From ea2324a3833892d0e8c0ba0a05f3cea7874535c1 Mon Sep 17 00:00:00 2001
From: Isabelle Tan <isabelle.tan@medivation.ch>
Date: Tue, 3 Jan 2023 16:20:25 +0100
Subject: [PATCH 1/6] Fix getprojection() methods for ND case for
 ScaleKeepAspect, ScaleFixed and PinOrigin. Also add ScaleFixed and Zoom to
 the 3D test to catch the bug.

---
 src/projective/affine.jl  | 18 +++++++++---------
 test/projective/affine.jl |  2 ++
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/projective/affine.jl b/src/projective/affine.jl
index 6d92e687..940ca455 100644
--- a/src/projective/affine.jl
+++ b/src/projective/affine.jl
@@ -39,7 +39,7 @@ struct ScaleKeepAspect{N} <: ProjectiveTransform
 end
 
 
-function getprojection(scale::ScaleKeepAspect{N}, bounds; randstate = nothing) where N
+function getprojection(scale::ScaleKeepAspect{N}, bounds::Bounds{N}; randstate = nothing) where N
     # If no scaling needs to be done, return a noop transform
     scale.minlengths == length.(bounds.rs) && return IdentityTransformation()
 
@@ -47,7 +47,7 @@ function getprojection(scale::ScaleKeepAspect{N}, bounds; randstate = nothing) w
     ratio = maximum((scale.minlengths .+ 1) ./ length.(bounds.rs))
     upperleft = SVector{N, Float32}(minimum.(bounds.rs)) .- 0.5
     P = scaleprojection(Tuple(ratio for _ in 1:N))
-    if upperleft != SVector(0, 0)
+    if any(upperleft .!= 0)
         P = P ∘ Translation((Float32.(P(upperleft)) .+ 0.5f0))
     end
     return P
@@ -75,11 +75,11 @@ struct ScaleFixed{N} <: ProjectiveTransform
 end
 
 
-function getprojection(scale::ScaleFixed, bounds; randstate = nothing)
+function getprojection(scale::ScaleFixed, bounds::Bounds{N}; randstate = nothing) where N
     ratios = (scale.sizes .+ 1) ./ length.(bounds.rs)
-    upperleft = SVector{2, Float32}(minimum.(bounds.rs)) .- 1
+    upperleft = SVector{N, Float32}(minimum.(bounds.rs)) .- 1
     P = scaleprojection(ratios)
-    if upperleft != SVector(0, 0)
+    if any(upperleft .!= 0)
         P = P  ∘ Translation(-upperleft)
     end
     return P
@@ -88,7 +88,7 @@ end
 
 function projectionbounds(tfm::ScaleFixed{N}, P, bounds::Bounds{N}; randstate = nothing) where N
     bounds_ = transformbounds(bounds, P)
-    return offsetcropbounds(tfm.sizes, bounds_, (1., 1.))
+    return offsetcropbounds(tfm.sizes, bounds_, ntuple(_ -> 1., N))
 end
 
 """
@@ -167,7 +167,7 @@ struct Reflect <: ProjectiveTransform
 end
 
 
-function getprojection(tfm::Reflect, bounds; randstate = getrandstate(tfm))
+function getprojection(tfm::Reflect, bounds::Bounds{2}; randstate = getrandstate(tfm))
     r = tfm.γ / 360 * 2pi
     return centered(LinearMap(reflectionmatrix(r)), bounds)
 end
@@ -213,8 +213,8 @@ at one.
 """
 struct PinOrigin <: ProjectiveTransform end
 
-function getprojection(::PinOrigin, bounds; randstate = nothing)
-    p = (-SVector{2, Float32}(minimum.(bounds.rs))) .+ 1
+function getprojection(::PinOrigin, bounds::Bounds{N}; randstate = nothing) where N
+    p = (-SVector{N, Float32}(minimum.(bounds.rs))) .+ 1
     P = Translation(p)
     return P
 end
diff --git a/test/projective/affine.jl b/test/projective/affine.jl
index a8c0ae09..bd09dd74 100644
--- a/test/projective/affine.jl
+++ b/test/projective/affine.jl
@@ -177,8 +177,10 @@ end
         )
 
         tfms = compose(
+            ScaleFixed((30, 40, 50)),
             ScaleRatio((.8, .8, .8)),
             ScaleKeepAspect((12, 10, 10)),
+            Zoom((1., 1.2)),
             RandomCrop((10, 10, 10))
         )
         testprojective(tfms, items)

From 424ea6f2075a3a5fa692b5327cfe3e65933a50d7 Mon Sep 17 00:00:00 2001
From: Isabelle Tan <isabelle.tan@medivation.ch>
Date: Tue, 3 Jan 2023 16:36:13 +0100
Subject: [PATCH 2/6] make centered() ND compatible, add Flips for ND data and
 test them in the 3D test

---
 docs/literate/projective/gallery.md |  6 +++---
 docs/literate/projective/intro.md   |  2 +-
 docs/literate/projective/usage.md   |  4 ++--
 docs/literate/stochastic.md         |  2 +-
 src/DataAugmentation.jl             |  1 +
 src/projective/affine.jl            | 33 +++++++++++++++++++++++------
 test/projective/affine.jl           |  9 +++++---
 7 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/docs/literate/projective/gallery.md b/docs/literate/projective/gallery.md
index 47fb3736..59e99b0f 100644
--- a/docs/literate/projective/gallery.md
+++ b/docs/literate/projective/gallery.md
@@ -147,15 +147,15 @@ tfms = [
 o = showtransforms(tfms, (image, bbox))
 ```
 
-### [`FlipX`](#), [`FlipY`](#), [`Reflect`](#)
+### [`FlipX`](#), [`FlipY`](#), [`FlipZ`](#), [`FlipDim`](#), [`Reflect`](#)
 
 Flip the data on the horizontally and vertically, respectively. More generally, reflect around an angle from the x-axis.
 
 {cell=main result=false}
 ```julia
 tfms = [
-    FlipX(),
-    FlipY(),
+    FlipX(2),
+    FlipY(2),
     Reflect(30),
 ]
 ```
diff --git a/docs/literate/projective/intro.md b/docs/literate/projective/intro.md
index 7a2a8c61..a1f96796 100644
--- a/docs/literate/projective/intro.md
+++ b/docs/literate/projective/intro.md
@@ -19,7 +19,7 @@ We can break down most augmentation used in practive into a single (possibly sto
 As an example, consider an image augmentation pipeline: A random horizontal flip, followed by a random resized crop. The latter resizes and crops (irregularly sized) images to a common size without distorting the aspect ratio.
 
 ```julia
-Maybe(FlipX()) |> RandomResizeCrop((h, w))
+Maybe(FlipX(2)) |> RandomResizeCrop((h, w))
 ```
 
 Let's pull apart the steps involved. 
diff --git a/docs/literate/projective/usage.md b/docs/literate/projective/usage.md
index eb5f3699..257e524f 100644
--- a/docs/literate/projective/usage.md
+++ b/docs/literate/projective/usage.md
@@ -3,7 +3,7 @@
 Using projective transformations is as simple as any other transformations. Simply `compose` them:
 
 ```julia
-Rotate(-10:10) |> ScaleRatio(0.7:0.1:1.2) |> FlipX() |> Crop((128, 128))
+Rotate(-10:10) |> ScaleRatio(0.7:0.1:1.2) |> FlipX(2) |> Crop((128, 128))
 ```
 
 The composition will automatically create a single projective transformation and evaluate only the cropped area.
@@ -14,7 +14,7 @@ Affine transformations are a subgroup of projective transformations that can be
 
 - [`ScaleRatio`](#), [`ScaleKeepAspect`](#)
 - [`Rotate`](#)
-- [`FlipX`](#), [`FlipY`](#), [`Reflect`](#)
+- [`FlipX`](#), [`FlipY`](#), [`FlipZ`](#), [`FlipDim`](#), [`Reflect`](#)
 - [`WarpAffine`](#)
 
 ## Crops
diff --git a/docs/literate/stochastic.md b/docs/literate/stochastic.md
index b9d04dc8..05c0b34f 100644
--- a/docs/literate/stochastic.md
+++ b/docs/literate/stochastic.md
@@ -13,7 +13,7 @@ Let's say we have an image classification dataset. For most datasets, horizontal
 ```julia
 using DataAugmentation, TestImages
 item = Image(testimage("lighthouse"))
-tfm = Maybe(FlipX())
+tfm = Maybe(FlipX(2))
 titems = [apply(tfm, item) for _ in 1:8]
 showgrid(titems; ncol = 4, npad = 16)
 ```
\ No newline at end of file
diff --git a/src/DataAugmentation.jl b/src/DataAugmentation.jl
index d2df407e..5f295fd6 100644
--- a/src/DataAugmentation.jl
+++ b/src/DataAugmentation.jl
@@ -82,6 +82,7 @@ export Item,
     WarpAffine,
     FlipX,
     FlipY,
+    FlipZ,
     PinOrigin,
     AdjustBrightness,
     AdjustContrast,
diff --git a/src/projective/affine.jl b/src/projective/affine.jl
index 940ca455..7491082f 100644
--- a/src/projective/affine.jl
+++ b/src/projective/affine.jl
@@ -178,24 +178,45 @@ end
 Transform `P` so that is applied around the center of `bounds`
 instead of the origin
 """
-function centered(P, bounds::Bounds{2})
+function centered(P, bounds::Bounds{N}) where N
     upperleft = minimum.(bounds.rs)
     bottomright = maximum.(bounds.rs)
 
-    midpoint = SVector{2, Float32}((bottomright .- upperleft) ./ 2) .+ SVector{2, Float32}(.5, .5)
+    midpoint = SVector{N, Float32}((bottomright .- upperleft) ./ 2) .+ .5f0
     return recenter(P, midpoint)
 end
 
-
-FlipX() = Reflect(180)
-FlipY() = Reflect(90)
-
 function reflectionmatrix(r)
     A = SMatrix{2, 2, Float32}(cos(2r), sin(2r), sin(2r), -cos(2r))
     return round.(A; digits = 12)
 end
 
 
+"""
+    FlipDim{N}()
+Reflect `N` dimensional data along the axis of dimension `dim`. Must satisfy 1 <= `dim` <= `N`.
+## Examples
+```julia
+tfm = FlipDim{2}(1)
+```
+"""
+struct FlipDim{N} <: ProjectiveTransform
+    dim::Int
+    FlipDim{N}(dim) where {N} = 1 <= dim <= N ? new{N}(dim) : error("invalid dimension")
+end
+# 2D images use (r, c) = (y, x) convention
+FlipX(N) = FlipDim{N}(N==2 ? 2 : 1)
+FlipY(N) = FlipDim{N}(N==2 ? 1 : 2)
+FlipZ(N) = FlipDim{N}(3)
+
+function getprojection(tfm::FlipDim{N}, bounds::Bounds{N}; randstate = nothing) where N
+    arr = 1I(N)
+    arr[tfm.dim, tfm.dim] = -1
+    M = SMatrix{N, N, Float32}(arr)
+    return DataAugmentation.centered(LinearMap(M), bounds)
+end
+
+
 """
     PinOrigin()
 
diff --git a/test/projective/affine.jl b/test/projective/affine.jl
index bd09dd74..36b27eb1 100644
--- a/test/projective/affine.jl
+++ b/test/projective/affine.jl
@@ -142,7 +142,7 @@ include("../imports.jl")
     @testset ExtendedTestSet "`RandomCrop` correct indices" begin
         # Flipping and cropping should be the same as reverse-indexing
         # the flipped dimension
-        tfm = FlipX() |> RandomCrop((64, 64)) |> PinOrigin()
+        tfm = FlipX(2) |> RandomCrop((64, 64)) |> PinOrigin()
         img = rand(RGB, 64, 64)
         item = Image(img)
         titem = apply(tfm, item)
@@ -157,8 +157,8 @@ end
     @testset ExtendedTestSet "2D" begin
         tfms = compose(
             Rotate(10),
-            FlipX(),
-            FlipY(),
+            FlipX(2),
+            FlipY(2),
             ScaleRatio((.8, .8)),
             WarpAffine(0.1),
             Zoom((1., 1.2)),
@@ -177,6 +177,9 @@ end
         )
 
         tfms = compose(
+            FlipX(3),
+            FlipY(3),
+            FlipZ(3),
             ScaleFixed((30, 40, 50)),
             ScaleRatio((.8, .8, .8)),
             ScaleKeepAspect((12, 10, 10)),

From c05656f1b1d4d18aace441a8af9bea957efa953b Mon Sep 17 00:00:00 2001
From: Isabelle Tan <isabelle.tan@medivation.ch>
Date: Tue, 10 Jan 2023 15:27:58 +0100
Subject: [PATCH 3/6] Change N from argument to parametric type for FlipX,
 FlipY and FlipZ constructors, to match the FlipDim definition

---
 docs/literate/projective/gallery.md |  4 ++--
 docs/literate/projective/intro.md   |  2 +-
 docs/literate/stochastic.md         |  2 +-
 src/projective/affine.jl            | 19 ++++++++++++++-----
 test/projective/affine.jl           | 12 ++++++------
 5 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/docs/literate/projective/gallery.md b/docs/literate/projective/gallery.md
index 59e99b0f..5301029e 100644
--- a/docs/literate/projective/gallery.md
+++ b/docs/literate/projective/gallery.md
@@ -154,8 +154,8 @@ Flip the data on the horizontally and vertically, respectively. More generally,
 {cell=main result=false}
 ```julia
 tfms = [
-    FlipX(2),
-    FlipY(2),
+    FlipX{2}(),
+    FlipY{2}(),
     Reflect(30),
 ]
 ```
diff --git a/docs/literate/projective/intro.md b/docs/literate/projective/intro.md
index a1f96796..32bc7911 100644
--- a/docs/literate/projective/intro.md
+++ b/docs/literate/projective/intro.md
@@ -19,7 +19,7 @@ We can break down most augmentation used in practive into a single (possibly sto
 As an example, consider an image augmentation pipeline: A random horizontal flip, followed by a random resized crop. The latter resizes and crops (irregularly sized) images to a common size without distorting the aspect ratio.
 
 ```julia
-Maybe(FlipX(2)) |> RandomResizeCrop((h, w))
+Maybe(FlipX{2}()) |> RandomResizeCrop((h, w))
 ```
 
 Let's pull apart the steps involved. 
diff --git a/docs/literate/stochastic.md b/docs/literate/stochastic.md
index 05c0b34f..420c4ca2 100644
--- a/docs/literate/stochastic.md
+++ b/docs/literate/stochastic.md
@@ -13,7 +13,7 @@ Let's say we have an image classification dataset. For most datasets, horizontal
 ```julia
 using DataAugmentation, TestImages
 item = Image(testimage("lighthouse"))
-tfm = Maybe(FlipX(2))
+tfm = Maybe(FlipX{2}())
 titems = [apply(tfm, item) for _ in 1:8]
 showgrid(titems; ncol = 4, npad = 16)
 ```
\ No newline at end of file
diff --git a/src/projective/affine.jl b/src/projective/affine.jl
index 7491082f..53f5d31b 100644
--- a/src/projective/affine.jl
+++ b/src/projective/affine.jl
@@ -193,7 +193,7 @@ end
 
 
 """
-    FlipDim{N}()
+    FlipDim{N}(dim)
 Reflect `N` dimensional data along the axis of dimension `dim`. Must satisfy 1 <= `dim` <= `N`.
 ## Examples
 ```julia
@@ -202,12 +202,21 @@ tfm = FlipDim{2}(1)
 """
 struct FlipDim{N} <: ProjectiveTransform
     dim::Int
-    FlipDim{N}(dim) where {N} = 1 <= dim <= N ? new{N}(dim) : error("invalid dimension")
+    FlipDim{N}(dim) where N = 1 <= dim <= N ? new{N}(dim) : error("invalid dimension")
 end
+
 # 2D images use (r, c) = (y, x) convention
-FlipX(N) = FlipDim{N}(N==2 ? 2 : 1)
-FlipY(N) = FlipDim{N}(N==2 ? 1 : 2)
-FlipZ(N) = FlipDim{N}(3)
+struct FlipX{N}
+    FlipX{N}() where N = FlipDim{N}(N==2 ? 2 : 1)
+end
+
+struct FlipY{N}
+    FlipY{N}() where N = FlipDim{N}(N==2 ? 1 : 2)
+end
+
+struct FlipZ{N}
+    FlipZ{N}() where N = FlipDim{N}(3)
+end
 
 function getprojection(tfm::FlipDim{N}, bounds::Bounds{N}; randstate = nothing) where N
     arr = 1I(N)
diff --git a/test/projective/affine.jl b/test/projective/affine.jl
index 36b27eb1..926cbd2d 100644
--- a/test/projective/affine.jl
+++ b/test/projective/affine.jl
@@ -142,7 +142,7 @@ include("../imports.jl")
     @testset ExtendedTestSet "`RandomCrop` correct indices" begin
         # Flipping and cropping should be the same as reverse-indexing
         # the flipped dimension
-        tfm = FlipX(2) |> RandomCrop((64, 64)) |> PinOrigin()
+        tfm = FlipX{2}() |> RandomCrop((64, 64)) |> PinOrigin()
         img = rand(RGB, 64, 64)
         item = Image(img)
         titem = apply(tfm, item)
@@ -157,8 +157,8 @@ end
     @testset ExtendedTestSet "2D" begin
         tfms = compose(
             Rotate(10),
-            FlipX(2),
-            FlipY(2),
+            FlipX{2}(),
+            FlipY{2}(),
             ScaleRatio((.8, .8)),
             WarpAffine(0.1),
             Zoom((1., 1.2)),
@@ -177,9 +177,9 @@ end
         )
 
         tfms = compose(
-            FlipX(3),
-            FlipY(3),
-            FlipZ(3),
+            FlipX{3}(),
+            FlipY{3}(),
+            FlipZ{3}(),
             ScaleFixed((30, 40, 50)),
             ScaleRatio((.8, .8, .8)),
             ScaleKeepAspect((12, 10, 10)),

From 5458c76404d230419c14285acc9f8575f0fd340e Mon Sep 17 00:00:00 2001
From: Isabelle Tan <isabelle.tan@medivation.ch>
Date: Wed, 11 Jan 2023 16:29:52 +0100
Subject: [PATCH 4/6] add 2D and 3D test for flips: flip dimension size of 1
 means identity operation

---
 test/projective/affine.jl | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/test/projective/affine.jl b/test/projective/affine.jl
index 926cbd2d..8b7baa3e 100644
--- a/test/projective/affine.jl
+++ b/test/projective/affine.jl
@@ -139,8 +139,26 @@ include("../imports.jl")
         @test_nowarn apply!(buffer, tfm, image2)
     end
 
+    @testset ExtendedTestSet "FlipX 2D: flip dimension of 1 = identity" begin
+        tfm = FlipX{2}()
+        img = rand(RGB, 10, 1)
+        item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
+        titem = apply(tfm, item)
+        @test itemdata(titem) == img
+    end
+
+    @testset ExtendedTestSet "FlipZ 3D: flip dimension of 1 = identity" begin
+        tfm = FlipZ{3}()
+        img = rand(RGB, 10, 10, 1)
+        item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
+        titem = apply(tfm, item)
+        @test itemdata(titem) == img
+    end
+
     @testset ExtendedTestSet "`RandomCrop` correct indices" begin
-        # Flipping and cropping should be the same as reverse-indexing
+        # Flipping followed by cropping should be the same as reverse-indexing
         # the flipped dimension
         tfm = FlipX{2}() |> RandomCrop((64, 64)) |> PinOrigin()
         img = rand(RGB, 64, 64)

From a514e33240dcffcb0e5e8303e33a1d5cb706a5f0 Mon Sep 17 00:00:00 2001
From: Isabelle Tan <isabelle.tan@medivation.ch>
Date: Mon, 6 Mar 2023 17:27:50 +0100
Subject: [PATCH 5/6] add tests for all 2D and 3D flip indices, add test for
 double flip = identity

---
 test/projective/affine.jl | 58 ++++++++++++++++++++++++++++-----------
 1 file changed, 42 insertions(+), 16 deletions(-)

diff --git a/test/projective/affine.jl b/test/projective/affine.jl
index 8b7baa3e..6b8f9bc9 100644
--- a/test/projective/affine.jl
+++ b/test/projective/affine.jl
@@ -139,34 +139,60 @@ include("../imports.jl")
         @test_nowarn apply!(buffer, tfm, image2)
     end
 
-    @testset ExtendedTestSet "FlipX 2D: flip dimension of 1 = identity" begin
-        tfm = FlipX{2}()
-        img = rand(RGB, 10, 1)
+
+    @testset ExtendedTestSet "FlipX 2D correct indices" begin
+        tfm = FlipX{2}() |> RandomCrop((10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10)
         item = Image(img)
         @test_nowarn titem = apply(tfm, item)
         titem = apply(tfm, item)
-        @test itemdata(titem) == img
+        @test itemdata(titem) == img[:, end:-1:1]
     end
 
-    @testset ExtendedTestSet "FlipZ 3D: flip dimension of 1 = identity" begin
-        tfm = FlipZ{3}()
-        img = rand(RGB, 10, 10, 1)
+    @testset ExtendedTestSet "FlipY 2D correct indices" begin
+        tfm = FlipY{2}() |> RandomCrop((10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10)
         item = Image(img)
         @test_nowarn titem = apply(tfm, item)
         titem = apply(tfm, item)
-        @test itemdata(titem) == img
+        @test itemdata(titem) == img[end:-1:1, :]
     end
 
-    @testset ExtendedTestSet "`RandomCrop` correct indices" begin
-        # Flipping followed by cropping should be the same as reverse-indexing
-        # the flipped dimension
-        tfm = FlipX{2}() |> RandomCrop((64, 64)) |> PinOrigin()
-        img = rand(RGB, 64, 64)
+
+    @testset ExtendedTestSet "FlipX 3D correct indices" begin
+        tfm = FlipX{3}() |> RandomCrop((10,10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10, 10)
         item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
         titem = apply(tfm, item)
-        timg = itemdata(titem)
-        rimg = img[:, end:-1:1]
-        @test titem.data == rimg
+        @test itemdata(titem) == img[end:-1:1, :, :]
+    end
+
+    @testset ExtendedTestSet "FlipY 3D correct indices" begin
+        tfm = FlipY{3}() |> RandomCrop((10,10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10, 10)
+        item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
+        titem = apply(tfm, item)
+        @test itemdata(titem) == img[:, end:-1:1, :]
+    end
+
+    @testset ExtendedTestSet "FlipZ 3D correct indices" begin
+        tfm = FlipZ{3}() |> RandomCrop((10,10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10, 10)
+        item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
+        titem = apply(tfm, item)
+        @test itemdata(titem) == img[:, :, end:-1:1]
+    end
+
+    @testset ExtendedTestSet "Double flip is identity" begin
+        tfm = FlipZ{3}() |> FlipZ{3}() |> RandomCrop((10,10,10)) |> PinOrigin()
+        img = rand(RGB, 10, 10, 10)
+        item = Image(img)
+        @test_nowarn titem = apply(tfm, item)
+        titem = apply(tfm, item)
+        @test itemdata(titem) == img
     end
 end
 

From 65eb33cf1d22a9eb57c376c3a819aa9444d26201 Mon Sep 17 00:00:00 2001
From: Paul Novotny <mail@paulnovo.us>
Date: Sat, 28 Sep 2024 10:26:23 -0400
Subject: [PATCH 6/6] Fix Flips documentation and tests errors caused by master
 merge

This adds missing documentation for the Flip transformations, and adds
FlipDim to the reference page. Also, fixes the "Big Pipeline/3D" unit
test that was failing due to not being able to compose two
ComposedProjectiveTransforms.
---
 docs/src/ref.md             |  1 +
 docs/src/transformations.md |  1 +
 src/DataAugmentation.jl     |  1 +
 src/projective/affine.jl    | 23 ++++++++++++++++++++++-
 src/projective/compose.jl   |  3 +++
 5 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/docs/src/ref.md b/docs/src/ref.md
index 2790a29c..433e0425 100644
--- a/docs/src/ref.md
+++ b/docs/src/ref.md
@@ -6,6 +6,7 @@ BoundingBox
 CenterCrop
 CenterResizeCrop
 Crop
+FlipDim
 FlipX
 FlipY
 FlipZ
diff --git a/docs/src/transformations.md b/docs/src/transformations.md
index 472c51c1..13e154bc 100644
--- a/docs/src/transformations.md
+++ b/docs/src/transformations.md
@@ -26,6 +26,7 @@ Projective transformations include:
 Affine transformations are a subgroup of projective transformations that can be composed very efficiently: composing two affine transformations results in another affine transformation. Affine transformations can represent translation, scaling, reflection and rotation. Available `Transform`s are:
 
 ```@docs; canonical=false
+FlipDim
 FlipX
 FlipY
 FlipZ
diff --git a/src/DataAugmentation.jl b/src/DataAugmentation.jl
index 76ed2b9f..2f307f37 100644
--- a/src/DataAugmentation.jl
+++ b/src/DataAugmentation.jl
@@ -84,6 +84,7 @@ export Item,
     apply,
     Reflect,
     WarpAffine,
+    FlipDim,
     FlipX,
     FlipY,
     FlipZ,
diff --git a/src/projective/affine.jl b/src/projective/affine.jl
index b9352ca7..e53798ca 100644
--- a/src/projective/affine.jl
+++ b/src/projective/affine.jl
@@ -258,8 +258,11 @@ end
 
 """
     FlipDim{N}(dim)
+
 Reflect `N` dimensional data along the axis of dimension `dim`. Must satisfy 1 <= `dim` <= `N`.
+
 ## Examples
+
 ```julia
 tfm = FlipDim{2}(1)
 ```
@@ -269,15 +272,33 @@ struct FlipDim{N} <: ProjectiveTransform
     FlipDim{N}(dim) where N = 1 <= dim <= N ? new{N}(dim) : error("invalid dimension")
 end
 
-# 2D images use (r, c) = (y, x) convention
+"""
+    FlipX{N}()
+
+Flip `N` dimensional data along the x-axis. 2D images use (r, c) = (y, x)
+convention such that x-axis flips occur along the second dimension. For N >= 3,
+x-axis flips occur along the first dimension.
+"""
 struct FlipX{N}
     FlipX{N}() where N = FlipDim{N}(N==2 ? 2 : 1)
 end
 
+"""
+    FlipY{N}()
+
+Flip `N` dimensional data along the y-axis. 2D images use (r, c) = (y, x)
+convention such that y-axis flips occur along the first dimension. For N >= 3,
+y-axis flips occur along the second dimension.
+"""
 struct FlipY{N}
     FlipY{N}() where N = FlipDim{N}(N==2 ? 1 : 2)
 end
 
+"""
+    FlipZ{N}()
+
+Flip `N` dimensional data along the z-axis.
+"""
 struct FlipZ{N}
     FlipZ{N}() where N = FlipDim{N}(3)
 end
diff --git a/src/projective/compose.jl b/src/projective/compose.jl
index 4562b30e..48b62cf7 100644
--- a/src/projective/compose.jl
+++ b/src/projective/compose.jl
@@ -26,6 +26,9 @@ compose(composed::ComposedProjectiveTransform, tfm::ProjectiveTransform) =
 compose(tfm::ProjectiveTransform, composed::ComposedProjectiveTransform) =
     ComposedProjectiveTransform(tfm, composed.tfms...)
 
+compose(composed1::ComposedProjectiveTransform, composed2::ComposedProjectiveTransform) =
+    ComposedProjectiveTransform(composed1.tfms..., composed2.tfms...)
+
 
 # The random state is collected from the transformations that make up the
 # `ComposedProjectiveTransform`: