implementing pso for image

I wan to implement pso algorithm for image enhancement using the file from http://www.mathworks.com/matlabcentral/fileexchange/29519-pso.. my objective function is 'g' grayImage=imread('cameraman.tif'); a=1.5; b=.5; c=1; k=1.5; gMean=mean2(double(grayImage)); J=stdfilt(grayImage); slidingmean=conv2(double(grayImage),ones(3)/9,'same'); K=(k.*gMean)./(J+b);

g=K.*(double(grayImage)-(c.*slidingmean))+(slidingmean).^a;

Can someone help?