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/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkColorPriv_DEFINED
#define SkColorPriv_DEFINED
#include "SkMath.h"
/** Turn 0..255 into 0..256 by adding 1 at the half-way point. Used to turn a
byte into a scale value, so that we can say scale * value >> 8 instead of
alpha * value / 255.
In debugging, asserts that alpha is 0..255
*/
static inline unsigned SkAlpha255To256(U8CPU alpha) {
SkASSERT(SkToU8(alpha) == alpha);
// this one assues that blending on top of an opaque dst keeps it that way
// even though it is less accurate than a+(a>>7) for non-opaque dsts
return alpha + 1;
}
/** Multiplify value by 0..256, and shift the result down 8
(i.e. return (value * alpha256) >> 8)
*/
#define SkAlphaMul(value, alpha256) (((value) * (alpha256)) >> 8)
static inline U8CPU SkUnitScalarClampToByte(SkScalar x) {
return static_cast<U8CPU>(SkScalarPin(x, 0, 1) * 255 + 0.5);
}
#define SK_A32_BITS 8
#define SK_R32_BITS 8
#define SK_G32_BITS 8
#define SK_B32_BITS 8
#define SK_A32_MASK ((1 << SK_A32_BITS) - 1)
#define SK_R32_MASK ((1 << SK_R32_BITS) - 1)
#define SK_G32_MASK ((1 << SK_G32_BITS) - 1)
#define SK_B32_MASK ((1 << SK_B32_BITS) - 1)
#define SkGetPackedA32(packed) ((uint32_t)((packed) << (24 - SK_A32_SHIFT)) >> 24)
#define SkGetPackedR32(packed) ((uint32_t)((packed) << (24 - SK_R32_SHIFT)) >> 24)
#define SkGetPackedG32(packed) ((uint32_t)((packed) << (24 - SK_G32_SHIFT)) >> 24)
#define SkGetPackedB32(packed) ((uint32_t)((packed) << (24 - SK_B32_SHIFT)) >> 24)
#define SkA32Assert(a) SkASSERT((unsigned)(a) <= SK_A32_MASK)
#define SkR32Assert(r) SkASSERT((unsigned)(r) <= SK_R32_MASK)
#define SkG32Assert(g) SkASSERT((unsigned)(g) <= SK_G32_MASK)
#define SkB32Assert(b) SkASSERT((unsigned)(b) <= SK_B32_MASK)
/**
* Pack the components into a SkPMColor, checking (in the debug version) that
* the components are 0..255, and are already premultiplied (i.e. alpha >= color)
*/
static inline SkPMColor SkPackARGB32(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
SkA32Assert(a);
SkASSERT(r <= a);
SkASSERT(g <= a);
SkASSERT(b <= a);
return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
(g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
}
/**
* Same as SkPackARGB32, but this version guarantees to not check that the
* values are premultiplied in the debug version.
*/
static inline SkPMColor SkPackARGB32NoCheck(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
return (a << SK_A32_SHIFT) | (r << SK_R32_SHIFT) |
(g << SK_G32_SHIFT) | (b << SK_B32_SHIFT);
}
static inline
SkPMColor SkPremultiplyARGBInline(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
SkA32Assert(a);
SkR32Assert(r);
SkG32Assert(g);
SkB32Assert(b);
if (a != 255) {
r = SkMulDiv255Round(r, a);
g = SkMulDiv255Round(g, a);
b = SkMulDiv255Round(b, a);
}
return SkPackARGB32(a, r, g, b);
}
// When Android is compiled optimizing for size, SkAlphaMulQ doesn't get
// inlined; forcing inlining significantly improves performance.
static SK_ALWAYS_INLINE uint32_t SkAlphaMulQ(uint32_t c, unsigned scale) {
uint32_t mask = 0xFF00FF;
uint32_t rb = ((c & mask) * scale) >> 8;
uint32_t ag = ((c >> 8) & mask) * scale;
return (rb & mask) | (ag & ~mask);
}
static inline SkPMColor SkPMSrcOver(SkPMColor src, SkPMColor dst) {
return src + SkAlphaMulQ(dst, SkAlpha255To256(255 - SkGetPackedA32(src)));
}
#endif
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