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
10SkDiscreteMapper::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
23uint16_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
30SkDiscreteMapper::SkDiscreteMapper(SkFlattenableReadBuffer& rb)
31        : SkUnitMapper(rb) {
32    fSegments = rb.readU32();
33    fScale = rb.readU32();
34}
35
36SkFlattenable::Factory SkDiscreteMapper::getFactory() {
37    return Create;
38}
39
40SkFlattenable* SkDiscreteMapper::Create(SkFlattenableReadBuffer& rb) {
41    return SkNEW_ARGS(SkDiscreteMapper, (rb));
42}
43
44void SkDiscreteMapper::flatten(SkFlattenableWriteBuffer& wb) {
45    this->INHERITED::flatten(wb);
46
47    wb.write32(fSegments);
48    wb.write32(fScale);
49}
50
51///////////////////////////////////////////////////////////////////////////////
52
53uint16_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
65SkCosineMapper::SkCosineMapper(SkFlattenableReadBuffer& rb)
66    : SkUnitMapper(rb) {}
67
68SkFlattenable::Factory SkCosineMapper::getFactory() {
69    return Create;
70}
71
72SkFlattenable* SkCosineMapper::Create(SkFlattenableReadBuffer& rb) {
73    return SkNEW_ARGS(SkCosineMapper, (rb));
74}
75
76