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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 "GrColor.h"
#include "SkRandom.h"
/** Represents a rgba swizzle. It can be converted either into a string or a eight bit int.
Currently there is no way to specify an arbitrary swizzle, just some static swizzles and an
assignment operator. That could be relaxed. */
class GrSwizzle {
public:
GrSwizzle() { *this = RGBA(); }
GrSwizzle(const GrSwizzle& that) { *this = that; }
GrSwizzle& operator=(const GrSwizzle& that) {
memcpy(this, &that, sizeof(GrSwizzle));
return *this;
}
/** Recreates a GrSwizzle from the output of asKey() */
void setFromKey(uint8_t key) {
fKey = key;
for (int i = 0; i < 4; ++i) {
fSwiz[i] = IdxToChar(key & 3);
key >>= 2;
}
SkASSERT(fSwiz[4] == 0);
}
bool operator==(const GrSwizzle& that) const { return this->asUInt() == that.asUInt(); }
bool operator!=(const GrSwizzle& that) const { return !(*this == that); }
/** Compact representation of the swizzle suitable for a key. */
uint8_t asKey() const { return fKey; }
/** 4 char null terminated string consisting only of chars 'r', 'g', 'b', 'a'. */
const char* c_str() const { return fSwiz; }
/** Applies this swizzle to the input color and returns the swizzled color. */
GrColor applyTo(GrColor color) const {
int idx;
uint32_t key = fKey;
// Index of the input color that should be mapped to output r.
idx = (key & 3);
uint32_t outR = (color >> idx * 8) & 0xFF;
key >>= 2;
idx = (key & 3);
uint32_t outG = (color >> idx * 8) & 0xFF;
key >>= 2;
idx = (key & 3);
uint32_t outB = (color >> idx * 8) & 0xFF;
key >>= 2;
idx = (key & 3);
uint32_t outA = (color >> idx * 8) & 0xFF;
return GrColorPackRGBA(outR, outG, outB, outA);
}
static const GrSwizzle& RGBA() {
static GrSwizzle gRGBA("rgba");
return gRGBA;
}
static const GrSwizzle& AAAA() {
static GrSwizzle gAAAA("aaaa");
return gAAAA;
}
static const GrSwizzle& RRRR() {
static GrSwizzle gRRRR("rrrr");
return gRRRR;
}
static const GrSwizzle& BGRA() {
static GrSwizzle gBGRA("bgra");
return gBGRA;
}
static const GrSwizzle& CreateRandom(SkRandom* random) {
switch (random->nextU() % 4) {
case 0:
return RGBA();
case 1:
return BGRA();
case 2:
return RRRR();
case 3:
return AAAA();
default:
SkFAIL("Mod is broken?!?");
return RGBA();
}
}
private:
char fSwiz[5];
uint8_t fKey;
static int CharToIdx(char c) {
switch (c) {
case 'r':
return (GrColor_SHIFT_R / 8);
case 'g':
return (GrColor_SHIFT_G / 8);
case 'b':
return (GrColor_SHIFT_B / 8);
case 'a':
return (GrColor_SHIFT_A / 8);
default:
SkFAIL("Invalid swizzle char");
return 0;
}
}
static /* constexpr */ char IToC(int idx) {
return (8*idx) == GrColor_SHIFT_R ? 'r' :
(8*idx) == GrColor_SHIFT_G ? 'g' :
(8*idx) == GrColor_SHIFT_B ? 'b' : 'a';
}
static char IdxToChar(int c) {
// Hopefully this array gets computed at compile time.
static const char gStr[4] = { IToC(0), IToC(1), IToC(2), IToC(3) };
return gStr[c];
}
explicit GrSwizzle(const char* str) {
SkASSERT(strlen(str) == 4);
fSwiz[0] = str[0];
fSwiz[1] = str[1];
fSwiz[2] = str[2];
fSwiz[3] = str[3];
fSwiz[4] = 0;
fKey = SkToU8(CharToIdx(fSwiz[0]) | (CharToIdx(fSwiz[1]) << 2) |
(CharToIdx(fSwiz[2]) << 4) | (CharToIdx(fSwiz[3]) << 6));
}
uint32_t* asUIntPtr() { return SkTCast<uint32_t*>(fSwiz); }
uint32_t asUInt() const { return *SkTCast<const uint32_t*>(fSwiz); }
GR_STATIC_ASSERT(sizeof(char[4]) == sizeof(uint32_t));
};
#endif
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