Fix misaligned colors in colorbar?

[briochemc]

Description

Fixes #4121?

Currently the Colorbar built from a contourf may have misaligned colors. For a MWE see #4121 or

l = [1, 2, 5, 10, 20, 50]
x = 0:0.1:51
y = 0:0.1:51
z = [y for x in x, y in y]
fig, ax, plt = contourf(x, y, z; levels = l, extendhigh=:auto, extendlow=:auto)
cb = Colorbar(fig[1, 2], plt; tellheight = false)

which produces this misalignment (I edited the image in Preview to show the differences in colors):

The issue seems to be that the continuous_pixels (used to draw the heatmap for the colorbar) are not scaled properly. Simply adding the colorrange kwarg to that call fixes this issue for me, with properly matching colors:

However, I'm not if this breaks other things elsewhere, so hopefully someone can hold my hand to finish this PR?

Type of change

Delete options that do not apply:

• Bug fix (non-breaking change which fixes an issue)

Checklist

• Added an entry in CHANGELOG.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[ffreyer]

Seems fine to me. The plot colormapping code should always consider colorrange so I don't see why Colorbar shouldn't. With the ColorMapping type being constructed, the colorrange should also always be in a standard form.

I would say this can be merged after adding a release note to https://github.com/MakieOrg/Makie.jl/blob/master/CHANGELOG.md and adding a reference image test probably in https://github.com/MakieOrg/Makie.jl/blob/master/ReferenceTests/src/tests/figures_and_makielayout.jl.

[briochemc]

I think I did what you asked:

• Add changelog item
• Add reference test

I also "fixed" formatting (spacing around kwarg = sign) and added the colorrange kwarg to the heatmap call in the continuous case, assuming it should be there as well.

Please let me know if I missed something!

[briochemc]

BTW the reference test is a slightly simplified version of the MWE (removed the colorbar extensions):

master	PR

[briochemc]

I'm not sure how/where to upload the reference image for the added reference test. Could you help with that?

[ffreyer]

I'm not sure how/where to upload the reference image for the added reference test. Could you help with that?

That's something Simon, Julius or I need to do.

[briochemc]

Is there anything else I need to do?

[ffreyer]

To things changed in Colorbar for recipes:

old	new

On the center right, the Colorbar now has (slightly) different colors in the -0.5..-0.25 and -0.25..0.5 regions. These now match the colors in the plot exactly, so that's an improvement.

On the center left, the very wide Colorbar got stretched slightly in y direction. It comes from a 3D contour() plot, which lowers to a volume plot. I'm not sure how exactly the colors work here - but it seems like it's all handled early, i.e. in Makie through the ColorMapping object. Colorbar should be reading that more accurately now, so this should be an improvement?

Either way, I updated refimages. If the volume Colorbar is slightly off now it doesn't need to be fixed here.