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/SkSweepGradient.h"
13
14SkSweepGradient::SkSweepGradient(const SkPoint& center, SkScalar t0, SkScalar t1,
15 const Descriptor& desc)
16 : SkGradientShaderBase(desc, SkMatrix::MakeTrans(-center.x(), -center.y()))
17 , fCenter(center)
18 , fTBias(-t0)
19 , fTScale(1 / (t1 - t0))
20{
21 SkASSERT(t0 < t1);
22}
23
24SkShader::GradientType SkSweepGradient::asAGradient(GradientInfo* info) const {
25 if (info) {
26 commonAsAGradient(info);
27 info->fPoint[0] = fCenter;
28 }
29 return kSweep_GradientType;
30}
31
32static std::tuple<SkScalar, SkScalar> angles_from_t_coeff(SkScalar tBias, SkScalar tScale) {
33 return std::make_tuple(-tBias * 360, (sk_ieee_float_divide(1, tScale) - tBias) * 360);
34}
35
36sk_sp<SkFlattenable> SkSweepGradient::CreateProc(SkReadBuffer& buffer) {
37 DescriptorScope desc;
38 if (!desc.unflatten(buffer)) {
39 return nullptr;
40 }
41 const SkPoint center = buffer.readPoint();
42
43 SkScalar startAngle = 0,
44 endAngle = 360;
45 if (!buffer.isVersionLT(SkPicturePriv::kTileInfoInSweepGradient_Version)) {
46 const auto tBias = buffer.readScalar(),
47 tScale = buffer.readScalar();
48 std::tie(startAngle, endAngle) = angles_from_t_coeff(tBias, tScale);
49 }
50
51 return SkGradientShader::MakeSweep(center.x(), center.y(), desc.fColors,
52 std::move(desc.fColorSpace), desc.fPos, desc.fCount,
53 desc.fTileMode, startAngle, endAngle,
54 desc.fGradFlags, desc.fLocalMatrix);
55}
56
57void SkSweepGradient::flatten(SkWriteBuffer& buffer) const {
58 this->INHERITED::flatten(buffer);
59 buffer.writePoint(fCenter);
60 buffer.writeScalar(fTBias);
61 buffer.writeScalar(fTScale);
62}
63
64void SkSweepGradient::appendGradientStages(SkArenaAlloc* alloc, SkRasterPipeline* p,
65 SkRasterPipeline*) const {
66 p->append(SkRasterPipeline::xy_to_unit_angle);
67 p->append_matrix(alloc, SkMatrix::Concat(SkMatrix::MakeScale(fTScale, 1),
68 SkMatrix::MakeTrans(fTBias , 0)));
69}
70
71skvm::F32 SkSweepGradient::transformT(skvm::Builder* p, skvm::Uniforms* uniforms,
72 skvm::F32 x, skvm::F32 y, skvm::I32* mask) const {
73 skvm::F32 xabs = abs(x),
74 yabs = abs(y),
75 slope = min(xabs, yabs) / max(xabs, yabs);
76 skvm::F32 s = slope * slope;
77
78 // Use a 7th degree polynomial to approximate atan.
79 // This was generated using sollya.gforge.inria.fr.
80 // A float optimized polynomial was generated using the following command.
81 // P1 = fpminimax((1/(2*Pi))*atan(x),[|1,3,5,7|],[|24...|],[2^(-40),1],relative);
82 skvm::F32 phi = slope * poly(s, -7.0547382347285747528076171875e-3f,
83 +2.476101927459239959716796875e-2f,
84 -5.185396969318389892578125e-2f,
85 +0.15912117063999176025390625f);
86 phi = select(xabs < yabs, (1/4.0f) - phi, phi);
87 phi = select( x < 0.0f, (1/2.0f) - phi, phi);
88 phi = select( y < 0.0f, (1/1.0f) - phi, phi);
89
90 skvm::F32 t = select(is_NaN(phi), p->splat(0.0f)
91 , phi);
92
93 if (fTScale != 1.0f || fTBias != 0.0f) {
94 t = t * p->uniformF(uniforms->pushF(fTScale))
95 + p->uniformF(uniforms->pushF(fTScale*fTBias));
96 }
97 return t;
98}
99
100/////////////////////////////////////////////////////////////////////
101
102#if SK_SUPPORT_GPU
103
104#include "src/gpu/gradients/GrGradientShader.h"
105
106std::unique_ptr<GrFragmentProcessor> SkSweepGradient::asFragmentProcessor(
107 const GrFPArgs& args) const {
108 return GrGradientShader::MakeSweep(*this, args);
109}
110
111#endif
112