Do not modify original image when resizing (#151)

Author: Anton Smirnov

CHANGELOG.md

@@ -1,13 +1,17 @@
 # ImageTransformations
 
+## Version `v0.9.3`
+
+- ![Bugfix][badge-bugfix] Do not modify original image when resizing. ([#151][github-151])
+
 ## Version `v0.9.2`
 
-- ![Enhancement][badge-enhancement] The in-place version of resize function `imresize!` is optimized and exported. ([#150](github-150))
+- ![Enhancement][badge-enhancement] The in-place version of resize function `imresize!` is optimized and exported. ([#150][github-150])
 
 ## Version `v0.9.1`
 
 - ![Enhancement][badge-enhancement] angles in `imrotate` are processed with high precision, restoring it to the same behavior you'd get from a manually-constructed
-  `tform` supplied to `warp`. This can change the presence/absence of padding on the edges. ([#148][github-148], [#149](github-149))
+  `tform` supplied to `warp`. This can change the presence/absence of padding on the edges. ([#148][github-148], [#149][github-149])
 
 ## Version `v0.9.0`
 
@@ -29,7 +33,8 @@ whether a "fill-value" is used instead of interpolation.
 - ![Bugfix][badge-bugfix] `restrict` on `OffsetArray` always returns an `OffsetArray` result. ([ImageBase#4][github-base-4])
 
 
-[github-150]: https://github.com/JuliaImages/ImageTransformations.jl/pull/149
+[github-151]: https://github.com/JuliaImages/ImageTransformations.jl/pull/151
+[github-150]: https://github.com/JuliaImages/ImageTransformations.jl/pull/150
 [github-149]: https://github.com/JuliaImages/ImageTransformations.jl/pull/149
 [github-148]: https://github.com/JuliaImages/ImageTransformations.jl/pull/148
 [github-143]: https://github.com/JuliaImages/ImageTransformations.jl/pull/143

src/resizing.jl

@@ -137,11 +137,11 @@ imresize_type(c) = typeof((c*1)/1)
 function imresize!(resized::AbstractArray{T,N}, original::AbstractArray{S,N}; method::Union{Interpolations.Degree,Interpolations.InterpolationType}=BSpline(Linear()), kwargs...) where {T,S,N}
     _imresize!(resized, original, method; kwargs...)
 end
-function _imresize!(resized::AbstractArray{T,N}, original::AbstractArray{S,N}, method::Union{Interpolations.Degree, Interpolations.BSpline{D}}; kwargs...) where {T,S,N,D}
+@inline function _imresize!(resized, original, method::Union{D, Interpolations.BSpline{D}}; kwargs...) where D <: Union{Constant, Linear}
     imresize!(resized, interpolate!(original, wrap_BSpline(method)))
 end
-function _imresize!(resized::AbstractArray{T,N}, original::AbstractArray{S,N}, method::Interpolations.InterpolationType; kwargs...) where {T,S,N}
-    imresize!(resized, interpolate(original, method))
+@inline function _imresize!(resized, original, method; kwargs...)
+    imresize!(resized, interpolate(original, wrap_BSpline(method)))
 end
 
 function imresize!(resized::AbstractArray{T,N}, original::AbstractInterpolation{S,N}) where {T,S,N}

test/resizing.jl

@@ -180,4 +180,22 @@ end
             @test ref ≈ Gray.(out)
         end
     end
+
+    @testset "In-place resizing should not modify original image" begin
+        for c in testcolor
+            image = rand(c, 128, 128)
+            original = copy(image)
+            out = zeros(eltype(image), 32, 32)
+
+            methods = (
+                Constant(), Linear(),
+                Quadratic(Reflect(OnCell())),
+                Quadratic(InPlace(OnCell())),
+                Cubic(Line(OnGrid())), Lanczos4OpenCV())
+            for method in methods
+                imresize!(out, image, method=method)
+                @test image == original
+            end
+        end
+    end
 end