# Extract coordinates from a specific contour

**URL:** <https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393>\
**Category:** Visualization\
**Tags:** gmt\
**Created:** [April 28, 2020, 7:17pm UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393 "2020-04-28T19:17:42Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Cristian\_Suciava](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cristian_suciava/32/14433_2.png) [@Cristian\_Suciava](https://discourse.julialang.org/u/Cristian_Suciava)\
**Post date:** [April 28, 2020, 7:17pm UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/1 "2020-04-28T19:17:42Z")

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I am new with Julia.  
Is there a library, a way, to extract cartesian coordinates from a drawing?  
At the end I need an array with point from a drawing.

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**Author:** ![sdanisch](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sdanisch/32/1406_2.png) [@sdanisch](https://discourse.julialang.org/u/sdanisch)\
**Post date:** [April 28, 2020, 7:39pm UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/2 "2020-04-28T19:39:49Z")

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This should be what you’re looking for:

> **[GitHub - JuliaGeometry/Contour.jl: Calculating contour curves for 2D scalar...](https://github.com/JuliaGeometry/Contour.jl)**
>
> Calculating contour curves for 2D scalar fields in Julia - GitHub - JuliaGeometry/Contour.jl: Calculating contour curves for 2D scalar fields in Julia

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<div class="post-metadata">

**Author:** ![sdanisch](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sdanisch/32/1406_2.png) [@sdanisch](https://discourse.julialang.org/u/sdanisch)\
**Post date:** [April 28, 2020, 7:40pm UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/3 "2020-04-28T19:40:42Z")

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Btw, there is this website, to discover packages:  
[JuliaHub](https://juliahub.com/ui/Packages?q=Contour) 🙂

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<div class="post-metadata">

**Author:** ![Cristian\_Suciava](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cristian_suciava/32/14433_2.png) [@Cristian\_Suciava](https://discourse.julialang.org/u/Cristian_Suciava)\
**Post date:** [April 30, 2020, 5:25am UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/4 "2020-04-30T05:25:43Z")

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this only makes contour from points. so not quite what I need.  
Thanks for the searching tip.

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**Author:** ![Zach\_Christensen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/zach_christensen/32/7220_2.png) [@Zach\_Christensen](https://discourse.julialang.org/u/Zach_Christensen)\
**Post date:** [April 30, 2020, 5:50am UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/5 "2020-04-30T05:50:47Z")

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You can extract cartesian points from the output of Contour.jl. If you want to find cartesian coordinates that meet some feature requirement within the drawing then we’d need to know what it is your doing before we could provide any more help.

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<div class="post-metadata">

**Author:** ![joa-quim](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/joa-quim/32/227_2.png) [@joa-quim](https://discourse.julialang.org/u/joa-quim)\
**Post date:** [April 30, 2020, 11:53am UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/6 "2020-04-30T11:53:39Z")

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Easy with [GMT.jl](https://github.com/GenericMappingTools/GMT.jl)

```julia
using GMT
# Create an example grid
G = GMT.peaks();

# Get the contours a interval of 2
D = grdcontour(G, cont=2, dump=true)
Array{GMT.GMTdataset,1} with 11 segments
Header1: -6 contour -Z-6
Header2: -4 contour -Z-4
Header3: -2 contour -Z-2
Header4: -2 contour -Z-2
Header5: 0 contour -Z0
Header6: 0 contour -Z0
Header7: 2 contour -Z2
Header8: 2 contour -Z2
Header9: 4 contour -Z4
Header10: 6 contour -Z6
Header11: 8 contour -Z8
First segment DATA
15×3 Array{Float64,2}:
  0.125 -1.47679 -6.0
  0.25 -1.44115 -6.0
  0.375 -1.46158 -6.0
  0.428516 -1.5 -6.0
  ...

# Plot them if wanted.
plot(D, aspect=:equal, name="contours.png", show=true)

```

 ![contours](https://global.discourse-cdn.com/julialang/original/3X/d/1/d177d5aedd398d0380d23d5ccafd2309bf45abb7.png)

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<div class="post-metadata">

**Author:** ![Cristian\_Suciava](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cristian_suciava/32/14433_2.png) [@Cristian\_Suciava](https://discourse.julialang.org/u/Cristian_Suciava)\
**Post date:** [May 2, 2020, 6:38pm UTC](https://discourse.julialang.org/t/extract-coordinates-from-a-specific-contour/38393/7 "2020-05-02T18:38:30Z")

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thank you for your replies.  
I tried ImageSegmentation.  
Not yet there.