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internal/f32color: extract color mixing into separate function

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Refactor to enable Hovered for light widgets.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
This commit is contained in:
Elias Naur
2022-02-28 13:13:14 +01:00
parent 73eabb352d
commit b74c9f9603
1 changed files with 16 additions and 12 deletions
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internal/f32color/rgba.go
+16 -12
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@@ -146,22 +146,26 @@ func MulAlpha(c color.NRGBA, alpha uint8) color.NRGBA {
func Disabled(c color.NRGBA) (d color.NRGBA) {
const r = 80 // blend ratio
lum := approxLuminance(c)
return color.NRGBA{
R: byte((int(c.R)*r + int(lum)*(256-r)) / 256),
G: byte((int(c.G)*r + int(lum)*(256-r)) / 256),
B: byte((int(c.B)*r + int(lum)*(256-r)) / 256),
A: byte(int(c.A) * (128 + 32) / 256),
}
d = mix(c, color.NRGBA{A: c.A, R: lum, G: lum, B: lum}, r)
d = MulAlpha(d, 128+32)
return
}
// Hovered blends color towards a brighter color.
func Hovered(c color.NRGBA) (d color.NRGBA) {
// Hovered blends color towards a brighter color. It is approximate
// because it operates in non-linear sRGB space.
func Hovered(c color.NRGBA) (h color.NRGBA) {
const r = 0x20 // lighten ratio
return mix(color.NRGBA{R: 0xff, G: 0xff, B: 0xff, A: c.A}, c, r)
}
// mix mixes c1 and c2 weighted by (1 - a/256) and a/256 respectively.
func mix(c1, c2 color.NRGBA, a uint8) color.NRGBA {
ai := int(a)
return color.NRGBA{
R: byte(255 - int(255-c.R)*(255-r)/256),
G: byte(255 - int(255-c.G)*(255-r)/256),
B: byte(255 - int(255-c.B)*(255-r)/256),
A: c.A,
R: byte((int(c1.R)*ai + int(c2.R)*(256-ai)) / 256),
G: byte((int(c1.G)*ai + int(c2.G)*(256-ai)) / 256),
B: byte((int(c1.B)*ai + int(c2.B)*(256-ai)) / 256),
A: byte((int(c1.A)*ai + int(c2.A)*(256-ai)) / 256),
}
}