function M = perform_blurring(M, sigma, options)% perform_blurring - gaussian blurs an image%%   M = perform_blurring(M, sigma, options);%%   M is the original data%   sigma is the width of blurs (in pixels)%%   Copyright (c) 2007 Gabriel Peyreoptions.null = 0;n = size(M,1);eta = 4;p = round((sigma*eta)/2)*2+1;p = min(p,round(n/2)*2-1);h = compute_gaussian_filter(p*[1 1],sigma/(2*n),[n n]);M = perform_convolution(M, h, options);