Source/platform/graphics/Color.cpp

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This source file includes following definitions.
makeRGB
makeRGBA
colorFloatToRGBAByte
makeRGBA32FromFloats
colorWithOverrideAlpha
calcHue
makeRGBAFromHSLA
makeRGBAFromCMYKA
parseHexColorInternal
parseHexColor
parseHexColor
parseHexColor
differenceSquared
setFromString
serializedAsCSSComponentValue
serialized
nameForRenderTreeAsText
findNamedColor
setNamedColor
light
dark
combineWithAlpha
blendComponent
blend
blendWithWhite
getRGBA
getRGBA
getHSL
colorFromPremultipliedARGB
premultipliedARGBFromColor
/*
 * Copyright (C) 2003, 2004, 2005, 2006, 2008 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 COMPUTER, INC. ``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 COMPUTER, INC. OR
 * 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 "platform/graphics/Color.h"

#include "wtf/Assertions.h"
#include "wtf/DecimalNumber.h"
#include "wtf/HexNumber.h"
#include "wtf/MathExtras.h"
#include "wtf/text/StringBuilder.h"

using namespace std;

namespace WebCore {

#if !COMPILER(MSVC)
const RGBA32 Color::black;
const RGBA32 Color::white;
const RGBA32 Color::darkGray;
const RGBA32 Color::gray;
const RGBA32 Color::lightGray;
const RGBA32 Color::transparent;
#endif

static const RGBA32 lightenedBlack = 0xFF545454;
static const RGBA32 darkenedWhite = 0xFFABABAB;

RGBA32 makeRGB(int r, int g, int b)
{
    return 0xFF000000 | max(0, min(r, 255)) << 16 | max(0, min(g, 255)) << 8 | max(0, min(b, 255));
}

RGBA32 makeRGBA(int r, int g, int b, int a)
{
    return max(0, min(a, 255)) << 24 | max(0, min(r, 255)) << 16 | max(0, min(g, 255)) << 8 | max(0, min(b, 255));
}

static int colorFloatToRGBAByte(float f)
{
    // We use lroundf and 255 instead of nextafterf(256, 0) to match CG's rounding
    return max(0, min(static_cast<int>(lroundf(255.0f * f)), 255));
}

RGBA32 makeRGBA32FromFloats(float r, float g, float b, float a)
{
    return colorFloatToRGBAByte(a) << 24 | colorFloatToRGBAByte(r) << 16 | colorFloatToRGBAByte(g) << 8 | colorFloatToRGBAByte(b);
}

RGBA32 colorWithOverrideAlpha(RGBA32 color, float overrideAlpha)
{
    RGBA32 rgbOnly = color & 0x00FFFFFF;
    RGBA32 rgba = rgbOnly | colorFloatToRGBAByte(overrideAlpha) << 24;
    return rgba;
}

static double calcHue(double temp1, double temp2, double hueVal)
{
    if (hueVal < 0.0)
        hueVal++;
    else if (hueVal > 1.0)
        hueVal--;
    if (hueVal * 6.0 < 1.0)
        return temp1 + (temp2 - temp1) * hueVal * 6.0;
    if (hueVal * 2.0 < 1.0)
        return temp2;
    if (hueVal * 3.0 < 2.0)
        return temp1 + (temp2 - temp1) * (2.0 / 3.0 - hueVal) * 6.0;
    return temp1;
}

// Explanation of this algorithm can be found in the CSS3 Color Module
// specification at http://www.w3.org/TR/css3-color/#hsl-color with further
// explanation available at http://en.wikipedia.org/wiki/HSL_color_space

// all values are in the range of 0 to 1.0
RGBA32 makeRGBAFromHSLA(double hue, double saturation, double lightness, double alpha)
{
    const double scaleFactor = nextafter(256.0, 0.0);

    if (!saturation) {
        int greyValue = static_cast<int>(lightness * scaleFactor);
        return makeRGBA(greyValue, greyValue, greyValue, static_cast<int>(alpha * scaleFactor));
    }

    double temp2 = lightness < 0.5 ? lightness * (1.0 + saturation) : lightness + saturation - lightness * saturation;
    double temp1 = 2.0 * lightness - temp2;

    return makeRGBA(static_cast<int>(calcHue(temp1, temp2, hue + 1.0 / 3.0) * scaleFactor),
                    static_cast<int>(calcHue(temp1, temp2, hue) * scaleFactor),
                    static_cast<int>(calcHue(temp1, temp2, hue - 1.0 / 3.0) * scaleFactor),
                    static_cast<int>(alpha * scaleFactor));
}

RGBA32 makeRGBAFromCMYKA(float c, float m, float y, float k, float a)
{
    double colors = 1 - k;
    int r = static_cast<int>(nextafter(256, 0) * (colors * (1 - c)));
    int g = static_cast<int>(nextafter(256, 0) * (colors * (1 - m)));
    int b = static_cast<int>(nextafter(256, 0) * (colors * (1 - y)));
    return makeRGBA(r, g, b, static_cast<float>(nextafter(256, 0) * a));
}

// originally moved here from the CSS parser
template <typename CharacterType>
static inline bool parseHexColorInternal(const CharacterType* name, unsigned length, RGBA32& rgb)
{
    if (length != 3 && length != 6)
        return false;
    unsigned value = 0;
    for (unsigned i = 0; i < length; ++i) {
        if (!isASCIIHexDigit(name[i]))
            return false;
        value <<= 4;
        value |= toASCIIHexValue(name[i]);
    }
    if (length == 6) {
        rgb = 0xFF000000 | value;
        return true;
    }
    // #abc converts to #aabbcc
    rgb = 0xFF000000
        | (value & 0xF00) << 12 | (value & 0xF00) << 8
        | (value & 0xF0) << 8 | (value & 0xF0) << 4
        | (value & 0xF) << 4 | (value & 0xF);
    return true;
}

bool Color::parseHexColor(const LChar* name, unsigned length, RGBA32& rgb)
{
    return parseHexColorInternal(name, length, rgb);
}

bool Color::parseHexColor(const UChar* name, unsigned length, RGBA32& rgb)
{
    return parseHexColorInternal(name, length, rgb);
}

bool Color::parseHexColor(const String& name, RGBA32& rgb)
{
    unsigned length = name.length();

    if (!length)
        return false;
    if (name.is8Bit())
        return parseHexColor(name.characters8(), name.length(), rgb);
    return parseHexColor(name.characters16(), name.length(), rgb);
}

int differenceSquared(const Color& c1, const Color& c2)
{
    int dR = c1.red() - c2.red();
    int dG = c1.green() - c2.green();
    int dB = c1.blue() - c2.blue();
    return dR * dR + dG * dG + dB * dB;
}

bool Color::setFromString(const String& name)
{
    if (name[0] != '#')
        return setNamedColor(name);
    if (name.is8Bit())
        return parseHexColor(name.characters8() + 1, name.length() - 1, m_color);
    return parseHexColor(name.characters16() + 1, name.length() - 1, m_color);
}

String Color::serializedAsCSSComponentValue() const
{
    StringBuilder result;
    result.reserveCapacity(32);
    bool colorHasAlpha = hasAlpha();
    if (colorHasAlpha)
        result.append("rgba(", 5);
    else
        result.append("rgb(", 4);

    result.appendNumber(static_cast<unsigned char>(red()));
    result.append(", ", 2);

    result.appendNumber(static_cast<unsigned char>(green()));
    result.append(", ", 2);

    result.appendNumber(static_cast<unsigned char>(blue()));
    if (colorHasAlpha) {
        result.append(", ", 2);

        NumberToStringBuffer buffer;
        const char* alphaString = numberToFixedPrecisionString(alpha() / 255.0f, 6, buffer, true);
        result.append(alphaString, strlen(alphaString));
    }

    result.append(')');
    return result.toString();
}

String Color::serialized() const
{
    if (!hasAlpha()) {
        StringBuilder builder;
        builder.reserveCapacity(7);
        builder.append('#');
        appendByteAsHex(red(), builder, Lowercase);
        appendByteAsHex(green(), builder, Lowercase);
        appendByteAsHex(blue(), builder, Lowercase);
        return builder.toString();
    }

    StringBuilder result;
    result.reserveCapacity(28);
    const char commaSpace[] = ", ";
    const char rgbaParen[] = "rgba(";

    result.append(rgbaParen, 5);
    result.appendNumber(red());
    result.append(commaSpace, 2);
    result.appendNumber(green());
    result.append(commaSpace, 2);
    result.appendNumber(blue());
    result.append(commaSpace, 2);

    if (!alpha())
        result.append('0');
    else {
        NumberToLStringBuffer buffer;
        unsigned length = DecimalNumber(alpha() / 255.0).toStringDecimal(buffer, WTF::NumberToStringBufferLength);
        result.append(buffer, length);
    }

    result.append(')');
    return result.toString();
}

String Color::nameForRenderTreeAsText() const
{
    if (alpha() < 0xFF)
        return String::format("#%02X%02X%02X%02X", red(), green(), blue(), alpha());
    return String::format("#%02X%02X%02X", red(), green(), blue());
}

static inline const NamedColor* findNamedColor(const String& name)
{
    char buffer[64]; // easily big enough for the longest color name
    unsigned length = name.length();
    if (length > sizeof(buffer) - 1)
        return 0;
    for (unsigned i = 0; i < length; ++i) {
        UChar c = name[i];
        if (!c || c > 0x7F)
            return 0;
        buffer[i] = toASCIILower(static_cast<char>(c));
    }
    buffer[length] = '\0';
    return findColor(buffer, length);
}

bool Color::setNamedColor(const String& name)
{
    const NamedColor* foundColor = findNamedColor(name);
    m_color = foundColor ? foundColor->ARGBValue : 0;
    return foundColor;
}

Color Color::light() const
{
    // Hardcode this common case for speed.
    if (m_color == black)
        return lightenedBlack;

    const float scaleFactor = nextafterf(256.0f, 0.0f);

    float r, g, b, a;
    getRGBA(r, g, b, a);

    float v = max(r, max(g, b));

    if (v == 0.0f)
        // Lightened black with alpha.
        return Color(0x54, 0x54, 0x54, alpha());

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

    return Color(static_cast<int>(multiplier * r * scaleFactor),
                 static_cast<int>(multiplier * g * scaleFactor),
                 static_cast<int>(multiplier * b * scaleFactor),
                 alpha());
}

Color Color::dark() const
{
    // Hardcode this common case for speed.
    if (m_color == white)
        return darkenedWhite;

    const float scaleFactor = nextafterf(256.0f, 0.0f);

    float r, g, b, a;
    getRGBA(r, g, b, a);

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

    return Color(static_cast<int>(multiplier * r * scaleFactor),
                 static_cast<int>(multiplier * g * scaleFactor),
                 static_cast<int>(multiplier * b * scaleFactor),
                 alpha());
}

Color Color::combineWithAlpha(float otherAlpha) const
{
    return colorWithOverrideAlpha(rgb(), (alpha() / 255.f) * otherAlpha);
}

static int blendComponent(int c, int a)
{
    // We use white.
    float alpha = a / 255.0f;
    int whiteBlend = 255 - a;
    c -= whiteBlend;
    return static_cast<int>(c / alpha);
}

const int cStartAlpha = 153; // 60%
const int cEndAlpha = 204; // 80%;
const int cAlphaIncrement = 17; // Increments in between.

Color Color::blend(const Color& source) const
{
    if (!alpha() || !source.hasAlpha())
        return source;

    if (!source.alpha())
        return *this;

    int d = 255 * (alpha() + source.alpha()) - alpha() * source.alpha();
    int a = d / 255;
    int r = (red() * alpha() * (255 - source.alpha()) + 255 * source.alpha() * source.red()) / d;
    int g = (green() * alpha() * (255 - source.alpha()) + 255 * source.alpha() * source.green()) / d;
    int b = (blue() * alpha() * (255 - source.alpha()) + 255 * source.alpha() * source.blue()) / d;
    return Color(r, g, b, a);
}

Color Color::blendWithWhite() const
{
    // If the color contains alpha already, we leave it alone.
    if (hasAlpha())
        return *this;

    Color newColor;
    for (int alpha = cStartAlpha; alpha <= cEndAlpha; alpha += cAlphaIncrement) {
        // We have a solid color.  Convert to an equivalent color that looks the same when blended with white
        // at the current alpha.  Try using less transparency if the numbers end up being negative.
        int r = blendComponent(red(), alpha);
        int g = blendComponent(green(), alpha);
        int b = blendComponent(blue(), alpha);

        newColor = Color(r, g, b, alpha);

        if (r >= 0 && g >= 0 && b >= 0)
            break;
    }
    return newColor;
}

void Color::getRGBA(float& r, float& g, float& b, float& a) const
{
    r = red() / 255.0f;
    g = green() / 255.0f;
    b = blue() / 255.0f;
    a = alpha() / 255.0f;
}

void Color::getRGBA(double& r, double& g, double& b, double& a) const
{
    r = red() / 255.0;
    g = green() / 255.0;
    b = blue() / 255.0;
    a = alpha() / 255.0;
}

void Color::getHSL(double& hue, double& saturation, double& lightness) const
{
    // http://en.wikipedia.org/wiki/HSL_color_space. This is a direct copy of
    // the algorithm therein, although it's 360^o based and we end up wanting
    // [0...1) based. It's clearer if we stick to 360^o until the end.
    double r = static_cast<double>(red()) / 255.0;
    double g = static_cast<double>(green()) / 255.0;
    double b = static_cast<double>(blue()) / 255.0;
    double max = std::max(std::max(r, g), b);
    double min = std::min(std::min(r, g), b);

    if (max == min)
        hue = 0.0;
    else if (max == r)
        hue = (60.0 * ((g - b) / (max - min))) + 360.0;
    else if (max == g)
        hue = (60.0 * ((b - r) / (max - min))) + 120.0;
    else
        hue = (60.0 * ((r - g) / (max - min))) + 240.0;

    if (hue >= 360.0)
        hue -= 360.0;

    // makeRGBAFromHSLA assumes that hue is in [0...1).
    hue /= 360.0;

    lightness = 0.5 * (max + min);
    if (max == min)
        saturation = 0.0;
    else if (lightness <= 0.5)
        saturation = ((max - min) / (max + min));
    else
        saturation = ((max - min) / (2.0 - (max + min)));
}

Color colorFromPremultipliedARGB(RGBA32 pixelColor)
{
    int alpha = alphaChannel(pixelColor);
    if (alpha && alpha < 255) {
        return Color::createUnchecked(
            redChannel(pixelColor) * 255 / alpha,
            greenChannel(pixelColor) * 255 / alpha,
            blueChannel(pixelColor) * 255 / alpha,
            alpha);
    } else
        return Color(pixelColor);
}

RGBA32 premultipliedARGBFromColor(const Color& color)
{
    unsigned pixelColor;

    unsigned alpha = color.alpha();
    if (alpha < 255) {
        pixelColor = Color::createUnchecked(
            (color.red() * alpha  + 254) / 255,
            (color.green() * alpha  + 254) / 255,
            (color.blue() * alpha  + 254) / 255,
            alpha).rgb();
    } else
         pixelColor = color.rgb();

    return pixelColor;
}

} // namespace WebCore
/* [<][>][^][v][top][bottom][index][help] */
root/Source/platform/graphics/Color.cpp

DEFINITIONS
