These functions extract and change the current default colours
used for plotting colour images in the spatstat family of
packages, in particular by the functions
plot.im
and plot.linim.
The default colour values are a vector of
character strings which can be interpreted as colours.
In any particular instance of
plot.im
or plot.linim,
the default colours are interpolated to obtain a vector of colour
values of the required length (usually 256, controlled by the
argument ncolours to the plot command).
default.image.colours() returns the current default colours.
reset.default.image.colours(col) sets the default colours to
be the vector col.
reset.default.image.colours() or
reset.default.image.colours(NULL) resets the
factory default, which is row 29 of the Kovesi uniform
perceptual contrast table described in Kovesi.