Source/WebCore/platform/graphics/ColorNormalization.h

/*
 * Copyright (C) 2021 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * 1.  Redistributions of source code must retain the above copyright
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 *     notice, this list of conditions and the following disclaimer in the
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#pragma once

#include "Color.h"
#include "ColorConversion.h"
#include "ColorTypes.h"
#include <wtf/MathExtras.h>

namespace WebCore {

template<typename ColorType> ColorType makeColorTypeByNormalizingComponents(const ColorComponents<float, 4>&);
template<typename ColorType> Color makeCanonicalColor(ColorType);


// MARK: - Normalization

template<typename ComponentType> struct WhitenessBlackness {
    ComponentType whiteness;
    ComponentType blackness;
};

template<typename ComponentType> static auto normalizeClampedWhitenessBlacknessDisallowingNone(ComponentType whiteness, ComponentType blackness) -> WhitenessBlackness<ComponentType>
{
    //   If the sum of these two arguments is greater than 100%, then at
    //   computed-value time they are further normalized to add up to 100%, with
    //   the same relative ratio.
    if (auto sum = whiteness + blackness; sum >= 100)
        return { whiteness * 100.0 / sum, blackness * 100.0 / sum };

    return { whiteness, blackness };
}

template<typename ComponentType> static auto normalizeClampedWhitenessBlacknessAllowingNone(ComponentType whiteness, ComponentType blackness) -> WhitenessBlackness<ComponentType>
{
    if (std::isnan(whiteness) || std::isnan(blackness))
        return { whiteness, blackness };

    return normalizeClampedWhitenessBlacknessDisallowingNone(whiteness, blackness);
}

template<typename ComponentType> inline auto normalizeWhitenessBlackness(ComponentType whiteness, ComponentType blackness) -> WhitenessBlackness<ComponentType>
{
    //   Values outside of these ranges are not invalid, but are clamped to the
    //   ranges defined here at computed-value time.
    WhitenessBlackness<ComponentType> result {
        clampTo<ComponentType>(whiteness, 0.0, 100.0),
        clampTo<ComponentType>(blackness, 0.0, 100.0)
    };

    //   If the sum of these two arguments is greater than 100%, then at
    //   computed-value time they are further normalized to add up to 100%, with
    //   the same relative ratio.
    if (auto sum = result.whiteness + result.blackness; sum >= 100) {
        result.whiteness *= 100.0 / sum;
        result.blackness *= 100.0 / sum;
    }

    return result;
}

template<typename ComponentType> inline ComponentType normalizeHue(ComponentType hue)
{
    return std::fmod(std::fmod(hue, 360.0) + 360.0, 360.0);
}

template<typename ColorType> inline ColorType makeColorTypeByNormalizingComponents(const ColorComponents<float, 4>& colorComponents)
{
    return makeFromComponents<ColorType>(colorComponents);
}

template<> inline HWBA<float> makeColorTypeByNormalizingComponents<HWBA<float>>(const ColorComponents<float, 4>& colorComponents)
{
    auto [hue, whiteness, blackness, alpha] = colorComponents;
    auto [normalizedWhitness, normalizedBlackness] = normalizeWhitenessBlackness(whiteness, blackness);
    float normalizedHue = normalizeHue(hue);

    return { normalizedHue, normalizedWhitness, normalizedBlackness, alpha };
}

template<> inline HSLA<float> makeColorTypeByNormalizingComponents<HSLA<float>>(const ColorComponents<float, 4>& colorComponents)
{
    auto [hue, saturation, lightness, alpha] = colorComponents;
    float normalizedHue = normalizeHue(hue);

    return { normalizedHue, saturation, lightness, alpha };
}

template<> inline LCHA<float> makeColorTypeByNormalizingComponents<LCHA<float>>(const ColorComponents<float, 4>& colorComponents)
{
    auto [lightness, chroma, hue, alpha] = colorComponents;
    float normalizedHue = normalizeHue(hue);

    return { lightness, chroma, normalizedHue, alpha };
}

template<> inline OKLCHA<float> makeColorTypeByNormalizingComponents<OKLCHA<float>>(const ColorComponents<float, 4>& colorComponents)
{
    auto [lightness, chroma, hue, alpha] = colorComponents;
    float normalizedHue = normalizeHue(hue);

    return { lightness, chroma, normalizedHue, alpha };
}

// MARK: - Canonicalization

template<typename ColorType> inline Color makeCanonicalColor(ColorType color)
{
    return color;
}

template<> inline Color makeCanonicalColor<HWBA<float>>(HWBA<float> color)
{
    return convertColor<SRGBA<uint8_t>>(color);
}

template<> inline Color makeCanonicalColor<HSLA<float>>(HSLA<float> color)
{
    return convertColor<SRGBA<uint8_t>>(color);
}

}