How to Export Maps

Timothée Giraud

2024-04-26

mf_export() exports maps in PNG or SVG formats.
The exported map width/height ratio will match the one of a spatial object.
If width is specified, then height is deduced from the width/height ratio of x and some theme parameters (figure margins and title size).
If height is specified, then width is deduced from the width/height ratio of xand some theme parameters (figure margins and title size).
Additionally, mf_export() (and mf_map()) can be used to extend the map space on one or several side of the figure, or to center a map on a specific area.

Simple Export

In this example we only set the width of the exported figure.

library(mapsf)
mtq <- mf_get_mtq()
mf_export(
  x = mtq,
  filename = "fixed_width.png",
  width = 500
)
mf_map(mtq, add = TRUE)
mf_title(txt = "PNG export: width=500px, height=605px (deduced)")
dev.off()

Note that we have to set add = TRUE to the first layer plotted. Internally, mf_export() start a device (PNG or SVG) with a specific dimension (figure size) and extent (x extent).

Export with Extra Space on the Figure

Here we have added some space on the right side of the plot (50% of x width).

mf_theme("dark")
mf_export(
  x = mtq,
  filename = "fixed_width_expand.png",
  width = 500,
  expandBB = c(0, 0, 0, .5),
)
mf_map(mtq, add = TRUE)
mf_title(txt = "PNG export: width=500px, height=432px (deduced)")
dev.off()
mf_theme(NULL)

Note that mf_export() uses the current theme. If a theme is set between an mf_export() call and a dev.off() call it will not be correctly applied.

Center the Map on a Specific Area

In this export, the map is focused on a specific spatial object. height is fixed and width is deduced.

target <- mtq[5, ]
mf_export(x = target, filename = "fixed_height_centered.png", height = 600)
mf_map(mtq, add = TRUE)
mf_shadow(target, add = TRUE)
mf_map(target, add = TRUE)
mf_title(txt = "PNG export: height=600px, width=433px (deduced)")
mf_scale(1, pos = "bottomleft")
dev.off()

Other Parameters

mf_export() can produce SVG figures (with export = "svg") and use other parameters of png() or svg() functions (e.g. res, bg or family).

mf_theme("nevermind")
mf_export(
  x = mtq,
  filename = "fixed_width.svg",
  width = 5,
  bg = "black"
)
mf_map(mtq, add = TRUE)
mf_title(txt = "SVG export: bg = 'black'")
dev.off()
mf_theme(NULL)