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 #ifndef SkInterpolator_DEFINED
11 #define SkInterpolator_DEFINED
12 
13 #include "SkScalar.h"
14 
15 class SkInterpolatorBase : SkNoncopyable {
16 public:
17     enum Result {
18         kNormal_Result,
19         kFreezeStart_Result,
20         kFreezeEnd_Result
21     };
22 protected:
23     SkInterpolatorBase();
24     ~SkInterpolatorBase();
25 public:
26     void    reset(int elemCount, int frameCount);
27 
28     /** Return the start and end time for this interpolator.
29         If there are no key frames, return false.
30         @param startTime If not null, returns the time (in milliseconds) of the
31                          first keyframe. If there are no keyframes, this param
32                          is ignored (left unchanged).
33         @param endTime If not null, returns the time (in milliseconds) of the
34                        last keyframe. If there are no keyframes, this parameter
35                        is ignored (left unchanged).
36         @return True if there are key frames, or false if there are none.
37     */
38     bool    getDuration(SkMSec* startTime, SkMSec* endTime) const;
39 
40 
41     /** Set the whether the repeat is mirrored.
42         @param mirror If true, the odd repeats interpolate from the last key
43                       frame and the first.
44     */
setMirror(bool mirror)45     void setMirror(bool mirror) {
46         fFlags = SkToU8((fFlags & ~kMirror) | (int)mirror);
47     }
48 
49     /** Set the repeat count. The repeat count may be fractional.
50         @param repeatCount Multiplies the total time by this scalar.
51     */
setRepeatCount(SkScalar repeatCount)52     void    setRepeatCount(SkScalar repeatCount) { fRepeat = repeatCount; }
53 
54     /** Set the whether the repeat is mirrored.
55         @param reset If true, the odd repeats interpolate from the last key
56                      frame and the first.
57     */
setReset(bool reset)58     void setReset(bool reset) {
59         fFlags = SkToU8((fFlags & ~kReset) | (int)reset);
60     }
61 
62     Result  timeToT(SkMSec time, SkScalar* T, int* index, bool* exact) const;
63 
64 protected:
65     enum Flags {
66         kMirror = 1,
67         kReset = 2,
68         kHasBlend = 4
69     };
70     static SkScalar ComputeRelativeT(SkMSec time, SkMSec prevTime,
71                              SkMSec nextTime, const SkScalar blend[4] = NULL);
72     int16_t fFrameCount;
73     uint8_t fElemCount;
74     uint8_t fFlags;
75     SkScalar fRepeat;
76     struct SkTimeCode {
77         SkMSec  fTime;
78         SkScalar fBlend[4];
79     };
80     SkTimeCode* fTimes;     // pointer into fStorage
81     void* fStorage;
82 #ifdef SK_DEBUG
83     SkTimeCode(* fTimesArray)[10];
84 #endif
85 };
86 
87 class SkInterpolator : public SkInterpolatorBase {
88 public:
89     SkInterpolator();
90     SkInterpolator(int elemCount, int frameCount);
91     void    reset(int elemCount, int frameCount);
92 
93     /** Add or replace a key frame, copying the values[] data into the
94         interpolator.
95         @param index    The index of this frame (frames must be ordered by time)
96         @param time The millisecond time for this frame
97         @param values   The array of values [elemCount] for this frame. The data
98                         is copied into the interpolator.
99         @param blend    A positive scalar specifying how to blend between this
100                         and the next key frame. [0...1) is a cubic lag/log/lag
101                         blend (slow to change at the beginning and end)
102                         1 is a linear blend (default)
103     */
104     bool setKeyFrame(int index, SkMSec time, const SkScalar values[],
105                      const SkScalar blend[4] = NULL);
106 
107     /** Return the computed values given the specified time. Return whether
108         those values are the result of pinning to either the first
109         (kFreezeStart) or last (kFreezeEnd), or from interpolated the two
110         nearest key values (kNormal).
111         @param time The time to sample (in milliseconds)
112         @param (may be null) where to write the computed values.
113     */
114     Result timeToValues(SkMSec time, SkScalar values[] = NULL) const;
115 
116 private:
117     SkScalar* fValues;  // pointer into fStorage
118 #ifdef SK_DEBUG
119     SkScalar(* fScalarsArray)[10];
120 #endif
121     typedef SkInterpolatorBase INHERITED;
122 };
123 
124 /** Interpolate a cubic curve, typically to provide an ease-in ease-out transition.
125     All the parameters are in the range of [0...1].
126     The input value is treated as the x-coordinate of the cubic.
127     The output value is the y-coordinate on the cubic at the x-coordinate.
128 
129     @param value        The x-coordinate pinned between [0..1].
130     @param bx,by,cx,cy  The cubic control points where the cubic is specified
131                         as (0,0) (bx,by) (cx,cy) (1,1)
132     @return             the corresponding y-coordinate value, from [0..1].
133 */
134 SkScalar SkUnitCubicInterp(SkScalar value, SkScalar bx, SkScalar by,
135                            SkScalar cx, SkScalar cy);
136 
137 #endif
138