/usr/share/octave/packages/image-2.6.1/imfilter.m is in octave-image 2.6.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | ## Copyright (C) 2007 Søren Hauberg <soren@hauberg.org>
##
## 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 3 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, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} @var{J} = imfilter(@var{I}, @var{f})
## @deftypefnx{Function File} @var{J} = imfilter(@var{I}, @var{f}, @var{options}, @dots{})
## Computes the linear filtering of the image @var{I} and the filter @var{f}.
## The computation is performed using double precision floating point numbers,
## but the class of the input image is preserved as the following example shows.
## @example
## I = 255*ones(100, 100, "uint8");
## f = fspecial("average", 3);
## J = imfilter(I, f);
## class(J)
## @result{} ans = uint8
## @end example
##
## The function also accepts a number of optional arguments that control the
## details of the filtering. The following options is currently accepted
## @table @samp
## @item S
## If a scalar input argument is given, the image is padded with this scalar
## as part of the filtering. The default value is 0.
## @item "symmetric"
## The image is padded symmetrically.
## @item "replicate"
## The image is padded using the border of the image.
## @item "circular"
## The image is padded by circular repeating of the image elements.
## @item "same"
## The size of the output image is the same as the input image. This is the default
## behaviour.
## @item "full"
## Returns the full filtering result.
## @item "corr"
## The filtering is performed using correlation. This is the default behaviour.
## @item "conv"
## The filtering is performed using convolution.
## @end table
## @seealso{conv2, filter2, fspecial, padarray}
## @end deftypefn
function retval = imfilter(im, f, varargin)
if (nargin < 2)
print_usage ();
endif
## Check image
if (! isimage (im))
error("imfilter: IM must be an image");
endif
[imrows, imcols, imchannels, tmp] = size(im);
if (tmp != 1 || (imchannels != 1 && imchannels != 3))
error("imfilter: first input argument must be an image");
endif
C = class(im);
## Check filter (XXX: matlab support 3D filter, but I have no idea what they do with them)
if (! isnumeric (f))
error("imfilter: F must be a numeric array");
endif
[frows, fcols, tmp] = size(f);
if (tmp != 1)
error("imfilter: second argument must be a 2-dimensional matrix");
endif
## Parse options
res_size = "same";
res_size_options = {"same", "full"};
pad = 0;
pad_options = {"symmetric", "replicate", "circular"};
ftype = "corr";
ftype_options = {"corr", "conv"};
for i = 1:length(varargin)
v = varargin{i};
if (any(strcmpi(v, pad_options)) || isscalar(v))
pad = v;
elseif (any(strcmpi(v, res_size_options)))
res_size = v;
elseif (any(strcmpi(v, ftype_options)))
ftype = v;
else
warning("imfilter: cannot handle input argument number %d", i+2);
endif
endfor
## Pad the image
im = padarray(im, floor([frows/2, fcols/2]), pad);
if (mod(frows,2) == 0)
im = im(2:end, :, :);
endif
if (mod(fcols,2) == 0)
im = im(:, 2:end, :);
endif
## Do the filtering
if (strcmpi(res_size, "same"))
res_size = "valid";
else # res_size == "full"
res_size = "same";
endif
if (strcmpi(ftype, "corr"))
for i = imchannels:-1:1
retval(:,:,i) = filter2(f, im(:,:,i), res_size);
endfor
else
for i = imchannels:-1:1
retval(:,:,i) = conv2(im(:,:,i), f, res_size);
endfor
endif
## Change the class of the output to the class of the input
## (the filtering functions returns doubles)
retval = cast(retval, C);
endfunction
%!test
%! img = [
%! 8 2 6 7 4 3 7 8 4 1
%! 9 9 1 1 4 7 3 3 8 1
%! 2 9 8 3 7 6 5 8 6 5
%! 9 5 9 1 8 2 7 3 5 8
%! 6 8 7 1 2 2 9 9 9 9
%! 1 2 7 8 5 5 9 4 3 2
%! 3 4 7 7 5 9 5 2 7 6
%! 5 9 4 3 6 4 2 3 7 5
%! 9 8 6 9 7 6 2 6 4 1
%! 9 9 2 1 7 3 3 5 6 4];
%!
%! expected_corr = [
%! 46 53 30 34 44 42 40 51 42 19
%! 48 66 57 42 46 50 59 58 49 34
%! 48 67 55 54 44 58 50 50 64 39
%! 44 77 52 43 28 55 57 75 70 50
%! 29 51 65 51 42 50 60 62 55 42
%! 23 44 58 59 63 59 55 57 50 36
%! 36 50 52 56 56 47 48 45 47 39
%! 51 64 70 62 56 50 40 38 41 31
%! 58 72 50 49 58 45 41 42 49 28
%! 27 37 27 21 19 26 16 23 24 17];
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2]), expected_corr)
%!
%! ## test order of options (and matching with defaults)
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2], 0), expected_corr)
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2], "corr"), expected_corr)
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2], "corr", 0), expected_corr)
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2], 0, "corr"), expected_corr)
%!
%! expected_conv = [
%! 21 31 23 22 21 28 29 26 22 6
%! 47 55 43 43 51 44 49 64 44 24
%! 56 69 53 34 47 50 57 48 52 37
%! 38 70 60 56 41 57 54 61 66 44
%! 46 67 53 48 32 54 59 65 63 46
%! 28 56 63 50 36 54 58 66 63 47
%! 20 43 55 62 67 57 52 53 44 28
%! 42 51 54 61 57 53 44 46 48 39
%! 53 70 63 50 57 42 38 38 43 33
%! 53 62 50 54 52 44 38 40 40 20];
%! assert (imfilter (img, [0 1 0; 2 1 1; 1 2 2], "conv"), expected_conv)
%!
%! ## alternative class
%! assert (imfilter (single (img), [0 1 0; 2 1 1; 1 2 2]),
%! single (expected_corr))
%! assert (imfilter (int8 (img), [0 1 0; 2 1 1; 1 2 2]),
%! int8 (expected_corr))
%! assert (imfilter (uint8 (img), [0 1 0; 2 1 1; 1 2 2]),
%! uint8 (expected_corr))
%!
%! assert (imfilter (single (img), [0 1 0; 2 1 1; 1 2 2], "conv"),
%! single (expected_conv))
%! assert (imfilter (int8 (img), [0 1 0; 2 1 1; 1 2 2], "conv"),
%! int8 (expected_conv))
%! assert (imfilter (uint8 (img), [0 1 0; 2 1 1; 1 2 2], "conv"),
%! uint8 (expected_conv))
%!
## test padding with even sized filters (bug #45568)
%!test
%! I = zeros (6);
%! I(2:3,2:3) = 1;
%! F = zeros (4);
%! F(2,2:3) = 1;
%! result = [0 0 0 0 0 0
%! 1 2 1 0 0 0
%! 1 2 1 0 0 0
%! 0 0 0 0 0 0
%! 0 0 0 0 0 0
%! 0 0 0 0 0 0];
%! assert (imfilter (I, F), result)
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