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1 
2 /*
3  * Copyright 2011 Google Inc.
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 #include "SkUnitMappers.h"
9 
SkDiscreteMapper(int segments)10 SkDiscreteMapper::SkDiscreteMapper(int segments) {
11     if (segments < 2) {
12         fSegments = 0;
13         fScale = 0;
14     } else {
15         if (segments > 0xFFFF) {
16             segments = 0xFFFF;
17         }
18         fSegments = segments;
19         fScale = SK_Fract1 / (segments - 1);
20     }
21 }
22 
mapUnit16(uint16_t input)23 uint16_t SkDiscreteMapper::mapUnit16(uint16_t input) {
24     SkFixed x = input * fSegments >> 16;
25     x = x * fScale >> 14;
26     x += x << 15 >> 31; // map 0x10000 to 0xFFFF
27     return SkToU16(x);
28 }
29 
SkDiscreteMapper(SkFlattenableReadBuffer & rb)30 SkDiscreteMapper::SkDiscreteMapper(SkFlattenableReadBuffer& rb)
31         : SkUnitMapper(rb) {
32     fSegments = rb.readU32();
33     fScale = rb.readU32();
34 }
35 
getFactory()36 SkFlattenable::Factory SkDiscreteMapper::getFactory() {
37     return Create;
38 }
39 
Create(SkFlattenableReadBuffer & rb)40 SkFlattenable* SkDiscreteMapper::Create(SkFlattenableReadBuffer& rb) {
41     return SkNEW_ARGS(SkDiscreteMapper, (rb));
42 }
43 
flatten(SkFlattenableWriteBuffer & wb)44 void SkDiscreteMapper::flatten(SkFlattenableWriteBuffer& wb) {
45     this->INHERITED::flatten(wb);
46 
47     wb.write32(fSegments);
48     wb.write32(fScale);
49 }
50 
51 ///////////////////////////////////////////////////////////////////////////////
52 
mapUnit16(uint16_t input)53 uint16_t SkCosineMapper::mapUnit16(uint16_t input)
54 {
55     /*  we want to call cosine(input * pi/2) treating input as [0...1)
56         however, the straight multitply would overflow 32bits since input is
57         16bits and pi/2 is 17bits, so we shift down our pi const before we mul
58     */
59     SkFixed rads = (unsigned)(input * (SK_FixedPI >> 2)) >> 15;
60     SkFixed x = SkFixedCos(rads);
61     x += x << 15 >> 31; // map 0x10000 to 0xFFFF
62     return SkToU16(x);
63 }
64 
SkCosineMapper(SkFlattenableReadBuffer & rb)65 SkCosineMapper::SkCosineMapper(SkFlattenableReadBuffer& rb)
66     : SkUnitMapper(rb) {}
67 
getFactory()68 SkFlattenable::Factory SkCosineMapper::getFactory() {
69     return Create;
70 }
71 
Create(SkFlattenableReadBuffer & rb)72 SkFlattenable* SkCosineMapper::Create(SkFlattenableReadBuffer& rb) {
73     return SkNEW_ARGS(SkCosineMapper, (rb));
74 }
75 
76