/* ============================================================
 *
 * This file is a part of digiKam project
 * https://www.digikam.org
 *
 * Date        : 2023-05-15
 * Description : geolocation engine based on Marble.
 *               (c) 2007-2022 Marble Team
 *               https://invent.kde.org/education/marble/-/raw/master/data/credits_authors.html
 *
 * SPDX-FileCopyrightText: 2023-2026 by Gilles Caulier <caulier dot gilles at gmail dot com>
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * ============================================================ */

#include "BlendingAlgorithms.h"

// C++ includes

#include <cmath>

// Qt includes

#include <QImage>
#include <QPainter>

// Local includes

#include "TextureTile.h"

namespace Marble
{

void OverpaintBlending::blend(QImage* const bottom, TextureTile const* const top) const
{
    Q_ASSERT(bottom);
    Q_ASSERT(top);
    Q_ASSERT(top->image());
    Q_ASSERT(bottom->size() == top->image()->size());
    Q_ASSERT(bottom->format() == QImage::Format_ARGB32_Premultiplied);

    QPainter painter(bottom);

    painter.drawImage(0, 0, *top->image());
}

void GrayscaleBlending::blend(QImage* const bottom, TextureTile const* const top) const
{
    Q_ASSERT(bottom);
    Q_ASSERT(top);
    Q_ASSERT(top->image());
    Q_ASSERT(bottom->size() == top->image()->size());
    Q_ASSERT(bottom->format() == QImage::Format_ARGB32_Premultiplied);
    QImage const topImagePremult = top->image()->convertToFormat(QImage::Format_ARGB32_Premultiplied);

    // Draw a grayscale version of the bottom image
    int const width = bottom->width();
    int const height = bottom->height();

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            QRgb const topPixel = topImagePremult.pixel(x, y);
            int const gray = qGray(topPixel);
            QRgb const grayPixel = qRgb(gray, gray, gray);
            bottom->setPixel(x, y, grayPixel);
        }
    }

}

void InvertColorBlending::blend(QImage* const bottom, TextureTile const* const top) const
{
    Q_ASSERT(bottom);
    Q_ASSERT(top);
    Q_ASSERT(top->image());
    Q_ASSERT(bottom->size() == top->image()->size());
    Q_ASSERT(bottom->format() == QImage::Format_ARGB32_Premultiplied);
    QImage const topImagePremult = top->image()->convertToFormat(QImage::Format_ARGB32_Premultiplied);

    // Draw an inverted version of the bottom image
    int const width = bottom->width();
    int const height = bottom->height();

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            QRgb const topPixel = topImagePremult.pixel(x, y);
            QRgb const invertedPixel = qRgb(255 - qRed(topPixel), 255 - qGreen(topPixel), 255 - qBlue(topPixel));
            bottom->setPixel(x, y, invertedPixel);
        }
    }
}

void InvertHueBlending::blend(QImage* const bottom, TextureTile const* const top) const
{
    Q_ASSERT(bottom);
    Q_ASSERT(top);
    Q_ASSERT(top->image());
    Q_ASSERT(bottom->size() == top->image()->size());
    Q_ASSERT(bottom->format() == QImage::Format_ARGB32_Premultiplied);
    QImage const topImagePremult = top->image()->convertToFormat(QImage::Format_ARGB32_Premultiplied);

    // Draw an inverted version of the bottom image
    int const width = bottom->width();
    int const height = bottom->height();

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            QRgb const topPixel = topImagePremult.pixel(x, y);
            QColor invertedColor(255 - qRed(topPixel), 255 - qGreen(topPixel), 255 - qBlue(topPixel));
            int hue = invertedColor.hslHue();
            int saturation = invertedColor.hslSaturation();
            int lightness = invertedColor.lightness();
            QColor naturalInvertedColor = QColor::fromHsl((hue + 195) % 255, saturation, lightness);
            QRgb naturalInvertedPixel = naturalInvertedColor.rgb();
            bottom->setPixel(x, y, naturalInvertedPixel);
        }
    }
}

// pre-conditions:
// - bottom and top image have the same size
// - bottom image format is ARGB32_Premultiplied
void IndependentChannelBlending::blend(QImage* const bottom,
                                       TextureTile const* const top) const
{
    QImage const* const topImage = top->image();
    Q_ASSERT(topImage);
    Q_ASSERT(bottom->size() == topImage->size());
    Q_ASSERT(bottom->format() == QImage::Format_ARGB32_Premultiplied);

    int const width = bottom->width();
    int const height = bottom->height();
    QImage const topImagePremult = topImage->convertToFormat(QImage::Format_ARGB32_Premultiplied);

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            QRgb const bottomPixel = bottom->pixel(x, y);
            QRgb const topPixel = topImagePremult.pixel(x, y);
            qreal const resultRed = blendChannel(qRed(bottomPixel) / 255.0,
                                                 qRed(topPixel) / 255.0);
            qreal const resultGreen = blendChannel(qGreen(bottomPixel) / 255.0,
                                                   qGreen(topPixel) / 255.0);
            qreal const resultBlue = blendChannel(qBlue(bottomPixel) / 255.0,
                                                  qBlue(topPixel) / 255.0);
            bottom->setPixel(x, y, qRgb(resultRed * 255.0,
                                        resultGreen * 255.0,
                                        resultBlue * 255.0));
        }
    }
}


// Neutral blendings

qreal AllanonBlending::blendChannel(qreal const bottomColorIntensity,
                                    qreal const topColorIntensity) const
{
    return (bottomColorIntensity + topColorIntensity) / 2.0;
}

qreal ArcusTangentBlending::blendChannel(qreal const bottomColorIntensity,
                                         qreal const topColorIntensity) const
{
    return 2.0 * atan(topColorIntensity / bottomColorIntensity) / M_PI;
}

qreal GeometricMeanBlending::blendChannel(qreal const bottomColorIntensity,
                                          qreal const topColorIntensity) const
{
    return sqrt(bottomColorIntensity * topColorIntensity);
}

qreal LinearLightBlending::blendChannel(qreal const bottomColorIntensity,
                                        qreal const topColorIntensity) const
{
    return qMin(qreal(1.0),
                qMax(qreal(0.0), qreal(bottomColorIntensity + 2.0 * topColorIntensity - 1.0)));
}

qreal OverlayBlending::blendChannel(qreal const bottomColorIntensity,
                                    qreal const topColorIntensity) const
{
    if (bottomColorIntensity < 0.5)
    {
        return 2.0 * bottomColorIntensity * topColorIntensity;
    }

    else
    {
        return 1.0 - 2.0 * (1.0 - bottomColorIntensity) * (1.0 - topColorIntensity);
    }
}

qreal ParallelBlending::blendChannel(qreal const bottomColorIntensity,
                                     qreal const topColorIntensity) const
{
    Q_UNUSED(bottomColorIntensity);
    Q_UNUSED(topColorIntensity);
    // FIXME:    return qMin( qMax( 2.0 / ( 1.0 / bottomColorIntensity + 1.0 / topColorIntensity )), 0.0, 1.0 );
    return 0.0;
}

qreal TextureBlending::blendChannel(qreal const bottomColorIntensity,
                                    qreal const topColorIntensity) const
{
    Q_UNUSED(bottomColorIntensity);
    Q_UNUSED(topColorIntensity);
    // FIXME: return qMax( qMin( topColorIntensity + bottomColorIntensity ) - 0.5 ), 1.0 ), 0.0 );
    return 0.0;
}


// Darkening blendings

qreal ColorBurnBlending::blendChannel(qreal const bottomColorIntensity,
                                      qreal const topColorIntensity) const
{
    Q_UNUSED(bottomColorIntensity);
    Q_UNUSED(topColorIntensity);
    // FIXME: check if this formula makes sense
    return qMin(qreal(1.0),
                qMax(qreal(0.0), qreal(1.0 - (1.0 - bottomColorIntensity) / topColorIntensity)));
}

qreal DarkBlending::blendChannel(qreal const bottomColorIntensity,
                                 qreal const topColorIntensity) const
{
    return (bottomColorIntensity + 1.0 - topColorIntensity) * topColorIntensity;
}

qreal DarkenBlending::blendChannel(qreal const bottomColorIntensity,
                                   qreal const topColorIntensity) const
{
    // FIXME: is this really ok? not vice versa?
    return bottomColorIntensity > topColorIntensity ? topColorIntensity : bottomColorIntensity;
}

qreal DivideBlending::blendChannel(qreal const bottomColorIntensity,
                                   qreal const topColorIntensity) const
{
    return log1p(bottomColorIntensity / (1.0  - topColorIntensity) / 8.0) / log(2.0);
}

qreal GammaDarkBlending::blendChannel(qreal const bottomColorIntensity,
                                      qreal const topColorIntensity) const
{
    return pow(bottomColorIntensity, 1.0 / topColorIntensity);
}

qreal LinearBurnBlending::blendChannel(qreal const bottomColorIntensity,
                                       qreal const topColorIntensity) const
{
    return qMax(qreal(0.0), bottomColorIntensity + topColorIntensity - qreal(1.0));
}

qreal MultiplyBlending::blendChannel(qreal const bottomColorIntensity,
                                     qreal const topColorIntensity) const
{
    return bottomColorIntensity * topColorIntensity;
}

qreal SubtractiveBlending::blendChannel(qreal const bottomColorIntensity,
                                        qreal const topColorIntensity) const
{
    return qMax(bottomColorIntensity - topColorIntensity, qreal(0.0));
}


// Lightning blendings

qreal AdditiveBlending::blendChannel(qreal const bottomColorIntensity,
                                     qreal const topColorIntensity) const
{
    return qMin(topColorIntensity + bottomColorIntensity, qreal(1.0));
}

qreal ColorDodgeBlending::blendChannel(qreal const bottomColorIntensity,
                                       qreal const topColorIntensity) const
{
    return qMin(qreal(1.0),
                qMax(qreal(0.0), qreal(bottomColorIntensity / (1.0 - topColorIntensity))));
}

qreal GammaLightBlending::blendChannel(qreal const bottomColorIntensity,
                                       qreal const topColorIntensity) const
{
    return pow(bottomColorIntensity, topColorIntensity);
}

qreal HardLightBlending::blendChannel(qreal const bottomColorIntensity,
                                      qreal const topColorIntensity) const
{
    return topColorIntensity < 0.5
           ? 2.0 * bottomColorIntensity * topColorIntensity
           : 1.0 - 2.0 * (1.0 - bottomColorIntensity) * (1.0 - topColorIntensity);
}

qreal LightBlending::blendChannel(qreal const bottomColorIntensity,
                                  qreal const topColorIntensity) const
{
    return bottomColorIntensity * (1.0 - topColorIntensity) + pow(topColorIntensity, 2);
}

qreal LightenBlending::blendChannel(qreal const bottomColorIntensity,
                                    qreal const topColorIntensity) const
{
    // is this ok?
    return bottomColorIntensity < topColorIntensity ? topColorIntensity : bottomColorIntensity;
}

qreal PinLightBlending::blendChannel(qreal const bottomColorIntensity,
                                     qreal const topColorIntensity) const
{
    return qMax(qreal(0.0), qMax(qreal(2.0 + topColorIntensity - 1.0),
                                 qMin(bottomColorIntensity, qreal(2.0 * topColorIntensity))));
}

qreal ScreenBlending::blendChannel(qreal const bottomColorIntensity,
                                   qreal const topColorIntensity) const
{
    return 1.0 - (1.0 - bottomColorIntensity) * (1.0 - topColorIntensity);
}

qreal SoftLightBlending::blendChannel(qreal const bottomColorIntensity,
                                      qreal const topColorIntensity) const
{
    return pow(bottomColorIntensity, pow(2.0, (2.0 * (0.5 - topColorIntensity))));
}

qreal VividLightBlending::blendChannel(qreal const bottomColorIntensity,
                                       qreal const topColorIntensity) const
{
    return topColorIntensity < 0.5
           ? qMin(qreal(1.0),
                  qMax(qreal(0.0), qreal(1.0 - (1.0 - bottomColorIntensity) / (2.0 * topColorIntensity))))
           : qMin(qreal(1.0),
                  qMax(qreal(0.0), qreal(bottomColorIntensity / (2.0 * (1.0 - topColorIntensity)))));
}


// Inverter blendings

qreal AdditiveSubtractiveBlending::blendChannel(qreal const bottomColorIntensity,
                                                qreal const topColorIntensity) const
{
    Q_UNUSED(bottomColorIntensity);
    Q_UNUSED(topColorIntensity);
    // FIXME:
    //    return qMin( 1.0, qMax( 0.0, abs( bottomColorIntensity * bottomColorIntensity
    //                                      - topColorIntensity * topColorIntensity )));
    return 0.0;
}

qreal BleachBlending::blendChannel(qreal const bottomColorIntensity,
                                   qreal const topColorIntensity) const
{
    // FIXME: "why this is the same formula as Screen Blending? Please correct.)"
    return 1.0 - (1.0 - bottomColorIntensity) * (1.0 - topColorIntensity);
}

qreal DifferenceBlending::blendChannel(qreal const bottomColorIntensity,
                                       qreal const topColorIntensity) const
{
    return qMax(qMin(qreal(1.0), qreal(bottomColorIntensity - topColorIntensity + 0.5)),
                qreal(0.0));
}

qreal EquivalenceBlending::blendChannel(qreal const bottomColorIntensity,
                                        qreal const topColorIntensity) const
{
    return 1.0 - qAbs(bottomColorIntensity - topColorIntensity);
}

qreal HalfDifferenceBlending::blendChannel(qreal const bottomColorIntensity,
                                           qreal const topColorIntensity) const
{
    return bottomColorIntensity + topColorIntensity
           - 2.0 * (bottomColorIntensity * topColorIntensity);
}


// Special purpose blendings

void CloudsBlending::blend(QImage* const bottom, TextureTile const* const top) const
{
    QImage const* const topImage = top->image();
    Q_ASSERT(topImage);
    Q_ASSERT(bottom->size() == topImage->size());
    int const width = bottom->width();
    int const height = bottom->height();

    for (int y = 0; y < height; ++y)
    {
        for (int x = 0; x < width; ++x)
        {
            qreal const c = qRed(topImage->pixel(x, y)) / 255.0;
            QRgb const bottomPixel = bottom->pixel(x, y);
            int const bottomRed = qRed(bottomPixel);
            int const bottomGreen = qGreen(bottomPixel);
            int const bottomBlue = qBlue(bottomPixel);
            bottom->setPixel(x, y, qRgb((int)(bottomRed + (255 - bottomRed) * c),
                                        (int)(bottomGreen + (255 - bottomGreen) * c),
                                        (int)(bottomBlue + (255 - bottomBlue) * c)));
        }
    }
}

} // namespace Marble
