Ylim shifts image in plot

Specific Domains Visualization
, , ,
1

I’m trying to plot a section of an image file using Plots.jl and then draw in certain points in the image.

It works nicely when I plot the whole image:

using Plots
using FileIO, HTTP, ImageIO
bg_img2 = load(HTTP.URI("https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/GoldenGateBridge-001.jpg/640px-GoldenGateBridge-001.jpg"));

begin
	plot(bg_img2)
	scatter!([385], [315])
end

whole_image

When introducing a xlim to the plot, everything still behaves as expected:

begin
	plot(bg_img2,
		xlim=(350, 420),
	)
	scatter!([385], [315])
end

xlim

However, as soon as I introduce a ylim to the plot, the image shifts. This get apparent because the plotted point is positioned differently relative to the image.

begin
	plot(bg_img2,
		ylim=(270, 350)
	)
	scatter!([385], [315])
end

ylim

What am I missing? Or is this a bug in the plotting library?

Pluto notebook to reproduce:
ylim_image_shift.jl (43.5 KB)

2

I’ve done some more digging and this seems to be related to yflip=true (the default when plotting an image). Everything works as expected with yflip=false, apart from the flipped image of course.

I’ve opened a bug with Plots.jl: [BUG] `ylims` does not respect `yflip=true` · Issue #4903 · JuliaPlots/Plots.jl · GitHub

3

I do not see the bug in Julia Version 1.10.0, Plots v1.40.1:

Plots_image_ylims
Plots_image_ylims3544×553 150 KB

PS:
You can also plot single points as tuples:
scatter!((385, 315))

4

Interesting, I can consistently reproduce using Julia v1.10.2, Plots v1.40.2. What code exactly did you use to make it work on your setup?

5

Exactly your code.

And tested now also with Plots v1.40.2, and can’t see the issue.

PS:
I run the code from VS Code on Windows.

6

Mysterious. I’m able to reproduce the problem on different Linux machines, as well as on Windows, in Pluto and in VS Code.

I have created another Pluto notebook as a minimal working example:
mwe_yflip_ylim_shift.jl (43.2 KB)
Is nobody else able to reproduce the issue?