bpdq_random_fourier_locations : Compute random Fourier locations [useind,loc]=bpdq_random_fourier_locations(dim,K,varargin) Choses 2*K (or 2*K-1 if center is chosen) random locations respecting fft symmetry, i.e. if x of dimension dim is real then ifft2( ifftshift( fftshift(fft2(x)) .* loc ) ) will also be real. Inputs: dim - dimensions of image K - # of independent locations desired Selectable Control Parameters : forcecenter - set to 1 to enforce DC coefficient to be chosen seed - pseudorandom seed, set to a real number to seed random number generator Outputs: useind : indices of Fourier coefficient locations loc : binary mask of size dim indicating Fourier coefficient locations This file is part of BPDQ Toolbox (Basis Pursuit DeQuantizer) Copyright (C) 2009, the BPDQ Team (see the file AUTHORS distributed with this library) (See the notice at the end of the file.)
0001 % bpdq_random_fourier_locations : Compute random Fourier locations 0002 % 0003 % [useind,loc]=bpdq_random_fourier_locations(dim,K,varargin) 0004 % 0005 % Choses 2*K (or 2*K-1 if center is chosen) random locations 0006 % respecting fft symmetry, i.e. if x of dimension dim is real 0007 % then ifft2( ifftshift( fftshift(fft2(x)) .* loc ) ) 0008 % will also be real. 0009 % 0010 % Inputs: 0011 % dim - dimensions of image 0012 % K - # of independent locations desired 0013 % 0014 % Selectable Control Parameters : 0015 % forcecenter - set to 1 to enforce DC coefficient to be chosen 0016 % seed - pseudorandom seed, set to a real number to seed random number 0017 % generator 0018 % 0019 % Outputs: 0020 % useind : indices of Fourier coefficient locations 0021 % loc : binary mask of size dim indicating Fourier coefficient locations 0022 % 0023 % This file is part of BPDQ Toolbox (Basis Pursuit DeQuantizer) 0024 % Copyright (C) 2009, the BPDQ Team (see the file AUTHORS distributed with 0025 % this library) (See the notice at the end of the file.) 0026 0027 function [useind,loc]=bpdq_random_fourier_locations(dim,K,varargin) 0028 control_params={'forcecenter',1,... 0029 'seed',nan}; 0030 argselectAssign(control_params); 0031 argselectCheck(control_params,varargin); 0032 argselectAssign(varargin); 0033 0034 if ~isnan(seed) 0035 rand('seed',seed); 0036 end 0037 0038 % odim : smallest even dimension less than or equal to dim 0039 odim=floor((dim-1)/2)*2+1; 0040 0041 if (2*K>prod(odim)) 0042 error('too many locations wanted') 0043 end 0044 0045 % pick random locations from odim 0046 rloc=rand(odim); 0047 rloc=rloc+flipud(fliplr(rloc)); 0048 if forcecenter==1 0049 ctr=floor((odim+1)/2); 0050 rloc(ctr)=-1; % smaller, will be picked first 0051 end 0052 0053 [v,ind]=sort(rloc(:)); 0054 thresh=v(2*K); 0055 eind=ind(find(v<=thresh)); 0056 oloc=zeros(odim); 0057 oloc(eind)=1; 0058 0059 % then pad with zeros to recover size dim 0060 % If I do this correctly, the center of size odim matrix 0061 % will be center of size dim matrix 0062 % and zero padded regions will correspond to highest frequencies 0063 % that must be real-valued for fft to be real 0064 0065 if(odim(1)~=dim(1)) 0066 % pad on top 0067 oloc=[zeros(1,size(oloc,2));oloc]; 0068 end 0069 if(odim(2)~=dim(2)) 0070 oloc=[zeros(size(oloc,1),1),oloc]; 0071 % pad on left 0072 end 0073 loc=oloc; 0074 useind=find(loc); 0075 0076 0077 % The BPDQ Toolbox is free software: you can redistribute it and/or modify 0078 % it under the terms of the GNU General Public License as published by 0079 % the Free Software Foundation, either version 3 of the License, or 0080 % (at your option) any later version. 0081 % 0082 % The BPDQ Toolbox is distributed in the hope that it will be useful, 0083 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0084 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0085 % GNU General Public License for more details. 0086 % 0087 % You should have received a copy of the GNU General Public License 0088 % along with The BPDQ Toolbox. If not, see <http://www.gnu.org/licenses/>.