Use affine logic interactively georegister a raster

User clicks are collected in a controlled way for use by domath().

affinething(x, rgb = FALSE)

Arguments

x	a raster
rgb	use RGB plot for a raster with 3 layers

Value

matrix of x,y coordinates in the space of the current raster extent

Details

Obtain control points for the simple affine transform (offset and scale) on an ungeoreferenced image.

Examples

# \donttest{
if (FALSE) {
library(raster)
r <- raster("my_unreferenced_raster.png")
xy <- affinething(r)  ## click on two points that you know a location of
my_x <- c(1000, 2000)
my_y <- c(-1000, -500)
prj <- "+proj=laea +lon=147 +lat_0=-42" ## use your own map projection, that correspond to my_x/my_y
pt <- cbind(my_x, my_y)
## now convert those control points to an extent for your raster
ex <- domath(pt, xy, r, prj)

## now we can fix up the data
r <- raster::setExtent(r, ex)
raster::projection(r) <- prj
## hooray!
}
# }