gpu/include/GrColor.h

/*
    Copyright 2010 Google Inc.

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

         http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 */


#ifndef GrColor_DEFINED
#define GrColor_DEFINED

#include "GrTypes.h"

/**
 *  GrColor is 4 bytes for R, G, B, A, in a compile-time specific order. The
 *  components are stored premultiplied.
 */
typedef uint32_t GrColor;

// indices for address a GrColor as an array of bytes

#define GrColor_INDEX_R     0
#define GrColor_INDEX_G     1
#define GrColor_INDEX_B     2
#define GrColor_INDEX_A     3

// shfit amount to assign a component to a GrColor int

#define GrColor_SHIFT_R     0
#define GrColor_SHIFT_G     8
#define GrColor_SHIFT_B     16
#define GrColor_SHIFT_A     24

/**
 *  Pack 4 components (RGBA) into a GrColor int
 */
static inline GrColor GrColorPackRGBA(unsigned r, unsigned g,
                                      unsigned b, unsigned a) {
    GrAssert((uint8_t)r == r);
    GrAssert((uint8_t)g == g);
    GrAssert((uint8_t)b == b);
    GrAssert((uint8_t)a == a);
    return  (r << GrColor_SHIFT_R) |
            (g << GrColor_SHIFT_G) |
            (b << GrColor_SHIFT_B) |
            (a << GrColor_SHIFT_A);
}

// extract a component (byte) from a GrColor int

#define GrColorUnpackR(color)   (((color) >> GrColor_SHIFT_R) & 0xFF)
#define GrColorUnpackG(color)   (((color) >> GrColor_SHIFT_G) & 0xFF)
#define GrColorUnpackB(color)   (((color) >> GrColor_SHIFT_B) & 0xFF)
#define GrColorUnpackA(color)   (((color) >> GrColor_SHIFT_A) & 0xFF)

/**
 *  Since premultiplied means that alpha >= color, we construct a color with
 *  each component==255 and alpha == 0 to be "illegal"
 */
#define GrColor_ILLEGAL     (~(0xFF << GrColor_SHIFT_A))

#endif