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      1 /* libs/graphics/effects/SkDiscretePathEffect.cpp
      2 **
      3 ** Copyright 2006, The Android Open Source Project
      4 **
      5 ** Licensed under the Apache License, Version 2.0 (the "License");
      6 ** you may not use this file except in compliance with the License.
      7 ** You may obtain a copy of the License at
      8 **
      9 **     http://www.apache.org/licenses/LICENSE-2.0
     10 **
     11 ** Unless required by applicable law or agreed to in writing, software
     12 ** distributed under the License is distributed on an "AS IS" BASIS,
     13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 ** See the License for the specific language governing permissions and
     15 ** limitations under the License.
     16 */
     17 
     18 #include "SkDiscretePathEffect.h"
     19 #include "SkBuffer.h"
     20 #include "SkPathMeasure.h"
     21 #include "SkRandom.h"
     22 
     23 static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) {
     24     SkVector normal = tangent;
     25     normal.rotateCCW();
     26     normal.setLength(scale);
     27     *p += normal;
     28 }
     29 
     30 
     31 SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, SkScalar deviation)
     32     : fSegLength(segLength), fPerterb(deviation)
     33 {
     34 }
     35 
     36 bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
     37                                       SkScalar* width) {
     38     bool doFill = *width < 0;
     39 
     40     SkPathMeasure   meas(src, doFill);
     41     uint32_t        seed = SkScalarRound(meas.getLength());
     42     SkRandom        rand(seed ^ ((seed << 16) | (seed >> 16)));
     43     SkScalar        scale = fPerterb;
     44     SkPoint         p;
     45     SkVector        v;
     46 
     47     do {
     48         SkScalar    length = meas.getLength();
     49 
     50         if (fSegLength * (2 + doFill) > length) {
     51             meas.getSegment(0, length, dst, true);  // to short for us to mangle
     52         } else {
     53             int         n = SkScalarRound(SkScalarDiv(length, fSegLength));
     54             SkScalar    delta = length / n;
     55             SkScalar    distance = 0;
     56 
     57             if (meas.isClosed()) {
     58                 n -= 1;
     59                 distance += delta/2;
     60             }
     61             meas.getPosTan(distance, &p, &v);
     62             Perterb(&p, v, SkScalarMul(rand.nextSScalar1(), scale));
     63             dst->moveTo(p);
     64             while (--n >= 0) {
     65                 distance += delta;
     66                 meas.getPosTan(distance, &p, &v);
     67                 Perterb(&p, v, SkScalarMul(rand.nextSScalar1(), scale));
     68                 dst->lineTo(p);
     69             }
     70             if (meas.isClosed()) {
     71                 dst->close();
     72             }
     73         }
     74     } while (meas.nextContour());
     75     return true;
     76 }
     77 
     78 SkFlattenable::Factory SkDiscretePathEffect::getFactory() {
     79     return CreateProc;
     80 }
     81 
     82 SkFlattenable* SkDiscretePathEffect::CreateProc(SkFlattenableReadBuffer& buffer) {
     83     return SkNEW_ARGS(SkDiscretePathEffect, (buffer));
     84 }
     85 
     86 void SkDiscretePathEffect::flatten(SkFlattenableWriteBuffer& buffer) {
     87     buffer.writeScalar(fSegLength);
     88     buffer.writeScalar(fPerterb);
     89 }
     90 
     91 SkDiscretePathEffect::SkDiscretePathEffect(SkFlattenableReadBuffer& buffer) {
     92     fSegLength = buffer.readScalar();
     93     fPerterb = buffer.readScalar();
     94 }
     95 
     96