/usr/share/octave/packages/image-2.6.1/findbounds.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 | ## Copyright (C) 2012 Pantxo Diribarne
##
## 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 Octave; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{outbnd} =} findbounds (@var{T}, @var{inbnd})
## Estimate bounds for spatial transformation.
##
## Given a transformation structure @var{T} (see e.g. maketform)
## and bounds @var{inbnd} (2-by-ndims_in) in an input space, returns
## an estimation of the bounds in the output space @var{outbnd}
## (2-by-ndims_out). For instance two dimensionnal bounds could
## be represented as : [xmin ymin; xmax ymax]. If @var{T} does not
## define a forward transform (i.e. for 'polynomial'), the output
## bounds are infered using fsolve and the inverse transform.
##
## @seealso{maketform, cp2tform, tformfwd}
## @end deftypefn
## Author: Pantxo Diribarne <pantxo@dibona>
function [outbnd] = findbounds (T, inbnd)
if (nargin != 2)
print_usage ();
elseif (! istform (T))
error ("imtransform: T must be a transformation structure (see `maketform')");
elseif (! all (size (inbnd) == [2 T.ndims_in]))
error ("imtransform: INBDN must have same size as T.ndims_in");
endif
## Control points grid
if (columns (inbnd) == 2)
[xcp, ycp] = meshgrid (linspace (inbnd(1,1), inbnd(2,1), 3),
linspace (inbnd(1,2), inbnd(2,2), 3));
xcp = reshape (xcp, numel (xcp), 1);
ycp = reshape (ycp, numel (ycp), 1);
xycp = [xcp, ycp];
else
error ("findbounds: support only 2D inputbounds.");
endif
## Output bounds
if (!is_function_handle (T.forward_fcn))
outbnd = zeros (size (xycp));
for ii = 1:rows (xycp)
fun = @(x) tforminv (T, x) - xycp(ii,:);
outbnd(ii,:) = fsolve (fun, xycp(ii,:));
endfor
else
outbnd = tformfwd (T, xycp);
endif
outbnd = [min(outbnd); max(outbnd)];
endfunction
%!test
%! im = checkerboard ();
%! theta = pi/6;
%! T = maketform ('affine', [cos(theta) -sin(theta); ...
%! sin(theta) cos(theta); 0 0]);
%! inbnd = [0 0; 1 1];
%! outbnd = findbounds (T, inbnd);
%! diag = 2^.5;
%! ang = pi/4;
%! assert (diff (outbnd(:,1)), diag * abs (cos (theta - ang)), eps)
%! assert (diff (outbnd(:,2)), diag * abs (cos (theta - ang)), eps)
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