michael@0: 
michael@0: /*
michael@0:  * Copyright 2011 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: #include "SkUnitMappers.h"
michael@0: #include "SkReadBuffer.h"
michael@0: #include "SkWriteBuffer.h"
michael@0: 
michael@0: 
michael@0: SkDiscreteMapper::SkDiscreteMapper(int segments) {
michael@0:     if (segments < 2) {
michael@0:         fSegments = 0;
michael@0:         fScale = 0;
michael@0:     } else {
michael@0:         if (segments > 0xFFFF) {
michael@0:             segments = 0xFFFF;
michael@0:         }
michael@0:         fSegments = segments;
michael@0:         fScale = (1 << 30) / (segments - 1);
michael@0:     }
michael@0: }
michael@0: 
michael@0: uint16_t SkDiscreteMapper::mapUnit16(uint16_t input) {
michael@0:     SkFixed x = input * fSegments >> 16;
michael@0:     x = x * fScale >> 14;
michael@0:     x += x << 15 >> 31; // map 0x10000 to 0xFFFF
michael@0:     return SkToU16(x);
michael@0: }
michael@0: 
michael@0: SkDiscreteMapper::SkDiscreteMapper(SkReadBuffer& rb)
michael@0:         : SkUnitMapper(rb) {
michael@0:     fSegments = rb.readInt();
michael@0:     fScale = rb.read32();
michael@0: }
michael@0: 
michael@0: void SkDiscreteMapper::flatten(SkWriteBuffer& wb) const {
michael@0:     this->INHERITED::flatten(wb);
michael@0: 
michael@0:     wb.writeInt(fSegments);
michael@0:     wb.write32(fScale);
michael@0: }
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: uint16_t SkCosineMapper::mapUnit16(uint16_t input)
michael@0: {
michael@0:     /*  we want to call cosine(input * pi/2) treating input as [0...1)
michael@0:         however, the straight multitply would overflow 32bits since input is
michael@0:         16bits and pi/2 is 17bits, so we shift down our pi const before we mul
michael@0:     */
michael@0:     SkFixed rads = (unsigned)(input * (SK_FixedPI >> 2)) >> 15;
michael@0:     SkFixed x = SkFixedCos(rads);
michael@0:     x += x << 15 >> 31; // map 0x10000 to 0xFFFF
michael@0:     return SkToU16(x);
michael@0: }
michael@0: 
michael@0: SkCosineMapper::SkCosineMapper(SkReadBuffer& rb)
michael@0:     : SkUnitMapper(rb) {}