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/private/base/SkMath.h"
13 #include "include/private/base/SkTPin.h"
14 #include "include/private/base/SkTo.h"
15
16 #include <algorithm>
17
18 /** Turn 0..255 into 0..256 by adding 1 at the half-way point. Used to turn a
19 byte into a scale value, so that we can say scale * value >> 8 instead of
20 alpha * value / 255.
21
22 In debugging, asserts that alpha is 0..255
23 */
SkAlpha255To256(U8CPU alpha)24 static inline unsigned SkAlpha255To256(U8CPU alpha) {
25 SkASSERT(SkToU8(alpha) == alpha);
26 // this one assues that blending on top of an opaque dst keeps it that way
27 // even though it is less accurate than a+(a>>7) for non-opaque dsts
28 return alpha + 1;
29 }
30
31 /** Multiplify value by 0..256, and shift the result down 8
32 (i.e. return (value * alpha256) >> 8)
33 */
34 #define SkAlphaMul(value, alpha256) (((value) * (alpha256)) >> 8)
35
SkUnitScalarClampToByte(SkScalar x)36 static inline U8CPU SkUnitScalarClampToByte(SkScalar x) {
37 return static_cast<U8CPU>(SkTPin(x, 0.0f, 1.0f) * 255 + 0.5);
38 }
39
40 #define SK_A32_BITS 8
41 #define SK_R32_BITS 8
42 #define SK_G32_BITS 8
43 #define SK_B32_BITS 8
44
45 #define SK_A32_MASK ((1 << SK_A32_BITS) - 1)
46 #define SK_R32_MASK ((1 << SK_R32_BITS) - 1)
47 #define SK_G32_MASK ((1 << SK_G32_BITS) - 1)
48 #define SK_B32_MASK ((1 << SK_B32_BITS) - 1)
49
50 /*
51 * Skia's 32bit backend only supports 1 swizzle order at a time (compile-time).
52 * This is specified by SK_R32_SHIFT=0 or SK_R32_SHIFT=16.
53 *
54 * For easier compatibility with Skia's GPU backend, we further restrict these
55 * to either (in memory-byte-order) RGBA or BGRA. Note that this "order" does
56 * not directly correspond to the same shift-order, since we have to take endianess
57 * into account.
58 *
59 * Here we enforce this constraint.
60 */
61
62 #define SK_RGBA_R32_SHIFT 0
63 #define SK_RGBA_G32_SHIFT 8
64 #define SK_RGBA_B32_SHIFT 16
65 #define SK_RGBA_A32_SHIFT 24
66
67 #define SK_BGRA_B32_SHIFT 0
68 #define SK_BGRA_G32_SHIFT 8
69 #define SK_BGRA_R32_SHIFT 16
70 #define SK_BGRA_A32_SHIFT 24
71
72 #if defined(SK_PMCOLOR_IS_RGBA) || defined(SK_PMCOLOR_IS_BGRA)
73 #error "Configure PMCOLOR by setting SK_R32_SHIFT."
74 #endif
75
76 // Deduce which SK_PMCOLOR_IS_ to define from the _SHIFT defines
77
78 #if (SK_A32_SHIFT == SK_RGBA_A32_SHIFT && \
79 SK_R32_SHIFT == SK_RGBA_R32_SHIFT && \
80 SK_G32_SHIFT == SK_RGBA_G32_SHIFT && \
81 SK_B32_SHIFT == SK_RGBA_B32_SHIFT)
82 #define SK_PMCOLOR_IS_RGBA
83 #elif (SK_A32_SHIFT == SK_BGRA_A32_SHIFT && \
84 SK_R32_SHIFT == SK_BGRA_R32_SHIFT && \
85 SK_G32_SHIFT == SK_BGRA_G32_SHIFT && \
86 SK_B32_SHIFT == SK_BGRA_B32_SHIFT)
87 #define SK_PMCOLOR_IS_BGRA
88 #else
89 #error "need 32bit packing to be either RGBA or BGRA"
90 #endif
91
92 #define SkGetPackedA32(packed) ((uint32_t)((packed) << (24 - SK_A32_SHIFT)) >> 24)
93 #define SkGetPackedR32(packed) ((uint32_t)((packed) << (24 - SK_R32_SHIFT)) >> 24)
94 #define SkGetPackedG32(packed) ((uint32_t)((packed) << (24 - SK_G32_SHIFT)) >> 24)
95 #define SkGetPackedB32(packed) ((uint32_t)((packed) << (24 - SK_B32_SHIFT)) >> 24)
96
97 #define SkA32Assert(a) SkASSERT((unsigned)(a) <= SK_A32_MASK)
98 #define SkR32Assert(r) SkASSERT((unsigned)(r) <= SK_R32_MASK)
99 #define SkG32Assert(g) SkASSERT((unsigned)(g) <= SK_G32_MASK)
100 #define SkB32Assert(b) SkASSERT((unsigned)(b) <= SK_B32_MASK)
101
102 /**
103 * Pack the components into a SkPMColor, checking (in the debug version) that
104 * the components are 0..255, and are already premultiplied (i.e. alpha >= color)
105 */
SkPackARGB32(U8CPU a,U8CPU r,U8CPU g,U8CPU b)106 static inline SkPMColor SkPackARGB32(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
107 SkA32Assert(a);
108 SkASSERT(r <= a);
109 SkASSERT(g <= a);
110 SkASSERT(b <= a);
111
112 return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
113 (g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
114 }
115
116 /**
117 * Same as SkPackARGB32, but this version guarantees to not check that the
118 * values are premultiplied in the debug version.
119 */
SkPackARGB32NoCheck(U8CPU a,U8CPU r,U8CPU g,U8CPU b)120 static inline SkPMColor SkPackARGB32NoCheck(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
121 return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
122 (g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
123 }
124
125 static inline
SkPremultiplyARGBInline(U8CPU a,U8CPU r,U8CPU g,U8CPU b)126 SkPMColor SkPremultiplyARGBInline(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
127 SkA32Assert(a);
128 SkR32Assert(r);
129 SkG32Assert(g);
130 SkB32Assert(b);
131
132 if (a != 255) {
133 r = SkMulDiv255Round(r, a);
134 g = SkMulDiv255Round(g, a);
135 b = SkMulDiv255Round(b, a);
136 }
137 return SkPackARGB32(a, r, g, b);
138 }
139
140 // When Android is compiled optimizing for size, SkAlphaMulQ doesn't get
141 // inlined; forcing inlining significantly improves performance.
SkAlphaMulQ(uint32_t c,unsigned scale)142 static SK_ALWAYS_INLINE uint32_t SkAlphaMulQ(uint32_t c, unsigned scale) {
143 uint32_t mask = 0xFF00FF;
144
145 uint32_t rb = ((c & mask) * scale) >> 8;
146 uint32_t ag = ((c >> 8) & mask) * scale;
147 return (rb & mask) | (ag & ~mask);
148 }
149
SkPMSrcOver(SkPMColor src,SkPMColor dst)150 static inline SkPMColor SkPMSrcOver(SkPMColor src, SkPMColor dst) {
151 uint32_t scale = SkAlpha255To256(255 - SkGetPackedA32(src));
152
153 uint32_t mask = 0xFF00FF;
154 uint32_t rb = (((dst & mask) * scale) >> 8) & mask;
155 uint32_t ag = (((dst >> 8) & mask) * scale) & ~mask;
156
157 rb += (src & mask);
158 ag += (src & ~mask);
159
160 // Color channels (but not alpha) can overflow, so we have to saturate to 0xFF in each lane.
161 return std::min(rb & 0x000001FF, 0x000000FFU) |
162 std::min(ag & 0x0001FF00, 0x0000FF00U) |
163 std::min(rb & 0x01FF0000, 0x00FF0000U) |
164 (ag & 0xFF000000);
165 }
166
167 #endif
168