Add single-plot rasterization capability to CairoMakie

[asinghvi17]

Description

Allows the user to tell CairoMakie to rasterize individual Plots in a Scene, by setting plt.rasterize = scale::Int || true.

CairoMakie will rasterize that specific plot to an image with scale^2 pixels per Scene pixel (1 px per scene px if scale=1 or scale=true) and draw it to the main context. The drawing order also preserves the z-order of the scene.

This has the potential to drastically decrease file sizes, which is extremely useful for publication plots and large meshes.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• Added an entry in NEWS.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.

[greimel]

That's a great feature! This will be handy for plotting maps.

It would be great to have that as a global option as well. Pluto displays pngs by default because to many svgs slow down the browser. Probably this problem could be solved by rasterizing all plots, while keeping axis decorations and text as vector graphics.

[asinghvi17]

I think that this could actually be themable as it is now - if you set rasterize = true in the default themes of Heatmap and Surface, for example, that should "just work". The only potential issue right now is having too many rasterized plots - since each one gets its own image, that would cause a lot of size bloat. Fixing that would be a bit complicated, though.

[SimonDanisch]

Could you add a test a la: https://github.com/JuliaPlots/Makie.jl/blob/master/CairoMakie/test/svg_tests.jl ?

[asinghvi17]

The CI failure on Makie/Julia 1 does not appear to be related - seems related to mouse click detection.

[asinghvi17]

@Datseris this may be useful if you are saving GeoMakie plots to pdf - just pass rasterize = 5 or so as a keyword argument to surface or heatmap!