make_backdrop: Make an OpenStreetMap, Stamen or other map backdrop
In chrisbrunsdon/caricRture: 'Sketchy' style maps with R

Description Usage Arguments Details Value Examples

Create a backdrop for sketchy maps, based on the extent of spdf. The backdrop can be from OpenStreetMap, Google, Stamen, ESRI, bing, Apple or other sources depending on location.

1 2	make_backdrop(spdf,bw,sepia,...) spdf

`spdf`	a SpatialPolygons or SpatialPolygonsDataFrame object
`bw`	A variable indicating whether to create a monochrome backdrop - 0 indicates use colour, 1 is standard brightness, other values vary brightness
`sepia`	A variable indicating whether to create a sepia backdrop - 0 indicates use colour, 1 is standard brightness, other values vary brightness - this overwrites `bw`
`...`	parameters passed on to openmap

This function requires that spdf has a well-defined proj4string in order to match the backdrop map with the extent of the spatial object.

Echos spdf - this is useful for pipelines using %>%

# Here make_canvas is inserted in a pipeline after a simplified and tidied 
# map of Irish NUTS3 regions is created.  A sketchy rendition is then added to the
# backdrop of type osm-bw (monochrome OpenStreetMap)
data(RA) 
RA.spdf %>% small_chop %>% gSimplify(tol=11000) %>% tidy_it %>% 
  make_backdrop(type='osm',sepia=0.8) %>% sketch_it(col='darkred',lwd=2,rough=0.08)