[Images] 🧹 Deprecate bilinear_interpolation in favor of imresize

johnnychen94 · johnnychen94 · commit ec7696bc4d96 · 2021-11-01T03:58:08.000+08:00
I didn't do the archaeology but I believe this function existed
long before we have Interpolations and ImageTransformations. Since
we now have much much better support on these two packages, we won't
need this legacy `bilinear_interpolation` method anymore.
diff --git a/packages/Images/src/Images.jl b/packages/Images/src/Images.jl
@@ -186,7 +186,6 @@ export
     canny,
     integral_image,
     boxdiff,
-    bilinear_interpolation,
     gaussian_pyramid,
 
     # phantoms
@@ -219,7 +218,6 @@ Algorithms:
     - Blob detection: `blob_LoG`, `findlocalmaxima`, `findlocalminima`
     - Morphological operations: `dilate`, `erode`, `closing`, `opening`, `tophat`, `bothat`, `morphogradient`, `morpholaplace`, `feature_transform`, `distance_transform`, `convexhull`
     - Connected components: `label_components`, `component_boxes`, `component_lengths`, `component_indices`, `component_subscripts`, `component_centroids`
-    - Interpolation: `bilinear_interpolation`
 
 Test images and phantoms (see also TestImages.jl):
 
diff --git a/packages/Images/src/algorithms.jl b/packages/Images/src/algorithms.jl
@@ -447,47 +447,6 @@ function boxdiff(int_img::AbstractArray{T, 2}, tl_y::Integer, tl_x::Integer, br_
     sum
 end
 
-"""
-```
-P = bilinear_interpolation(img, r, c)
-```
-
-Bilinear Interpolation is used to interpolate functions of two variables
-on a rectilinear 2D grid.
-
-The interpolation is done in one direction first and then the values obtained
-are used to do the interpolation in the second direction.
-
-"""
-function bilinear_interpolation(img::AbstractArray{T, 2}, y::Number, x::Number) where T
-    y_min = floor(Int, y)
-    x_min = floor(Int, x)
-    y_max = ceil(Int, y)
-    x_max = ceil(Int, x)
-
-    topleft = chkbounds(Bool, img, y_min, x_min) ? img[y_min, x_min] : zero(T)
-    bottomleft = chkbounds(Bool, img, y_max, x_min) ? img[y_max, x_min] : zero(T)
-    topright = chkbounds(Bool, img, y_min, x_max) ? img[y_min, x_max] : zero(T)
-    bottomright = chkbounds(Bool, img, y_max, x_max) ? img[y_max, x_max] : zero(T)
-
-    if x_max == x_min
-        if y_max == y_min
-            return T(topleft)
-        end
-        return T(((y_max - y) * topleft + (y - y_min) * bottomleft) / (y_max - y_min))
-    elseif y_max == y_min
-        return T(((x_max - x) * topleft + (x - x_min) * topright) / (x_max - x_min))
-    end
-
-    r1 = ((x_max - x) * topleft + (x - x_min) * topright) / (x_max - x_min)
-    r2 = ((x_max - x) * bottomleft + (x - x_min) * bottomright) / (x_max - x_min)
-
-    T(((y_max - y) * r1 + (y - y_min) * r2) / (y_max - y_min))
-
-end
-
-chkbounds(::Type{Bool}, img, x, y) = checkbounds(Bool, img, x, y)
-
 """
 ```
 pyramid = gaussian_pyramid(img, n_scales, downsample, sigma)
diff --git a/packages/Images/src/deprecations.jl b/packages/Images/src/deprecations.jl
@@ -1076,3 +1076,15 @@ function ColorVectorSpace.complement(x::AbstractArray)
     complement.(x)
 end
 
+# This is now replaced by ImageTransformations and Interpolations
+using ImageTransformations.Interpolations: BSpline, Linear, interpolate
+function bilinear_interpolation(img::AbstractArray{T,N}, xs::Vararg{<:Number, N}) where {T,N}
+    Base.depwarn("`bilinear_interpolation` is deprecated, please use `warp`, `imresize` from ImageTransformations or `extrapolate`, `interpolate` from Interpolations", :bilinear_interpolation)
+    pad_ax = map(axes(img), xs) do ax, x
+        min(floor(Int, x), first(ax)):max(ceil(Int, x), last(ax))
+    end
+    padded_img = PaddedView(zero(T), img, pad_ax)
+    itp = interpolate(padded_img, BSpline(Linear()))
+    return itp(xs...)
+end
+export bilinear_interpolation
diff --git a/packages/Images/test/algorithms.jl b/packages/Images/test/algorithms.jl
@@ -366,38 +366,6 @@ using Test, Suppressor
         @test eltype(img2) == RGB{Float32}
     end
 
-    @testset "Interpolations" begin
-
-        img = zeros(Float64, 5, 5)
-        @test bilinear_interpolation(img, 4.5, 5.5) == 0.0
-        @test bilinear_interpolation(img, 4.5, 3.5) == 0.0
-
-        for i in [1.0, 2.0, 5.0, 7.0, 9.0]
-            img = ones(Float64, 5, 5) * i
-            @test (bilinear_interpolation(img, 3.5, 4.5) == i)
-            @test (bilinear_interpolation(img, 3.2, 4) == i)  # X_MAX == X_MIN
-            @test (bilinear_interpolation(img, 3.2, 4) == i)  # Y_MAX == Y_MIN
-            @test (bilinear_interpolation(img, 3.2, 4) == i)  # BOTH EQUAL
-            @test (bilinear_interpolation(img, 2.8, 1.9) == i)
-            # One dim out of bounds
-            @test isapprox(bilinear_interpolation(img, 0.5, 1.5), 0.5 * i)
-            @test isapprox(bilinear_interpolation(img, 0.5, 1.6), 0.5 * i)
-            @test isapprox(bilinear_interpolation(img, 0.5, 1.8), 0.5 * i)
-            # Both out of bounds (corner)
-            @test isapprox(bilinear_interpolation(img, 0.5, 0.5), 0.25 * i)
-        end
-
-        img = reshape(1.0:1.0:25.0, 5, 5)
-        @test bilinear_interpolation(img, 1.5, 2) == 6.5
-        @test bilinear_interpolation(img, 2, 1.5) == 4.5
-        @test bilinear_interpolation(img, 2, 1) == 2.0
-        @test bilinear_interpolation(img, 1.5, 2.5) == 9.0
-        @test bilinear_interpolation(img, 1.5, 3.5) == 14.0
-        @test bilinear_interpolation(img, 1.5, 4.5) == 19.0
-        @test bilinear_interpolation(img, 1.5, 5.5) == 10.75
-
-    end
-
     @testset "Convex Hull" begin
         A = zeros(50, 30)
         A= convert(Array{Bool}, A)
diff --git a/packages/Images/test/deprecated.jl b/packages/Images/test/deprecated.jl
@@ -13,4 +13,34 @@
         imgmeta = ImageMeta(imgcol, myprop=1)
         @test isa(restrict(imgmeta, [1, 2]), ImageMeta)
     end
+
+    @testset "Interpolations" begin
+        img = zeros(Float64, 5, 5)
+        @test bilinear_interpolation(img, 4.5, 5.5) == 0.0
+        @test bilinear_interpolation(img, 4.5, 3.5) == 0.0
+
+        for i in [1.0, 2.0, 5.0, 7.0, 9.0]
+            img = ones(Float64, 5, 5) * i
+            @test (bilinear_interpolation(img, 3.5, 4.5) == i)
+            @test (bilinear_interpolation(img, 3.2, 4) == i)  # X_MAX == X_MIN
+            @test (bilinear_interpolation(img, 3.2, 4) == i)  # Y_MAX == Y_MIN
+            @test (bilinear_interpolation(img, 3.2, 4) == i)  # BOTH EQUAL
+            @test (bilinear_interpolation(img, 2.8, 1.9) == i)
+            # One dim out of bounds
+            @test isapprox(bilinear_interpolation(img, 0.5, 1.5), 0.5 * i)
+            @test isapprox(bilinear_interpolation(img, 0.5, 1.6), 0.5 * i)
+            @test isapprox(bilinear_interpolation(img, 0.5, 1.8), 0.5 * i)
+            # Both out of bounds (corner)
+            @test isapprox(bilinear_interpolation(img, 0.5, 0.5), 0.25 * i)
+        end
+
+        img = reshape(1.0:1.0:25.0, 5, 5)
+        @test bilinear_interpolation(img, 1.5, 2) == 6.5
+        @test bilinear_interpolation(img, 2, 1.5) == 4.5
+        @test bilinear_interpolation(img, 2, 1) == 2.0
+        @test bilinear_interpolation(img, 1.5, 2.5) == 9.0
+        @test bilinear_interpolation(img, 1.5, 3.5) == 14.0
+        @test bilinear_interpolation(img, 1.5, 4.5) == 19.0
+        @test bilinear_interpolation(img, 1.5, 5.5) == 10.75
+    end
 end
