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imresize/imrotate fixed point #129

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imresize/imrotate fixed point #129

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515f11b
add imresize with fixed_point
ginkulv Jun 6, 2021
342c9fd
add struct FixedPoint
ginkulv Jun 7, 2021
8c60c63
add examples of imresize with fixed point
ginkulv Jun 7, 2021
1d3fee9
rename FixedPoint to CenterPoint
ginkulv Jun 8, 2021
81ffd49
refactor imresize with FixedPoint
ginkulv Jun 30, 2021
cb837d7
add some tests and fix the description for CenterPoint
ginkulv Jul 2, 2021
dd9d5c7
add some tests
ginkulv Jul 23, 2021
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4 changes: 3 additions & 1 deletion src/ImageTransformations.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,10 @@ export
warpedview,
InvWarpedView,
invwarpedview,
imrotate
imrotate,
CenterPoint

include("centerpoint.jl")
include("autorange.jl")
include("interpolations.jl")
include("warp.jl")
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16 changes: 16 additions & 0 deletions src/centerpoint.jl
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
"""
CenterPoint(dims) -> cp

Create a fixed point which can be used in `imresize` and `imrotate`
functions in order to keep the value in this point the same, i.e.,

```julia
img[cp] == imgr[cp]
```
"""
struct CenterPoint{N}
p::CartesianIndex{N}
end

CenterPoint(dims::Dims{N}) where N = CenterPoint{N}(CartesianIndex(dims))
CenterPoint(dims::Int64...) = CenterPoint(Tuple(dims))
21 changes: 20 additions & 1 deletion src/resizing.jl
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Expand Up @@ -57,7 +57,7 @@ upsample/downsample the image `img` to a given size `sz` or axes `inds` using in
The output size is `ceil(Int, size(img).*ratio)`. If `ratio` is larger than `1`, it is
an upsample operation. Otherwise it is a downsample operation. `ratio` can also be a tuple,
in which case `ratio[i]` specifies the resize ratio at dimension `i`.
- `method::InterpolationType`:
- `method::InterpolationType`:
specify the interpolation method used for reconstruction. conveniently, `methold` can
also be a `Degree` type, in which case a `BSpline` object will be created.
For example, `method = Linear()` is equivalent to `method = BSpline(Linear())`.
Expand All @@ -83,6 +83,10 @@ imresize(img, (1:256, )) # 256*768
imresize(img, ratio = 0.5) #256*384
imresize(img, ratio = (2, 1)) # 1024*768

# pass `CenterPoint`
imresize(img, (256, 384), CenterPoint(10, 15)) # 256*384, img[10,15] ≈ imgr[10,15]
imresize(img, CenterPoint(10, 15), ratio = 0.5) # 256*384, img[10,15] ≈ imgr[10,15]

# use different interpolation method
imresize(img, (256, 384), method=Linear()) # 256*384 bilinear interpolation
imresize(img, (256, 384), method=Lanczos4OpenCV()) # 256*384 OpenCV-compatible Lanczos 4 interpolation
Expand Down Expand Up @@ -120,6 +124,21 @@ function imresize(original::AbstractArray{T,N}, new_inds::Indices{N}; kwargs...)
end
end

function imresize(original::AbstractArray{T,N}, new_size::Dims{N}, center_point::CenterPoint{N}; kwargs...) where {T,N}
Tnew = imresize_type(first(original))
cp = center_point.p
checkbounds(original, cp)
topleft = firstindex.(Ref(original), Tuple(1:N))
offset = @. cp.I - new_size * (cp.I - topleft) ÷ $size(original) - 1
newimage = OffsetArray(similar(original, Tnew, new_size), offset)
imresize!(newimage, original; kwargs...)
end

function imresize(original::AbstractArray{T,N}, center_point::CenterPoint{N}; ratio, kwargs...) where {T,N}
all(ratio .> 0) || throw(ArgumentError("ratio $ratio should be positive"))
new_size = ceil.(Int, size(original) .* ratio) # use ceil to avoid 0
imresize(original, new_size, center_point; kwargs...)
end
# To choose the output type, rather than forcing everything to
# Float64 by multiplying by 1.0, we exploit the fact that the scale
# changes correspond to integer ratios. We mimic ratio arithmetic
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32 changes: 32 additions & 0 deletions test/resizing.jl
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Expand Up @@ -47,17 +47,23 @@ end
test_imresize_interface(img, (5,10), (5,))
test_imresize_interface(img, (5,10), 1:5) # FIXME: @inferred failed
test_imresize_interface(img, (5,10), (1:5,)) # FIXME: @inferred failed
test_imresize_interface(img, (5,5), (5,5), CenterPoint(1, 1))
test_imresize_interface(img, (20,20), CenterPoint(1, 1), ratio = 2)
test_imresize_interface(img, (20,10), CenterPoint(1, 1), ratio = (2, 1))
Comment on lines +50 to +52
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This only makes sure the function gets called and outputs something. We also need to test if the output is correct, for example:

  • test if imresize(img, (20,20), CenterPoint(1, 1)) works the same as imresize(img, (20,20))
  • test if imresize(img, (20, 20), CenterPoint(5, 5); method=Constant())[5, 5] == img[5, 5] (If I'm right about the implementation, I'm not sure if it's [5, 5] here).
  • If it's not supported, test if imresize(imag, (20, 20), CenterPoint(-10, -10)) errors.

Also, OffsetArray is used widely in the ecosystem, so it would be great to also test OffsetArray(img, -1, -1) works normally for the above test cases.

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About testing if the CenterPoint doesn't change, without overriding the value it can be actully quite different, so either we should override it or it won't be ensured. Except this point I'm working on it.

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@johnnychen94 johnnychen94 Jul 8, 2021 •
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Yep, I also noticed this. BSpline(Constant()) is the nearest interpolation, I believe by using this method, it won't doesn't change the value?

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Yes, that's right.


@test_throws MethodError imresize(img,5.0,5.0)
@test_throws MethodError imresize(img,(5.0,5.0))
@test_throws MethodError imresize(img,(5, 5.0))
@test_throws MethodError imresize(img,[5,5])
@test_throws UndefKeywordError imresize(img)
@test_throws UndefKeywordError imresize(img, CenterPoint(1, 1))
@test_throws DimensionMismatch imresize(img,(5,5,5))
@test_throws ArgumentError imresize(img, ratio = -0.5)
@test_throws ArgumentError imresize(img, ratio = (-0.5, 1))
@test_throws ArgumentError imresize(img, CenterPoint(1, 1), ratio = -0.5)
@test_throws DimensionMismatch imresize(img, ratio=(5,5,5))
@test_throws DimensionMismatch imresize(img, (5,5,1))
@test_throws BoundsError imresize(img, (5,5), CenterPoint(100, 100))
end
end

Expand Down Expand Up @@ -149,6 +155,32 @@ end
out = imresize(img, (0:127, 0:127), method=Lanczos4OpenCV())
@test axes(out) == (0:127, 0:127)
@test OffsetArrays.no_offset_view(out) == imresize(img, (128, 128), method=Lanczos4OpenCV())

@test imresize(img, (128,128), method=Linear()) == imresize(img, (128,128), CenterPoint(1,1), method=Linear())
@test imresize(img, (128,128), method=BSpline(Linear())) == imresize(img, (128,128), CenterPoint(1,1), method=BSpline(Linear()))
@test imresize(img, (128,128), method=Lanczos4OpenCV()) == imresize(img, (128,128), CenterPoint(1,1), method=Lanczos4OpenCV())

out = imresize(OffsetArray(img, -1, -1), (128,128), CenterPoint(1,1), method=Linear())
@test imresize(img, (128,128), method=Linear()) == OffsetArrays.no_offset_view(out)

out = imresize(OffsetArray(img, -1, -1), (128,128), CenterPoint(1,1), method=BSpline(Linear()))
@test imresize(img, (128,128), method=BSpline(Linear())) == OffsetArrays.no_offset_view(out)

out = imresize(OffsetArray(img, -1, -1), (128,128), CenterPoint(1,1), method=Lanczos4OpenCV())
@test imresize(img, (128,128), method=Lanczos4OpenCV()) == OffsetArrays.no_offset_view(out)

#check negative CenterPoint
out = imresize(OffsetArray(img, -2, -2), (128,128), CenterPoint(-1,-1), method=Linear())
@test imresize(img, (128,128), method=Linear()) == OffsetArrays.no_offset_view(out)

out = imresize(OffsetArray(img, -2, -2), (128,128), CenterPoint(-1,-1), method=BSpline(Linear()))
@test imresize(img, (128,128), method=BSpline(Linear())) == OffsetArrays.no_offset_view(out)

out = imresize(OffsetArray(img, -2, -2), (128,128), CenterPoint(-1,-1), method=Lanczos4OpenCV())
@test imresize(img, (128,128), method=Lanczos4OpenCV()) == OffsetArrays.no_offset_view(out)

#check CenterPoint consistency
@test imresize(img, (128, 128), CenterPoint(5, 5), method=Constant())[5,5] == img[5,5]
end
end

Expand Down