imedge3d

 imgdiff=imedge3d(binimg,isdiff)

 Extract the boundary voxels from a binary image
 
 author: Aslak Grinsted <ag at glaciology.net>
 modified by Qianqian Fang <fangq at nmr.mgh.harvard.edu>

 input: 
   binimg: a 3D binary image
   isdiff: if isdiff=1, output will be all voxels which 
         is different from its neighbors; if isdiff=0 or 
         ignored, output will be the edge voxels of the 
         non-zero regions in binimg

 output:
   imgdiff: a 3D logical array with the same size as binimg
            with 1 for voxels on the boundary and 0 otherwise 
 
 -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)

0001 function imgdiff=imedge3d(binimg,isdiff)
0002 %
0003 % imgdiff=imedge3d(binimg,isdiff)
0004 %
0005 % Extract the boundary voxels from a binary image
0006 %
0007 % author: Aslak Grinsted <ag at glaciology.net>
0008 % modified by Qianqian Fang <fangq at nmr.mgh.harvard.edu>
0009 %
0010 % input:
0011 %   binimg: a 3D binary image
0012 %   isdiff: if isdiff=1, output will be all voxels which
0013 %         is different from its neighbors; if isdiff=0 or
0014 %         ignored, output will be the edge voxels of the
0015 %         non-zero regions in binimg
0016 %
0017 % output:
0018 %   imgdiff: a 3D logical array with the same size as binimg
0019 %            with 1 for voxels on the boundary and 0 otherwise
0020 %
0021 % -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)
0022 %
0023 
0024 invol=1;
0025 if(nargin==2)
0026     invol=isdiff;
0027 end
0028 binimg=logical(binimg);
0029 imgdiff=xor(binimg,binimg(:,:,[1 1:end-1]));
0030 imgdiff=imgdiff|xor(binimg,binimg(:,:,[2:end end]));
0031 imgdiff=imgdiff|xor(binimg,binimg(:,[1 1:end-1],:));
0032 imgdiff=imgdiff|xor(binimg,binimg(:,[2:end end],:));
0033 imgdiff=imgdiff|xor(binimg,binimg([1 1:end-1],:,:));
0034 imgdiff=imgdiff|xor(binimg,binimg([2:end end],:,:));
0035 if(invol)
0036     imgdiff=imgdiff&binimg;
0037 end