Border display depends on fig size

[ijunier]

The smaller figsize, the thinner the border at a given thickness, which is normal. However, if figsize is too small, the border in the generated pdf/png figure may disappear. A "nice" example is the one from our current ms, where the border has many holes.

A possible solution: imposing a minimum figsize.

fig_20_20_thick0.01.pdf
fig_10_10_thick0.01.pdf

[ijunier]

• first: add interpolation='None' in border (see issues)
• After a few test: a good compromise is to have figsize>=8,8 and border_thickness not below 0.005 for figsize=8,8
• Obviously, this is not very convenient to generate e.g. figures with multiple subplots. We should think of a solution where border_thickness is, by default, automatically adapted to lead to the "thinnest" apparent border (a linear relationship wrt figsize?)
• rem: it also depends on the value of outer_radius (may not be the case with interpolation='None')