# How to use dilate in Julia

**URL:** https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241
**Category:** Signal and Image Processing
**Tags:** images, python
**Created:** [July 17, 2020, 2:26pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241 "2020-07-17T14:26:11Z")
**Posts on this page:** 10
**Page:** 1

<div class="post-metadata">

### Author: ![sudo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sudo/32/16342_2.png) [@sudo](https://discourse.julialang.org/u/sudo)
#### Post date: [July 17, 2020, 2:26pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/1 "2020-07-17T14:26:11Z")

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Hi! I am looking for something similar to python’s dilation function in skimage.morphology. I want to achieve precisely the following functionality:

```julia
>>> import numpy as np
>>> from skimage.morphology import dilation
>>> from skimage.morphology import disk

>>> bright_pixel = np.array([[0, 0, 0, 0, 0], 
                             [0, 0, 0, 0, 0], 
                             [0, 0, 1, 0, 0], 
                             [0, 0, 0, 0, 0], 
                             [0, 0, 0, 0, 0]], dtype=np.uint8)
>>> dilation(bright_pixel, disk(1))
array([[0, 0, 0, 0, 0],
       [0, 0, 1, 0, 0],
       [0, 1, 1, 1, 0],
       [0, 0, 1, 0, 0],
       [0, 0, 0, 0, 0]], dtype=uint8)

```

Can you suggest how to implement the same in Julia?

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### Author: ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)
#### Post date: [July 17, 2020, 2:36pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/2 "2020-07-17T14:36:49Z")

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Images.jl’s morphology tools currently only allow operations on rectangular windows (see [https://github.com/JuliaImages/ImageMorphology.jl/issues/11](https://github.com/JuliaImages/ImageMorphology.jl/issues/11)). If a rectangular window is acceptable,

```julia
julia> using Images

julia> bright_pixel = zeros(Gray{N0f8}, 5, 5); bright_pixel[3,3] = 1;

julia> dilate(bright_pixel)
5×5 Array{Gray{N0f8},2} with eltype Gray{Normed{UInt8,8}}:
 Gray{N0f8}(0.0) Gray{N0f8}(0.0) … Gray{N0f8}(0.0) Gray{N0f8}(0.0)
 Gray{N0f8}(0.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(0.0)
 Gray{N0f8}(0.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(0.0)
 Gray{N0f8}(0.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(0.0)
 Gray{N0f8}(0.0) Gray{N0f8}(0.0) Gray{N0f8}(0.0) Gray{N0f8}(0.0)

julia> Int.(ans)
5×5 Array{Int64,2}:
 0 0 0 0 0
 0 1 1 1 0
 0 1 1 1 0
 0 1 1 1 0
 0 0 0 0 0

```

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### Author: ![sudo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sudo/32/16342_2.png) [@sudo](https://discourse.julialang.org/u/sudo)
#### Post date: [July 17, 2020, 3:48pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/3 "2020-07-17T15:48:33Z")

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I tried using the same function but I couldn’t find how to specify squares for dilation. For instance, can you tell me how do I modify the above code to get dilation of mode than one pixel on each side?

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### Author: ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)
#### Post date: [July 17, 2020, 4:12pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/4 "2020-07-17T16:12:38Z")

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Sorry, I assumed it allowed rectangular windows, but all you can do is include/exclude dimensions from dilation:

```julia
help?> dilate
search: dilate dilate! assert_timedim_last AdaptiveEqualization

  imgd = dilate(img, [region])

  perform a max-filter over nearest-neighbors. The default is 8-connectivity
  in 2d, 27-connectivity in 3d, etc. You can specify the list of dimensions
  that you want to include in the connectivity, e.g., region = [1,2] would
  exclude the third dimension from filtering.

```

You could instead use `mapwindow` as follows:

```julia
julia> mapwindow(maximum, bright_pixel, (3, 5))
5×5 Array{Gray{N0f8},2} with eltype Gray{Normed{UInt8,8}}:
 Gray{N0f8}(0.0) Gray{N0f8}(0.0) … Gray{N0f8}(0.0) Gray{N0f8}(0.0)
 Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0)
 Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0)
 Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0) Gray{N0f8}(1.0)
 Gray{N0f8}(0.0) Gray{N0f8}(0.0) Gray{N0f8}(0.0) Gray{N0f8}(0.0)

julia> Int.(ans)
5×5 Array{Int64,2}:
 0 0 0 0 0
 1 1 1 1 1
 1 1 1 1 1
 1 1 1 1 1
 0 0 0 0 0

```

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### Author: ![sudo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sudo/32/16342_2.png) [@sudo](https://discourse.julialang.org/u/sudo)
#### Post date: [July 17, 2020, 4:29pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/5 "2020-07-17T16:29:33Z")

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Thanks for your pointer. I think I can work with this for now. However, do you have an idea how to implement the max filter in case I want to implement it myself? Any pointer in that direction will be helpful.

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### Author: ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)
#### Post date: [July 17, 2020, 4:52pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/6 "2020-07-17T16:52:12Z")

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You can always inspect how Julia’s functions are implemented with `@edit`, e.g. `@edit dilate(bright_pixel)`. You may want to look at `StaticKernels.jl` or `LoopVectorization.jl` if you need a particular dilation region.

```julia
julia> using StaticKernels

julia> k = StaticKernels.Kernel{(-1:1, -2:2)}(w -> maximum(Tuple(w)))
Kernel{(-1:1, -2:2)} with window function #13

julia> map(k, extend(bright_pixel, StaticKernels.ExtensionNothing())) .|> Int
5×5 Array{Int64,2}:
 0 0 0 0 0
 1 1 1 1 1
 1 1 1 1 1
 1 1 1 1 1
 0 0 0 0 0

```

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### Author: ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)
#### Post date: [July 17, 2020, 7:48pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/8 "2020-07-17T19:48:36Z")

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Can you post a MWE? It works fine for me:

```julia
julia> bright_pixel = zeros(N0f8, 5300, 3050); bright_pixel[3,3] = 1;

julia> mapwindow(maximum, bright_pixel, (3, 5))
5300×3050 Array{N0f8,2} with eltype Normed{UInt8,8}:
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 … 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 1.0 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 1.0 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 1.0 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 … 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 ⋮ ⋮ ⋱ ⋮
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 … 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 … 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
```

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### Author: ![sudo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sudo/32/16342_2.png) [@sudo](https://discourse.julialang.org/u/sudo)
#### Post date: [July 19, 2020, 6:30am UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/9 "2020-07-19T06:30:15Z")

</div>

I did not assign the value to any variable and was losing the progress. I thought mapwindow changed the array in place. My bad.

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### Author: ![GunnarFarneback](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gunnarfarneback/32/1827_2.png) [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)
#### Post date: [July 19, 2020, 8:46am UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/10 "2020-07-19T08:46:02Z")

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If you have binary images you can emulate dilation with linear filtering.

```julia
using ImageFiltering
kernel = centered([0 1 0;1 1 1;0 1 0])
dilated = imfilter(bright_pixel, kernel) .> 0

```

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### Author: ![aplavin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/aplavin/32/222056_2.png) [@aplavin](https://discourse.julialang.org/u/aplavin)
#### Post date: [July 19, 2020, 1:58pm UTC](https://discourse.julialang.org/t/how-to-use-dilate-in-julia/43241/11 "2020-07-19T13:58:05Z")

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There is a `dilate` function doing exactly what you need in `LocalFilters.jl`: `dilate(array, 5)` for a rectangular kernel of size 5, or `dilate(array, kernel)` for an arbitrary kernel that is represented as an array.