Fix imrotate for Irrational θ

Author: timholy

src/warp.jl

@@ -244,13 +244,19 @@ mosaicview([imgr for _ in 1:9]; nrow=3)
 """
 function imrotate(img::AbstractArray{T}, θ::Real, inds::Union{Tuple, Nothing} = nothing; kwargs...) where T
     # TODO: expose rotation center as a keyword
-    Δ = eps(θ)
-    θ = mod2pi(θ)
+    Δ = eps(float(θ))
+    θ = _mod2pi(θ)
     if abs(θ) <= Δ || abs(θ - 2π) <= Δ
         θ = zero(θ)
     end
-    tform = recenter(RotMatrix{2}(θ), center(img))
+    tform = recenter(rotmtrx2(θ), center(img))
     # Use the `nothing` trick here because moving the `autorange` as default value is not type-stable
     inds = isnothing(inds) ? autorange(img, inv(tform)) : inds
     warp(img, tform, inds; kwargs...)
 end
+_mod2pi(θ) = mod2pi(θ)
+_mod2pi(θ::Irrational{:π}) = θ
+_mod2pi(θ::Irrational) = mod2pi(float(θ))
+
+rotmtrx2(θ) = RotMatrix{2}(θ)
+rotmtrx2(θ::Irrational{:π}) = @SMatrix [-1 0; 0 1]

test/warp.jl

@@ -465,5 +465,11 @@ NaN  NaN      NaN      NaN      NaN      NaN      NaN
             @test !any(isnan, imrotate(img, π/3, axes(img); fillvalue=0.0))
             @test !any(isnan, imrotate(img, π/3, axes(img), fillvalue=0.0))
         end
+
+        @testset "Examples from #79" begin
+            @test axes(imrotate(img_camera, pi/2)) == axes(img_camera)
+            @test imrotate(imrotate(imrotate(imrotate(img_camera, pi/2), pi/2), pi/2), pi/2) ≈ img_camera
+            @test imrotate(imrotate(img_camera, pi), pi) == img_camera
+        end
     end
 end