include/QtGui/qrgb.h

0001 // Copyright (C) 2016 The Qt Company Ltd.
0002 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
0003
0004 #ifndef QRGB_H
0005 #define QRGB_H
0006
0007 #include <QtGui/qtguiglobal.h>
0008 #include <QtCore/qprocessordetection.h>
0009
0010 QT_BEGIN_NAMESPACE
0011
0012
0013 typedef unsigned int QRgb;                        // RGB triplet
0014
0015 // non-namespaced Qt global variable
0016  inline constexpr QRgb RGB_MASK = 0x00ffffff;     // masks RGB values
0017
0018 inline constexpr int qRed(QRgb rgb)                     // get red part of RGB
0019 { return ((rgb >> 16) & 0xff); }
0020
0021 inline constexpr int qGreen(QRgb rgb)                   // get green part of RGB
0022 { return ((rgb >> 8) & 0xff); }
0023
0024 inline constexpr int qBlue(QRgb rgb)                    // get blue part of RGB
0025 { return (rgb & 0xff); }
0026
0027 inline constexpr int qAlpha(QRgb rgb)                   // get alpha part of RGBA
0028 { return rgb >> 24; }
0029
0030 inline constexpr QRgb qRgb(int r, int g, int b)         // set RGB value
0031 { return (0xffu << 24) | ((r & 0xffu) << 16) | ((g & 0xffu) << 8) | (b & 0xffu); }
0032
0033 inline constexpr QRgb qRgba(int r, int g, int b, int a) // set RGBA value
0034 { return ((a & 0xffu) << 24) | ((r & 0xffu) << 16) | ((g & 0xffu) << 8) | (b & 0xffu); }
0035
0036 inline constexpr int qGray(int r, int g, int b)         // convert R,G,B to gray 0..255
0037 { return (r*11+g*16+b*5)/32; }
0038
0039 inline constexpr int qGray(QRgb rgb)                    // convert RGB to gray 0..255
0040 { return qGray(qRed(rgb), qGreen(rgb), qBlue(rgb)); }
0041
0042 inline constexpr bool qIsGray(QRgb rgb)
0043 { return qRed(rgb) == qGreen(rgb) && qRed(rgb) == qBlue(rgb); }
0044
0045 inline constexpr QRgb qPremultiply(QRgb x)
0046 {
0047     const uint a = qAlpha(x);
0048     uint t = (x & 0xff00ff) * a;
0049     t = (t + ((t >> 8) & 0xff00ff) + 0x800080) >> 8;
0050     t &= 0xff00ff;
0051
0052     x = ((x >> 8) & 0xff) * a;
0053     x = (x + ((x >> 8) & 0xff) + 0x80);
0054     x &= 0xff00;
0055     return x | t | (a << 24);
0056 }
0057
0058 Q_GUI_EXPORT extern const uint qt_inv_premul_factor[];
0059
0060 inline QRgb qUnpremultiply(QRgb p)
0061 {
0062     const uint alpha = qAlpha(p);
0063     // Alpha 255 and 0 are the two most common values, which makes them beneficial to short-cut.
0064     if (alpha == 255)
0065         return p;
0066     if (alpha == 0)
0067         return 0;
0068     // (p*(0x00ff00ff/alpha)) >> 16 == (p*255)/alpha for all p and alpha <= 256.
0069     const uint invAlpha = qt_inv_premul_factor[alpha];
0070     // We add 0x8000 to get even rounding. The rounding also ensures that qPremultiply(qUnpremultiply(p)) == p for all p.
0071     return qRgba((qRed(p)*invAlpha + 0x8000)>>16, (qGreen(p)*invAlpha + 0x8000)>>16, (qBlue(p)*invAlpha + 0x8000)>>16, alpha);
0072 }
0073
0074 QT_END_NAMESPACE
0075
0076 #endif // QRGB_H