| /* |
| * Copyright 2006 The Android Open Source Project |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| |
| #include "include/core/SkPathMeasure.h" |
| #include "include/core/SkStrokeRec.h" |
| #include "include/effects/SkDiscretePathEffect.h" |
| #include "include/private/SkFixed.h" |
| #include "src/core/SkPointPriv.h" |
| #include "src/core/SkReadBuffer.h" |
| #include "src/core/SkWriteBuffer.h" |
| |
| sk_sp<SkPathEffect> SkDiscretePathEffect::Make(SkScalar segLength, SkScalar deviation, |
| uint32_t seedAssist) { |
| if (!SkScalarIsFinite(segLength) || !SkScalarIsFinite(deviation)) { |
| return nullptr; |
| } |
| if (segLength <= SK_ScalarNearlyZero) { |
| return nullptr; |
| } |
| return sk_sp<SkPathEffect>(new SkDiscretePathEffect(segLength, deviation, seedAssist)); |
| } |
| |
| static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) { |
| SkVector normal = tangent; |
| SkPointPriv::RotateCCW(&normal); |
| normal.setLength(scale); |
| *p += normal; |
| } |
| |
| SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, |
| SkScalar deviation, |
| uint32_t seedAssist) |
| : fSegLength(segLength), fPerterb(deviation), fSeedAssist(seedAssist) |
| { |
| } |
| |
| /** \class LCGRandom |
| |
| Utility class that implements pseudo random 32bit numbers using a fast |
| linear equation. Unlike rand(), this class holds its own seed (initially |
| set to 0), so that multiple instances can be used with no side-effects. |
| |
| Copied from the original implementation of SkRandom. Only contains the |
| methods used by SkDiscretePathEffect::filterPath, with methods that were |
| not called directly moved to private. |
| */ |
| |
| class LCGRandom { |
| public: |
| LCGRandom(uint32_t seed) : fSeed(seed) {} |
| |
| /** Return the next pseudo random number expressed as a SkScalar |
| in the range [-SK_Scalar1..SK_Scalar1). |
| */ |
| SkScalar nextSScalar1() { return SkFixedToScalar(this->nextSFixed1()); } |
| |
| private: |
| /** Return the next pseudo random number as an unsigned 32bit value. |
| */ |
| uint32_t nextU() { uint32_t r = fSeed * kMul + kAdd; fSeed = r; return r; } |
| |
| /** Return the next pseudo random number as a signed 32bit value. |
| */ |
| int32_t nextS() { return (int32_t)this->nextU(); } |
| |
| /** Return the next pseudo random number expressed as a signed SkFixed |
| in the range [-SK_Fixed1..SK_Fixed1). |
| */ |
| SkFixed nextSFixed1() { return this->nextS() >> 15; } |
| |
| // See "Numerical Recipes in C", 1992 page 284 for these constants |
| enum { |
| kMul = 1664525, |
| kAdd = 1013904223 |
| }; |
| uint32_t fSeed; |
| }; |
| |
| bool SkDiscretePathEffect::onFilterPath(SkPath* dst, const SkPath& src, |
| SkStrokeRec* rec, const SkRect*) const { |
| bool doFill = rec->isFillStyle(); |
| |
| SkPathMeasure meas(src, doFill); |
| |
| /* Caller may supply their own seed assist, which by default is 0 */ |
| uint32_t seed = fSeedAssist ^ SkScalarRoundToInt(meas.getLength()); |
| |
| LCGRandom rand(seed ^ ((seed << 16) | (seed >> 16))); |
| SkScalar scale = fPerterb; |
| SkPoint p; |
| SkVector v; |
| |
| do { |
| SkScalar length = meas.getLength(); |
| |
| if (fSegLength * (2 + doFill) > length) { |
| meas.getSegment(0, length, dst, true); // to short for us to mangle |
| } else { |
| int n = SkScalarRoundToInt(length / fSegLength); |
| constexpr int kMaxReasonableIterations = 100000; |
| n = SkTMin(n, kMaxReasonableIterations); |
| SkScalar delta = length / n; |
| SkScalar distance = 0; |
| |
| if (meas.isClosed()) { |
| n -= 1; |
| distance += delta/2; |
| } |
| |
| if (meas.getPosTan(distance, &p, &v)) { |
| Perterb(&p, v, rand.nextSScalar1() * scale); |
| dst->moveTo(p); |
| } |
| while (--n >= 0) { |
| distance += delta; |
| if (meas.getPosTan(distance, &p, &v)) { |
| Perterb(&p, v, rand.nextSScalar1() * scale); |
| dst->lineTo(p); |
| } |
| } |
| if (meas.isClosed()) { |
| dst->close(); |
| } |
| } |
| } while (meas.nextContour()); |
| return true; |
| } |
| |
| sk_sp<SkFlattenable> SkDiscretePathEffect::CreateProc(SkReadBuffer& buffer) { |
| SkScalar segLength = buffer.readScalar(); |
| SkScalar perterb = buffer.readScalar(); |
| uint32_t seed = buffer.readUInt(); |
| return Make(segLength, perterb, seed); |
| } |
| |
| void SkDiscretePathEffect::flatten(SkWriteBuffer& buffer) const { |
| buffer.writeScalar(fSegLength); |
| buffer.writeScalar(fPerterb); |
| buffer.writeUInt(fSeedAssist); |
| } |