1 /*
2  * Copyright 2016 Google Inc.
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 Sk4fGradientPriv_DEFINED
9 #define Sk4fGradientPriv_DEFINED
10 
11 #include "SkColor.h"
12 #include "SkColorData.h"
13 #include "SkHalf.h"
14 #include "SkImageInfo.h"
15 #include "SkNx.h"
16 #include "SkUtils.h"
17 
18 // Templates shared by various 4f gradient flavors.
19 
20 namespace {  // NOLINT(google-build-namespaces)
21 
22 enum class ApplyPremul { True, False };
23 
24 template <ApplyPremul>
25 struct PremulTraits;
26 
27 template <>
28 struct PremulTraits<ApplyPremul::False> {
29     static Sk4f apply(const Sk4f& c) { return c; }
30 };
31 
32 template <>
33 struct PremulTraits<ApplyPremul::True> {
34     static Sk4f apply(const Sk4f& c) {
35         const float alpha = c[3];
36         // FIXME: portable swizzle?
37         return c * Sk4f(alpha, alpha, alpha, 1);
38     }
39 };
40 
41 // Struct encapsulating various dest-dependent ops:
42 //
43 //   - load()       Load a SkPMColor4f value into Sk4f.  Normally called once per interval
44 //                  advance.  Also applies a scale and swizzle suitable for DstType.
45 //
46 //   - store()      Store one Sk4f to dest.  Optionally handles premul, color space
47 //                  conversion, etc.
48 //
49 //   - store(count) Store the Sk4f value repeatedly to dest, count times.
50 //
51 //   - store4x()    Store 4 Sk4f values to dest (opportunistic optimization).
52 //
53 
54 template <ApplyPremul premul>
55 struct DstTraits {
56     using PM   = PremulTraits<premul>;
57 
58     // For L32, prescaling by 255 saves a per-pixel multiplication when premul is not needed.
59     static Sk4f load(const SkPMColor4f& c) {
60         Sk4f c4f = swizzle_rb_if_bgra(Sk4f::Load(c.vec()));
61         return premul == ApplyPremul::False
62             ? c4f * Sk4f(255)
63             : c4f;
64     }
65 
66     static void store(const Sk4f& c, SkPMColor* dst, const Sk4f& bias) {
67         if (premul == ApplyPremul::False) {
68             // c is pre-scaled by 255 and pre-biased, just store.
69             SkNx_cast<uint8_t>(c).store(dst);
70         } else {
71             *dst = Sk4f_toL32(PM::apply(c) + bias);
72         }
73     }
74 
75     static void store(const Sk4f& c, SkPMColor* dst, int n) {
76         SkPMColor pmc;
77         store(c, &pmc, Sk4f(0));
78         sk_memset32(dst, pmc, n);
79     }
80 
81     static void store4x(const Sk4f& c0, const Sk4f& c1,
82                         const Sk4f& c2, const Sk4f& c3,
83                         SkPMColor* dst,
84                         const Sk4f& bias0,
85                         const Sk4f& bias1) {
86         if (premul == ApplyPremul::False) {
87             // colors are pre-scaled and pre-biased.
88             Sk4f_ToBytes((uint8_t*)dst, c0, c1, c2, c3);
89         } else {
90             store(c0, dst + 0, bias0);
91             store(c1, dst + 1, bias1);
92             store(c2, dst + 2, bias0);
93             store(c3, dst + 3, bias1);
94         }
95     }
96 
97     static Sk4f pre_lerp_bias(const Sk4f& bias) {
98         // We can apply the bias before interpolation when the colors are premultiplied.
99         return premul == ApplyPremul::False ? bias : 0;
100     }
101 };
102 
103 } // anonymous namespace
104 
105 #endif // Sk4fGradientPriv_DEFINED
106