Convert RasterBrick into data.frame of colors that can be used for plotting
This function is used internally by
plot_layer to convert a
RasterBrick object to a data.frame of colors for each pixel that can be used
for plotting with ggplot2. Note that this function assumes that the first
three bands in the RasterBrick objects are the RGB values and all additional
bands are ignored.
# S4 method for RasterBrick raster_colors(x)