mapmisc (version 2.1.0)

tonerToTrans: Convert RGB maps to semi-transparent

Description

Stamen-toner maps are 3-layer RGB rasters, which are converted to single-layer rasters with indexed colours with whites becoming transparent.

Usage

tonerToTrans(x,  pattern="(red|green|blue)$", power = 0.5,
	col='black',  threshold=Inf,  mostCommon=1)

Value

A SpatRast with indexed colours

Arguments

x

A RasterStack with RGB colours, such as from openmap with path='stamen-toner'

pattern

string passed to grep to find RGB layers.

power

Values below 1 increase opacity, above 1 increases transparency

col

colour for resulting map

threshold

colours above this value are transparent

mostCommon

integer vector, the most common colours are converted to transparent

Author

Patrick Brown

See Also

openmap

Examples

	origMap = openmap(
	   c(-11, 9),
	  path='cartodb-nolabels',   
		buffer=2, verbose=TRUE
	)


	oldpar=	map.new(origMap, bg='green')
	plot(origMap, add=TRUE)
	
	transMap = tonerToTrans(origMap, mostCommon=1)
	names(transMap)
  map.new(transMap, bg='green')
	plot(transMap, add=TRUE)



	par(oldpar)