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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrSwizzle_DEFINED
#define GrSwizzle_DEFINED
#include "include/core/SkString.h"
#include "include/private/SkColorData.h"
#include "src/gpu/GrColor.h"
class SkRasterPipeline;
/** Represents a rgba swizzle. It can be converted either into a string or a eight bit int. */
class GrSwizzle {
public:
constexpr GrSwizzle() : GrSwizzle("rgba") {}
explicit constexpr GrSwizzle(const char c[4]);
constexpr GrSwizzle(const GrSwizzle&);
constexpr GrSwizzle& operator=(const GrSwizzle& that);
static constexpr GrSwizzle Concat(const GrSwizzle& a, const GrSwizzle& b);
constexpr bool operator==(const GrSwizzle& that) const { return fKey == that.fKey; }
constexpr bool operator!=(const GrSwizzle& that) const { return !(*this == that); }
/** Compact representation of the swizzle suitable for a key. */
constexpr uint16_t asKey() const { return fKey; }
/** 4 char null terminated string consisting only of chars 'r', 'g', 'b', 'a', '0', and '1'. */
SkString asString() const;
constexpr char operator[](int i) const {
SkASSERT(i >= 0 && i < 4);
int idx = (fKey >> (4U * i)) & 0xfU;
return IToC(idx);
}
/** Applies this swizzle to the input color and returns the swizzled color. */
constexpr std::array<float, 4> applyTo(std::array<float, 4> color) const;
/** Convenience version for SkRGBA colors. */
template <SkAlphaType AlphaType>
constexpr SkRGBA4f<AlphaType> applyTo(SkRGBA4f<AlphaType> color) const {
std::array<float, 4> result = this->applyTo(color.array());
return {result[0], result[1], result[2], result[3]};
}
void apply(SkRasterPipeline*) const;
static constexpr GrSwizzle RGBA() { return GrSwizzle("rgba"); }
static constexpr GrSwizzle BGRA() { return GrSwizzle("bgra"); }
static constexpr GrSwizzle RRRA() { return GrSwizzle("rrra"); }
static constexpr GrSwizzle RGB1() { return GrSwizzle("rgb1"); }
private:
explicit constexpr GrSwizzle(uint16_t key) : fKey(key) {}
static constexpr float ComponentIndexToFloat(std::array<float, 4>, int idx);
static constexpr int CToI(char c);
static constexpr char IToC(int idx);
uint16_t fKey;
};
constexpr GrSwizzle::GrSwizzle(const char c[4])
: fKey((CToI(c[0]) << 0) | (CToI(c[1]) << 4) | (CToI(c[2]) << 8) | (CToI(c[3]) << 12)) {}
constexpr GrSwizzle::GrSwizzle(const GrSwizzle& that)
: fKey(that.fKey) {}
constexpr GrSwizzle& GrSwizzle::operator=(const GrSwizzle& that) {
fKey = that.fKey;
return *this;
}
constexpr std::array<float, 4> GrSwizzle::applyTo(std::array<float, 4> color) const {
uint32_t key = fKey;
// Index of the input color that should be mapped to output r.
int idx = (key & 15);
float outR = ComponentIndexToFloat(color, idx);
key >>= 4;
idx = (key & 15);
float outG = ComponentIndexToFloat(color, idx);
key >>= 4;
idx = (key & 15);
float outB = ComponentIndexToFloat(color, idx);
key >>= 4;
idx = (key & 15);
float outA = ComponentIndexToFloat(color, idx);
return { outR, outG, outB, outA };
}
constexpr float GrSwizzle::ComponentIndexToFloat(std::array<float, 4> color, int idx) {
if (idx <= 3) {
return color[idx];
}
if (idx == CToI('1')) {
return 1.0f;
}
if (idx == CToI('0')) {
return 0.0f;
}
SkUNREACHABLE;
}
constexpr int GrSwizzle::CToI(char c) {
switch (c) {
// r...a must map to 0...3 because other methods use them as indices into fSwiz.
case 'r': return 0;
case 'g': return 1;
case 'b': return 2;
case 'a': return 3;
case '0': return 4;
case '1': return 5;
default: SkUNREACHABLE;
}
}
constexpr char GrSwizzle::IToC(int idx) {
switch (idx) {
case CToI('r'): return 'r';
case CToI('g'): return 'g';
case CToI('b'): return 'b';
case CToI('a'): return 'a';
case CToI('0'): return '0';
case CToI('1'): return '1';
default: SkUNREACHABLE;
}
}
constexpr GrSwizzle GrSwizzle::Concat(const GrSwizzle& a, const GrSwizzle& b) {
uint16_t key = 0;
for (int i = 0; i < 4; ++i) {
int idx = (b.fKey >> (4U * i)) & 0xfU;
if (idx != CToI('0') && idx != CToI('1')) {
SkASSERT(idx >= 0 && idx < 4);
// Get the index value stored in a at location idx.
idx = ((a.fKey >> (4U * idx)) & 0xfU);
}
key |= (idx << (4U * i));
}
return GrSwizzle(key);
}
#endif