Fix BoundingBox rotations (#95)

Bounding boxes are not transformed correctly with rotation transforms.
This is due to only storing the min and max corners, and assuming that
after rotations the corners still contain the minimum and maximum
coordinates.  This change stores all 4 corners (for 2D; 8 corners for
3D) in the BoundingBox. All of these corner points are transformed, and
we can accurately calculate the min and max as needed (by itemdata).

Fixes #94

Author: paulnovo

src/items/keypoints.jl

@@ -40,16 +40,14 @@ getbounds(keypoints::Keypoints) = keypoints.bounds
 
 
 function project(P, keypoints::Keypoints{N, T}, bounds::Bounds{N}) where {N, T}
-    # TODO: convert back to `T`?
     return Keypoints(
-        map(fmap(P), keypoints.data),
+        collect(SVector{N, T}, map(fmap(P), keypoints.data)),
         bounds,
     )
 end
 function project!(buf, P, keypoints::Keypoints{N, T}, bounds::Bounds{N}) where {N, T}
-    # TODO: convert back to `T`?
     return Keypoints(
-        map(fmap(P), keypoints.data),
+        collect(SVector{N, T}, map(fmap(P), keypoints.data)),
         bounds,
     )
 end
@@ -126,11 +124,16 @@ struct BoundingBox{N, T, S} <: ItemWrapper{Keypoints{N, T, S, 1}}
     item::Keypoints{N, T, S, 1}
 end
 
-function BoundingBox(data::AbstractVector{<:SVector{N}}, bounds) where N
-    length(data) == N || error("Give $N corner points for an $N-dimensional bounding box")
-    BoundingBox(Keypoints(data, bounds))
+function BoundingBox(data::AbstractVector{<:SVector{N, T}}, bounds) where {N, T}
+    length(data) == 2 || error("Give 2 corner points for an $N-dimensional bounding box")
+    corners = reduce(vcat, Iterators.product(zip(data...)...))
+    corners = collect(SVector{N, T}, corners)
+    corners = SVector{2^N, SVector{N, T}}(corners)
+    BoundingBox{N, T, SVector{N, T}}(Keypoints(corners, bounds))
 end
 
+itemdata(box::BoundingBox{N, T}) where {N, T} =
+    [min.(box.item.data...), max.(box.item.data...)]
 
 Base.show(io::IO, item::BoundingBox{N, T}) where {N, T} =
     print(io, "BoundingBox{$N, $T}()")

test/Project.toml

@@ -8,6 +8,8 @@ CoordinateTransformations = "150eb455-5306-5404-9cee-2592286d6298"
 DataAugmentation = "88a5189c-e7ff-4f85-ac6b-e6158070f02e"
 FixedPointNumbers = "53c48c17-4a7d-5ca2-90c5-79b7896eea93"
 ImageShow = "4e3cecfd-b093-5904-9786-8bbb286a6a31"
+LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
+Rotations = "6038ab10-8711-5258-84ad-4b1120ba62dc"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 TestSetExtensions = "98d24dd4-01ad-11ea-1b02-c9a08f80db04"

test/imports.jl

@@ -5,6 +5,8 @@ using TestSetExtensions
 using CoordinateTransformations
 using Colors
 using FixedPointNumbers: N0f8
+using LinearAlgebra
+using Rotations
 
 
 using DataAugmentation: Item, Transform, getrandstate, itemdata, setdata, ComposedProjectiveTransform,

test/items/keypoints.jl

@@ -10,3 +10,31 @@ include("../imports.jl")
 
     @test_nowarn apply(tfm, Polygon(keypoints))
 end
+
+@testset ExtendedTestSet "$(N)D BoundingBox" for N in 2:4
+    bounds = Bounds{N}(ntuple(_ -> -50:50, N))
+
+    min = SVector{N, Float64}(ntuple(i -> i==1 ? -20 : -10, N)) # [-20, -10, ...]
+    max = SVector{N, Float64}(ntuple(i -> i==1 ? 20 : 10, N)) # [20, 10, ...]
+    widebbox = BoundingBox(SVector{N, Float64}[min, max], bounds)
+
+    min = SVector{N, Float64}(ntuple(i -> i==2 ? -20 : -10, N)) # [-10, -20, ...]
+    max = SVector{N, Float64}(ntuple(i -> i==2 ? 20 : 10, N)) # [10, 20, ...]
+    tallbbox = BoundingBox(SVector{N, Float64}[min, max], bounds)
+
+    rotation = Matrix(1.0I, N, N)
+    rotation[1:2, 1:2] = RotMatrix(pi/2.0)
+    tfm90 = Project(LinearMap(rotation))
+    @test_nowarn apply(tfm90, tallbbox)
+
+    # Rotation by 90 degrees should make the wide bounding box equal to the
+    # tall bounding box and vice versa.
+    transformed = apply(tfm90, widebbox)
+    @test itemdata(transformed) ≈ itemdata(tallbbox)
+    transformed = apply(tfm90, transformed)
+    @test itemdata(transformed) ≈ itemdata(widebbox)
+    transformed = apply(tfm90, transformed)
+    @test itemdata(transformed) ≈ itemdata(tallbbox)
+    transformed = apply(tfm90, transformed)
+    @test itemdata(transformed) ≈ itemdata(widebbox)
+end