A nativeRaster in R looks like an integer matrix, but is interpreted
different by graphics devices:
nr_new(width, height, fill = "white")Image dimensions in pixels
Background fill color as a character string. Either a standard R color
or a hex colour of the form #rrggbbaa or #rrggbb
The data should be treated as RGBA pixels in row-major ordering
Each 32-bit integer should be interpreted as 4-bytes - one for each of the R, G, B and A colour channels