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+## Copyright (C) 2004 Josep Mones i Teixidor
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{B} = } blkproc (@var{A}, [@var{m},@var{n}], @var{fun})
+## @deftypefnx {Function File} {@var{B} = } blkproc (@var{A}, [@var{m},@var{n}], @var{fun}, ...)
+## @deftypefnx {Function File} {@var{B} = } blkproc (@var{A}, [@var{m},@var{n}], [@var{mborder},@var{nborder}], @var{fun}, @var{...})
+## @deftypefnx {Function File} {@var{B} = } blkproc (@var{A}, 'indexed', ...)
+## Processes image in blocks using user-supplied function
+##
+## @code{B=blkproc(A,[m,n],fun)} divides image @var{A} in
+## @var{m}-by-@var{n} blocks, and passes them to user-supplied function
+## @var{fun}, which result is concatenated to build returning matrix
+## @var{B}. If padding is needed to build @var{m}-by-@var{n}, it is added
+## at the bottom and right borders of the image.  0 is used as a padding
+## value.
+##
+## @code{B=blkproc(A,[m,n],fun,...)} behaves as described above but
+## passes extra parameters to function @var{fun}.
+##
+## @code{B=blkproc(A,[m,n],[mborder,nborder],fun,...)} behaves as
+## described but uses blocks which overlap with neighbour blocks.
+## Overlapping dimensions are @var{mborder} vertically and @var{nborder}
+## horizontally. This doesn't change the number of blocks in an image
+## (which depends only on size(@var{A}) and [@var{m},@var{n}]). Adding a
+## border requires extra padding on all edges of the image. 0 is used as
+## a padding value.
+##
+## @code{B=blkproc(A,'indexed',...)} assumes that @var{A} is an indexed
+## image, so it pads the image using proper value: 0 for uint8 and
+## uint16 images and 1 for double images. Keep in mind that if 'indexed'
+## is not specified padding is always done using 0.
+##
+## @end deftypefn
+## @seealso{colfilt,inline,bestblk}
+
+## Author:  Josep Mones i Teixidor <jmones@puntbarra.com>
+
+function B = blkproc(A, varargin)
+  if(nargin<3)
+    error("blkproc: invalid number of parameters.");
+  endif
+  
+  ## check 'indexed' presence
+  indexed=false;
+  p=1;
+  if(isstr(varargin{1}) && strcmp(varargin{1}, "indexed"))
+    indexed=true;
+    p+=1;
+    if(strcmp(typeinfo(A), 'uint8 matrix'))
+      padval=0; ## padval=uint8(0); in future...
+    elseif(strcmp(typeinfo(A), 'uint16 matrix'))
+      padval=0; ## padval=uint16(0); in future...
+    else
+      padval=1; ## array of double
+    endif
+  else
+    padval=0;
+  endif
+
+  ## check [m,n]
+  if(!isvector(varargin{p}))
+    error("blkproc: expected [m,n] but param is not a vector.");
+  endif
+  if(length(varargin{p})!=2)
+    error("blkproc: expected [m,n] but param has wrong length.");
+  endif
+  sblk=varargin{p}(:);
+  p+=1;
+
+  ## check [mborder,nborder]
+  if(nargin<p)
+    error("blkproc: required parameters haven't been supplied.");
+  endif
+
+  ## This is weird but isvector in my Octave 2.1.57 reports 1 for inline
+  ## functions
+  if(!(isstr(varargin{p}) || 
+       strcmp(typeinfo(varargin{p}),"function handle")) && \
+     isvector(varargin{p}))
+    if(length(varargin{p})!=2)
+      error("blkproc: expected [mborder,nborder] but param has wrong length.");
+    endif
+    sborder=varargin{p}(:);
+    p+=1;
+  else
+    sborder=[0;0];
+  endif
+
+  ## check fun
+  ## TODO: add proper checks for this one
+  if(nargin<p)
+    error("blkproc: required parameters haven't been supplied.");
+  endif
+  fun=varargin{p};
+  
+  ## remaining params are params to fun
+  ## extra params are p+1:nargin-1
+
+  ## First of all we calc needed padding which will be applied on bottom
+  ## and right borders
+  ## The "-" makes the function output needed elements to fill another
+  ## block directly
+  sp=mod(-size(A)',sblk);
+
+  ## TODO: check if this prevents A data type in ver>2.1.57
+  if(any(sp))
+    A=padarray(A,sp,padval,'post');
+  endif
+
+  ## we store A size without border padding to iterate later
+  soa=size(A);
+  
+  ## If we have borders then we need more padding
+  if(any(sborder))
+    A=padarray(A,sborder,padval);
+  endif
+
+  ## calculate end of block
+  eblk=sblk+sborder*2-1;
+
+  ## now we can process by blocks
+  ## we try to preserve fun return type by concatenating everything
+  ## TODO: check if return type is preserved in ver>2.1.57
+  for i=1:sblk(1):soa(1)
+    r=[];
+    for j=1:sblk(2):soa(2)
+      r=horzcat(r,feval(fun,A(i:i+eblk(1),j:j+eblk(2)),varargin{p+1:nargin-1}));
+    endfor
+    if(i==1) ## this workarrounds a bug in ver<=2.1.57 cat implementation
+      B=r;
+    else
+      B=vertcat(B,r);
+    endif
+  endfor
+endfunction
+
+%!demo
+%! blkproc(eye(6),[2,2],inline("any(x(:))","x"))
+%! # Returns a 3-by-3 diagonal
+
+
+%!assert(blkproc(eye(6),[2,2],inline("any(x(:))","x")),eye(3));
+%!assert(blkproc(eye(6),[1,2],[1,1],inline("sum(x(:))","x")),[2,1,0;3,2,0;2,3,1;1,3,2;0,2,3;0,1,2]);
+%!assert(blkproc(eye(6),'indexed',[1,2],[1,1],inline("sum(x(:))","x")),[8,5,6;6,2,3;5,3,4;4,3,5;3,2,6;6,5,8]);
+%!assert(blkproc(eye(6),[2,3],[4,3],inline("sum(x(:))","x")),ones(3,2)*6);
+
+
+%
+% $Log$
+% Revision 1.1  2004/08/15 19:27:46  jmones
+% blkproc: block process an image using user-supplied function
+%
+%
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