qcolor.cpp

奇趣公司比较新的qt/emd版本

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#include "qcolor.h"
#include "qcolor_p.h"
#include "qnamespace.h"
#include "qcolormap.h"
#include "qdatastream.h"
#include "qvariant.h"
#include "qdebug.h"

#ifdef Q_WS_X11
#  include "qapplication.h"
#  include "qx11info_x11.h"
#  include "private/qt_x11_p.h"

static bool allowX11ColorNames = false;

#endif

#include <math.h>
#include <stdio.h>
#include <limits.h>


/*!
    \class QColor
    \brief The QColor class provides colors based on RGB, HSV or CMYK values.

    \ingroup multimedia
    \ingroup appearance
    \mainclass

    A color is normally specified in terms of RGB (red, green, and
    blue) components, but it is also possible to specify it in terms
    of HSV (hue, saturation, and value) and CMYK (cyan, magenta,
    yellow and black) components. In addition a color can be specified
    using a color name. The color name can be any of the SVG 1.0 color
    names.

    \table
    \row
    \o \inlineimage qcolor-rgb.png
    \o \inlineimage qcolor-hsv.png
    \o \inlineimage qcolor-cmyk.png
    \header
    \o RGB \o HSV \o CMYK
    \endtable

    The QColor constructor creates the color based on RGB values.  To
    create a QColor based on either HSV or CMYK values, use the
    toHsv() and toCmyk() functions respectively. These functions
    return a copy of the color using the desired format. In addition
    the static fromRgb(), fromHsv() and fromCmyk() functions create
    colors from the specified values. Alternatively, a color can be
    converted to any of the three formats using the convertTo()
    function (returning a copy of the color in the desired format), or
    any of the setRgb(), setHsv() and setCmyk() functions altering \e
    this color's format. The spec() function tells how the color was
    specified.

    A color can be set by passing an RGB string (such as "#112233"),
    or a color name (such as "blue"), to the setNamedColor() function.
    The color names are taken from the SVG 1.0 color names. The name()
    function returns the name of the color in the format
    "#RRGGBB". Colors can also be set using setRgb(), setHsv() and
    setCmyk(). To get a lighter or darker color use the lighter() and
    darker() functions respectively.

    The isValid() function indicates whether a QColor is legal at
    all. For example, a RGB color with RGB values out of range is
    illegal. For performance reasons, QColor mostly disregards illegal
    colors, and for that reason, the result of using an invalid color
    is undefined.

    The color components can be retrieved individually, e.g with
    red(), hue() and cyan(). The values of the color components can
    also be retrieved in one go using the getRgb(), getHsv() and
    getCmyk() functions. Using the RGB color model, the color
    components can in addition be accessed with rgb().

    There are several related non-members: QRgb is a typdef for an
    unsigned int representing the RGB value triplet (r, g, b). Note
    that it also can hold a value for the alpha-channel (for more
    information, see the \l {QColor#Alpha-Blended
    Drawing}{Alpha-Blended Drawing} section). The qRed(), qBlue() and
    qGreen() functions return the respective component of the given
    QRgb value, while the qRgb() and qRgba() functions create and
    return the QRgb triplet based on the given component
    values. Finally, the qAlpha() function returns the alpha component
    of the provided QRgb, and the qGray() function calculates and
    return a gray value based on the given value.

    QColor is platform and device independent. The QColormap class
    maps the color to the hardware.

    For more information about painting in general, see \l{The Paint
    System} documentation.

    \tableofcontents

    \section1 Integer vs. Floating Point Precision

    QColor supports floating point precision and provides floating
    point versions of all the color components functions,
    e.g. getRgbF(), hueF() and fromCmykF(). Note that since the
    components are stored using 16-bit integers, there might be minor
    deviations between the values set using, for example, setRgbF()
    and the values returned by the getRgbF() function due to rounding.

    While the integer based functions take values in the range 0-255
    (except hue() which must have values within the range 0-359),
    the floating point functions accept values in the range 0.0 - 1.0.

    \section1 Alpha-Blended Drawing

    QColor also support alpha-blended outlining and filling. The
    alpha channel of a color specifies the transparency effect, 0
    represents a fully transparent color, while 255 represents a fully
    opaque color. For example:

    \code
    // Specfiy semi-transparent red
    painter.setBrush(QColor(255, 0, 0, 127));
    painter.drawRect(0, 0, width()/2, height());

    // Specify semi-transparend blue
    painter.setBrush(QColor(0, 0, 255, 127));
    painter.drawRect(0, 0, width(), height()/2);
    \endcode

    The code above produces the following output:

    \img alphafill.png

    Alpha-blended drawing is supported on Windows, Mac OS X, and on
    X11 systems that have the X Render extension installed.

    The alpha channel of a color can be retrieved and set using the
    alpha() and setAlpha() functions if its value is an integer, and
    alphaF() and setAlphaF() if its value is qreal (double). By
    default, the alpha-channel is set to 255 (opaque). To retrieve and
    set \e all the RGB color components (including the alpha-channel)
    in one go, use the rgba() and setRgba() functions.

    \section1 Predefined Colors

    There are 20 predefined QColors: Qt::white, Qt::black,
    Qt::red, Qt::darkRed, Qt::green, Qt::darkGreen, Qt::blue,
    Qt::darkBlue, Qt::cyan, Qt::darkCyan, Qt::magenta,
    Qt::darkMagenta, Qt::yellow, Qt::darkYellow, Qt::gray,
    Qt::darkGray, Qt::lightGray, Qt::color0, Qt::color1, and
    Qt::transparent.

    \img qt-colors.png Qt Colors

    QColor provides the static colorNames() function which returns a
    QStringList containing the color names Qt knows about.

    The colors Qt::color0 (zero pixel value) and Qt::color1 (non-zero
    pixel value) are special colors for drawing in QBitmaps. Painting with
    Qt::color0 sets the bitmap bits to 0 (transparent, i.e. background), and
    painting with Qt::color1 sets the bits to 1 (opaque, i.e. foreground).

    \section1 The HSV Color Model

    The RGB model is hardware-oriented. Its representation is close to
    what most monitors show. In contrast, HSV represents color in a way
    more suited to the human perception of color. For example, the
    relationships "stronger than", "darker than", and "the opposite of"
    are easily expressed in HSV but are much harder to express in RGB.

    HSV, like RGB, has three components:

    \list
    \o H, for hue, is in the range 0 to 359 if the color is chromatic (not
    gray), or meaningless if it is gray. It represents degrees on the
    color wheel familiar to most people. Red is 0 (degrees), green is
    120, and blue is 240.

    \inlineimage qcolor-hue.png

    \o S, for saturation, is in the range 0 to 255, and the bigger it is,
    the stronger the color is. Grayish colors have saturation near 0; very
    strong colors have saturation near 255.

    \inlineimage qcolor-saturation.png

    \o V, for value, is in the range 0 to 255 and represents lightness or
    brightness of the color. 0 is black; 255 is as far from black as
    possible.

    \inlineimage qcolor-value.png
    \endlist

    Here are some examples: pure red is H=0, S=255, V=255; a dark red,
    moving slightly towards the magenta, could be H=350 (equivalent to
    -10), S=255, V=180; a grayish light red could have H about 0 (say
    350-359 or 0-10), S about 50-100, and S=255.

    Qt returns a hue value of -1 for achromatic colors. If you pass a
    hue value that is too large, Qt forces it into range. Hue 360 or 720 is
    treated as 0; hue 540 is treated as 180.

    In addition to the standard HSV model, Qt provides an
    alpha-channel to feature \l {QColor#Alpha-Blended
    Drawing}{alpha-blended drawing}.

    \section1 The CMYK Color Model

    While the RGB and HSV color models are used for display on
    computer monitors, the CMYK model is used in the four-color
    printing process of printing presses and some hard-copy
    devices.

    CMYK has four components, all in the range 0-255: cyan (C),
    magenta (M), yellow (Y) and black (K).  Cyan, magenta and yellow
    are called subtractive colors; the CMYK color model creates color
    by starting with a white surface and then subtracting color by
    applying the appropriate components. While combining cyan, magenta
    and yellow gives the color black, subtracting one or more will
    yield any other color. When combined in various percentages, these
    three colors can create the entire spectrum of colors.

    Mixing 100 percent of cyan, magenta and yellow \e does produce
    black, but the result is unsatisfactory since it wastes ink,
    increases drying time, and gives a muddy colour when printing. For
    that reason, black is added in professional printing to provide a
    solid black tone; hence the term 'four color process'.

    In addition to the standard CMYK model, Qt provides an
    alpha-channel to feature \l {QColor#Alpha-Blended
    Drawing}{alpha-blended drawing}.

    \sa QPalette, QBrush, QApplication::setColorSpec()
*/

#define QCOLOR_INT_RANGE_CHECK(fn, var) \
    do { \
        if (var < 0 || var > 255) { \
            qWarning(#fn": invalid value %d", var); \
            var = qMax(0, qMin(var, 255)); \
        } \
    } while (0)

#define QCOLOR_REAL_RANGE_CHECK(fn, var) \
    do { \
        if (var < qreal(0.0) || var > qreal(1.0)) { \
            qWarning(#fn": invalid value %g", var); \
            var = qMax(qreal(0.0), qMin(var, qreal(1.0)));      \
        } \
    } while (0)

/*****************************************************************************
  QColor member functions
 *****************************************************************************/

/*!
    \enum QColor::Spec

    The type of color specified, either RGB, HSV or CMYK.

    \value Rgb
    \value Hsv
    \value Cmyk
    \value Invalid

    \sa spec(), convertTo()
*/

/*!
    \fn Spec QColor::spec() const

    Returns how the color was specified.

    \sa Spec, convertTo()
*/


/*!
    \fn QColor::QColor()

    Constructs an invalid color with the RGB value (0, 0, 0). An
    invalid color is a color that is not properly set up for the
    underlying window system.

    The alpha value of an invalid color is unspecified.

    \sa isValid()
*/

/*!
    \overload

    Constructs a new color with a color value of \a color.

    \sa isValid(), {QColor#Predefined Colors}{Predefined Colors}
 */
QColor::QColor(Qt::GlobalColor color)
{
#define QRGB(r, g, b) \
    QRgb(((0xff << 24) | ((r & 0xff) << 16) | ((g & 0xff) << 8) | (b & 0xff)))
#define QRGBA(r, g, b, a) \
    QRgb(((a & 0xff) << 24) | ((r & 0xff) << 16) | ((g & 0xff) << 8) | (b & 0xff))

    static const QRgb global_colors[] = {
        QRGB(255, 255, 255), // Qt::color0
        QRGB(  0,   0,   0), // Qt::color1
        QRGB(  0,   0,   0), // black
        QRGB(255, 255, 255), // white
        /*
         * From the "The Palette Manager: How and Why" by Ron Gery,
         * March 23, 1992, archived on MSDN:
         *
         *     The Windows system palette is broken up into two
         *     sections, one with fixed colors and one with colors
         *     that can be changed by applications. The system palette
         *     predefines 20 entries; these colors are known as the
         *     static or reserved colors and consist of the 16 colors
         *     found in the Windows version 3.0 VGA driver and 4
         *     additional colors chosen for their visual appeal.  The
         *     DEFAULT_PALETTE stock object is, as the name implies,
         *     the default palette selected into a device context (DC)
         *     and consists of these static colors. Applications can
         *     set the remaining 236 colors using the Palette Manager.
         *
         * The 20 reserved entries have indices in [0,9] and
         * [246,255]. We reuse 17 of them.
         */
        QRGB(128, 128, 128), // index 248   medium gray
        QRGB(160, 160, 164), // index 247   light gray
        QRGB(192, 192, 192), // index 7     light gray
        QRGB(255,   0,   0), // index 249   red
        QRGB(  0, 255,   0), // index 250   green
        QRGB(  0,   0, 255), // index 252   blue
        QRGB(  0, 255, 255), // index 254   cyan
        QRGB(255,   0, 255), // index 253   magenta
        QRGB(255, 255,   0), // index 251   yellow
        QRGB(128,   0,   0), // index 1     dark red
        QRGB(  0, 128,   0), // index 2     dark green
        QRGB(  0,   0, 128), // index 4     dark blue
        QRGB(  0, 128, 128), // index 6     dark cyan
        QRGB(128,   0, 128), // index 5     dark magenta
        QRGB(128, 128,   0), // index 3     dark yellow
        QRGBA(0, 0, 0, 0)    //             transparent
    };
#undef QRGB
#undef QRGBA

    setRgb(qRed(global_colors[color]),
           qGreen(global_colors[color]),
           qBlue(global_colors[color]),
           qAlpha(global_colors[color]));
}

/*!
    \fn QColor::QColor(int r, int g, int b, int a = 255)

    Constructs a color with the RGB value \a r, \a g, \a b, and the
    alpha-channel (transparency) value of \a a.

    The color is left invalid if any of the arguments are invalid.

    \sa setRgba(), isValid()
*/

/*!
    Constructs a color with the value \a color. The alpha component is
    ignored and set to solid.

    \sa fromRgb(), isValid()
*/

QColor::QColor(QRgb color)
{
    cspec = Rgb;
    ct.argb.alpha = 0xffff;
    ct.argb.red   = qRed(color)   * 0x101;
    ct.argb.green = qGreen(color) * 0x101;
    ct.argb.blue  = qBlue(color)  * 0x101;
    ct.argb.pad   = 0;
}


/*!
    \internal

    Constructs a color with the given \a spec.

    This function is primarly present to avoid that QColor::Invalid
    becomes a valid color by accident.
*/

QColor::QColor(Spec spec)
{
    switch (spec) {
    case Invalid:
        invalidate();
        break;
    case Rgb:
        setRgb(0, 0, 0);
        break;
    case Hsv:
        setHsv(0, 0, 0);
        break;
    case Cmyk:
        setCmyk(0, 0, 0, 0);
        break;
    }
}

/*!
    \fn QColor::QColor(const QString &name)

    Constructs a named color in the same way as setNamedColor() using
    the given \a name.