add new colors to the current colormap
ids of the colors defined in c in the new color table.
matrix with 3 columns, RGB color definition.
addcolor adds new colors given in the
c argument to the
c must be a matrix with 3 columns
[R G B]
R is red component,
G is green component,
B is blue component). Each entry in
c must be a non
negative number less or equal to 1.
The ids of the new colors are returned into
If a color defined in
c is already present in the current colormap
it is not added.