add missing Gray{T} constructor for colorant

JuliaGraphics · May 15, 2022 · 033baf4 · 033baf4
1 parent b8ed378
commit 033baf4
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diff --git a/src/types.jl b/src/types.jl
@@ -515,6 +515,7 @@ function (::Type{C})() where {N, C <: ColorantN{N}}
     C(ntuple(_ -> d0, Val(N - 1))..., dx)
 end
 
+Gray{T}(c::Colorant) where {T<:Union{Fractional,Bool}} = _new_colorant(Gray{T}, c)
 (::Type{C})(x         ) where {C <: Color    } = _new_colorant(C, x)
 (::Type{C})(x, y      ) where {C <: ColorN{2}} = _new_colorant(C, x, y)
 (::Type{C})(x, y, z   ) where {C <: ColorN{3}} = _new_colorant(C, x, y, z)

diff --git a/test/conversions.jl b/test/conversions.jl
@@ -753,6 +753,14 @@ end
     end
 end
 
+@testset "conversions from rgb to gray" begin
+    # The rules are defined in Colors.jl, but we want to make sure it calls
+    # the `convert` method.
+    # Issue #277
+    msg = "No conversion of RGB{N0f8}(0.0, 0.0, 0.0) to Gray{Float32} has been defined"
+    @test_throws ErrorException(msg) Gray{Float32}(RGB())
+end
+
 @testset "conversions between different spaces" begin
     @test_throws ErrorException convert(HSV, RGB(1,0,1))
     @test_throws ErrorException convert(AHSV, RGB(1,0,1), 0.5)