关于soft matting的MATLAB代码

注：代码来自A closed form solution to Natural Image Matting

A. Levin D. Lischinski and Y. Weiss 求Matting Laplacian矩阵L代码：

function [A,A1]=getLaplacian1(I,consts,epsilon,win_size)

  

  if (~exist('epsilon','var'))

    epsilon=0.0000001;

  end  

  if (isempty(epsilon))

    epsilon=0.0000001;

  end

  if (~exist('win_size','var'))

    win_size=1;

  end     

  if (isempty(win_size))

    win_size=1;

  end     

  neb_size=(win_size*2+1)^2;

  [h,w,c]=size(I);

  n=h; m=w;

  img_size=w*h;

  consts=imerode(consts,ones(win_size*2+1));

  

  indsM=reshape([1:img_size],h,w);

  tlen=sum(sum(1-consts(win_size+1:end-win_size,win_size+1:end-win_size)))*(neb_size^2);

  row_inds=zeros(tlen ,1);

  col_inds=zeros(tlen,1);

  vals=zeros(tlen,1);

  len=0;

  for j=1+win_size:w-win_size

    for i=win_size+1:h-win_size

      if (consts(i,j))

        continue

      end  

      win_inds=indsM(i-win_size:i+win_size,j-win_size:j+win_size);

      win_inds=win_inds(:);

      winI=I(i-win_size:i+win_size,j-win_size:j+win_size,:);

      winI=reshape(winI,neb_size,c);

      win_mu=mean(winI,1)';

      win_var=inv(winI'*winI/neb_size-win_mu*win_mu' +epsilon/neb_size*eye(c));

      

      winI=winI-repmat(win_mu',neb_size,1);

      tvals=(1+winI*win_var*winI')/neb_size;

      

      row_inds(1+len:neb_size^2+len)=reshape(repmat(win_inds,1,neb_size),...

                                             neb_size^2,1);

      col_inds(1+len:neb_size^2+len)=reshape(repmat(win_inds',neb_size,1),...

                                             neb_size^2,1);

      vals(1+len:neb_size^2+len)=tvals(:);

      len=len+neb_size^2;

    end

  end  

    

  vals=vals(1:len);

  row_inds=row_inds(1:len);

  col_inds=col_inds(1:len);

  A=sparse(row_inds,col_inds,vals,img_size,img_size);

  

  sumA=sum(A,2);

  A=spdiags(sumA(:),0,img_size,img_size)-A;

  

return