srgba8.go

// Copyright (c) 2013-2018 Laurent Moussault. All rights reserved.
// Licensed under a simplified BSD license (see LICENSE file).

package color

////////////////////////////////////////////////////////////////////////////////

// SRGBA8 represents a 32-bit color in alpha-premultiplied sRGB color space.
// There is 8 bits for each components.
//
// An alpha-premultiplied color component c has been scaled by alpha (a), so has
// valid values 0 <= c <= a.
//
// Note that additive blending can also be achieved when alpha is set to 0 while
// the color components are non-null.
type SRGBA8 struct {
	R uint8
	G uint8
	B uint8
	A uint8
}

////////////////////////////////////////////////////////////////////////////////

// SRGBA8of converts any color to alpha-premultiplied sRGB color space.
func SRGBA8of(c Color) SRGBA8 {
	cc, ok := c.(SRGBA8)
	if ok {
		return cc
	}
	ccc, ok := c.(SRGB8)
	if ok {
		return SRGBA8{ccc.R, ccc.G, ccc.B, 1}
	}
	r, g, b, a := c.Standard()
	return SRGBA8{uint8(r * 0xFF), uint8(g * 0xFF), uint8(b * 0xFF), uint8(a * 0xFF)}
}

////////////////////////////////////////////////////////////////////////////////

// Linear implements the Colour interface.
func (c SRGBA8) Linear() (r, g, b, a float32) {
	r = linearOf(float32(c.R) / float32(0xFF))
	g = linearOf(float32(c.G) / float32(0xFF))
	b = linearOf(float32(c.B) / float32(0xFF))
	a = float32(c.A) / float32(0xFF)
	return r, g, b, a
}

// Standard implements the Colour interface.
func (c SRGBA8) Standard() (r, g, b, a float32) {
	r = float32(c.R) / float32(0xFF)
	g = float32(c.R) / float32(0xFF)
	b = float32(c.R) / float32(0xFF)
	a = float32(c.A) / float32(0xFF)
	return r, g, b, a
}

////////////////////////////////////////////////////////////////////////////////

// RGBA implements the image.Color interface.
func (c SRGBA8) RGBA() (r, g, b, a uint32) {
	r = uint32((float64(c.R) / float64(0xFF)) * float64(0xFFFF))
	g = uint32((float64(c.G) / float64(0xFF)) * float64(0xFFFF))
	b = uint32((float64(c.B) / float64(0xFF)) * float64(0xFFFF))
	a = uint32((float64(c.A) / float64(0xFF)) * float64(0xFFFF))
	return r, g, b, a
}

////////////////////////////////////////////////////////////////////////////////