SkDiscretePathEffect.cpp revision e0e7cfe44bb9d66d76120a79e5275c294bacaa22 
1
2/*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#include "SkDiscretePathEffect.h"
11#include "SkFlattenableBuffers.h"
12#include "SkPathMeasure.h"
13#include "SkRandom.h"
14
15static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) {
16    SkVector normal = tangent;
17    normal.rotateCCW();
18    normal.setLength(scale);
19    *p += normal;
20}
21
22
23SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, SkScalar deviation)
24    : fSegLength(segLength), fPerterb(deviation)
25{
26}
27
28bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
29                                      SkStrokeRec* rec, const SkRect*) const {
30    bool doFill = rec->isFillStyle();
31
32    SkPathMeasure   meas(src, doFill);
33    uint32_t        seed = SkScalarRound(meas.getLength());
34    SkLCGRandom     rand(seed ^ ((seed << 16) | (seed >> 16)));
35    SkScalar        scale = fPerterb;
36    SkPoint         p;
37    SkVector        v;
38
39    do {
40        SkScalar    length = meas.getLength();
41
42        if (fSegLength * (2 + doFill) > length) {
43            meas.getSegment(0, length, dst, true);  // to short for us to mangle
44        } else {
45            int         n = SkScalarRound(SkScalarDiv(length, fSegLength));
46            SkScalar    delta = length / n;
47            SkScalar    distance = 0;
48
49            if (meas.isClosed()) {
50                n -= 1;
51                distance += delta/2;
52            }
53
54            if (meas.getPosTan(distance, &p, &v)) {
55                Perterb(&p, v, SkScalarMul(rand.nextSScalar1(), scale));
56                dst->moveTo(p);
57            }
58            while (--n >= 0) {
59                distance += delta;
60                if (meas.getPosTan(distance, &p, &v)) {
61                    Perterb(&p, v, SkScalarMul(rand.nextSScalar1(), scale));
62                    dst->lineTo(p);
63                }
64            }
65            if (meas.isClosed()) {
66                dst->close();
67            }
68        }
69    } while (meas.nextContour());
70    return true;
71}
72
73void SkDiscretePathEffect::flatten(SkFlattenableWriteBuffer& buffer) const {
74    this->INHERITED::flatten(buffer);
75    buffer.writeScalar(fSegLength);
76    buffer.writeScalar(fPerterb);
77}
78
79SkDiscretePathEffect::SkDiscretePathEffect(SkFlattenableReadBuffer& buffer) {
80    fSegLength = buffer.readScalar();
81    fPerterb = buffer.readScalar();
82}
83