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