%COL2GRAY Mapping for converting multi-band images into single band images%%  B = COL2GRAY(A,V)%  B = A*COL2GRAY([],V)%% INPUT%   A    Multiband image or dataset with multi-band images as objects%   V    Weight vector, one weight per band. Default: equal weights.%% OUTPUT%   B    Output image or dataset.%% DESCRIPTION% The multi-band components in the image A (3rd dimension) or in the% objects in the dataset A are weigthed (default: equal weights) and% averaged.%% SEE ALSO% MAPPINGS, DATASTS, DATAFILES% Copyright: R.P.W. Duin, r.p.w.duin@prtools.org% Faculty EWI, Delft University of Technology% P.O. Box 5031, 2600 GA Delft, The Netherlandsfunction b = col2gray(a,v)		prtrace(mfilename,2);	  if nargin < 2, v = []; end  if nargin < 1 | isempty(a)    b = mapping(mfilename,'fixed',{v});    b = setname(b,'Color-to-gray conversion');	elseif isa(a,'dataset') % allows datafiles too		isobjim(a);    b = filtm(a,mfilename,v);    imsize = getfeatsize(a);    b = setfeatsize(b,imsize(1:2));  elseif isa(a,'double')    imsize = size(a);    if isempty(v)      if length(imsize) == 3        b = mean(a,3);        b = squeeze(b);      elseif length(imsize) == 2        b = a;      else        error('Illegal image size')      end    else      if length(imsize) == 2        b = a;      else        b = zeros(imsize(1),imsize(2),size(a,1));        for i=1:size(a,1)          for j=1:size(im,3)            b(:,:,i) =b(:,:,i) + b(:,:,j,i)*v(j);          end        end      end    end  else    error('Illegal datatype for input')  endreturn