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gradient.go
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gradient.go
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package spectogram
import "image/color"
type Gradient []color.RGBA
func NewGradient() Gradient {
return make(Gradient, 0)
}
func (grad *Gradient) Append(c ...color.RGBA) {
*grad = append(*grad, c...)
}
func clamp(v, min, max float64) float64 {
if v < min {
return min
}
if v > max {
return max
}
return v
}
func (grad Gradient) Index(i float64) (int, float64) {
n := len(grad)
if n == 0 {
return -1, -1
}
c := clamp(i, 0, 1)
if c == 1 {
return n - 1, 0.0
}
x := int(c * float64(n-1))
return x, (c - float64(x)/float64(n-1)) * float64(n-1)
}
func (grad Gradient) ColorAt(i float64) color.RGBA {
n := len(grad)
if n == 0 {
return color.RGBA{}
}
if n == 1 {
return grad[0]
}
nx, ni := grad.Index(i)
if nx >= n-1 {
return grad[nx]
}
return color.RGBA{
R: uint8((float64(grad[nx+1].R)-float64(grad[nx].R))*ni + float64(grad[nx].R)),
G: uint8((float64(grad[nx+1].G)-float64(grad[nx].G))*ni + float64(grad[nx].G)),
B: uint8((float64(grad[nx+1].B)-float64(grad[nx].B))*ni + float64(grad[nx].B)),
A: uint8((float64(grad[nx+1].A)-float64(grad[nx].A))*ni + float64(grad[nx].A)),
}
}