func LinearC(value float64) utils.Composable {
return func(c color.Color) color.Color {
r, g, b, a := utils.RatioRGBA(c)
r = utils.Truncatef((((r - 0.5) * value) + 0.5) * 255)
g = utils.Truncatef((((g - 0.5) * value) + 0.5) * 255)
b = utils.Truncatef((((b - 0.5) * value) + 0.5) * 255)
a = a * 255
return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
}
}
func SigmoidalC(factor, midpoint float64) utils.Composable {
sigmoidal := func(x float64) float64 {
return 1.0 / (1.0 + math.Exp(factor*(midpoint-x)))
}
// Pre-compute useful terms
sig0 := sigmoidal(0.0)
sig1 := sigmoidal(1.0)
var scaledSigmoidal func(float64) float64
if factor == 0 {
scaledSigmoidal = func(x float64) float64 {
return x
}
} else if factor > 0 {
scaledSigmoidal = func(x float64) float64 {
return (sigmoidal(x) - sig0) / (sig1 - sig0)
}
} else {
scaledSigmoidal = func(x float64) float64 {
argument := (sig1-sig0)*x + sig0
var clamped float64
if argument < Epsilon {
clamped = Epsilon
} else {
if argument > 1-Epsilon {
clamped = 1 - Epsilon
} else {
clamped = argument
}
}
return midpoint - math.Log(1.0/clamped-1.0)/factor
}
}
return func(c color.Color) color.Color {
r, g, b, a := utils.RatioRGBA(c)
r = utils.Truncatef(scaledSigmoidal(r) * 255)
g = utils.Truncatef(scaledSigmoidal(g) * 255)
b = utils.Truncatef(scaledSigmoidal(b) * 255)
a = a * 255
return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
}
}
// BUG: Conversion is broken _somewhere_, check against IM results.
func (col HSLA) RGBA() (red, green, blue, alpha uint32) {
h := col.H
s := col.S
l := col.L
a := col.A
h = math.Mod(h, 360)
c := (1.0 - math.Abs(2.0*l-1.0)) * s
hdash := h / 60.0
x := c * (1 - math.Abs(math.Mod(hdash, 2)-1))
var r, g, b float64
if hdash < 1 {
r = c
g = x
b = 0
} else if hdash < 2 {
r = x
g = c
b = 0
} else if hdash < 3 {
r = 0
g = c
b = x
} else if hdash < 4 {
r = 0
g = x
b = c
} else if hdash < 5 {
r = x
g = 0
b = c
} else if hdash < 6 {
r = c
g = 0
b = x
}
m := l - 0.5*c
red = uint32(utils.Truncatef((r+m)*a*255)) << 8
green = uint32(utils.Truncatef((g+m)*a*255)) << 8
blue = uint32(utils.Truncatef((b+m)*a*255)) << 8
alpha = uint32(a*255) << 8
return
}
func (col HSIA) RGBA() (red, green, blue, alpha uint32) {
var r, g, b float64
h := col.H
s := col.S
i := col.I
a := col.A
// normalise h
h = math.Mod(h, 360)
// need h in radians for trig. calculations
hrad := h
// need hrad to be in interval [0, 2/3*Pi)
if h >= 240 {
hrad -= 240
} else if h >= 120 {
hrad -= 120
}
// finally do the conversion to radians
hrad *= math.Pi / 180
x := i * (1 - s)
y := i * (1 + (s*math.Cos(hrad))/math.Cos(math.Pi/3-hrad))
z := 3*i - (x + y)
if h < 120 {
b = x
r = y
g = z
} else if h < 240 {
r = x
g = y
b = z
} else {
g = x
b = y
r = z
}
red = uint32(utils.Truncatef(r*a*255)) << 8
green = uint32(utils.Truncatef(g*a*255)) << 8
blue = uint32(utils.Truncatef(b*a*255)) << 8
alpha = uint32(a*255) << 8
return
}
// UnsharpMask sharpens the given Image using the unsharp mask technique.
// Basically the image is blurred, then subtracted from the original for
// differences above the threshold value.
func UnsharpMask(in image.Image, radius int, sigma, amount, threshold float64) image.Image {
blurred := blur.Gaussian(in, radius, sigma, blur.IGNORE)
bounds := in.Bounds()
out := image.NewRGBA(bounds)
// Absolute difference between a and b, returns float64 between 0 and 1.
diff := func(a, b float64) float64 {
if a > b {
return a - b
}
return b - a
}
for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
for x := bounds.Min.X; x < bounds.Max.X; x++ {
ar, ag, ab, aa := utils.RatioRGBA(in.At(x, y))
br, bg, bb, _ := utils.RatioRGBA(blurred.At(x, y))
if diff(ar, br) >= threshold {
ar = amount*(ar-br) + ar
}
if diff(ag, bg) >= threshold {
ag = amount*(ag-bg) + ag
}
if diff(ab, bb) >= threshold {
ab = amount*(ab-bb) + ab
}
out.Set(x, y, color.NRGBA{
uint8(utils.Truncatef(ar * 255)),
uint8(utils.Truncatef(ag * 255)),
uint8(utils.Truncatef(ab * 255)),
uint8(aa * 255),
})
}
}
return out
}
// AdjustC returns a Composable function that increases the saturation and
// decreases the lightness of unsaturated colours.
//
// Uses the same method as Darktable:
// https://github.com/darktable-org/darktable/blob/24c4a087fd020df587b5260f438bfaf494203cec/src/iop/vibrance.c
func AdjustC(amount float64) utils.Composable {
return func(c color.Color) color.Color {
r, g, b, a := utils.RatioRGBA(c)
ll, la, lb := colorful.Color{r, g, b}.Lab()
// saturation weight [0, 1]
sw := math.Sqrt(la*la+lb*lb) / 2
ls := 1.0 - amount*sw*0.25
ss := 1.0 + amount*sw
ll *= ls
la *= ss
lb *= ss
f := colorful.Lab(ll, la, lb)
fr := utils.Truncatef(f.R * 255)
fg := utils.Truncatef(f.G * 255)
fb := utils.Truncatef(f.B * 255)
return color.NRGBA{uint8(fr), uint8(fg), uint8(fb), uint8(a * 255)}
}
}
func Convolve(in image.Image, weights Kernel, style Style) image.Image {
bnds := in.Bounds()
mid := weights.Mid()
o := image.NewRGBA(bnds)
for y := bnds.Min.Y; y < bnds.Max.Y; y++ {
for x := bnds.Min.X; x < bnds.Max.X; x++ {
var r, g, b, a, offset float64
for oy := 0; oy < weights.Height(); oy++ {
for ox := 0; ox < weights.Width(); ox++ {
factor := weights[oy][ox]
pt := image.Pt(x+ox-mid.X, y+oy-mid.Y)
if pt == weights.Mid() {
// Ignore!
} else if pt.In(bnds) {
or, og, ob, oa := in.At(pt.X, pt.Y).RGBA()
r += float64(or) * factor
g += float64(og) * factor
b += float64(ob) * factor
a += float64(oa) * factor
} else {
switch style {
case CLAMP:
offset += factor
case WRAP:
if pt.X >= bnds.Max.X {
pt.X = pt.X - bnds.Max.X
} else if pt.X < bnds.Min.X {
pt.X = bnds.Dx() + pt.X
}
if pt.Y >= bnds.Max.Y {
pt.Y = pt.Y - bnds.Max.Y
} else if pt.Y < bnds.Min.Y {
pt.Y = bnds.Dy() + pt.Y
}
or, og, ob, oa := in.At(pt.X, pt.Y).RGBA()
r += float64(or) * factor
g += float64(og) * factor
b += float64(ob) * factor
a += float64(oa) * factor
}
}
}
}
if offset != 0 && style == CLAMP {
or, og, ob, oa := in.At(x, y).RGBA()
r += float64(or) * offset
g += float64(og) * offset
b += float64(ob) * offset
a += float64(oa) * offset
}
o.Set(x, y, color.RGBA{
uint8(utils.Truncatef(r / 255)),
uint8(utils.Truncatef(g / 255)),
uint8(utils.Truncatef(b / 255)),
uint8(utils.Truncatef(a / 255)),
})
}
}
return o
}
func (_ blueCh) Set(c color.Color, v float64) color.Color {
r, g, _, a := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(r), uint8(g), uint8(v), uint8(a)}
}
func (_ redCh) Set(c color.Color, v float64) color.Color {
_, g, b, a := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(v), uint8(g), uint8(b), uint8(a)}
}
func (_ alphaCh) Set(c color.Color, v float64) color.Color {
r, g, b, _ := utils.NormalisedRGBA(c)
v = utils.Truncatef(255 * v)
return color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(v)}
}