Source/WebCore/platform/graphics/ColorUtilities.cpp

/*
 * Copyright (C) 2017, 2020 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 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 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.
 */

#include "config.h"
#include "ColorUtilities.h"

namespace WebCore {

SRGBA<float> premultiplied(const SRGBA<float>& color)
{
    auto [r, g, b, a] = color;
    return { r * a, g * a, b * a, a };
}

SRGBA<float> unpremultiplied(const SRGBA<float>& color)
{
    auto [r, g, b, a] = color;
    if (!a)
        return color;
    return makeFromComponentsClampingExceptAlpha<SRGBA<float>>(r / a, g / a, b / a, a);
}

SRGBA<uint8_t> premultipliedFlooring(SRGBA<uint8_t> color)
{
    auto [r, g, b, a] = color;
    if (!a)
        return { 0, 0, 0, 0 };
    if (a == 255)
        return color;
    return makeFromComponentsClampingExceptAlpha<SRGBA<uint8_t>>(fastDivideBy255(r * a), fastDivideBy255(g * a), fastDivideBy255(b * a), a);
}

SRGBA<uint8_t> premultipliedCeiling(SRGBA<uint8_t> color)
{
    auto [r, g, b, a] = color;
    if (!a)
        return { 0, 0, 0, 0 };
    if (a == 255)
        return color;
    return makeFromComponentsClampingExceptAlpha<SRGBA<uint8_t>>(fastDivideBy255(r * a + 254), fastDivideBy255(g * a + 254), fastDivideBy255(b * a + 254), a);
}

static inline uint16_t unpremultipliedComponentByte(uint8_t c, uint8_t a)
{
    return (fastMultiplyBy255(c) + a - 1) / a;
}

SRGBA<uint8_t> unpremultiplied(SRGBA<uint8_t> color)
{
    auto [r, g, b, a] = color;
    if (!a || a == 255)
        return color;
    return makeFromComponentsClampingExceptAlpha<SRGBA<uint8_t>>(unpremultipliedComponentByte(r, a), unpremultipliedComponentByte(g, a), unpremultipliedComponentByte(b, a), a);
}

} // namespace WebCore