JuliaGraphics · timholy · Aug 2, 2023 · Aug 1, 2023
diff --git a/README.md b/README.md
@@ -252,6 +252,25 @@ struct LCHuv{T} <: Color{T,3}
 end
 ```
 
+### Oklab and Oklch
+
+A perceptually uniform colorspace developed by
+[Björn Ottosson](https://bottosson.github.io/posts/oklab/) and its
+reparameterization using cylindrical coordinates.
+
+```julia
+struct Oklab{T} <: Color{T,3}
+    l::T # Lightness in [0,1]
+    a::T # Red/Green
+    b::T # Blue/Yellow
+end
+
+struct Oklch{T} <: Color{T,3}
+    l::T # Lightness in [0,1]
+    c::T # Chroma
+    h::T # Hue in [0,360]
+end
+```
 
 ### DIN99
 

diff --git a/src/ColorTypes.jl b/src/ColorTypes.jl
@@ -24,6 +24,7 @@ export HSV, HSB, HSL, HSI
 export XYZ, xyY, LMS, Lab, LCHab, Luv, LCHuv
 export DIN99, DIN99d, DIN99o
 export YIQ, YCbCr
+export Oklab, Oklch
 
 export Gray
 
@@ -65,8 +66,8 @@ ColorTypes summary:
 - `RGB`, `BGR`, `XRGB`, `RGBX`, `RGB24` are all subtypes of `AbstractRGB`
 
 - `HSV`, `HSL`, `HSI`, `XYZ`, `xyY`, `Lab`, `LCHab`, `Luv`, `LCHuv`,
-  `DIN99`, `DIN99d`, `DIN99o`, `LMS`, `YIQ`, `YCbCR` are subtypes of
-  `Color{T,3}`
+  `DIN99`, `DIN99d`, `DIN99o`, `LMS`, `YIQ`, `YCbCR`, `Oklab`, and
+  `Oklch` are subtypes of `Color{T,3}`
 
 - Alpha-channel analogs in such as `ARGB` and `RGBA` for most of those
   types (with a few exceptions like `RGB24`, which has `ARGB32`)

diff --git a/src/operations.jl b/src/operations.jl
@@ -128,6 +128,11 @@ gamutmin(::Type{<:YIQ}) = (0, -0.5957, -0.5226)
 gamutmax(::Type{<:YCbCr}) = (235, 240, 240)
 gamutmin(::Type{<:YCbCr}) = (16, 16, 16)
 
+gamutmax(::Type{<:Oklab}) = (1, 0.4, 0.4)
+gamutmin(::Type{<:Oklab}) = (0, -0.4, -0.4)
+
+gamutmax(::Type{<:Oklch}) = (1, 0.4, 360)
+
 gamutmax(::Type{C}) where {C<:TransparentColor} = (gamutmax(color_type(C))..., 1)
 gamutmin(::Type{C}) where {C<:TransparentColor} = (gamutmin(color_type(C))..., 0)
 

diff --git a/src/traits.jl b/src/traits.jl
@@ -37,22 +37,22 @@ gray(c::AGray32) = reinterpret(N0f8, c.color % UInt8)
 gray(x::Number)  = convert(eltype(ccolor(Gray, typeof(x))), x)   # ensures it's a type supported by Gray
 
 """
-`chroma(c)` returns the chroma of a `Lab`, `Luv` or their variants color.
+`chroma(c)` returns the chroma of a `Lab`, `Luv`, `Oklab` or their variants color.
 !!! note
     The other color types (e.g. `RGB`, `HSV` or `YCbCr`) are not supported
     because their definitions of *chroma* are not clear. Colorfulness, chroma
     and saturation are defined as distinct aspects by the CIE.
 """
-chroma(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{Lab,DIN99,DIN99o,DIN99d}} = sqrt(c.a^2 + c.b^2)
+chroma(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{Lab,DIN99,DIN99o,DIN99d,Oklab}} = sqrt(c.a^2 + c.b^2)
 chroma(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Luv} = sqrt(c.u^2 + c.v^2)
-chroma(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{LCHab,LCHuv}} = c.c
+chroma(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{LCHab,LCHuv,Oklch}} = c.c
 
 """
 `hue(c)` returns the hue in degrees. This function does not guarantee that the
 return value is in [0, 360].
 """
-hue(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{HSV,HSL,HSI,LCHab,LCHuv}} = c.h
-hue(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{Lab,DIN99,DIN99o,DIN99d}} =
+hue(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{HSV,HSL,HSI,LCHab,LCHuv,Oklch}} = c.h
+hue(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Union{Lab,DIN99,DIN99o,DIN99d,Oklab}} =
     (h = atand(c.b, c.a); h < 0 ? h + 360 : h)
 hue(c::Union{C,AlphaColor{C},ColorAlpha{C}}) where {C<:Luv} =
     (h = atand(c.v, c.u); h < 0 ? h + 360 : h)

diff --git a/src/types.jl b/src/types.jl
@@ -271,6 +271,20 @@ struct YCbCr{T<:AbstractFloat} <: Color{T,3}
     cr::T
 end
 
+"`Oklab` is the Oklab colorspace."
+struct Oklab{T<:AbstractFloat} <: Color{T,3}
+    l::T # Lightness in [0,1]
+    a::T # Red/Green
+    b::T # Blue/Yellow
+end
+
+"`Oklch` is the Luminance-Chroma-Hue, Polar-Oklab colorspace."
+struct Oklch{T<:AbstractFloat} <: Color{T,3}
+    l::T # Lightness in [0,1]
+    c::T # Chroma
+    h::T # Hue in [0,360]
+end
+
 """
 `RGB24` uses a `UInt32` representation of color, 0xAARRGGBB, where
 R=red, G=green, B=blue and A is irrelevant. This format is often used
@@ -491,7 +505,9 @@ for (C, acol, cola) in [(DIN99d, :ADIN99d, :DIN99dA),
                         (xyY, :AxyY, :xyYA),
                         (BGR, :ABGR, :BGRA),
                         (RGB, :ARGB, :RGBA),
-                        (Gray, :AGray, :GrayA)]
+                        (Gray, :AGray, :GrayA),
+                        (Oklab, :AOklab, :OklabA),
+                        (Oklch, :AOklch, :OklchA)]
     fn  = Expr(:tuple, fieldnames(C)...)
     cfn = Expr(:tuple, colorfields(C)...)
     elty = eltype_default(C)

diff --git a/test/operations.jl b/test/operations.jl
@@ -57,7 +57,8 @@ end
     for (a, b) in ((RGB(1, 0.5, 0), RGBA(1, 0.5, 0, 0.9)),
                    (RGB(0.5, 0.5, 0.5), Gray(0.5)),
                    (HSV(0, 0, 0.5), HSV(100, 0, 0.5)), # grays
-                   (Lab(70, 0, 60), LCHab(70, 60, 90)))
+                   (Lab(70, 0, 60), LCHab(70, 60, 90)),
+                   (Oklab(0.7, 0, 0.2), Oklch(0.7, 0.2, 90)))
         local a, b
         @test a != b
         @test !isequal(a, b)
@@ -195,7 +196,7 @@ end
             ARGB{Float32}, RGBA{N0f16}, XRGB{N0f8}, RGBX{Float64},
             BGR{Float16}, ABGR{N0f32}, BGRA{N2f14},
             HSV{Float32}, HSL{Float64}, ALab{Float32}, LCHabA{Float16},
-            Gray, AGray, GrayA,
+            AOklab{Float32}, Oklch{Float16}, Gray, AGray, GrayA,
             unique(ColorTypes.parametric3)...,
             AHSV, HSLA)
         CC = isconcretetype(C) ? C : C{Float64}

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -12,7 +12,8 @@ doctest(ColorTypes, manual = false)
 ctypes = union(setdiff(ColorTypes.parametric3, (XRGB, RGBX)), (Gray,))
 @test Set(ctypes) ==
     Set([DIN99d, DIN99o, DIN99, HSI, HSL, HSV, LCHab, LCHuv,
-         LMS, Lab, Luv, XYZ, YCbCr, YIQ, xyY, BGR, RGB, Gray])
+         LMS, Lab, Luv, XYZ, YCbCr, YIQ, xyY, BGR, RGB, Gray,
+         Oklab, Oklch])
 
 if isdefined(Base, :Experimental) && isdefined(Base.Experimental, :register_error_hint)
     @testset "error_hints" begin

diff --git a/test/traits.jl b/test/traits.jl
@@ -95,8 +95,10 @@ end
     @test chroma(LCHuv(60, 40, 30)) ≈ 40.0
     @test chroma(LabA(60, -40, 30, 0.5)) ≈ 50.0
     @test chroma(ALab(60, -40, 30, 0.5)) ≈ 50.0
+    @test chroma(Oklab(0.6, -0.4, 0.3)) ≈ 0.5
     @inferred chroma(LCHab(60, 40, 30))
     @inferred chroma(LCHuv(6f1, 4f1, 3f1))
+    @inferred chroma(Oklch(0.6f1, 0.3f1, 3f1))
     @inferred chroma(LabA(60, -40, 30, 0.5))
     @test_throws MethodError chroma(HSV(30, 0.4, 0.6))
 end
@@ -112,7 +114,9 @@ end
     @test hue(LCHuv(60, 40, 30)) ≈ 30.0
     @test hue(LabA(60, -30, 30, 0.5)) ≈ 135.0
     @test hue(ALab(60, -30, 30, 0.5)) ≈ 135.0
+    @test hue(Oklab(0.6, -0.3, 0.3)) ≈ 135.0
     @inferred hue(LCHab(60, -30, 30))
+    @inferred hue(Oklch(0.6, 0.1, 30))
     @inferred hue(LCHuv(6f1, -3f1, 3f1))
     @inferred hue(LabA(60, -30, 30, 0.5))
     @test hue(HSV(999, 0.4, 0.6)) == 999 # without normalization

diff --git a/test/types.jl b/test/types.jl
@@ -222,6 +222,7 @@ end
     @test RGB(0.2, Gray24(0.3), 0.4) === RGB(0.2, 0.3N0f8, 0.4)
     @test HSV(0.2, 0.3, Gray(0.4)) === HSV(0.2, 0.3, 0.4)
     @test ALab(0.2, 0.3, 0.4, Gray24(0.5)) === ALab(0.2, 0.3, 0.4, 0.5N0f8)
+    @test AOklab(0.2, 0.3, 0.4, Gray24(0.5)) === AOklab(0.2, 0.3, 0.4, 0.5N0f8)
 end
 
 @testset "gray constructors" begin