为什么golang RGBA.RGBA()方法使用| 和？？ |

Jam*_*dge 7

color.RGBARGBAcolor.Color

type Color interface {
    // RGBA returns the alpha-premultiplied red, green, blue and alpha values
    // for the color. Each value ranges within [0, 0xffff], but is represented
    // by a uint32 so that multiplying by a blend factor up to 0xffff will not
    // overflow.
    //
    // An alpha-premultiplied color component c has been scaled by alpha (a),
    // so has valid values 0 <= c <= a.
    RGBA() (r, g, b, a uint32)
}

uint8uint32

适当的转换将是这样的:

r = uint32((float64(c.R) / 0xff) * 0xffff)

0xffff / 0xff0x0101

r = c.R * 0x0101
  = c.R * 0x0100 + c.R
  = (c.R << 8) + c.R    # multiply by power of 2 is equivalent to shift
  = (c.R << 8) | c.R    # equivalent, since bottom 8 bits of first operand are 0

这基本上就是标准库中的代码所做的事情.