limage - indexed.go

     1  package lcolor
     2  
     3  import "image/color"
     4  
     5  // AlphaPalette is an extension to the normal color.Palette type.
     6  type AlphaPalette color.Palette
     7  
     8  // Convert converts the given color to the nearest color in the palette, but
     9  // preserves the alpha channel.
    10  func (ap AlphaPalette) Convert(c color.Color) color.Color {
    11  	r, g, b, _ := color.Palette(ap).Convert(c).RGBA()
    12  	_, _, _, a := c.RGBA()
    13  
    14  	return color.NRGBA64{
    15  		R: uint16(r),
    16  		G: uint16(g),
    17  		B: uint16(b),
    18  		A: uint16(a),
    19  	}
    20  }
    21  
    22  // Index returns the palette index of the nearest color.
    23  func (ap AlphaPalette) Index(c color.Color) int {
    24  	return color.Palette(ap).Index(c)
    25  }
    26  
    27  // IndexedAlpha is the combination of a palette index and an Alpha channel.
    28  type IndexedAlpha struct {
    29  	I, A uint8
    30  }
    31