Generalize conversions within the same base color (#264)

This supports adding/stripping alpha for colors other than `Color3`.
JuliaGraphics · Aug 16, 2021 · 8574435 · 8574435
1 parent 38bb9dc
commit 8574435
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diff --git a/src/conversions.jl b/src/conversions.jl
@@ -78,17 +78,22 @@ convert(::Type{C}, c::Color, alpha) where {C<:TransparentColor} = cconvert(ccolo
 cconvert(::Type{C}, c::Color, alpha) where {C<:TransparentColor} =_convert(C, base_color_type(C), base_color_type(c), c, alpha)
 
 # Fallback definitions that print nice error messages
-_convert(::Type{C}, ::Any, ::Any, c) where {C} = error("No conversion of ", c, " to ", C, " has been defined")
-_convert(::Type{C}, C1::Any, C2::Any, c, alpha) where {C} = error("No conversion of (", c, ",alpha=$alpha) to ", C, " with consistency-types $C1 and $C2 has been defined")
+_convert(C::Type, ::Any, ::Any, c) = error("No conversion of ", c, " to ", C, " has been defined")
+_convert(C::Type, C1::Any, C2::Any, c, alpha) = error("No conversion of (", c, ",alpha=$alpha) to ", C, " with consistency-types $C1 and $C2 has been defined")
 
 # Any AbstractRGB types can be interconverted
 _convert(::Type{Cout}, ::Type{C1}, ::Type{C2}, c) where {Cout<:AbstractRGB,C1<:AbstractRGB,C2<:AbstractRGB} = Cout(red(c), green(c), blue(c))
 _convert(::Type{A}, ::Type{C1}, ::Type{C2}, c, alpha=alpha(c)) where {A<:TransparentRGB,C1<:AbstractRGB,C2<:AbstractRGB} = A(red(c), green(c), blue(c), alpha)
 
 # Implementations for when the base color type is not changing
 # These might strip/add transparency, however
-_convert(::Type{Cout}, ::Type{Ccmp}, ::Type{Ccmp}, c) where {Cout<:Color3,Ccmp<:Color3} = Cout(comp1(c), comp2(c), comp3(c))
-_convert(::Type{A}, ::Type{Ccmp}, ::Type{Ccmp}, c, alpha=alpha(c)) where {A<:Transparent3,Ccmp<:Color3} = A(comp1(c), comp2(c), comp3(c), alpha)
+function _convert(::Type{Cout}, ::Type{C1}, ::Type{C1}, c) where {Cout<:Color, C1<:Color}
+    Cout(comps(color(c))...)
+end
+function _convert(::Type{Cout}, ::Type{C1}, ::Type{C1}, c,
+                  alpha=alpha(c)) where {Cout<:TransparentColor, C1<:Color}
+    Cout(comps(color(c))..., alpha)
+end
 
 # Grayscale
 _convert(::Type{Cout}, ::Type{C1}, ::Type{C2}, c) where {Cout<:AbstractGray,C1<:AbstractGray,C2<:AbstractGray} = Cout(gray(c))

diff --git a/test/conversions.jl b/test/conversions.jl
@@ -3,6 +3,9 @@ using ColorTypes.FixedPointNumbers
 using Test
 using ColorTypes: ColorTypeResolutionError
 
+@isdefined(CustomTypes) || include("customtypes.jl")
+using .CustomTypes
+
 @testset "rgb promotions" begin
     @test promote( RGB{N0f8}(0.2,0.3,0.4),  RGB(0.3,0.8,0.1)) === ( RGB{Float64}(0.2N0f8,0.3N0f8,0.4N0f8),  RGB{Float64}(0.3,0.8,0.1))
     @test promote( RGB{N0f8}(0.2,0.3,0.4), RGBA(0.3,0.8,0.1)) === (RGBA{Float64}(0.2N0f8,0.3N0f8,0.4N0f8), RGBA{Float64}(0.3,0.8,0.1))
@@ -664,6 +667,24 @@ end
     end
 end
 
+@testset "conversions in the same color space" begin
+    @test convert(Cyanotype{Float32}, Cyanotype{Float64}(0.8)) === Cyanotype{Float32}(0.8)
+
+    @test convert(C2, C2{Float64}(0.4,0.6)) === C2{Float64}(0.4,0.6)
+    @test convert(C2{Float32}, C2{Float64}(0.4,0.6)) === C2{Float32}(0.4,0.6)
+    @test convert(C2, C2A{Float64}(0.4,0.6,0.5)) === C2{Float64}(0.4,0.6)
+    @test convert(C2A, C2A{Float32}(0.4,0.6,0.5)) === C2A{Float32}(0.4,0.6,0.5)
+    @test convert(C2A, C2{Float64}(0.4,0.6)) === C2A{Float64}(0.4,0.6,1.0)
+    @test convert(C2A, C2{Float32}(0.4,0.6), 0.25) === C2A{Float32}(0.4,0.6,0.25)
+
+    @test convert(CMYK, CMYK{Float64}(0.2,0.4,0.6,0.8)) === CMYK{Float64}(0.2,0.4,0.6,0.8)
+    @test convert(CMYK{Float32}, CMYK{Float64}(0.2,0.4,0.6,0.8)) === CMYK{Float32}(0.2,0.4,0.6,0.8)
+    @test convert(CMYK, ACMYK{Float64}(0.2,0.4,0.6,0.8,0.5)) === CMYK{Float64}(0.2,0.4,0.6,0.8)
+    @test convert(ACMYK, ACMYK{Float32}(0.2,0.4,0.6,0.8,0.5)) === ACMYK{Float32}(0.2,0.4,0.6,0.8,0.5)
+    @test convert(ACMYK, CMYK{Float64}(0.2,0.4,0.6,0.8)) === ACMYK{Float64}(0.2,0.4,0.6,0.8,1.0)
+    @test convert(ACMYK, CMYK{Float32}(0.2,0.4,0.6,0.8), 0.25) === ACMYK{Float32}(0.2,0.4,0.6,0.8,0.25)
+end
+
 @testset "conversions from gray to rgb" begin
     Crgb = filter(T -> T <: AbstractRGB, ColorTypes.parametric3)
     Ctransparent = unique(vcat(coloralpha.(Crgb), alphacolor.(Crgb)))