1/*
2 * Copyright 2006 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkColorPriv_DEFINED
9#define SkColorPriv_DEFINED
10
11#include "include/core/SkColor.h"
12#include "include/core/SkMath.h"
13#include "include/private/SkTo.h"
14
15/** Turn 0..255 into 0..256 by adding 1 at the half-way point. Used to turn a
16 byte into a scale value, so that we can say scale * value >> 8 instead of
17 alpha * value / 255.
18
19 In debugging, asserts that alpha is 0..255
20*/
21static inline unsigned SkAlpha255To256(U8CPU alpha) {
22 SkASSERT(SkToU8(alpha) == alpha);
23 // this one assues that blending on top of an opaque dst keeps it that way
24 // even though it is less accurate than a+(a>>7) for non-opaque dsts
25 return alpha + 1;
26}
27
28/** Multiplify value by 0..256, and shift the result down 8
29 (i.e. return (value * alpha256) >> 8)
30 */
31#define SkAlphaMul(value, alpha256) (((value) * (alpha256)) >> 8)
32
33static inline U8CPU SkUnitScalarClampToByte(SkScalar x) {
34 return static_cast<U8CPU>(SkTPin(x, 0.0f, 1.0f) * 255 + 0.5);
35}
36
37#define SK_A32_BITS 8
38#define SK_R32_BITS 8
39#define SK_G32_BITS 8
40#define SK_B32_BITS 8
41
42#define SK_A32_MASK ((1 << SK_A32_BITS) - 1)
43#define SK_R32_MASK ((1 << SK_R32_BITS) - 1)
44#define SK_G32_MASK ((1 << SK_G32_BITS) - 1)
45#define SK_B32_MASK ((1 << SK_B32_BITS) - 1)
46
47/*
48 * Skia's 32bit backend only supports 1 swizzle order at a time (compile-time).
49 * This is specified by SK_R32_SHIFT=0 or SK_R32_SHIFT=16.
50 *
51 * For easier compatibility with Skia's GPU backend, we further restrict these
52 * to either (in memory-byte-order) RGBA or BGRA. Note that this "order" does
53 * not directly correspond to the same shift-order, since we have to take endianess
54 * into account.
55 *
56 * Here we enforce this constraint.
57 */
58
59#define SK_RGBA_R32_SHIFT 0
60#define SK_RGBA_G32_SHIFT 8
61#define SK_RGBA_B32_SHIFT 16
62#define SK_RGBA_A32_SHIFT 24
63
64#define SK_BGRA_B32_SHIFT 0
65#define SK_BGRA_G32_SHIFT 8
66#define SK_BGRA_R32_SHIFT 16
67#define SK_BGRA_A32_SHIFT 24
68
69#if defined(SK_PMCOLOR_IS_RGBA) || defined(SK_PMCOLOR_IS_BGRA)
70 #error "Configure PMCOLOR by setting SK_R32_SHIFT."
71#endif
72
73// Deduce which SK_PMCOLOR_IS_ to define from the _SHIFT defines
74
75#if (SK_A32_SHIFT == SK_RGBA_A32_SHIFT && \
76 SK_R32_SHIFT == SK_RGBA_R32_SHIFT && \
77 SK_G32_SHIFT == SK_RGBA_G32_SHIFT && \
78 SK_B32_SHIFT == SK_RGBA_B32_SHIFT)
79 #define SK_PMCOLOR_IS_RGBA
80#elif (SK_A32_SHIFT == SK_BGRA_A32_SHIFT && \
81 SK_R32_SHIFT == SK_BGRA_R32_SHIFT && \
82 SK_G32_SHIFT == SK_BGRA_G32_SHIFT && \
83 SK_B32_SHIFT == SK_BGRA_B32_SHIFT)
84 #define SK_PMCOLOR_IS_BGRA
85#else
86 #error "need 32bit packing to be either RGBA or BGRA"
87#endif
88
89#define SkGetPackedA32(packed) ((uint32_t)((packed) << (24 - SK_A32_SHIFT)) >> 24)
90#define SkGetPackedR32(packed) ((uint32_t)((packed) << (24 - SK_R32_SHIFT)) >> 24)
91#define SkGetPackedG32(packed) ((uint32_t)((packed) << (24 - SK_G32_SHIFT)) >> 24)
92#define SkGetPackedB32(packed) ((uint32_t)((packed) << (24 - SK_B32_SHIFT)) >> 24)
93
94#define SkA32Assert(a) SkASSERT((unsigned)(a) <= SK_A32_MASK)
95#define SkR32Assert(r) SkASSERT((unsigned)(r) <= SK_R32_MASK)
96#define SkG32Assert(g) SkASSERT((unsigned)(g) <= SK_G32_MASK)
97#define SkB32Assert(b) SkASSERT((unsigned)(b) <= SK_B32_MASK)
98
99/**
100 * Pack the components into a SkPMColor, checking (in the debug version) that
101 * the components are 0..255, and are already premultiplied (i.e. alpha >= color)
102 */
103static inline SkPMColor SkPackARGB32(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
104 SkA32Assert(a);
105 SkASSERT(r <= a);
106 SkASSERT(g <= a);
107 SkASSERT(b <= a);
108
109 return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
110 (g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
111}
112
113/**
114 * Same as SkPackARGB32, but this version guarantees to not check that the
115 * values are premultiplied in the debug version.
116 */
117static inline SkPMColor SkPackARGB32NoCheck(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
118 return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
119 (g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
120}
121
122static inline
123SkPMColor SkPremultiplyARGBInline(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
124 SkA32Assert(a);
125 SkR32Assert(r);
126 SkG32Assert(g);
127 SkB32Assert(b);
128
129 if (a != 255) {
130 r = SkMulDiv255Round(r, a);
131 g = SkMulDiv255Round(g, a);
132 b = SkMulDiv255Round(b, a);
133 }
134 return SkPackARGB32(a, r, g, b);
135}
136
137// When Android is compiled optimizing for size, SkAlphaMulQ doesn't get
138// inlined; forcing inlining significantly improves performance.
139static SK_ALWAYS_INLINE uint32_t SkAlphaMulQ(uint32_t c, unsigned scale) {
140 uint32_t mask = 0xFF00FF;
141
142 uint32_t rb = ((c & mask) * scale) >> 8;
143 uint32_t ag = ((c >> 8) & mask) * scale;
144 return (rb & mask) | (ag & ~mask);
145}
146
147static inline SkPMColor SkPMSrcOver(SkPMColor src, SkPMColor dst) {
148 return src + SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
149}
150
151#endif
152