1// Copyright (C) 2016 The Qt Company Ltd.
2// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
3
4#ifndef QRGB_H
5#define QRGB_H
6
7#include <QtGui/qtguiglobal.h>
8#include <QtCore/qprocessordetection.h>
9
10QT_BEGIN_NAMESPACE
11
12
13typedef unsigned int QRgb; // RGB triplet
14
15// non-namespaced Qt global variable
16 inline constexpr QRgb RGB_MASK = 0x00ffffff; // masks RGB values
17
18inline constexpr int qRed(QRgb rgb) // get red part of RGB
19{ return ((rgb >> 16) & 0xff); }
20
21inline constexpr int qGreen(QRgb rgb) // get green part of RGB
22{ return ((rgb >> 8) & 0xff); }
23
24inline constexpr int qBlue(QRgb rgb) // get blue part of RGB
25{ return (rgb & 0xff); }
26
27inline constexpr int qAlpha(QRgb rgb) // get alpha part of RGBA
28{ return rgb >> 24; }
29
30inline constexpr QRgb qRgb(int r, int g, int b) // set RGB value
31{ return (0xffu << 24) | ((r & 0xffu) << 16) | ((g & 0xffu) << 8) | (b & 0xffu); }
32
33inline constexpr QRgb qRgba(int r, int g, int b, int a) // set RGBA value
34{ return ((a & 0xffu) << 24) | ((r & 0xffu) << 16) | ((g & 0xffu) << 8) | (b & 0xffu); }
35
36inline constexpr int qGray(int r, int g, int b) // convert R,G,B to gray 0..255
37{ return (r*11+g*16+b*5)/32; }
38
39inline constexpr int qGray(QRgb rgb) // convert RGB to gray 0..255
40{ return qGray(r: qRed(rgb), g: qGreen(rgb), b: qBlue(rgb)); }
41
42inline constexpr bool qIsGray(QRgb rgb)
43{ return qRed(rgb) == qGreen(rgb) && qRed(rgb) == qBlue(rgb); }
44
45inline constexpr QRgb qPremultiply(QRgb x)
46{
47 const uint a = qAlpha(rgb: x);
48 uint t = (x & 0xff00ff) * a;
49 t = (t + ((t >> 8) & 0xff00ff) + 0x800080) >> 8;
50 t &= 0xff00ff;
51
52 x = ((x >> 8) & 0xff) * a;
53 x = (x + ((x >> 8) & 0xff) + 0x80);
54 x &= 0xff00;
55 return x | t | (a << 24);
56}
57
58Q_GUI_EXPORT extern const uint qt_inv_premul_factor[];
59
60inline QRgb qUnpremultiply(QRgb p)
61{
62 const uint alpha = qAlpha(rgb: p);
63 // Alpha 255 and 0 are the two most common values, which makes them beneficial to short-cut.
64 if (alpha == 255)
65 return p;
66 if (alpha == 0)
67 return 0;
68 // (p*(0x00ff00ff/alpha)) >> 16 == (p*255)/alpha for all p and alpha <= 256.
69 const uint invAlpha = qt_inv_premul_factor[alpha];
70 // We add 0x8000 to get even rounding. The rounding also ensures that qPremultiply(qUnpremultiply(p)) == p for all p.
71 return qRgba(r: (qRed(rgb: p)*invAlpha + 0x8000)>>16, g: (qGreen(rgb: p)*invAlpha + 0x8000)>>16, b: (qBlue(rgb: p)*invAlpha + 0x8000)>>16, a: alpha);
72}
73
74QT_END_NAMESPACE
75
76#endif // QRGB_H
77

source code of qtbase/src/gui/painting/qrgb.h