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restrict: only return OffsetArray when input is an OffsetArray #4

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May 22, 2021
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restrict: only return OffsetArray when input is an OffsetArray #4

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2 changes: 2 additions & 0 deletions src/ImageUtils.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,9 @@ export restrict

using Base.Cartesian: @nloops
using ImageCore
using ImageCore.OffsetArrays

include("restrict.jl")
include("compat.jl")

end
5 changes: 5 additions & 0 deletions src/compat.jl
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@@ -0,0 +1,5 @@
if VERSION < v"1.2"
require_one_based_indexing(A...) = !Base.has_offset_axes(A...) || throw(ArgumentError("offset arrays are not supported but got an array with index other than 1"))
else
const require_one_based_indexing = Base.require_one_based_indexing
end
13 changes: 12 additions & 1 deletion src/restrict.jl
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Expand Up @@ -76,9 +76,20 @@ function restrict(A::AbstractArray, region::Dims)
end

function restrict(A::AbstractArray{T,N}, dim::Integer) where {T,N}
require_one_based_indexing(A)

indsA = axes(A)
newinds = ntuple(i->i==dim ? restrict_indices(indsA[dim]) : indsA[i], Val(N))
out = Array{restrict_eltype(first(A)), N}(undef, last.(newinds))
restrict!(out, A, dim)
out
end
function restrict(A::OffsetArray{T,N}, dim::Integer) where {T,N}
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It would be better not to specialize on OffsetArray, because it's far from the only special array type in the universe. similar , supplied with appropriate axes for the result, should allocate the correct type for us. What's needed is a correct way to compute the axes of the returned value.

indsA = axes(A)
newinds = map(UnitRange, ntuple(i->i==dim ? restrict_indices(indsA[dim]) : indsA[i], Val(N)))
out = similar(Array{restrict_eltype(first(A)), N}, newinds)
# This calls OffsetArrays implementation: a type piracy
# https://github.com/JuliaArrays/OffsetArrays.jl/issues/87
out = similar(A, restrict_eltype(first(A)), newinds)
restrict!(out, A, dim)
out
end
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35 changes: 31 additions & 4 deletions test/restrict.jl
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@@ -1,4 +1,23 @@
@testset "restrict" begin
@testset "restrict" begin
@testset "interfaces" begin
A = rand(N0f8, 4, 5, 3)

Ar = @inferred restrict(A, 1)
@test typeof(Ar) <: Array
@test size(Ar) == (3, 5, 3)

Ar = @inferred restrict(A, (1, ))
@test typeof(Ar) <: Array
@test size(Ar) == (3, 5, 3)

Ar = @inferred restrict(A, (1, 2, 3))
@test typeof(Ar) <: Array
@test size(Ar) == (3, 3, 2)
@test Ar == restrict(A)

@test_throws MethodError restrict(A, 1, 2, 3)
end

@testset "numerical test" begin
A = reshape([UInt16(i) for i = 1:60], 4, 5, 3)
B = restrict(A, (1,2))
Expand Down Expand Up @@ -36,9 +55,17 @@
@testset "OffsetArray" begin
A = rand(5, 4, 3)
Ao = OffsetArray(A, (-2,1,0))
@test parent(@inferred(restrict(Ao, 1))) == restrict(A, 1)
@test parent(@inferred(restrict(Ao, 2))) == restrict(A, 2)
@test parent(@inferred(restrict(Ao, (1,2)))) == restrict(A, (1,2))

for (dims, offsets) in [
(1, (-1, 1, 0)),
(2, (-2, 0, 0)),
((1, 2), (-1, 0, 0))
]
Ar = @inferred restrict(Ao, dims)
@test typeof(Ar) <: OffsetArray
@test Ar.offsets == offsets
@test parent(Ar) == restrict(A, dims)
end
end

@testset "FixedPoint overflow" begin
Expand Down