Feature request: contour labels #832

briochemc · 2021-02-01T06:15:38Z

I don't think one can annotate contours with values in Makie (yet), for example (matplotlib):

I could not find an existing issue for this, so I thought I'd create one! 😃

FWIW, I only found this discourse post with a potential workaround, with this plot:

jkrumbiegel · 2021-02-01T09:48:18Z

For this we would need this PR JuliaPlots/AbstractPlotting.jl#430 to be merged, which is still stuck at the GLMakie implementation

carstenbauer · 2021-04-14T07:42:06Z

Came up on discourse again: https://discourse.julialang.org/t/how-to-add-value-labels-on-top-of-contours-in-makie/59242

Now that #430 is merged this should be possible somehow?

SimonDanisch · 2021-04-14T09:39:11Z

Yeah it does work nicely now:

using GLMakie

np = 500
nc = 200
f(x) = 2*x+1
x = LinRange(-1,1,f(np))
y = rand(f(np))*2 .- 1
x_c = LinRange(-nc/np,nc/np,f(nc))
y_c = LinRange(-nc/np,nc/np,f(nc))
c_mat = @. x_c^2 + y_c'^2
fig, ax, hp = heatmap(x_c, y_c, c_mat)
cplot = contour!(ax,x_c,y_c,c_mat, linewidth=2, color=:white)

beginnings = Point2f0[]; colors = RGBAf0[]
# First plot in contour is the line plot, first arguments are the points of the contour
segments = cplot.plots[1][1][]
for (i, p) in enumerate(segments)
    # the segments are separated by NaN, which signals that a new contour starts
    if isnan(p)
        push!(beginnings, segments[i-1])
    end
end
sc = scatter!(ax, beginnings, markersize=50, color=(:white, 0.1), strokecolor=:white)
translate!(sc, 0, 0, 1)
# Reshuffle the plot order, so that the scatter plot gets drawn before the line plot
delete!(ax, sc)
delete!(ax, cplot)
push!(ax.scene, sc)
push!(ax.scene, cplot)
anno = text!(ax, [(string(i), p) for (i, p) in enumerate(beginnings)], 
                   align=(:center, :center))
                    
# move, so that text is in front
translate!(anno, 0, 0, 2)

display(fig)

But this approach only works nicely with glmakie right now...

SimonDanisch · 2021-04-14T09:40:23Z

For CairoMakie transparent scatters don't block the line from being drawn, so it would need to be opaque:

aramirezreyes · 2021-04-14T16:59:44Z

There is a missing piece in this solution: Adding a colorbar shows that the labels do not correspond to the values in the contour:

fig = Figure(backgroundcolor =RGBf0(0.98, 0.98, 0.98))
ax = fig[1,1] = Axis(fig, title = "Heatmap and contours")

np = 500
nc = 200
f(x) = 2*x+1
x = LinRange(-1,1,f(np))
y = rand(f(np))*2 .- 1
x_c = LinRange(-nc/np,nc/np,f(nc))
y_c = LinRange(-nc/np,nc/np,f(nc))
c_mat = @. x_c^2 + y_c'^2
hp = heatmap!(x_c, y_c, c_mat)
cplot = contour!(ax,x_c,y_c,c_mat, linewidth=2, color=:white)

beginnings = Point2f0[]; colors = RGBAf0[]
# First plot in contour is the line plot, first arguments are the points of the contour
segments = cplot.plots[1][1][]
for (i, p) in enumerate(segments)
    # the segments are separated by NaN, which signals that a new contour starts
    if isnan(p)
        push!(beginnings, segments[i-1])
    end
end
sc = scatter!(ax, beginnings, markersize=50, color=(:white, 0.1), strokecolor=:white)
translate!(sc, 0, 0, 1)
# Reshuffle the plot order, so that the scatter plot gets drawn before the line plot
delete!(ax, sc)
delete!(ax, cplot)
push!(ax.scene, sc)
push!(ax.scene, cplot)
anno = text!(ax, [(string(i), p) for (i, p) in enumerate(beginnings)], 
                   align=(:center, :center))
                    
# move, so that text is in front
translate!(anno, 0, 0, 2)


cbar = fig[1,2] = Colorbar(fig,hp,label = "Values")
cbar.width = 15
cbar.height = Relative(4/5)


display(fig)

jkrumbiegel · 2021-04-14T17:29:07Z

I think they are just numbers from 1 to n for testing

aramirezreyes · 2021-04-14T18:06:16Z

Ah yes, thanks. Just wanted to point out that this is not the solution to the feature request yet but is a stepping stone. For some other person that arrives to this issue while looking for labeled contours.

aramirezreyes · 2021-05-25T02:50:56Z

Is there an easy way to extract the values each segment corresponds to in the snippet above so that we can create the labels accordingly?

briochemc · 2021-07-29T14:33:37Z

Here is to a gentle bump! It would be great to see a MWE that looks good with CairoMakie 😄 (for printing to PDF quality!)

briochemc · 2021-08-02T03:31:44Z

I just tried to reproduce this workaround using Makie v0.15.0 with GLMakie v0.4.4, but copy-pasting the codes above do not reproduce the plot for me. The annotations don't show for some reason:

FWIW I'm on OSX so maybe that's an issue?

briochemc · 2021-08-02T04:38:41Z

FWIW, reshuffling the order more (including the annotations) fixed that part for me. Here is a slightly smaller MWE:

using GLMakie

x = range(-3, 3, length=200)
y = range(-2, 2, length=100)
z = @. x^2 + y'^2
fig, ax, hp = heatmap(x, y, z)
levels = 0:1:100
cplot = contour!(ax, x, y, z, color=:black, levels=levels)

beginnings = Point2f0[]; colors = RGBAf0[]
# First plot in contour is the line plot, first arguments are the points of the contour
segments = cplot.plots[1][1][]
for (i, p) in enumerate(segments)
    # the segments are separated by NaN, which signals that a new contour starts
    if isnan(p)
        push!(beginnings, segments[i-1])
    end
end
sc = scatter!(ax, beginnings, markersize=30, color=(:white, 0.001), strokecolor=:white)
anno = text!(ax, [(string(float(i)), Point3(p..., 2f0)) for (i, p) in enumerate(beginnings)], align=(:center, :center), color=:black)
translate!(sc, 0, 0, 1)
translate!(anno, 0, 0, 2)
# Reshuffle the plot order, so that the scatter plot gets drawn before the line plot
delete!(ax, sc)
delete!(ax, cplot)
delete!(ax, anno)
push!(ax.scene, anno)
push!(ax.scene, sc)
push!(ax.scene, cplot)
# move, so that text is in front

fig

gives me (with GLMakie)

Maybe a list of remaining issues is useful?

making it work with CairoMakie
annotating with the level value (not just the iterator) as asked by @aramirezreyes
clipping the contours more accurately than using circles (maybe depending on the label to be displayed, use a rectangle matching the pixel size of the contour label?)
Improving contour label placement
porting the workaround into a function/recipe/kwarg

aramirezreyes · 2021-10-25T16:33:26Z

I worked a little bit in a workaround which I think is not elegant at all but It kind of works:

using CairoMakie
function name_contours!(ax,cplot,value)
    beginnings = Point2f0[]; colors = RGBAf0[]
    # First plot in contour is the line plot, first arguments are the points of the contour
    segments = cplot.plots[1][1][]
    #@info segments[1]
    for (i, p) in enumerate(segments)
        # the segments are separated by NaN, which signals that a new contour starts
        if isnan(p)
            push!(beginnings, segments[i-1])
        end
    end
    sc = scatter!(ax, beginnings, markersize=30, color=(:white, 0.1), strokecolor=:white)
    translate!(sc, 0, 0, 1)
    # Reshuffle the plot order, so that the scatter plot gets drawn before the line plot
    delete!(ax, sc)
    delete!(ax, cplot)
    push!(ax.scene, sc)
    push!(ax.scene, cplot)
    anno = text!(ax, [(string(value), p) for (i, p) in enumerate(beginnings)], 
                       align=(:center, :center), textsize=10)

    # move, so that text is in front
    translate!(anno, 0, 0, 2) 
end

x = range(-3, 3, length=200)
y = range(-2, 2, length=100)
z = 10(@. x^2 + y'^2)
fig, ax, hp = heatmap(x, y, z)
levels = 0:10:100
for contour_value in levels
        contour_plot = contour!(ax,x,y, z, color = :black, levels = [contour_value])
        name_contours!(ax,contour_plot,contour_value)
end
fig

This code produces:

This the second point in @briochemc's list by calling contour on each specified level
and doesn't solve any of the other four.

It is not much, but it is honest work.

ericphanson · 2022-11-04T12:19:03Z

gentle bump to say this would be nice to have in Makie!

t-bltg · 2022-12-13T10:11:53Z

This would be a great addition.

Here is the workaround adapted to latest Makie:

using CairoMakie

name_contours!(ax, cplot, value) = begin
  beginnings = Point2f[]; colors = RGBAf[]

  # first plot in contour is the line plot, first arguments are the points of the contour
  segments = cplot.plots[1][1][]
  # @info segments[1]
  for (i, p) in enumerate(segments)
    # the segments are separated by NaN, which signals that a new contour starts
    isnan(p) && push!(beginnings, segments[i-1])
  end
  sc = scatter!(ax, beginnings, marker = :rect, markersize=20, color=(:white, .1), strokecolor=:white)
  translate!(sc, 0, 0, 1)

  # reshuffle the plot order, so that the scatter plot gets drawn before the line plot
  delete!(ax, sc)
  delete!(ax, cplot)
  push!(ax.scene, sc)
  push!(ax.scene, cplot)
  ann = text!(ax, [(string(value), p) for (i, p) in enumerate(beginnings)], align=(:center, :center), fontsize=10)

  # move, so that text is in front
  translate!(ann, 0, 0, 2)
end

main() = begin
  cases = (
    paraboloid = (x, y) -> 10(x^2 + y^2),
    # en.wikipedia.org/wiki/Himmelblau%27s_function
    himmelblau = (x, y) -> (x^2 + y - 11)^2 + (x + y^2 - 7)^2,
    # en.wikipedia.org/wiki/Rosenbrock_function
    rosenbrock = (x, y) -> (1 - x^2) + 100(y - x^2)^2,
  )

  x = range(-3, 3; length=100)
  y = range(-3, 3; length=200)
  z = cases[1].(x, y')

  fig, ax, hm = heatmap(x, y, z; interpolate = true)
  Colorbar(fig[1, 2], hm)

  for level ∈ 0:10:100
    contour_plot = contour!(ax, x, y, z, color=:black, levels=[level])
    name_contours!(ax, contour_plot, level)
  end

  save("contour_labels.png", fig)
  fig
end

main()

jkrumbiegel · 2022-12-13T10:17:25Z

I think the tricky part is that after text locations have been chosen, the contour lines have to be hidden where they intersect the label bounding boxes. But this calculation needs to happen in screen space, so it needs to update whenever the projection changes.

t-bltg · 2022-12-13T10:22:51Z

Is there a way to get the plot background color (here the heatmap color) so that we can add a label with a custom opaque background allowing to hide the contour line ? That would allow an exact bounding box based on the label fontsize...

jkrumbiegel · 2022-12-13T10:34:24Z

Often, contour lines are plotted on top of filled contours or heatmaps, so this would look bad in all those cases. I think for a good solution, you can't get around removing the actual lines.. (It would be enough to NaN all unwanted points I guess)

jkrumbiegel · 2022-12-13T10:49:06Z

If anyone wants to start playing around with this, my approach would be:

don't pass computed contour lines directly to lines plot element, make another observable first which will hold a copy of the arrays with NaNs where the lines should be hidden
compute text positions and strings, add those to a new text object.
listen to projection matrix of parent scene, compare to hvlines or so for implementation
whenever projection, input data, any text style data that influences boundingbox like fontsize, change, compute all label boundingboxes, convert from screen coordinates into data coordinates using current projection, NaN out all points in all contours in the copied observable that intersect with those boundingboxes

t-bltg · 2022-12-13T10:54:07Z

Thanks for the comments, this is exactly what I'm doing at the moment (but lower level, not using scatter or translate ...).

jkrumbiegel · 2022-12-13T11:03:30Z

you can get the boundingboxes for each separate text by going into the text child plot object with a Vector{GlyphCollection} as input (textplotobj.plots[1]) and calling boundingbox on each glyphcollection in there

jkrumbiegel · 2022-12-13T11:03:53Z

don't know if there's currently an easier, official way

t-bltg · 2022-12-13T11:12:14Z

Great, yeah I can make the labels work now, but masking is a bit trickier because of those bounding boxes...
I think I'm going to try an unefficient way before trying to use text!(plot, all_labels)...

t-bltg mentioned this issue Dec 13, 2022

implement contour labels #2496

Merged

8 tasks

SimonDanisch closed this as completed in #2496 Apr 1, 2023

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Feature request: contour labels #832

Feature request: contour labels #832

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Feature request: contour labels #832

Feature request: contour labels #832

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briochemc commented Feb 1, 2021

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