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