Check if argument is valid colormap.
If in is not a valid colormap, gives a properly formatted error message. func_name is the name of the function to be used on the error message, var_name the name of the argument being checked (for the error message), and pos the position of the argument in the input.
A valid colormap is a 2-D matrix with 3 columns of doubles with values between 0 and 1 (inclusive), that refer to the intensity levels of red, green and blue.
See also: colormap.
Package: image