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#include "SkFlattenableBuffers.h"
10
11SkDiscreteMapper::SkDiscreteMapper(int segments) {
12    if (segments < 2) {
13        fSegments = 0;
14        fScale = 0;
15    } else {
16        if (segments > 0xFFFF) {
17            segments = 0xFFFF;
18        }
19        fSegments = segments;
20        fScale = SK_Fract1 / (segments - 1);
21    }
22}
23
24uint16_t SkDiscreteMapper::mapUnit16(uint16_t input) {
25    SkFixed x = input * fSegments >> 16;
26    x = x * fScale >> 14;
27    x += x << 15 >> 31; // map 0x10000 to 0xFFFF
28    return SkToU16(x);
29}
30
31SkDiscreteMapper::SkDiscreteMapper(SkFlattenableReadBuffer& rb)
32        : SkUnitMapper(rb) {
33    fSegments = rb.readInt();
34    fScale = rb.read32();
35}
36
37void SkDiscreteMapper::flatten(SkFlattenableWriteBuffer& wb) const {
38    this->INHERITED::flatten(wb);
39
40    wb.writeInt(fSegments);
41    wb.write32(fScale);
42}
43
44///////////////////////////////////////////////////////////////////////////////
45
46uint16_t SkCosineMapper::mapUnit16(uint16_t input)
47{
48    /*  we want to call cosine(input * pi/2) treating input as [0...1)
49        however, the straight multitply would overflow 32bits since input is
50        16bits and pi/2 is 17bits, so we shift down our pi const before we mul
51    */
52    SkFixed rads = (unsigned)(input * (SK_FixedPI >> 2)) >> 15;
53    SkFixed x = SkFixedCos(rads);
54    x += x << 15 >> 31; // map 0x10000 to 0xFFFF
55    return SkToU16(x);
56}
57
58SkCosineMapper::SkCosineMapper(SkFlattenableReadBuffer& rb)
59    : SkUnitMapper(rb) {}
60