tonerToTrans {mapmisc}

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)

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

Value

A SpatRast with indexed colours

Author(s)

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)