## Copyright (C) 2005 Søren Hauberg ## ## 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, see <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} @var{B}= imresize (@var{A}, @var{m}) ## Scales the image @var{A} by a factor @var{m} using nearest neighbour ## interpolation. If @var{m} is less than 1 the image size will be reduced, ## and if @var{m} is greater than 1 the image will be enlarged. If the image ## is being enlarged the it will be convolved with a 11x11 Gaussian FIR filter ## to reduce aliasing. See below on how to alter this behavior. ## ## @deftypefnx {Function File} @var{B}= imresize (@var{A}, @var{m}, @var{interp}) ## Same as above except @var{interp} interpolation is performed instead of ## using nearest neighbour. @var{interp} can be any interpolation method supported by interp2. ## ## @deftypefnx {Function File} @var{B}= imresize (@var{A}, [@var{mrow} @var{mcol}]) ## Scales the image @var{A} to be of size @var{mrow}x@var{mcol} using nearest ## neighbour interpolation. If the image is being enlarged it will be convolved ## with a lowpass FIR filter as described above. ## ## @deftypefnx {Function File} @var{B}= imresize (@var{A}, [@var{mrow} @var{mcol}], @var{interp}) ## Same as above except @var{interp} interpolation is performed instead of using ## nearest neighbour. @var{interp} can be any interpolation method supported by interp2. ## ## @deftypefnx {Function File} @var{B}= imresize (..., @var{interp}, @var{fsize}) ## If the image the image is being reduced it will usually be convolved with ## a 11x11 Gaussian FIR filter. By setting @var{fsize} to 0 this will be turned ## off, and if @var{fsize} > 0 the image will be convolved with a @var{fsize} ## by @var{fsize} Gaussian FIR filter. ## ## @deftypefnx {Function File} @var{B}= imresize (..., @var{interp}, @var{filter}) ## If the image size is being reduced and the @var{filter} argument is passed to ## imresize the image will be convolved with @var{filter} before the resizing ## takes place. ## ## @seealso{imremap, imrotate, interp2} ## @end deftypefn function ret = imresize(im, m, interp = "nearest", filter = 11) if (nargin < 2) error("imresize: not enough input arguments"); endif [row, col, num_planes, tmp] = size(im); if (tmp != 1 || (num_planes != 1 && num_planes != 3)) error("imresize: the first argument has must be an image"); endif ## Handle the argument that describes the size of the result if (length(m) == 1) new_row = round(row*m); new_col = round(col*m); elseif (length(m) == 2) new_row = m(1); new_col = m(2); m = min( new_row/row, new_col/col ); else error("imresize: second argument mest be a scalar or a 2-vector"); end ## Handle the method argument if (!any(strcmpi(interp, {"nearest", "linear", "bilinear", "cubic", "bicubic", "pchip"}))) error("imresize: unsupported interpolation method"); endif ## Handle the filter argument if (!strcmp(interp, "nearest") && m < 1) if (isscalar(filter) && filter > 0) ## If the image is being reduced and filter > 0 then ## convolve the image with a filter*filter gaussian. mu = (filter/2); sigma = mu/3; x = 1:filter; gauss = 1/sqrt(2*pi*sigma^2) * exp( (-(x-mu).^2)/(2*sigma^2) ); for i = 1:num_planes im(:,:,i) = conv2(gauss, gauss, im(:,:,i), "same"); endfor elseif (nargin >= 4 && ismatrix(filter) && ndims(filter) == 2) ## If the image size is being reduced and a fourth argument ## is given, use it as a FIR filter. for i = 1:num_planes im(:,:,i) = conv2(im(:,:,i), filter, "same"); endfor endif endif ## Perform the actual resizing [XI, YI] = meshgrid( linspace(1,col,new_col), linspace(1,row,new_row) ); ret = imremap(im, XI, YI, interp); endfunction

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