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Frontmatter

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Author 1

Click somewhere on the image

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8.2 ms
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@bind click_coord_fractional clicktracker(philip_head)
1.7 s

The bound variable is the click position, as fractional coordinate (x,y)∈[0,1]2.

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5.0 ms
missing
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click_coord_fractional
18.3 μs

We can use the dimensions of the image to turn that into integer indices:

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263 μs
click_pos = let
if click_coord_fractional === missing
(5,5)
else
x, y = click_coord_fractional

to_index(x, dim) = let
s = size(philip_head)[dim]
clamp(ceil(Int, x * s), 1, s)
end

to_index(y, 1), to_index(x, 2)
end
end
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1.3 ms
sample_1x1 = philip_head[click_pos[1], click_pos[2]]
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18.4 μs
sample_7x7 = let
row, col = click_pos
philip_head[row-3:row+3, col-3:col+3]
end
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39.7 μs

Tracker code

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222 μs
clicktracker (generic function with 1 method)
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5.2 ms

Appendix

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209 μs
begin
import Pkg
Pkg.activate(mktempdir())
Pkg.add([
Pkg.PackageSpec(name="Images", version="0.23"),
Pkg.PackageSpec(name="ImageMagick", version="1"),
Pkg.PackageSpec(name="PlutoUI", version="0.7"),
Pkg.PackageSpec(name="HypertextLiteral", version="0.5")
])

using Images
using PlutoUI
using HypertextLiteral
end
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❔
  Activating new project at `/tmp/jl_UCyAR8`
    Updating registry at `~/.julia/registries/General.toml`
   Resolving package versions...
   Installed PlutoUI ─ v0.7.9
    Updating `/tmp/jl_UCyAR8/Project.toml`
  [ac1192a8] + HypertextLiteral v0.5.2
  [6218d12a] + ImageMagick v1.3.0
  [916415d5] + Images v0.23.3
  [7f904dfe] + PlutoUI v0.7.9
    Updating `/tmp/jl_UCyAR8/Manifest.toml`
  [621f4979] + AbstractFFTs v1.5.0
  [79e6a3ab] + Adapt v4.2.0
  [13072b0f] + AxisAlgorithms v1.0.1
  [39de3d68] + AxisArrays v0.4.7
  [aafaddc9] + CatIndices v0.2.2
  [d360d2e6] + ChainRulesCore v1.25.1
  [9e997f8a] + ChangesOfVariables v0.1.9
  [3da002f7] + ColorTypes v0.10.12
  [c3611d14] + ColorVectorSpace v0.8.7
  [5ae59095] + Colors v0.12.11
  [34da2185] + Compat v4.16.0
  [ed09eef8] + ComputationalResources v0.3.2
  [150eb455] + CoordinateTransformations v0.6.3
  [dc8bdbbb] + CustomUnitRanges v1.0.2
  [9a962f9c] + DataAPI v1.16.0
  [864edb3b] + DataStructures v0.18.20
  [b4f34e82] + Distances v0.10.12
  [ffbed154] + DocStringExtensions v0.9.3
  [4f61f5a4] + FFTViews v0.3.2
  [7a1cc6ca] + FFTW v1.8.1
  [5789e2e9] + FileIO v1.17.0
  [53c48c17] + FixedPointNumbers v0.8.5
  [a2bd30eb] + Graphics v1.1.3
  [ac1192a8] + HypertextLiteral v0.5.2
  [bbac6d45] + IdentityRanges v0.3.1
  [2803e5a7] + ImageAxes v0.6.9
  [f332f351] + ImageContrastAdjustment v0.3.7
  [a09fc81d] + ImageCore v0.8.22
  [51556ac3] + ImageDistances v0.2.13
  [6a3955dd] + ImageFiltering v0.6.21
  [6218d12a] + ImageMagick v1.3.0
  [bc367c6b] + ImageMetadata v0.9.5
  [787d08f9] + ImageMorphology v0.2.11
  [2996bd0c] + ImageQualityIndexes v0.2.2
  [4e3cecfd] + ImageShow v0.2.3
  [02fcd773] + ImageTransformations v0.8.13
  [916415d5] + Images v0.23.3
  [9b13fd28] + IndirectArrays v0.5.1
  [a98d9a8b] + Interpolations v0.13.6
  [8197267c] + IntervalSets v0.7.10
  [3587e190] + InverseFunctions v0.1.17
  [92d709cd] + IrrationalConstants v0.1.1
  [c8e1da08] + IterTools v1.4.0
  [692b3bcd] + JLLWrappers v1.7.0
  [682c06a0] + JSON v0.21.4
  [2ab3a3ac] + LogExpFunctions v0.3.28
  [1914dd2f] + MacroTools v0.5.15
  [dbb5928d] + MappedArrays v0.4.2
  [e1d29d7a] + Missings v1.2.0
  [e94cdb99] + MosaicViews v0.3.4
  [77ba4419] + NaNMath v1.0.3
  [6fe1bfb0] + OffsetArrays v1.15.0
  [bac558e1] + OrderedCollections v1.8.0
  [5432bcbf] + PaddedViews v0.5.12
  [d96e819e] + Parameters v0.12.3
  [69de0a69] + Parsers v2.8.1
  [7f904dfe] + PlutoUI v0.7.9
  [aea7be01] + PrecompileTools v1.2.1
  [21216c6a] + Preferences v1.4.3
  [94ee1d12] + Quaternions v0.7.6
  [b3c3ace0] + RangeArrays v0.3.2
  [c84ed2f1] + Ratios v0.4.5
  [c1ae055f] + RealDot v0.1.0
  [3cdcf5f2] + RecipesBase v1.3.4
  [189a3867] + Reexport v1.2.2
  [ae029012] + Requires v1.3.1
  [6038ab10] + Rotations v1.7.1
  [699a6c99] + SimpleTraits v0.9.4
  [a2af1166] + SortingAlgorithms v1.2.1
  [276daf66] + SpecialFunctions v1.8.8
  [cae243ae] + StackViews v0.1.1
  [90137ffa] + StaticArrays v1.9.13
  [1e83bf80] + StaticArraysCore v1.4.3
  [82ae8749] + StatsAPI v1.7.0
  [2913bbd2] + StatsBase v0.33.21
  [fd094767] + Suppressor v0.2.8
  [06e1c1a7] + TiledIteration v0.3.1
  [3a884ed6] + UnPack v1.0.2
  [efce3f68] + WoodburyMatrices v0.5.6
  [f5851436] + FFTW_jll v3.3.10+3
  [c73af94c] + ImageMagick_jll v6.9.10-12+3
  [1d5cc7b8] + IntelOpenMP_jll v2025.0.4+0
  [aacddb02] + JpegTurbo_jll v3.1.1+0
  [88015f11] + LERC_jll v3.0.0+1
  [89763e89] + Libtiff_jll v4.4.0+0
  [856f044c] + MKL_jll v2025.0.1+1
  [efe28fd5] + OpenSpecFun_jll v0.5.6+0
  [3161d3a3] + Zstd_jll v1.5.7+1
  [b53b4c65] + libpng_jll v1.6.47+0
  [1317d2d5] + oneTBB_jll v2022.0.0+0
  [0dad84c5] + ArgTools
  [56f22d72] + Artifacts
  [2a0f44e3] + Base64
  [ade2ca70] + Dates
  [8ba89e20] + Distributed
  [f43a241f] + Downloads
  [7b1f6079] + FileWatching
  [b77e0a4c] + InteractiveUtils
  [4af54fe1] + LazyArtifacts
  [b27032c2] + LibCURL
  [76f85450] + LibGit2
  [8f399da3] + Libdl
  [37e2e46d] + LinearAlgebra
  [56ddb016] + Logging
  [d6f4376e] + Markdown
  [a63ad114] + Mmap
  [ca575930] + NetworkOptions
  [44cfe95a] + Pkg
  [de0858da] + Printf
  [3fa0cd96] + REPL
  [9a3f8284] + Random
  [ea8e919c] + SHA
  [9e88b42a] + Serialization
  [1a1011a3] + SharedArrays
  [6462fe0b] + Sockets
  [2f01184e] + SparseArrays
  [10745b16] + Statistics
  [fa267f1f] + TOML
  [a4e569a6] + Tar
  [8dfed614] + Test
  [cf7118a7] + UUIDs
  [4ec0a83e] + Unicode
  [e66e0078] + CompilerSupportLibraries_jll
  [deac9b47] + LibCURL_jll
  [29816b5a] + LibSSH2_jll
  [c8ffd9c3] + MbedTLS_jll
  [14a3606d] + MozillaCACerts_jll
  [4536629a] + OpenBLAS_jll
  [05823500] + OpenLibm_jll
  [83775a58] + Zlib_jll
  [8e850b90] + libblastrampoline_jll
  [8e850ede] + nghttp2_jll
  [3f19e933] + p7zip_jll
Precompiling project...
  ✓ PlutoUI
  1 dependency successfully precompiled in 2 seconds (96 already precompiled)
8.6 s
"https://user-images.githubusercontent.com/6933510/107239146-dcc3fd00-6a28-11eb-8c7b-41aaf6618935.png"
url = "https://user-images.githubusercontent.com/6933510/107239146-dcc3fd00-6a28-11eb-8c7b-41aaf6618935.png"
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13.8 μs
"/tmp/jl_kvVhUp"
philip_filename = download(url) # download to a local file. The filename is returned
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1.1 s
philip = load(philip_filename);
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1.3 s
philip_head = philip[400:800,100:400];
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406 μs