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 11 SK_DEFINE_INST_COUNT(SkUnitMapper) 12 13 SkDiscreteMapper::SkDiscreteMapper(int segments) { 14 if (segments < 2) { 15 fSegments = 0; 16 fScale = 0; 17 } else { 18 if (segments > 0xFFFF) { 19 segments = 0xFFFF; 20 } 21 fSegments = segments; 22 fScale = SK_Fract1 / (segments - 1); 23 } 24 } 25 26 uint16_t SkDiscreteMapper::mapUnit16(uint16_t input) { 27 SkFixed x = input * fSegments >> 16; 28 x = x * fScale >> 14; 29 x += x << 15 >> 31; // map 0x10000 to 0xFFFF 30 return SkToU16(x); 31 } 32 33 SkDiscreteMapper::SkDiscreteMapper(SkFlattenableReadBuffer& rb) 34 : SkUnitMapper(rb) { 35 fSegments = rb.readInt(); 36 fScale = rb.read32(); 37 } 38 39 void SkDiscreteMapper::flatten(SkFlattenableWriteBuffer& wb) const { 40 this->INHERITED::flatten(wb); 41 42 wb.writeInt(fSegments); 43 wb.write32(fScale); 44 } 45 46 /////////////////////////////////////////////////////////////////////////////// 47 48 uint16_t SkCosineMapper::mapUnit16(uint16_t input) 49 { 50 /* we want to call cosine(input * pi/2) treating input as [0...1) 51 however, the straight multitply would overflow 32bits since input is 52 16bits and pi/2 is 17bits, so we shift down our pi const before we mul 53 */ 54 SkFixed rads = (unsigned)(input * (SK_FixedPI >> 2)) >> 15; 55 SkFixed x = SkFixedCos(rads); 56 x += x << 15 >> 31; // map 0x10000 to 0xFFFF 57 return SkToU16(x); 58 } 59 60 SkCosineMapper::SkCosineMapper(SkFlattenableReadBuffer& rb) 61 : SkUnitMapper(rb) {} 62
