[07d29c]: im2col.m  Maximize  Restore  History

Download this file

253 lines (224 with data), 7.8 kB

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
## 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} = } im2col (@var{A}, [@var{m},@var{n}], @var{block_type})
## @deftypefnx {Function File} {@var{B} = } im2col (@var{A}, [@var{m},@var{n}])
## @deftypefnx {Function File} {@var{B} = } im2col (@var{A}, 'indexed', ...)
## Rearranges image blocks into columns
##
## @code{B=im2col(A, [m, n], blocktype)} rearranges blocks in @var{A}
## into columns in a way that's determined by @var{block_type}, which
## can take the following values:
##
## @table @code
## @item distinct
## Rearranges each distinct @var{m}-by-@var{n} block in image @var{A}
## into a column of @var{B}. Blocks are scanned from left to right and
## the up to bottom in @var{A}, and columns are added to @var{B} from
## left to right. If @var{A}'s size is not multiple @var{m}-by-@var{n}
## it is padded.
## @item sliding
## Rearranges any @var{m}-by-@var{n} sliding block of @var{A} in a
## column of @var{B}, without any padding, so only sliding blocks which
## can be built using a full @var{m}-by-@var{n} neighbourhood are taken.
## In consequence, @var{B} has @var{m}*@var{n} rows and
## (@var{mm}-@var{m}+1)*(@var{nn}-@var{n}+1) columns (where @var{mm} and
## @var{nn} are the size of @var{A}).
##
## This case is thought to be used applying operations on columns of
## @var{B} (for instance using sum(:)), so that result is a
## 1-by-(@var{mm}-@var{m}+1)*(@var{nn}-@var{n}+1) vector, that is what
## the complementary function @code{col2im} expects.
## @end table
##
## @code{B=im2col(A,[m,n])} takes @code{distinct} as a default value for
## @var{block_type}.
##
## @code{B=im2col(A,'indexed',...)} will treat @var{A} as an indexed
## image, so it will pad using 1 if @var{A} is double. All other cases
## (incluing indexed matrices with uint8 and uint16 types and
## non-indexed images) will use 0 as padding value.
##
## Any padding needed in 'distinct' processing will be added at right
## and bottom edges of the image.
##
## @strong{Compatibility notes:}
##
## @itemize @bullet
## @item
## 'sliding' blocks are arranged into @var{B} in a top-down and
## left-right order. Since this isn't explicity described in MATLAB
## documentation, we ignore if it does it this way. It has been
## deduced because im2col implements inverse operation as a simple
## reshape (if we chose left to right and then up to down order we would
## had to transpose result). If you have MATLAB please check this
## issue.
## @item
## MATLAB docs say that when using @code{'indexed'}, padding with 0 is
## done for uint8 type. Since most functions do that too for uint16, we
## have chosen to use 0 also for uint16, even if documentation doesn't
## say it explicity, since it looks as an omission.
## @end itemize
##
## @end deftypefn
## @seealso{col2im}
## Author: Josep Mones i Teixidor <jmones@puntbarra.com>
function B = im2col(A, varargin)
if(nargin<2 || nargin>4)
usage("B=im2col(B [, 'indexed'], [m,n] [, block_type])");
endif
## check 'indexed' presence
indexed=false;
p=1;
if(ischar(varargin{1}) && strcmp(varargin{1}, "indexed"))
if(nargin<3)
usage("B=im2col(B [, 'indexed'], [m,n] [, block_type])");
endif
indexed=true;
p+=1;
if(isa(A,"uint8") || isa(A,"uint16"))
padval=0;
else
padval=1;
endif
else
padval=0;
endif
## check [m,n]
if(!isvector(varargin{p}))
error("im2col: expected [m,n] but param is not a vector.");
endif
if(length(varargin{p})!=2)
error("im2col: expected [m,n] but param has wrong length.");
endif
m=varargin{p}(1);
n=varargin{p}(2);
p+=1;
block_type='sliding';
if(nargin>p)
## we have block_type param
if(!ischar(varargin{p}))
error("im2col: invalid parameter block_type.");
endif
block_type=varargin{p};
p+=1;
endif
## if we didn't have 'indexed' but had 4 parameters there's an error
if(nargin>p)
usage("B=im2col(B [, 'indexed'], [m,n] [, block_type])");
endif
## common checks
if(!ismatrix(A))
error("im2col: A should be a matrix (or vector).");
endif
switch(block_type)
case('distinct')
## calc needed padding
sp=mod(-size(A)',[m;n]);
if(any(sp))
A=padarray(A,sp,padval,'post');
endif
## iterate through all blocks
B=[];
for i=1:m:size(A,1) ## up to bottom
for j=1:n:size(A,2) ## left to right
## TODO: check if we can horzcat([],uint8([10;11])) in a
## future Octave version > 2.1.58
if(isempty(B))
B=A(i:i+m-1,j:j+n-1)(:);
else
B=horzcat(B, A(i:i+m-1,j:j+n-1)(:));
endif
endfor
endfor
case('sliding')
if(indexed)
disp("WARNING: 'indexed' has no sense when using sliding.");
endif
if(m>size(A,1) || n>size(A,2))
error("im2col: block size can't be greater than image size in sliding");
endif
## TODO: check if matlab uses top-down and left-right order
B=[];
for j=1:1:size(A,2)-n+1 ## left to right
for i=1:1:size(A,1)-m+1 ## up to bottom
## TODO: check if we can horzcat([],uint8([10;11])) in a
## future Octave version > 2.1.58
if(isempty(B))
B=A(i:i+m-1,j:j+n-1)(:);
else
B=horzcat(B, A(i:i+m-1,j:j+n-1)(:));
endif
endfor
endfor
otherwise
error("im2col: invalid block_type.");
endswitch
endfunction
%!demo
%! A=[1:10;11:20;21:30;31:40]
%! B=im2col(A,[2,5],'distinct')
%! C=col2im(B,[2,5],[4,10],'distinct')
%! # Divide A using distinct blocks and reverse operation
%!shared B, A, Bs, As, Ap, Bp0, Bp1
%! v=[1:10]';
%! r=reshape(v,2,5);
%! B=[v, v+10, v+20, v+30, v+40, v+50];
%! A=[r, r+10; r+20, r+30; r+40, r+50];
%! As=[1,2,3,4,5;6,7,8,9,10;11,12,13,14,15];
%! b1=As(1:2,1:4)(:);
%! b2=As(2:3,1:4)(:);
%! b3=As(1:2,2:5)(:);
%! b4=As(2:3,2:5)(:);
%! Bs=[b1,b2,b3,b4];
%! Ap=A(:,1:9);
%! Bp1=Bp0=B;
%! Bp0([9:10],[2,4,6])=0;
%! Bp1([9:10],[2,4,6])=1;
%!# bad block_type
%!error(im2col(A,[2,5],'wrong_block_type'));
%!# distinct
%!assert(im2col(A,[2,5],'distinct'), B);
%!# padding
%!assert(im2col(Ap,[2,5],'distinct'), Bp0);
%!assert(im2col(Ap,'indexed',[2,5],'distinct'), Bp1);
%!# now sliding
%!assert(im2col(As,[2,4]), Bs);
%!assert(im2col(As,[2,4],'sliding'), Bs);
%!assert(im2col(As,[3,5],'sliding'), As(:));
%!# disctint uint8 & uint16
%!assert(im2col(uint8(A),[2,5],'distinct'), uint8(B));
%!assert(im2col(uint16(A),[2,5],'distinct'), uint16(B));
%!# padding uint8 & uint16 (to 0 even in indexed case)
%!assert(im2col(uint8(Ap),[2,5],'distinct'), uint8(Bp0));
%!assert(im2col(uint8(Ap),'indexed',[2,5],'distinct'), uint8(Bp0));
%!assert(im2col(uint16(Ap),[2,5],'distinct'), uint16(Bp0));
%!assert(im2col(uint16(Ap),'indexed',[2,5],'distinct'), uint16(Bp0));
%!# now sliding uint8 & uint16
%!assert(im2col(uint8(As),[2,4],'sliding'), uint8(Bs));
%!assert(im2col(uint16(As),[2,4],'sliding'), uint16(Bs));
%
% $Log$
% Revision 1.3 2005/09/08 02:00:17 pkienzle
% [for Bill Denney] isstr -> ischar
%
% Revision 1.2 2004/09/03 17:37:08 jmones
% Added support for int* and uint* types
%
% Revision 1.1 2004/08/18 14:39:07 jmones
% im2col and col2im added
%
%

Get latest updates about Open Source Projects, Conferences and News.

Sign up for the SourceForge newsletter:





No, thanks