Source/WebCore/platform/graphics/Color.cpp

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 * modification, are permitted provided that the following conditions
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#include "config.h"
#include "Color.h"

#include "AnimationUtilities.h"
#include "ColorSerialization.h"
#include "ColorUtilities.h"
#include <wtf/Assertions.h>
#include <wtf/MathExtras.h>
#include <wtf/text/StringBuilder.h>
#include <wtf/text/TextStream.h>

namespace WebCore {

static constexpr SimpleColor lightenedBlack { 0xFF545454 };
static constexpr SimpleColor darkenedWhite { 0xFFABABAB };

Color::Color(const Color& other)
    : m_colorData(other.m_colorData)
{
    if (isExtended())
        m_colorData.extendedColor->ref();
}

Color::Color(Color&& other)
{
    *this = WTFMove(other);
}

Color& Color::operator=(const Color& other)
{
    if (*this == other)
        return *this;

    if (isExtended())
        m_colorData.extendedColor->deref();

    m_colorData = other.m_colorData;

    if (isExtended())
        m_colorData.extendedColor->ref();
    return *this;
}

Color& Color::operator=(Color&& other)
{
    if (*this == other)
        return *this;

    if (isExtended())
        m_colorData.extendedColor->deref();

    m_colorData = other.m_colorData;
    other.m_colorData.simpleColorAndFlags = invalidSimpleColor;

    return *this;
}

Color Color::lightened() const
{
    // Hardcode this common case for speed.
    if (isSimple() && asSimple() == black)
        return lightenedBlack;

    auto [r, g, b, a] = toSRGBALossy();
    float v = std::max({ r, g, b });

    if (v == 0.0f)
        return lightenedBlack.colorWithAlpha(alpha());

    float multiplier = std::min(1.0f, v + 0.33f) / v;

    return makeSimpleColor(SRGBA { multiplier * r, multiplier * g, multiplier * b, a });
}

Color Color::darkened() const
{
    // Hardcode this common case for speed.
    if (isSimple() && asSimple() == white)
        return darkenedWhite;
    
    auto [r, g, b, a] = toSRGBALossy();

    float v = std::max({ r, g, b });
    float multiplier = std::max(0.0f, (v - 0.33f) / v);

    return makeSimpleColor(SRGBA { multiplier * r, multiplier * g, multiplier * b, a });
}

float Color::lightness() const
{
    // FIXME: This can probably avoid conversion to sRGB by having per-colorspace algorithms for HSL.
    return WebCore::lightness(toSRGBALossy());
}

float Color::luminance() const
{
    // FIXME: This can probably avoid conversion to sRGB by having per-colorspace algorithms
    // for luminance (e.g. convertToXYZ(c).yComponent()).
    return WebCore::luminance(toSRGBALossy());
}

Color Color::colorWithAlpha(float alpha) const
{
    if (isExtended())
        return asExtended().colorWithAlpha(alpha);

    Color result = asSimple().colorWithAlpha(convertToComponentByte(alpha));

    // FIXME: Why is preserving the semantic bit desired and/or correct here?
    if (isSemantic())
        result.tagAsSemantic();
    return result;
}

Color Color::invertedColorWithAlpha(float alpha) const
{
    if (isExtended())
        return asExtended().invertedColorWithAlpha(alpha);
    return asSimple().invertedColorWithAlpha(convertToComponentByte(alpha));
}

Color Color::semanticColor() const
{
    if (isSemantic())
        return *this;

    return { toSRGBASimpleColorLossy(), Semantic };
}

std::pair<ColorSpace, ColorComponents<float>> Color::colorSpaceAndComponents() const
{
    if (isExtended())
        return { asExtended().colorSpace(), asExtended().components() };
    return { ColorSpace::SRGB, asColorComponents(asSimple().asSRGBA<float>()) };
}

SimpleColor Color::toSRGBASimpleColorLossy() const
{
    if (isExtended())
        return makeSimpleColor(asExtended().toSRGBALossy());
    return asSimple();
}

SRGBA<float> Color::toSRGBALossy() const
{
    if (isExtended())
        return asExtended().toSRGBALossy();
    return asSimple().asSRGBA<float>();
}

TextStream& operator<<(TextStream& ts, const Color& color)
{
    return ts << serializationForRenderTreeAsText(color);
}

TextStream& operator<<(TextStream& ts, ColorSpace colorSpace)
{
    switch (colorSpace) {
    case ColorSpace::SRGB:
        ts << "sRGB";
        break;
    case ColorSpace::LinearRGB:
        ts << "LinearRGB";
        break;
    case ColorSpace::DisplayP3:
        ts << "DisplayP3";
        break;
    }
    return ts;
}

} // namespace WebCore