aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/utils/SkInterpolator.cpp
blob: 97574e475b4ed791702cd688cd7e35672a5b06e2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271

/*
 * Copyright 2008 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 "SkInterpolator.h"
#include "SkMath.h"
#include "SkTSearch.h"

SkInterpolatorBase::SkInterpolatorBase() {
    fStorage    = NULL;
    fTimes      = NULL;
    SkDEBUGCODE(fTimesArray = NULL;)
}

SkInterpolatorBase::~SkInterpolatorBase() {
    if (fStorage) {
        sk_free(fStorage);
    }
}

void SkInterpolatorBase::reset(int elemCount, int frameCount) {
    fFlags = 0;
    fElemCount = SkToU8(elemCount);
    fFrameCount = SkToS16(frameCount);
    fRepeat = SK_Scalar1;
    if (fStorage) {
        sk_free(fStorage);
        fStorage = NULL;
        fTimes = NULL;
        SkDEBUGCODE(fTimesArray = NULL);
    }
}

/*  Each value[] run is formated as:
        <time (in msec)>
        <blend>
        <data[fElemCount]>

    Totaling fElemCount+2 entries per keyframe
*/

bool SkInterpolatorBase::getDuration(SkMSec* startTime, SkMSec* endTime) const {
    if (fFrameCount == 0) {
        return false;
    }

    if (startTime) {
        *startTime = fTimes[0].fTime;
    }
    if (endTime) {
        *endTime = fTimes[fFrameCount - 1].fTime;
    }
    return true;
}

SkScalar SkInterpolatorBase::ComputeRelativeT(SkMSec time, SkMSec prevTime,
                                  SkMSec nextTime, const SkScalar blend[4]) {
    SkASSERT(time > prevTime && time < nextTime);

    SkScalar t = SkScalarDiv((SkScalar)(time - prevTime),
                             (SkScalar)(nextTime - prevTime));
    return blend ?
            SkUnitCubicInterp(t, blend[0], blend[1], blend[2], blend[3]) : t;
}

SkInterpolatorBase::Result SkInterpolatorBase::timeToT(SkMSec time, SkScalar* T,
                                        int* indexPtr, SkBool* exactPtr) const {
    SkASSERT(fFrameCount > 0);
    Result  result = kNormal_Result;
    if (fRepeat != SK_Scalar1) {
        SkMSec startTime = 0, endTime = 0;  // initialize to avoid warning
        this->getDuration(&startTime, &endTime);
        SkMSec totalTime = endTime - startTime;
        SkMSec offsetTime = time - startTime;
        endTime = SkScalarFloorToInt(fRepeat * totalTime);
        if (offsetTime >= endTime) {
            SkScalar fraction = SkScalarFraction(fRepeat);
            offsetTime = fraction == 0 && fRepeat > 0 ? totalTime :
                (SkMSec) SkScalarFloorToInt(fraction * totalTime);
            result = kFreezeEnd_Result;
        } else {
            int mirror = fFlags & kMirror;
            offsetTime = offsetTime % (totalTime << mirror);
            if (offsetTime > totalTime) { // can only be true if fMirror is true
                offsetTime = (totalTime << 1) - offsetTime;
            }
        }
        time = offsetTime + startTime;
    }

    int index = SkTSearch<SkMSec>(&fTimes[0].fTime, fFrameCount, time,
                                  sizeof(SkTimeCode));

    bool    exact = true;

    if (index < 0) {
        index = ~index;
        if (index == 0) {
            result = kFreezeStart_Result;
        } else if (index == fFrameCount) {
            if (fFlags & kReset) {
                index = 0;
            } else {
                index -= 1;
            }
            result = kFreezeEnd_Result;
        } else {
            exact = false;
        }
    }
    SkASSERT(index < fFrameCount);
    const SkTimeCode* nextTime = &fTimes[index];
    SkMSec   nextT = nextTime[0].fTime;
    if (exact) {
        *T = 0;
    } else {
        SkMSec prevT = nextTime[-1].fTime;
        *T = ComputeRelativeT(time, prevT, nextT, nextTime[-1].fBlend);
    }
    *indexPtr = index;
    *exactPtr = exact;
    return result;
}


SkInterpolator::SkInterpolator() {
    INHERITED::reset(0, 0);
    fValues = NULL;
    SkDEBUGCODE(fScalarsArray = NULL;)
}

SkInterpolator::SkInterpolator(int elemCount, int frameCount) {
    SkASSERT(elemCount > 0);
    this->reset(elemCount, frameCount);
}

void SkInterpolator::reset(int elemCount, int frameCount) {
    INHERITED::reset(elemCount, frameCount);
    fStorage = sk_malloc_throw((sizeof(SkScalar) * elemCount +
                                sizeof(SkTimeCode)) * frameCount);
    fTimes = (SkTimeCode*) fStorage;
    fValues = (SkScalar*) ((char*) fStorage + sizeof(SkTimeCode) * frameCount);
#ifdef SK_DEBUG
    fTimesArray = (SkTimeCode(*)[10]) fTimes;
    fScalarsArray = (SkScalar(*)[10]) fValues;
#endif
}

#define SK_Fixed1Third      (SK_Fixed1/3)
#define SK_Fixed2Third      (SK_Fixed1*2/3)

static const SkScalar gIdentityBlend[4] = {
    0.33333333f, 0.33333333f, 0.66666667f, 0.66666667f
};

bool SkInterpolator::setKeyFrame(int index, SkMSec time,
                            const SkScalar values[], const SkScalar blend[4]) {
    SkASSERT(values != NULL);

    if (blend == NULL) {
        blend = gIdentityBlend;
    }

    bool success = ~index == SkTSearch<SkMSec>(&fTimes->fTime, index, time,
                                               sizeof(SkTimeCode));
    SkASSERT(success);
    if (success) {
        SkTimeCode* timeCode = &fTimes[index];
        timeCode->fTime = time;
        memcpy(timeCode->fBlend, blend, sizeof(timeCode->fBlend));
        SkScalar* dst = &fValues[fElemCount * index];
        memcpy(dst, values, fElemCount * sizeof(SkScalar));
    }
    return success;
}

SkInterpolator::Result SkInterpolator::timeToValues(SkMSec time,
                                                    SkScalar values[]) const {
    SkScalar T;
    int index;
    SkBool exact;
    Result result = timeToT(time, &T, &index, &exact);
    if (values) {
        const SkScalar* nextSrc = &fValues[index * fElemCount];

        if (exact) {
            memcpy(values, nextSrc, fElemCount * sizeof(SkScalar));
        } else {
            SkASSERT(index > 0);

            const SkScalar* prevSrc = nextSrc - fElemCount;

            for (int i = fElemCount - 1; i >= 0; --i) {
                values[i] = SkScalarInterp(prevSrc[i], nextSrc[i], T);
            }
        }
    }
    return result;
}

///////////////////////////////////////////////////////////////////////////////

typedef int Dot14;
#define Dot14_ONE       (1 << 14)
#define Dot14_HALF      (1 << 13)

#define Dot14ToFloat(x) ((x) / 16384.f)

static inline Dot14 Dot14Mul(Dot14 a, Dot14 b) {
    return (a * b + Dot14_HALF) >> 14;
}

static inline Dot14 eval_cubic(Dot14 t, Dot14 A, Dot14 B, Dot14 C) {
    return Dot14Mul(Dot14Mul(Dot14Mul(C, t) + B, t) + A, t);
}

static inline Dot14 pin_and_convert(SkScalar x) {
    if (x <= 0) {
        return 0;
    }
    if (x >= SK_Scalar1) {
        return Dot14_ONE;
    }
    return SkScalarToFixed(x) >> 2;
}

SkScalar SkUnitCubicInterp(SkScalar value, SkScalar bx, SkScalar by,
                           SkScalar cx, SkScalar cy) {
    // pin to the unit-square, and convert to 2.14
    Dot14 x = pin_and_convert(value);

    if (x == 0) return 0;
    if (x == Dot14_ONE) return SK_Scalar1;

    Dot14 b = pin_and_convert(bx);
    Dot14 c = pin_and_convert(cx);

    // Now compute our coefficients from the control points
    //  t   -> 3b
    //  t^2 -> 3c - 6b
    //  t^3 -> 3b - 3c + 1
    Dot14 A = 3*b;
    Dot14 B = 3*(c - 2*b);
    Dot14 C = 3*(b - c) + Dot14_ONE;

    // Now search for a t value given x
    Dot14   t = Dot14_HALF;
    Dot14   dt = Dot14_HALF;
    for (int i = 0; i < 13; i++) {
        dt >>= 1;
        Dot14 guess = eval_cubic(t, A, B, C);
        if (x < guess) {
            t -= dt;
        } else {
            t += dt;
        }
    }

    // Now we have t, so compute the coeff for Y and evaluate
    b = pin_and_convert(by);
    c = pin_and_convert(cy);
    A = 3*b;
    B = 3*(c - 2*b);
    C = 3*(b - c) + Dot14_ONE;
    return SkFixedToScalar(eval_cubic(t, A, B, C) << 2);
}