1 /*
2 * Copyright 2020 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 #include "modules/skottie/src/effects/Effects.h"
9
10 #include "include/core/SkColorFilter.h"
11 #include "include/effects/SkColorMatrix.h"
12 #include "include/effects/SkImageFilters.h"
13 #include "include/private/SkTPin.h"
14 #include "modules/skottie/src/Adapter.h"
15 #include "modules/skottie/src/SkottieValue.h"
16 #include "modules/sksg/include/SkSGRenderEffect.h"
17 #include "src/utils/SkJSON.h"
18
19 namespace skottie::internal {
20
21 namespace {
22
23 class ShadowAdapter final : public DiscardableAdapterBase<ShadowAdapter,
24 sksg::ExternalImageFilter> {
25 public:
26 enum Type {
27 kDropShadow,
28 kInnerShadow,
29 };
30
ShadowAdapter(const skjson::ObjectValue & jstyle,const AnimationBuilder & abuilder,Type type)31 ShadowAdapter(const skjson::ObjectValue& jstyle,
32 const AnimationBuilder& abuilder,
33 Type type)
34 : fType(type) {
35 this->bind(abuilder, jstyle["c"], fColor);
36 this->bind(abuilder, jstyle["o"], fOpacity);
37 this->bind(abuilder, jstyle["a"], fAngle);
38 this->bind(abuilder, jstyle["s"], fSize);
39 this->bind(abuilder, jstyle["d"], fDistance);
40 }
41
42 private:
onSync()43 void onSync() override {
44 const auto rad = SkDegreesToRadians(180 + fAngle), // 0deg -> left (style)
45 sigma = fSize * kBlurSizeToSigma,
46 opacity = SkTPin(fOpacity / 100, 0.0f, 1.0f);
47 const auto color = static_cast<SkColor4f>(fColor);
48 const auto offset = SkV2{ fDistance * SkScalarCos(rad),
49 -fDistance * SkScalarSin(rad)};
50
51 // Shadow effects largely follow the feDropShadow spec [1]:
52 //
53 // 1) isolate source alpha
54 // 2) apply a gaussian blur
55 // 3) apply an offset
56 // 4) modulate with a flood/color generator
57 // 5) composite with the source
58 //
59 // Note: as an optimization, we can fold #1 and #4 into a single color matrix filter.
60 //
61 // Inner shadow differences:
62 //
63 // a) operates on the inverse of source alpha
64 // b) the result is masked against the source
65 // c) composited on top of source
66 //
67 // [1] https://drafts.fxtf.org/filter-effects/#feDropShadowElement
68
69 // Select and colorize the source alpha channel.
70 SkColorMatrix cm{0, 0, 0, 0, color.fR,
71 0, 0, 0, 0, color.fG,
72 0, 0, 0, 0, color.fB,
73 0, 0, 0, opacity * color.fA, 0};
74
75 // Inner shadows use the alpha inverse.
76 if (fType == Type::kInnerShadow) {
77 cm.preConcat({1, 0, 0, 0, 0,
78 0, 1, 0, 0, 0,
79 0, 0, 1, 0, 0,
80 0, 0, 0,-1, 1});
81 }
82 auto f = SkImageFilters::ColorFilter(SkColorFilters::Matrix(cm), nullptr);
83
84 if (sigma > 0) {
85 f = SkImageFilters::Blur(sigma, sigma, std::move(f));
86 }
87
88 if (!SkScalarNearlyZero(offset.x) || !SkScalarNearlyZero(offset.y)) {
89 f = SkImageFilters::Offset(offset.x, offset.y, std::move(f));
90 }
91
92 sk_sp<SkImageFilter> source;
93
94 if (fType == Type::kInnerShadow) {
95 // Inner shadows draw on top of, and are masked with, the source.
96 f = SkImageFilters::Blend(SkBlendMode::kDstIn, std::move(f));
97
98 std::swap(source, f);
99 }
100
101 this->node()->setImageFilter(SkImageFilters::Merge(std::move(f),
102 std::move(source)));
103 }
104
105 const Type fType;
106
107 VectorValue fColor;
108 ScalarValue fOpacity = 100, // percentage
109 fAngle = 0, // degrees
110 fSize = 0,
111 fDistance = 0;
112
113 using INHERITED = DiscardableAdapterBase<ShadowAdapter, sksg::ExternalImageFilter>;
114 };
115
make_shadow_effect(const skjson::ObjectValue & jstyle,const AnimationBuilder & abuilder,sk_sp<sksg::RenderNode> layer,ShadowAdapter::Type type)116 static sk_sp<sksg::RenderNode> make_shadow_effect(const skjson::ObjectValue& jstyle,
117 const AnimationBuilder& abuilder,
118 sk_sp<sksg::RenderNode> layer,
119 ShadowAdapter::Type type) {
120 auto filter_node = abuilder.attachDiscardableAdapter<ShadowAdapter>(jstyle, abuilder, type);
121
122 return sksg::ImageFilterEffect::Make(std::move(layer), std::move(filter_node));
123 }
124
125 } // namespace
126
attachDropShadowStyle(const skjson::ObjectValue & jstyle,sk_sp<sksg::RenderNode> layer) const127 sk_sp<sksg::RenderNode> EffectBuilder::attachDropShadowStyle(const skjson::ObjectValue& jstyle,
128 sk_sp<sksg::RenderNode> layer) const {
129 return make_shadow_effect(jstyle, *fBuilder, std::move(layer),
130 ShadowAdapter::Type::kDropShadow);
131 }
132
attachInnerShadowStyle(const skjson::ObjectValue & jstyle,sk_sp<sksg::RenderNode> layer) const133 sk_sp<sksg::RenderNode> EffectBuilder::attachInnerShadowStyle(const skjson::ObjectValue& jstyle,
134 sk_sp<sksg::RenderNode> layer) const {
135 return make_shadow_effect(jstyle, *fBuilder, std::move(layer),
136 ShadowAdapter::Type::kInnerShadow);
137 }
138
139 } // namespace skottie::internal
140