profile);
        d->isMatrixShaper = cmsIsMatrixShaper(d->profile);
        d->isPerceptualCLUT = cmsIsCLUT(d->profile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT);
        d->isSaturationCLUT = cmsIsCLUT(d->profile, INTENT_SATURATION, LCMS_USED_AS_INPUT);
        d->isAbsoluteCLUT = cmsIsCLUT(d->profile, INTENT_SATURATION, LCMS_USED_AS_INPUT);
        d->isRelativeCLUT = cmsIsCLUT(d->profile, INTENT_RELATIVE_COLORIMETRIC, LCMS_USED_AS_INPUT);
 
        return true;
    }
 
    return false;
}
 
cmsHPROFILE LcmsColorProfileContainer::lcmsProfile() const
{
    return d->profile;
}
 
cmsColorSpaceSignature LcmsColorProfileContainer::colorSpaceSignature() const
{
    return d->colorSpaceSignature;
}
 
cmsProfileClassSignature LcmsColorProfileContainer::deviceClass() const
{
    return d->deviceClass;
}
 
QString LcmsColorProfileContainer::manufacturer() const
{
    return d->manufacturer;
}
 
QString LcmsColorProfileContainer::copyright() const
{
    return d->copyright;
}
 
bool LcmsColorProfileContainer::valid() const
{
    return d->valid;
}
 
float LcmsColorProfileContainer::version() const
{
    return d->version;
}
 
bool LcmsColorProfileContainer::isSuitableForOutput() const
{
    return d->suitableForOutput;
}
 
bool LcmsColorProfileContainer::isSuitableForPrinting() const
{
    return deviceClass() == cmsSigOutputClass;
}
 
bool LcmsColorProfileContainer::isSuitableForDisplay() const
{
    return deviceClass() == cmsSigDisplayClass;
}
 
bool LcmsColorProfileContainer::supportsPerceptual() const
{
    return d->isPerceptualCLUT;
}
bool LcmsColorProfileContainer::supportsSaturation() const
{
    return d->isSaturationCLUT;
}
bool LcmsColorProfileContainer::supportsAbsolute() const
{
    return d->isAbsoluteCLUT;//LCMS2 doesn't convert matrix shapers via absolute intent, because of V4 workflow.
}
bool LcmsColorProfileContainer::supportsRelative() const
{
    if (d->isRelativeCLUT || d->isMatrixShaper){
        return true;
    }
    return false;
}
bool LcmsColorProfileContainer::hasColorants() const
{
    return d->hasColorants;
}
bool LcmsColorProfileContainer::hasTRC() const
{
    return *d->hasTRC;
}
bool LcmsColorProfileContainer::isLinear() const
{
    return *d->isLinear;
}
QVector <double> LcmsColorProfileContainer::getColorantsXYZ() const
{
    QVector <double> colorants(9);
    colorants[0] = d->colorants.Red.X;
    colorants[1] = d->colorants.Red.Y;
    colorants[2] = d->colorants.Red.Z;
    colorants[3] = d->colorants.Green.X;
    colorants[4] = d->colorants.Green.Y;
    colorants[5] = d->colorants.Green.Z;
    colorants[6] = d->colorants.Blue.X;
    colorants[7] = d->colorants.Blue.Y;
    colorants[8] = d->colorants.Blue.Z;
    return colorants;
}
 
QVector <double> LcmsColorProfileContainer::getColorantsxyY() const
{
    cmsCIEXYZ temp1;
    cmsCIExyY temp2;
    QVector <double> colorants(9);
 
    temp1.X = d->colorants.Red.X;
    temp1.Y = d->colorants.Red.Y;
    temp1.Z = d->colorants.Red.Z;
    cmsXYZ2xyY(&temp2, &temp1);
    colorants[0] = temp2.x;
    colorants[1] = temp2.y;
    colorants[2] = temp2.Y;
 
    temp1.X = d->colorants.Green.X;
    temp1.Y = d->colorants.Green.Y;
    temp1.Z = d->colorants.Green.Z;
    cmsXYZ2xyY(&temp2, &temp1);
    colorants[3] = temp2.x;
    colorants[4] = temp2.y;
    colorants[5] = temp2.Y;
 
    temp1.X = d->colorants.Blue.X;
    temp1.Y = d->colorants.Blue.Y;
    temp1.Z = d->colorants.Blue.Z;
    cmsXYZ2xyY(&temp2, &temp1);
    colorants[6] = temp2.x;
    colorants[7] = temp2.y;
    colorants[8] = temp2.Y;
 
    return colorants;
}
 
QVector <double> LcmsColorProfileContainer::getWhitePointXYZ() const
{
    QVector <double> tempWhitePoint(3);
 
    tempWhitePoint[0] = d->mediaWhitePoint.X;
    tempWhitePoint[1] = d->mediaWhitePoint.Y;
    tempWhitePoint[2] = d->mediaWhitePoint.Z;
 
    return tempWhitePoint;
}
 
QVector <double> LcmsColorProfileContainer::getWhitePointxyY() const
{
    QVector <double> tempWhitePoint(3);
    tempWhitePoint[0] = d->whitePoint.x;
    tempWhitePoint[1] = d->whitePoint.y;
    tempWhitePoint[2] = d->whitePoint.Y;
    return tempWhitePoint;
}
 
QVector <double> LcmsColorProfileContainer::getEstimatedTRC() const
{
    QVector <double> TRCtriplet(3);
    if (d->hasColorants) {
        if (cmsIsToneCurveLinear(d->redTRC)) {
            TRCtriplet[0] = 1.0;
        } else {
            TRCtriplet[0] = cmsEstimateGamma(d->redTRC, 0.01);
        }
        if (cmsIsToneCurveLinear(d->greenTRC)) {
            TRCtriplet[1] = 1.0;
        } else {
            TRCtriplet[1] = cmsEstimateGamma(d->greenTRC, 0.01);
        }
        if (cmsIsToneCurveLinear(d->blueTRC)) {
            TRCtriplet[2] = 1.0;
        } else {
            TRCtriplet[2] = cmsEstimateGamma(d->blueTRC, 0.01);
        }
 
    } else {
        if (cmsIsTag(d->profile, cmsSigGrayTRCTag)) {
            if (cmsIsToneCurveLinear(d->grayTRC)) {
                TRCtriplet.fill(1.0);
            } else {
                TRCtriplet.fill(cmsEstimateGamma(d->grayTRC,  0.01));
            }
        } else {
            TRCtriplet.fill(1.0);
        }
    }
    return TRCtriplet;
}
 
void LcmsColorProfileContainer::LinearizeFloatValue(QVector <double> & Value) const
{
    if (d->hasColorants) {
        if (!cmsIsToneCurveLinear(d->redTRC)) {
            Value[0] = cmsEvalToneCurveFloat(d->redTRC, Value[0]);
        }
        if (!cmsIsToneCurveLinear(d->greenTRC)) {
            Value[1] = cmsEvalToneCurveFloat(d->greenTRC, Value[1]);
        }
        if (!cmsIsToneCurveLinear(d->blueTRC)) {
            Value[2] = cmsEvalToneCurveFloat(d->blueTRC, Value[2]);
        }
 
    } else {
        if (cmsIsTag(d->profile, cmsSigGrayTRCTag)) {
            Value[0] = cmsEvalToneCurveFloat(d->grayTRC, Value[0]);
        }
    }
}
 
void LcmsColorProfileContainer::DelinearizeFloatValue(QVector <double> & Value) const
{
    if (d->hasColorants) {
        if (!cmsIsToneCurveLinear(d->redTRC)) {
            Value[0] = cmsEvalToneCurveFloat(*d->redTRCReverse, Value[0]);
        }
        if (!cmsIsToneCurveLinear(d->greenTRC)) {
            Value[1] = cmsEvalToneCurveFloat(*d->greenTRCReverse, Value[1]);
        }
        if (!cmsIsToneCurveLinear(d->blueTRC)) {
            Value[2] = cmsEvalToneCurveFloat(*d->blueTRCReverse, Value[2]);
        }
 
    } else {
        if (cmsIsTag(d->profile, cmsSigGrayTRCTag)) {
            Value[0] = cmsEvalToneCurveFloat(*d->grayTRCReverse, Value[0]);
        }
    }
}
 
void LcmsColorProfileContainer::LinearizeFloatValueFast(QVector <double> & Value) const
{
    const qreal scale = 65535.0;
    const qreal invScale = 1.0 / scale;
 
    if (d->hasColorants) {
        //we can only reliably delinearise in the 0-1.0 range, outside of that leave the value alone.
 
        if (!cmsIsToneCurveLinear(d->redTRC) && Value[0]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(d->redTRC, Value[0] * scale);
            Value[0] = newValue * invScale;
        }
        if (!cmsIsToneCurveLinear(d->greenTRC) && Value[1]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(d->greenTRC, Value[1] * scale);
            Value[1] = newValue * invScale;
        }
        if (!cmsIsToneCurveLinear(d->blueTRC) && Value[2]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(d->blueTRC, Value[2] * scale);
            Value[2] = newValue * invScale;
        }
    } else {
        if (cmsIsTag(d->profile, cmsSigGrayTRCTag) && Value[0]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(d->grayTRC, Value[0] * scale);
            Value[0] = newValue * invScale;
        }
    }
}
void LcmsColorProfileContainer::DelinearizeFloatValueFast(QVector <double> & Value) const
{
    const qreal scale = 65535.0;
    const qreal invScale = 1.0 / scale;
 
    if (d->hasColorants) {
        //we can only reliably delinearise in the 0-1.0 range, outside of that leave the value alone.
 
        if (!cmsIsToneCurveLinear(d->redTRC) && Value[0]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(*d->redTRCReverse, Value[0] * scale);
            Value[0] = newValue * invScale;
        }
        if (!cmsIsToneCurveLinear(d->greenTRC) && Value[1]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(*d->greenTRCReverse, Value[1] * scale);
            Value[1] = newValue * invScale;
        }
        if (!cmsIsToneCurveLinear(d->blueTRC) && Value[2]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(*d->blueTRCReverse, Value[2] * scale);
            Value[2] = newValue * invScale;
        }
    } else {
        if (cmsIsTag(d->profile, cmsSigGrayTRCTag) && Value[0]<1.0) {
            quint16 newValue = cmsEvalToneCurve16(*d->grayTRCReverse, Value[0] * scale);
            Value[0] = newValue * invScale;
        }
    }
}
 
QString LcmsColorProfileContainer::name() const
{
    return d->name;
}
 
QString LcmsColorProfileContainer::info() const
{
    return d->productDescription;
}
 
QByteArray LcmsColorProfileContainer::getProfileUniqueId() const
{
    if (d->uniqueId.isEmpty() && d->profile) {
        QByteArray id(sizeof(cmsProfileID), 0);
        cmsGetHeaderProfileID(d->profile, (quint8*)id.data());
 
        bool isNull = std::all_of(id.constBegin(),
                                  id.constEnd(),
                                  [](char c) {return c == 0;});
        if (isNull) {
            if (cmsMD5computeID(d->profile)) {
                cmsGetHeaderProfileID(d->profile, (quint8*)id.data());
                isNull = false;
            }
        }
 
        if (!isNull) {
            d->uniqueId = id;
        }
    }
 
    return d->uniqueId;
}
 
bool LcmsColorProfileContainer::compareTRC(TransferCharacteristics characteristics, float error) const
{
    if (!*d->hasTRC) {
        return false;
    }
 
    std::array<cmsFloat32Number, 2> calcValues{};
 
    cmsToneCurve *mainCurve = [&]() {
        if (d->hasColorants) {
            return d->redTRC;
        }
        return d->grayTRC;
    }();
 
    cmsToneCurve *compareCurve = transferFunction(characteristics);
 
    // Number of sweep samples across the curve
    for (uint32_t i = 0; i < 32; i++) {
        const float step = float(i) / 31.0f;
        calcValues[0] = cmsEvalToneCurveFloat(mainCurve, step);
        calcValues[1] = cmsEvalToneCurveFloat(compareCurve, step);
        if (std::fabs(calcValues[0] - calcValues[1]) >= error) {
            return false;
        }
    }
 
    return true;
}
 
cmsToneCurve *LcmsColorProfileContainer::transferFunction(TransferCharacteristics transferFunction)
{
    cmsToneCurve *mainCurve;
 
    // Values courtesy of Elle Stone
    cmsFloat64Number srgb_parameters[5] =
    { 2.4, 1.0 / 1.055,  0.055 / 1.055, 1.0 / 12.92, 0.04045 };
    cmsFloat64Number rec709_parameters[5] =
    { 1.0 / 0.45, 1.0 / 1.099,  0.099 / 1.099,  1.0 / 4.5, 0.081 };
 
    // The following is basically a precise version of rec709.
    cmsFloat64Number rec202012bit_parameters[5] =
    { 1.0 / 0.45, 1.0 / 1.0993,  0.0993 / 1.0993,  1.0 / 4.5, 0.0812 };
 
    cmsFloat64Number SMPTE_240M_parameters[5] =
    { 1.0 / 0.45, 1.0 / 1.1115,  0.1115 / 1.1115,  1.0 / 4.0, 0.0913 };
 
    cmsFloat64Number prophoto_parameters[5] =
    { 1.8, 1.0,  0, 1.0 / 16, (16.0/512) };
 
    cmsFloat64Number log_100[5] = {1.0, 10, 2.0, -2.0, 0.0};
    cmsFloat64Number log_100_sqrt[5] = {1.0, 10, 2.5, -2.5, 0.0};
 
    cmsFloat64Number labl_parameters[5] = {3.0, 0.862076, 0.137924, 0.110703, 0.080002};
 
    switch (transferFunction) {
    case TRC_IEC_61966_2_4:
        // Not possible in ICC due to lack of a*pow(bX+c,y) construct.
    case TRC_ITU_R_BT_1361:
        // This is not possible in ICC due to lack of a*pow(bX+c,y) construct.
        qWarning() << "Neither IEC 61966 2-4 nor Bt. 1361 are supported, returning a rec 709 curve.";
        Q_FALLTHROUGH();
    case TRC_ITU_R_BT_709_5:
    case TRC_ITU_R_BT_601_6:
    case TRC_ITU_R_BT_2020_2_10bit:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, rec709_parameters);
        break;
    case TRC_ITU_R_BT_2020_2_12bit:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, rec202012bit_parameters);
        break;
    case TRC_ITU_R_BT_470_6_SYSTEM_M:
        mainCurve = cmsBuildGamma(NULL, 2.2);
        break;
    case TRC_ITU_R_BT_470_6_SYSTEM_B_G:
        mainCurve = cmsBuildGamma(NULL, 2.8);
        break;
    case TRC_SMPTE_240M:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, SMPTE_240M_parameters);
        break;
    case TRC_IEC_61966_2_1:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, srgb_parameters);
        break;
    case TRC_LOGARITHMIC_100:
        mainCurve = cmsBuildParametricToneCurve(NULL, 8, log_100);
        break;
    case TRC_LOGARITHMIC_100_sqrt10:
        mainCurve = cmsBuildParametricToneCurve(NULL, 8, log_100_sqrt);
        break;
    case TRC_A98:
        // gamma 563/256
        mainCurve = cmsBuildGamma(NULL, 563.0 / 256.0);
        break;
    case TRC_PROPHOTO:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, prophoto_parameters);
        break;
    case TRC_GAMMA_1_8:
        mainCurve = cmsBuildGamma(NULL, 1.8);
        break;
    case TRC_GAMMA_2_4:
        mainCurve = cmsBuildGamma(NULL, 2.4);
        break;
    case TRC_LAB_L:
        mainCurve = cmsBuildParametricToneCurve(NULL, 4, labl_parameters);
        break;
    case TRC_SMPTE_ST_428_1:
        // Requires an a*X^y construction, not possible.
    case TRC_ITU_R_BT_2100_0_PQ:
        // Perceptual Quantizer
    case TRC_ITU_R_BT_2100_0_HLG:
        // Hybrid log gamma.
        qWarning() << "Cannot generate an icc profile with this transfer function, will generate a linear profile";
        Q_FALLTHROUGH();
    case TRC_LINEAR:
    default:
        mainCurve = cmsBuildGamma(NULL, 1.0);
        break;
    }
 
    return mainCurve;
}