Save a ggplot at a DPI that cannot exceed the device's raster ceiling

A drop-in for ggplot2::ggsave() that lowers dpi – never raises it – when the requested canvas would produce a raster larger than the graphics device can allocate (about 32,767 px per side).

Usage

safe_ggsave(filename, plot, width, height, dpi = 300, ...)

Arguments

filename: Output path.
plot: A ggplot or patchwork object.
width, height: Canvas size in inches.
dpi: Requested resolution; the effective value may be lower.
...: Passed to ggplot2::ggsave().

Value

The path, invisibly.

Details

Several figures scale their width or height with the number of samples, populations or markers, so a large cohort or a wide panel can ask for a canvas bigger than the device supports; the run would then die on a figure rather than on the analysis. ggsave()'s own limitsize guards the opposite mistake – an accidentally huge size in inches – and does not help here.

Reducing DPI keeps the requested physical size, and therefore every relative font, point and line size in the theme, exactly as specified. At extreme scale the figure becomes less sharp; it does not become smaller or more crowded, and the run finishes.

The ceiling is getOption("cyRAVEN.max_raster_px"), default 30000.