limage - lcolor/gray.go

     1  package lcolor
     2  
     3  import "image/color"
     4  
     5  // GrayAlpha represents a Gray color with an Alpha channel
     6  type GrayAlpha struct {
     7  	Y, A uint8
     8  }
     9  
    10  // RGBA implements the color.Color interface
    11  func (c GrayAlpha) RGBA() (r, g, b, a uint32) {
    12  	y := uint32(c.Y)
    13  	y |= y << 8
    14  	a = uint32(c.A)
    15  	y *= a
    16  	y /= 0xff
    17  	a |= a << 8
    18  	return y, y, y, a
    19  }
    20  
    21  // ToNRGBA converts the HSV color into the RGB colorspace
    22  func (c GrayAlpha) ToNRGBA() color.NRGBA64 {
    23  	y := uint16(c.Y)
    24  	y |= y << 8
    25  	a := uint16(c.A)
    26  	a |= a << 8
    27  	return color.NRGBA64{y, y, y, a}
    28  }
    29  
    30  func grayAlphaColourModel(c color.Color) color.Color {
    31  	_, _, _, a := c.RGBA()
    32  	return GrayAlpha{
    33  		Y: color.GrayModel.Convert(c).(color.Gray).Y,
    34  		A: uint8(a >> 8),
    35  	}
    36  }
    37