kml_screen: Add a screen overlay

Description

Adds an image file (map legend or logo) as screen overlay. The same file connection is further accessible by other kml_*() functions such as kml_layer() and kml_close(). This allows creation of customized multi-layered KML files.

Usage

kml_screen(image.file, sname = "", 
     position = c("UL","ML","LL","BC","LR","MR","UR","TC")[1],
     overlayXY, screenXY, xyunits = c("fraction", "pixels", "insetPixels")[1], 
     rotation = 0, size = c(0,0) )

Arguments

image.file

image file to be used for screen overlay

sname

screen overlay name

position

one of the nine standard positions

overlayXY

manually specified tie point on the overlay image e.g. 'x="0" y="1"'

screenXY

manually specified matching tie point on the scren e.g. 'x="0" y="1"'

xyunits

values of the XY units (("pixels", "fraction", or "insetPixels")

rotation

(optional) rotation in degrees clock-wise

size

size correction in x and y direction

Details

If nothing else is specified the function looks for some of the nine typical positions: "UL" (upper left), "ML" (middle left), "LL" (lower left), "BC" (bottom centre), "LR" (lower right), "MR" (middle right), "UR" (upper right), and "TC" (top centre). The x and y values can be specified in three different ways: as pixels ("pixels"), as fractions of the image ("fraction"), or as inset pixels ("insetPixels") --- an offset in pixels from the upper right corner of the image.

References

KML Reference (http://code.google.com/apis/kml/documentation/)

Examples

Run this code

library(rgdal)
library(sp)
data(eberg_zones)
# add logo in the top-center:
kml_open("eberg_screen.kml")
kml_layer(eberg_zones)
logo = "http://meta.isric.org/images/ISRIC_right.png"
kml_screen(image.file = logo, position = "TC", sname = "ISRIC logo")
kml_close("eberg_screen.kml")
kml_compress("eberg_screen.kml")