.prepareRaster: Prepare raster for plotting
Description
Internal function. Takes a raster .spadesGrob, and converts zoomExtent into
a zoom, and legendRange into a legend.
Then calculates the maxpixels to plot for speed.
Usage
.prepareRaster(grobToPlot, zoomExtent, legendRange, takeFromPlotObj, arr, speedup, newArr)
Arguments
zoomExtent
an extent object
legendRange
a numeric vector of length >=2 indicating the desired legend range.
takeFromPlotObj
logical. Should the object be found in the Plot call or .GlobalEnv
arr
an .arrangement
object
speedup
numeric, greater than 1 will usually speed up plotting at the expense of resolution
newArr
logical, whether this is a new arrangement or just adding to a previous one