[BUG] Removing all margin does not work

[MagicMuscleMan]

Details

When trying to annotate a video frame with Plots, it would be really useful to remove all the margin around the axis when saving the file again (to create the modified video).

This does not seem to be possible (or I lack the knowledge -> please show the solution if that should be the case).

Minimal (non-working) example:

using Plots
using Plots.PlotMeasures
using VideoIO

reader = VideoIO.openvideo("file.MOV")
imgColor = read(reader)
plot(imgColor, size = (width, height), showaxis = false, ticks = false,
    left_margin = 0px, top_margin = 0px, right_margin = 0px,
    bottom_margin = 0px, padding = (0.0, 0.0))

Backends

This bug occurs on ( insert x below )

Backend	yes	no	untested
gr (default)	x
pyplot			x
plotlyjs			x
pgfplotsx			x
unicodeplots			x
inspectdr			x
gaston			x

Versions

Plots.jl version:
Backend version (]st -m <backend(s)>):
Output of versioninfo():

[BioTurboNick]

It's because there is a hard-coded baseline, so you have to add a negative margin to actually get rid of the margin.

See #3942