SkInterpolator.cpp revision fe17456d5e528078ce69b5f15cf7adf1fab963f9 
1/*
2 * Copyright 2008 The Android Open Source Project
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 "SkInterpolator.h"
9
10#include "SkFixed.h"
11#include "SkMath.h"
12#include "SkMalloc.h"
13#include "SkTSearch.h"
14
15SkInterpolatorBase::SkInterpolatorBase() {
16    fStorage    = nullptr;
17    fTimes      = nullptr;
18    SkDEBUGCODE(fTimesArray = nullptr;)
19}
20
21SkInterpolatorBase::~SkInterpolatorBase() {
22    if (fStorage) {
23        sk_free(fStorage);
24    }
25}
26
27void SkInterpolatorBase::reset(int elemCount, int frameCount) {
28    fFlags = 0;
29    fElemCount = SkToU8(elemCount);
30    fFrameCount = SkToS16(frameCount);
31    fRepeat = SK_Scalar1;
32    if (fStorage) {
33        sk_free(fStorage);
34        fStorage = nullptr;
35        fTimes = nullptr;
36        SkDEBUGCODE(fTimesArray = nullptr);
37    }
38}
39
40/*  Each value[] run is formated as:
41        <time (in msec)>
42        <blend>
43        <data[fElemCount]>
44
45    Totaling fElemCount+2 entries per keyframe
46*/
47
48bool SkInterpolatorBase::getDuration(SkMSec* startTime, SkMSec* endTime) const {
49    if (fFrameCount == 0) {
50        return false;
51    }
52
53    if (startTime) {
54        *startTime = fTimes[0].fTime;
55    }
56    if (endTime) {
57        *endTime = fTimes[fFrameCount - 1].fTime;
58    }
59    return true;
60}
61
62SkScalar SkInterpolatorBase::ComputeRelativeT(SkMSec time, SkMSec prevTime,
63                                  SkMSec nextTime, const SkScalar blend[4]) {
64    SkASSERT(time > prevTime && time < nextTime);
65
66    SkScalar t = (SkScalar)(time - prevTime) / (SkScalar)(nextTime - prevTime);
67    return blend ?
68            SkUnitCubicInterp(t, blend[0], blend[1], blend[2], blend[3]) : t;
69}
70
71SkInterpolatorBase::Result SkInterpolatorBase::timeToT(SkMSec time, SkScalar* T,
72                                        int* indexPtr, bool* exactPtr) const {
73    SkASSERT(fFrameCount > 0);
74    Result  result = kNormal_Result;
75    if (fRepeat != SK_Scalar1) {
76        SkMSec startTime = 0, endTime = 0;  // initialize to avoid warning
77        this->getDuration(&startTime, &endTime);
78        SkMSec totalTime = endTime - startTime;
79        SkMSec offsetTime = time - startTime;
80        endTime = SkScalarFloorToInt(fRepeat * totalTime);
81        if (offsetTime >= endTime) {
82            SkScalar fraction = SkScalarFraction(fRepeat);
83            offsetTime = fraction == 0 && fRepeat > 0 ? totalTime :
84                (SkMSec) SkScalarFloorToInt(fraction * totalTime);
85            result = kFreezeEnd_Result;
86        } else {
87            int mirror = fFlags & kMirror;
88            offsetTime = offsetTime % (totalTime << mirror);
89            if (offsetTime > totalTime) { // can only be true if fMirror is true
90                offsetTime = (totalTime << 1) - offsetTime;
91            }
92        }
93        time = offsetTime + startTime;
94    }
95
96    int index = SkTSearch<SkMSec>(&fTimes[0].fTime, fFrameCount, time,
97                                  sizeof(SkTimeCode));
98
99    bool    exact = true;
100
101    if (index < 0) {
102        index = ~index;
103        if (index == 0) {
104            result = kFreezeStart_Result;
105        } else if (index == fFrameCount) {
106            if (fFlags & kReset) {
107                index = 0;
108            } else {
109                index -= 1;
110            }
111            result = kFreezeEnd_Result;
112        } else {
113            exact = false;
114        }
115    }
116    SkASSERT(index < fFrameCount);
117    const SkTimeCode* nextTime = &fTimes[index];
118    SkMSec   nextT = nextTime[0].fTime;
119    if (exact) {
120        *T = 0;
121    } else {
122        SkMSec prevT = nextTime[-1].fTime;
123        *T = ComputeRelativeT(time, prevT, nextT, nextTime[-1].fBlend);
124    }
125    *indexPtr = index;
126    *exactPtr = exact;
127    return result;
128}
129
130
131SkInterpolator::SkInterpolator() {
132    INHERITED::reset(0, 0);
133    fValues = nullptr;
134    SkDEBUGCODE(fScalarsArray = nullptr;)
135}
136
137SkInterpolator::SkInterpolator(int elemCount, int frameCount) {
138    SkASSERT(elemCount > 0);
139    this->reset(elemCount, frameCount);
140}
141
142void SkInterpolator::reset(int elemCount, int frameCount) {
143    INHERITED::reset(elemCount, frameCount);
144    fStorage = sk_malloc_throw((sizeof(SkScalar) * elemCount +
145                                sizeof(SkTimeCode)) * frameCount);
146    fTimes = (SkTimeCode*) fStorage;
147    fValues = (SkScalar*) ((char*) fStorage + sizeof(SkTimeCode) * frameCount);
148#ifdef SK_DEBUG
149    fTimesArray = (SkTimeCode(*)[10]) fTimes;
150    fScalarsArray = (SkScalar(*)[10]) fValues;
151#endif
152}
153
154#define SK_Fixed1Third      (SK_Fixed1/3)
155#define SK_Fixed2Third      (SK_Fixed1*2/3)
156
157static const SkScalar gIdentityBlend[4] = {
158    0.33333333f, 0.33333333f, 0.66666667f, 0.66666667f
159};
160
161bool SkInterpolator::setKeyFrame(int index, SkMSec time,
162                            const SkScalar values[], const SkScalar blend[4]) {
163    SkASSERT(values != nullptr);
164
165    if (blend == nullptr) {
166        blend = gIdentityBlend;
167    }
168
169    bool success = ~index == SkTSearch<SkMSec>(&fTimes->fTime, index, time,
170                                               sizeof(SkTimeCode));
171    SkASSERT(success);
172    if (success) {
173        SkTimeCode* timeCode = &fTimes[index];
174        timeCode->fTime = time;
175        memcpy(timeCode->fBlend, blend, sizeof(timeCode->fBlend));
176        SkScalar* dst = &fValues[fElemCount * index];
177        memcpy(dst, values, fElemCount * sizeof(SkScalar));
178    }
179    return success;
180}
181
182SkInterpolator::Result SkInterpolator::timeToValues(SkMSec time,
183                                                    SkScalar values[]) const {
184    SkScalar T;
185    int index;
186    bool exact;
187    Result result = timeToT(time, &T, &index, &exact);
188    if (values) {
189        const SkScalar* nextSrc = &fValues[index * fElemCount];
190
191        if (exact) {
192            memcpy(values, nextSrc, fElemCount * sizeof(SkScalar));
193        } else {
194            SkASSERT(index > 0);
195
196            const SkScalar* prevSrc = nextSrc - fElemCount;
197
198            for (int i = fElemCount - 1; i >= 0; --i) {
199                values[i] = SkScalarInterp(prevSrc[i], nextSrc[i], T);
200            }
201        }
202    }
203    return result;
204}
205
206///////////////////////////////////////////////////////////////////////////////
207
208typedef int Dot14;
209#define Dot14_ONE       (1 << 14)
210#define Dot14_HALF      (1 << 13)
211
212#define Dot14ToFloat(x) ((x) / 16384.f)
213
214static inline Dot14 Dot14Mul(Dot14 a, Dot14 b) {
215    return (a * b + Dot14_HALF) >> 14;
216}
217
218static inline Dot14 eval_cubic(Dot14 t, Dot14 A, Dot14 B, Dot14 C) {
219    return Dot14Mul(Dot14Mul(Dot14Mul(C, t) + B, t) + A, t);
220}
221
222static inline Dot14 pin_and_convert(SkScalar x) {
223    if (x <= 0) {
224        return 0;
225    }
226    if (x >= SK_Scalar1) {
227        return Dot14_ONE;
228    }
229    return SkScalarToFixed(x) >> 2;
230}
231
232SkScalar SkUnitCubicInterp(SkScalar value, SkScalar bx, SkScalar by,
233                           SkScalar cx, SkScalar cy) {
234    // pin to the unit-square, and convert to 2.14
235    Dot14 x = pin_and_convert(value);
236
237    if (x == 0) return 0;
238    if (x == Dot14_ONE) return SK_Scalar1;
239
240    Dot14 b = pin_and_convert(bx);
241    Dot14 c = pin_and_convert(cx);
242
243    // Now compute our coefficients from the control points
244    //  t   -> 3b
245    //  t^2 -> 3c - 6b
246    //  t^3 -> 3b - 3c + 1
247    Dot14 A = 3*b;
248    Dot14 B = 3*(c - 2*b);
249    Dot14 C = 3*(b - c) + Dot14_ONE;
250
251    // Now search for a t value given x
252    Dot14   t = Dot14_HALF;
253    Dot14   dt = Dot14_HALF;
254    for (int i = 0; i < 13; i++) {
255        dt >>= 1;
256        Dot14 guess = eval_cubic(t, A, B, C);
257        if (x < guess) {
258            t -= dt;
259        } else {
260            t += dt;
261        }
262    }
263
264    // Now we have t, so compute the coeff for Y and evaluate
265    b = pin_and_convert(by);
266    c = pin_and_convert(cy);
267    A = 3*b;
268    B = 3*(c - 2*b);
269    C = 3*(b - c) + Dot14_ONE;
270    return SkFixedToScalar(eval_cubic(t, A, B, C) << 2);
271}
272