support UInt8/UInt16 for im_to_matlab

src/matlab.jl

@@ -218,18 +218,48 @@ im_to_matlab(::Type{T}, img::AbstractArray{CT}) where {T,CT<:TransparentColor} =
     im_to_matlab(T, of_eltype(base_color_type(CT), img))
 im_to_matlab(::Type{T}, img::AbstractArray{<:Color}) where {T} =
     im_to_matlab(T, of_eltype(RGB{T}, img))
-im_to_matlab(::Type{T}, img::AbstractArray{<:Gray}) where {T} =
-    no_offset_view(of_eltype(T, channelview(img)))
+im_to_matlab(::Type{T}, img::AbstractArray{CT}) where {T,CT<:Union{Gray,RGB,Number}} =
+    _im_to_matlab_try_reinterpret(T, img)
 
+# eltype conversion doesn't work in general, e.g., `UInt8(N0f8(0.3))` would fail. For special
+# types that we know solution, directly reinterpret them via `rawview`.
+function _im_to_matlab_try_reinterpret(::Type{T}, img::AbstractArray{CT}) where {T,CT<:Union{Gray,Real}}
+    throw(ArgumentError("Can not convert to MATLAB format: invalid conversion from `$(CT)` to `$T`."))
+end
+function _im_to_matlab_try_reinterpret(::Type{T}, img::AbstractArray{CT}) where {T<:Union{AbstractFloat, Normed},CT<:Union{Gray,Real}}
+    return no_offset_view(of_eltype(T, channelview(img)))
+end
+for (T, NT) in ((:UInt8, :N0f8), (:UInt16, :N0f16))
+    @eval function _im_to_matlab_try_reinterpret(::Type{$T}, img::AbstractArray{CT}) where {CT<:Union{Gray,Real}}
+        if eltype(CT) != $NT
+            nt_str = string($NT)
+            throw(ArgumentError("Can not convert to MATLAB format: invalid conversion from `$(CT)` to `$nt_str`."))
+        end
+        return no_offset_view(rawview(channelview(img)))
+    end
+end
 # for RGB, unroll the color channel in the last dimension
-function im_to_matlab(::Type{T}, img::AbstractArray{<:RGB, N}) where {T, N}
+_im_to_matlab_try_reinterpret(::Type{T}, img::AbstractArray{CT}) where {T,CT<:RGB} =
+    throw(ArgumentError("Can not convert to MATLAB format: invalid conversion from `$(CT)` to `$T`."))
+function _im_to_matlab_try_reinterpret(::Type{T}, img::AbstractArray{<:RGB,N}) where {T<:Union{AbstractFloat, Normed},N}
     v = no_offset_view(of_eltype(T, channelview(img)))
-    perm = (ntuple(i->i+1, N)..., 1)
+    perm = (ntuple(i -> i + 1, N)..., 1)
     return PermutedDimsArray(v, perm)
 end
+for (T, NT) in ((:UInt8, :N0f8), (:UInt16, :N0f16))
+    @eval function _im_to_matlab_try_reinterpret(::Type{$T}, img::AbstractArray{CT,N}) where {CT<:RGB,N}
+        if eltype(CT) != $NT
+            nt_str = string($NT)
+            throw(ArgumentError("Can not convert to MATLAB format: invalid conversion from `$(CT)` to `$nt_str`."))
+        end
+        v = no_offset_view(rawview(channelview(img)))
+        perm = (ntuple(i -> i + 1, N)..., 1)
+        return PermutedDimsArray(v, perm)
+    end
+end
 
 # indexed image
-function im_to_matlab(::Type{T}, img::IndirectArray{CT}) where {T<:Real, CT<:Colorant}
+function im_to_matlab(::Type{T}, img::IndirectArray{CT}) where {T<:Real,CT<:Colorant}
     return no_offset_view(img.index), im_to_matlab(T, img.values)
 end
 

test/matlab.jl

@@ -266,6 +266,41 @@
             @test eltype(m_values) == N0f8
             @test m_values == permutedims(channelview(values), (2, 1))
         end
+
+        @testset "UInt8/UInt16" begin
+            # directly doing eltype conversion doesn't work for UInt8/UInt16
+            # thus we can reinterpret, aka, `rawview`.
+            for (T, NT) in ((UInt8, N0f8), (UInt16, N0f16))
+                img = rand(Gray{NT}, 4, 5)
+                img_m_normed = im_to_matlab(NT, img)
+                img_m = im_to_matlab(T, img)
+                @test eltype(img_m_normed) == NT
+                @test eltype(img_m) == T
+                @test img_m_normed != img_m
+                @test img_m_normed == channelview(img)
+                @test img_m == rawview(channelview(img))
+
+                img = rand(RGB{NT}, 4, 5)
+                img_m_normed = im_to_matlab(NT, img)
+                img_m = im_to_matlab(T, img)
+                @test eltype(img_m_normed) == NT
+                @test eltype(img_m) == T
+                @test img_m_normed != img_m
+                @test img_m_normed == permutedims(channelview(img), (2, 3, 1))
+                @test img_m == permutedims(rawview(channelview(img)), (2, 3, 1))
+            end
+
+            # We only patch for special types that MATLAB expects, for anything that is
+            # non-standard MATLAB layout, manual conversions or other tools are needed. Here
+            # we test that we have informative error messages.
+            for CT in (Gray, RGB)
+                img = rand(CT{N0f8}, 4, 5)
+                msg = "Can not convert to MATLAB format: invalid conversion from `$CT{$N0f8}` to `$N0f16`."
+                @test_throws ArgumentError(msg) im_to_matlab(UInt16, img)
+                msg = "Can not convert to MATLAB format: invalid conversion from `$CT{$N0f8}` to `$Int`."
+                @test_throws ArgumentError(msg) im_to_matlab(Int, img)
+            end
+        end
     end
 
     # test `im_from_matlab` and `im_to_matlab` are inverses of each other.

test/runtests.jl

@@ -1,6 +1,7 @@
 module ImageCoreTests
 
 using ImageCore
+using OffsetArrays: OffsetArray
 using Test, ReferenceTests
 using Aqua, Documenter # for meta quality checks