Source/WebCore/platform/graphics/ColorModels.h

/*
 * Copyright (C) 2021 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <array>
#include <limits>

namespace WebCore {

enum class RGBBoundedness { Bounded, Extended };

template<typename, RGBBoundedness> struct RGBModel;
template<typename> struct AlphaTraits;
template<typename> struct ColorComponentInfo;
template<typename> struct HSLModel;
template<typename> struct HWBModel;
template<typename> struct LCHModel;
template<typename> struct LabModel;
template<typename> struct XYZModel;

// MARK: Resolved/Unresolved Defintitions

template<typename ColorType, typename ColorModel = typename ColorType::Model> struct ExposedColorType;
template<typename ColorType> struct ResolvedColorType;
template<typename ColorType> struct UnresolvedColorType;

template<typename ColorType> constexpr ResolvedColorType<ColorType> resolvedColor(ColorType input)
{
    return ResolvedColorType<ColorType> { input };
}

template<typename ColorType> constexpr UnresolvedColorType<ColorType> unresolvedColor(ColorType input)
{
    return UnresolvedColorType<ColorType> { input };
}

inline constexpr ColorComponents<uint8_t, 4> resolveColorComponents(const ColorComponents<uint8_t, 4>& colorComponents)
{
    return colorComponents;
}

inline constexpr ColorComponents<float, 4> resolveColorComponents(const ColorComponents<float, 4>& colorComponents)
{
    return colorComponents.map([] (float component) { return std::isnan(component) ? 0.0f : component; });
}


template<typename ColorType> struct ResolvedColorType : ExposedColorType<ColorType, typename ColorType::Model> {
    using CanonicalType = ColorType;

    // Calling resolved() or unresolved() on a type that is already resolved is a no-op, so we can
    // just return ourselves.
    constexpr auto resolved() const { return *this; }
    constexpr auto unresolved() const { return *this; }

private:
    template<typename C> friend constexpr ResolvedColorType<C> resolvedColor(C);

    explicit constexpr ResolvedColorType(ColorType color)
        : ExposedColorType<ColorType, typename ColorType::Model> { resolve(color) }
    {
    }

    template<typename C, typename std::enable_if_t<std::is_same_v<typename C::ComponentType, float>>* = nullptr>
    static constexpr C resolve(C color)
    {
        auto [c1, c2, c3, alpha] = resolveColorComponents(asColorComponents(ExposedColorType<C, typename C::Model> { color }));
        return ColorType { c1, c2, c3, alpha };
    }

    template<typename C, typename std::enable_if_t<std::is_same_v<typename C::ComponentType, uint8_t>>* = nullptr>
    static constexpr C resolve(C color)
    {
        return color;
    }
};

template<typename ColorType> struct UnresolvedColorType : ExposedColorType<ColorType, typename ColorType::Model> {
    using CanonicalType = ColorType;

    // Calling unresolved() on a type that is already unresolved is a no-op, so we can
    // just return ourselves.
    constexpr auto unresolved() const { return *this; }

private:
    template<typename C> friend constexpr UnresolvedColorType<C> unresolvedColor(C);

    explicit constexpr UnresolvedColorType(ColorType color)
        : ExposedColorType<ColorType, typename ColorType::Model> { color }
    {
    }
};


// MARK: - Color Model support types.

template<> struct AlphaTraits<float> {
    static constexpr float transparent = 0.0f;
    static constexpr float opaque = 1.0f;
};

template<> struct AlphaTraits<uint8_t> {
    static constexpr uint8_t transparent = 0;
    static constexpr uint8_t opaque = 255;
};

enum class ColorComponentType {
    Angle,
    Number,
    Percentage
};

enum class ColorSpaceCoordinateSystem {
    RectangularOrthogonal,
    CylindricalPolar
};

template<typename T> struct ColorComponentInfo {
    T min;
    T max;
    ColorComponentType type;
};

// MARK: - Color Model Definititions

// MARK: HSLModel

template<> struct HSLModel<float> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { 0, 360, ColorComponentType::Angle },
        { 0, 100, ColorComponentType::Percentage },
        { 0, 100, ColorComponentType::Percentage }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::CylindricalPolar;
};

template<typename ColorType> struct ExposedColorType<ColorType, HSLModel<typename ColorType::ComponentType>> : ColorType {
    using ColorType::hue;
    using ColorType::saturation;
    using ColorType::lightness;
    using ColorType::alpha;
};

template<typename T, typename ColorType> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, HSLModel<T>>& c)
{
    return { c.hue, c.saturation, c.lightness, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesHSLModel = std::is_same_v<typename ColorType::Model, HSLModel<typename ColorType::ComponentType>>;

// MARK: HWBModel

template<> struct HWBModel<float> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { 0, 360, ColorComponentType::Angle },
        { 0, 100, ColorComponentType::Percentage },
        { 0, 100, ColorComponentType::Percentage }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::CylindricalPolar;
};

template<typename ColorType> struct ExposedColorType<ColorType, HWBModel<typename ColorType::ComponentType>> : ColorType {
    using ColorType::hue;
    using ColorType::whiteness;
    using ColorType::blackness;
    using ColorType::alpha;
};

template<typename T, typename ColorType> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, HWBModel<T>>& c)
{
    return { c.hue, c.whiteness, c.blackness, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesHWBModel = std::is_same_v<typename ColorType::Model, HWBModel<typename ColorType::ComponentType>>;

// MARK: LabModel

template<> struct LabModel<float> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { 0, std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::RectangularOrthogonal;
};

template<typename ColorType> struct ExposedColorType<ColorType, LabModel<typename ColorType::ComponentType>> : ColorType {
    using ColorType::lightness;
    using ColorType::a;
    using ColorType::b;
    using ColorType::alpha;
};

template<typename T, typename ColorType> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, LabModel<T>>& c)
{
    return { c.lightness, c.a, c.b, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesLabModel = std::is_same_v<typename ColorType::Model, LabModel<typename ColorType::ComponentType>>;

// MARK: LCHModel

template<> struct LCHModel<float> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { 0, std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { 0, std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { 0, 360, ColorComponentType::Angle }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::CylindricalPolar;
};

template<typename ColorType> struct ExposedColorType<ColorType, LCHModel<typename ColorType::ComponentType>> : ColorType {
    using ColorType::lightness;
    using ColorType::chroma;
    using ColorType::hue;
    using ColorType::alpha;
};

template<typename T, typename ColorType> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, LCHModel<T>>& c)
{
    return { c.lightness, c.chroma, c.hue, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesLCHModel = std::is_same_v<typename ColorType::Model, LCHModel<typename ColorType::ComponentType>>;

// MARK: RGBModel

template<> struct RGBModel<float, RGBBoundedness::Bounded> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { 0, 1, ColorComponentType::Number },
        { 0, 1, ColorComponentType::Number },
        { 0, 1, ColorComponentType::Number }
    } };
    static constexpr bool isInvertible = true;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::RectangularOrthogonal;
};

template<> struct RGBModel<uint8_t, RGBBoundedness::Bounded> {
    static constexpr std::array<ColorComponentInfo<uint8_t>, 3> componentInfo { {
        { 0, 255, ColorComponentType::Number },
        { 0, 255, ColorComponentType::Number },
        { 0, 255, ColorComponentType::Number }
    } };
    static constexpr bool isInvertible = true;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::RectangularOrthogonal;
};

template<> struct RGBModel<float, RGBBoundedness::Extended> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::RectangularOrthogonal;
};

template<typename ColorType, RGBBoundedness boundedness> struct ExposedColorType<ColorType, RGBModel<typename ColorType::ComponentType, boundedness>> : ColorType {
    using ColorType::red;
    using ColorType::green;
    using ColorType::blue;
    using ColorType::alpha;
};

template<typename T, typename ColorType, RGBBoundedness boundedness> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, RGBModel<T, boundedness>>& c)
{
    return { c.red, c.green, c.blue, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesRGBModel =
       std::is_same_v<typename ColorType::Model, RGBModel<typename ColorType::ComponentType, RGBBoundedness::Bounded>>
    || std::is_same_v<typename ColorType::Model, RGBModel<typename ColorType::ComponentType, RGBBoundedness::Extended>>;


// MARK: XYZModel

template<> struct XYZModel<float> {
    static constexpr std::array<ColorComponentInfo<float>, 3> componentInfo { {
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number },
        { -std::numeric_limits<float>::infinity(), std::numeric_limits<float>::infinity(), ColorComponentType::Number }
    } };
    static constexpr bool isInvertible = false;
    static constexpr auto coordinateSystem = ColorSpaceCoordinateSystem::RectangularOrthogonal;
};

template<typename ColorType> struct ExposedColorType<ColorType, XYZModel<typename ColorType::ComponentType>> : ColorType {
    using ColorType::x;
    using ColorType::y;
    using ColorType::z;
    using ColorType::alpha;
};

template<typename T, typename ColorType> constexpr ColorComponents<T, 4> asColorComponents(const ExposedColorType<ColorType, XYZModel<T>>& c)
{
    return { c.x, c.y, c.z, c.alpha };
}

template<typename ColorType> inline constexpr bool UsesXYZModel = std::is_same_v<typename ColorType::Model, XYZModel<typename ColorType::ComponentType>>;


// get<> overload (along with std::tuple_size and std::tuple_element below) to support destructuring of explicitly resolved and unresolved colors.

template<size_t I, typename ColorType> constexpr typename ColorType::ComponentType get(const ExposedColorType<ColorType>& color)
{
    return asColorComponents(color)[I];
}

}

namespace std {

template<typename ColorType>
class tuple_size<WebCore::ResolvedColorType<ColorType>> : public std::integral_constant<size_t, 4> { };

template<size_t I, typename ColorType>
class tuple_element<I, WebCore::ResolvedColorType<ColorType>> {
public:
    using type = typename WebCore::ResolvedColorType<ColorType>::ComponentType;
};

template<typename ColorType>
class tuple_size<WebCore::UnresolvedColorType<ColorType>> : public std::integral_constant<size_t, 4> { };

template<size_t I, typename ColorType>
class tuple_element<I, WebCore::UnresolvedColorType<ColorType>> {
public:
    using type = typename WebCore::UnresolvedColorType<ColorType>::ComponentType;
};

}