Error using rgb2gray>parse_inputs

Im trying to run the attached piece of code.This the error: shadowremoval('4.jpg','additive'); Error using rgb2gray>parse_inputs (line 81) MAP must be a m x 3 array.

Error in rgb2gray (line 35) X = parse_inputs(varargin{:});

Error in shadowremoval (line 42) gray = rgb2gray(image); i read that the image being actually gray might be the problem but mine is rgb.

[Walter Roberson]

Duplicates http://www.mathworks.com/matlabcentral/answers/266463-error-using-rgb2gray-parse-input