1/*
2 * Copyright 2012 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 "include/private/SkFloatingPoint.h"
9#include "src/core/SkRasterPipeline.h"
10#include "src/core/SkReadBuffer.h"
11#include "src/core/SkWriteBuffer.h"
12#include "src/shaders/gradients/SkTwoPointConicalGradient.h"
13
14#include <utility>
15
16// Please see https://skia.org/dev/design/conical for how our shader works.
17
18bool SkTwoPointConicalGradient::FocalData::set(SkScalar r0, SkScalar r1, SkMatrix* matrix) {
19 fIsSwapped = false;
20 fFocalX = sk_ieee_float_divide(r0, (r0 - r1));
21 if (SkScalarNearlyZero(fFocalX - 1)) {
22 // swap r0, r1
23 matrix->postTranslate(-1, 0);
24 matrix->postScale(-1, 1);
25 std::swap(r0, r1);
26 fFocalX = 0; // because r0 is now 0
27 fIsSwapped = true;
28 }
29
30 // Map {focal point, (1, 0)} to {(0, 0), (1, 0)}
31 const SkPoint from[2] = { {fFocalX, 0}, {1, 0} };
32 const SkPoint to[2] = { {0, 0}, {1, 0} };
33 SkMatrix focalMatrix;
34 if (!focalMatrix.setPolyToPoly(from, to, 2)) {
35 return false;
36 }
37 matrix->postConcat(focalMatrix);
38 fR1 = r1 / SkScalarAbs(1 - fFocalX); // focalMatrix has a scale of 1/(1-f)
39
40 // The following transformations are just to accelerate the shader computation by saving
41 // some arithmatic operations.
42 if (this->isFocalOnCircle()) {
43 matrix->postScale(0.5, 0.5);
44 } else {
45 matrix->postScale(fR1 / (fR1 * fR1 - 1), 1 / sqrt(SkScalarAbs(fR1 * fR1 - 1)));
46 }
47 matrix->postScale(SkScalarAbs(1 - fFocalX), SkScalarAbs(1 - fFocalX)); // scale |1 - f|
48 return true;
49}
50
51sk_sp<SkShader> SkTwoPointConicalGradient::Create(const SkPoint& c0, SkScalar r0,
52 const SkPoint& c1, SkScalar r1,
53 const Descriptor& desc) {
54 SkMatrix gradientMatrix;
55 Type gradientType;
56
57 if (SkScalarNearlyZero((c0 - c1).length())) {
58 if (SkScalarNearlyZero(std::max(r0, r1)) || SkScalarNearlyEqual(r0, r1)) {
59 // Degenerate case; avoid dividing by zero. Should have been caught by caller but
60 // just in case, recheck here.
61 return nullptr;
62 }
63 // Concentric case: we can pretend we're radial (with a tiny twist).
64 const SkScalar scale = sk_ieee_float_divide(1, std::max(r0, r1));
65 gradientMatrix = SkMatrix::MakeTrans(-c1.x(), -c1.y());
66 gradientMatrix.postScale(scale, scale);
67
68 gradientType = Type::kRadial;
69 } else {
70 const SkPoint centers[2] = { c0 , c1 };
71 const SkPoint unitvec[2] = { {0, 0}, {1, 0} };
72
73 if (!gradientMatrix.setPolyToPoly(centers, unitvec, 2)) {
74 // Degenerate case.
75 return nullptr;
76 }
77
78 gradientType = SkScalarNearlyZero(r1 - r0) ? Type::kStrip : Type::kFocal;
79 }
80
81 FocalData focalData;
82 if (gradientType == Type::kFocal) {
83 const auto dCenter = (c0 - c1).length();
84 if (!focalData.set(r0 / dCenter, r1 / dCenter, &gradientMatrix)) {
85 return nullptr;
86 }
87 }
88 return sk_sp<SkShader>(new SkTwoPointConicalGradient(c0, r0, c1, r1, desc,
89 gradientType, gradientMatrix, focalData));
90}
91
92SkTwoPointConicalGradient::SkTwoPointConicalGradient(
93 const SkPoint& start, SkScalar startRadius,
94 const SkPoint& end, SkScalar endRadius,
95 const Descriptor& desc, Type type, const SkMatrix& gradientMatrix, const FocalData& data)
96 : SkGradientShaderBase(desc, gradientMatrix)
97 , fCenter1(start)
98 , fCenter2(end)
99 , fRadius1(startRadius)
100 , fRadius2(endRadius)
101 , fType(type)
102{
103 // this is degenerate, and should be caught by our caller
104 SkASSERT(fCenter1 != fCenter2 || fRadius1 != fRadius2);
105 if (type == Type::kFocal) {
106 fFocalData = data;
107 }
108}
109
110bool SkTwoPointConicalGradient::isOpaque() const {
111 // Because areas outside the cone are left untouched, we cannot treat the
112 // shader as opaque even if the gradient itself is opaque.
113 // TODO(junov): Compute whether the cone fills the plane crbug.com/222380
114 return false;
115}
116
117// Returns the original non-sorted version of the gradient
118SkShader::GradientType SkTwoPointConicalGradient::asAGradient(GradientInfo* info) const {
119 if (info) {
120 commonAsAGradient(info);
121 info->fPoint[0] = fCenter1;
122 info->fPoint[1] = fCenter2;
123 info->fRadius[0] = fRadius1;
124 info->fRadius[1] = fRadius2;
125 }
126 return kConical_GradientType;
127}
128
129sk_sp<SkFlattenable> SkTwoPointConicalGradient::CreateProc(SkReadBuffer& buffer) {
130 DescriptorScope desc;
131 if (!desc.unflatten(buffer)) {
132 return nullptr;
133 }
134 SkPoint c1 = buffer.readPoint();
135 SkPoint c2 = buffer.readPoint();
136 SkScalar r1 = buffer.readScalar();
137 SkScalar r2 = buffer.readScalar();
138
139 if (buffer.isVersionLT(SkPicturePriv::k2PtConicalNoFlip_Version) && buffer.readBool()) {
140 using std::swap;
141 // legacy flipped gradient
142 swap(c1, c2);
143 swap(r1, r2);
144
145 SkColor4f* colors = desc.mutableColors();
146 SkScalar* pos = desc.mutablePos();
147 const int last = desc.fCount - 1;
148 const int half = desc.fCount >> 1;
149 for (int i = 0; i < half; ++i) {
150 swap(colors[i], colors[last - i]);
151 if (pos) {
152 SkScalar tmp = pos[i];
153 pos[i] = SK_Scalar1 - pos[last - i];
154 pos[last - i] = SK_Scalar1 - tmp;
155 }
156 }
157 if (pos) {
158 if (desc.fCount & 1) {
159 pos[half] = SK_Scalar1 - pos[half];
160 }
161 }
162 }
163 if (!buffer.isValid()) {
164 return nullptr;
165 }
166 return SkGradientShader::MakeTwoPointConical(c1, r1, c2, r2, desc.fColors,
167 std::move(desc.fColorSpace), desc.fPos,
168 desc.fCount, desc.fTileMode, desc.fGradFlags,
169 desc.fLocalMatrix);
170}
171
172void SkTwoPointConicalGradient::flatten(SkWriteBuffer& buffer) const {
173 this->INHERITED::flatten(buffer);
174 buffer.writePoint(fCenter1);
175 buffer.writePoint(fCenter2);
176 buffer.writeScalar(fRadius1);
177 buffer.writeScalar(fRadius2);
178}
179
180void SkTwoPointConicalGradient::appendGradientStages(SkArenaAlloc* alloc, SkRasterPipeline* p,
181 SkRasterPipeline* postPipeline) const {
182 const auto dRadius = fRadius2 - fRadius1;
183
184 if (fType == Type::kRadial) {
185 p->append(SkRasterPipeline::xy_to_radius);
186
187 // Tiny twist: radial computes a t for [0, r2], but we want a t for [r1, r2].
188 auto scale = std::max(fRadius1, fRadius2) / dRadius;
189 auto bias = -fRadius1 / dRadius;
190
191 p->append_matrix(alloc, SkMatrix::Concat(SkMatrix::MakeTrans(bias, 0),
192 SkMatrix::MakeScale(scale, 1)));
193 return;
194 }
195
196 if (fType == Type::kStrip) {
197 auto* ctx = alloc->make<SkRasterPipeline_2PtConicalCtx>();
198 SkScalar scaledR0 = fRadius1 / this->getCenterX1();
199 ctx->fP0 = scaledR0 * scaledR0;
200 p->append(SkRasterPipeline::xy_to_2pt_conical_strip, ctx);
201 p->append(SkRasterPipeline::mask_2pt_conical_nan, ctx);
202 postPipeline->append(SkRasterPipeline::apply_vector_mask, &ctx->fMask);
203 return;
204 }
205
206 auto* ctx = alloc->make<SkRasterPipeline_2PtConicalCtx>();
207 ctx->fP0 = 1/fFocalData.fR1;
208 ctx->fP1 = fFocalData.fFocalX;
209
210 if (fFocalData.isFocalOnCircle()) {
211 p->append(SkRasterPipeline::xy_to_2pt_conical_focal_on_circle);
212 } else if (fFocalData.isWellBehaved()) {
213 p->append(SkRasterPipeline::xy_to_2pt_conical_well_behaved, ctx);
214 } else if (fFocalData.isSwapped() || 1 - fFocalData.fFocalX < 0) {
215 p->append(SkRasterPipeline::xy_to_2pt_conical_smaller, ctx);
216 } else {
217 p->append(SkRasterPipeline::xy_to_2pt_conical_greater, ctx);
218 }
219
220 if (!fFocalData.isWellBehaved()) {
221 p->append(SkRasterPipeline::mask_2pt_conical_degenerates, ctx);
222 }
223 if (1 - fFocalData.fFocalX < 0) {
224 p->append(SkRasterPipeline::negate_x);
225 }
226 if (!fFocalData.isNativelyFocal()) {
227 p->append(SkRasterPipeline::alter_2pt_conical_compensate_focal, ctx);
228 }
229 if (fFocalData.isSwapped()) {
230 p->append(SkRasterPipeline::alter_2pt_conical_unswap);
231 }
232 if (!fFocalData.isWellBehaved()) {
233 postPipeline->append(SkRasterPipeline::apply_vector_mask, &ctx->fMask);
234 }
235}
236
237skvm::F32 SkTwoPointConicalGradient::transformT(skvm::Builder* p, skvm::Uniforms* uniforms,
238 skvm::F32 x, skvm::F32 y, skvm::I32* mask) const {
239 // See https://skia.org/dev/design/conical, and onAppendStages() above.
240 // There's a lot going on here, and I'm not really sure what's independent
241 // or disjoint, what can be reordered, simplified, etc. Tweak carefully.
242
243 if (fType == Type::kRadial) {
244 float denom = 1.0f / (fRadius2 - fRadius1),
245 scale = std::max(fRadius1, fRadius2) * denom,
246 bias = -fRadius1 * denom;
247 return norm(x,y) * p->uniformF(uniforms->pushF(scale))
248 + p->uniformF(uniforms->pushF(bias ));
249 }
250
251 if (fType == Type::kStrip) {
252 float r = fRadius1 / this->getCenterX1();
253 skvm::F32 t = x + sqrt(p->splat(r*r) - y*y);
254
255 *mask = (t == t); // t != NaN
256 return t;
257 }
258
259 const skvm::F32 invR1 = p->uniformF(uniforms->pushF(1 / fFocalData.fR1));
260
261 skvm::F32 t;
262 if (fFocalData.isFocalOnCircle()) {
263 t = (y/x) * y + x; // (x^2 + y^2) / x ~~> x + y^2/x ~~> y/x * y + x
264 } else if (fFocalData.isWellBehaved()) {
265 t = norm(x,y) - x*invR1;
266 } else {
267 skvm::F32 k = sqrt(x*x - y*y);
268 if (fFocalData.isSwapped() || 1 - fFocalData.fFocalX < 0) {
269 k = -k;
270 }
271 t = k - x*invR1;
272 }
273
274 if (!fFocalData.isWellBehaved()) {
275 // TODO: not sure why we consider t == 0 degenerate
276 *mask = (t > 0.0f); // and implicitly, t != NaN
277 }
278
279 const skvm::F32 focalX = p->uniformF(uniforms->pushF(fFocalData.fFocalX));
280 if (1 - fFocalData.fFocalX < 0) { t = -t; }
281 if (!fFocalData.isNativelyFocal()) { t += focalX; }
282 if ( fFocalData.isSwapped()) { t = 1.0f - t; }
283 return t;
284}
285
286/////////////////////////////////////////////////////////////////////
287
288#if SK_SUPPORT_GPU
289
290#include "src/gpu/gradients/GrGradientShader.h"
291
292std::unique_ptr<GrFragmentProcessor> SkTwoPointConicalGradient::asFragmentProcessor(
293 const GrFPArgs& args) const {
294 return GrGradientShader::MakeConical(*this, args);
295}
296
297#endif
298