% 'ima_filter':  low-pass filter of an image followed by decimation 

%------------------------------------------------------------------------
%%%%  Use the general syntax for transform fields with a single input and parameters %%%%
% OUTPUT: 
% DataOut:   output field structure 
%
%INPUT:
% DataIn:  input field structure
% Param: matlab structure whose field Param.TransformInput contains the filter parameters
%-----------------------------------

%=======================================================================
% Copyright 2008-2024, LEGI UMR 5519 / CNRS UGA G-INP, Grenoble, France
%   http://www.legi.grenoble-inp.fr
%   Joel.Sommeria - Joel.Sommeria (A) legi.cnrs.fr
%
%     This file is part of the toolbox UVMAT.
%
%     UVMAT 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.
%
%     UVMAT 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 (see LICENSE.txt) for more details.
%=======================================================================

function DataOut=ima_filter(DataIn,Param)

%% request input parameters
if isfield(DataIn,'Action') && isfield(DataIn.Action,'RUN') && isequal(DataIn.Action.RUN,0)
    prompt = {'npx';'npy'};
    dlg_title = 'get the filter size in x and y';
    num_lines= 2;
    def     = { '20';'20'};
    if isfield(Param,'TransformInput')&&isfield(Param.TransformInput,'FilterBoxSize_x')&&...
            isfield(Param.TransformInput,'FilterBoxSize_y')
        def={num2str(Param.TransformInput.FilterBoxSize_x);num2str(Param.TransformInput.FilterBoxSize_y)};
    end
    answer = inputdlg(prompt,dlg_title,num_lines,def);
    DataOut.TransformInput.FilterBoxSize_x=str2num(answer{1}); %size of the filtering window
    DataOut.TransformInput.FilterBoxSize_y=str2num(answer{2}); %size of the filtering window
    return
end

DataOut=DataIn; %default

%definition of the cos shape matrix filter
bx=Param.TransformInput.FilterBoxSize_x;
by=Param.TransformInput.FilterBoxSize_y;
ix=1/2-bx/2:-1/2+bx/2;%
iy=1/2-by/2:-1/2+by/2;%
%del=np/3;
%fct=exp(-(ix/del).^2);
fct2_x=cos(ix/((Param.TransformInput.FilterBoxSize_x-1)/2)*pi/2);
fct2_y=cos(iy/((Param.TransformInput.FilterBoxSize_y-1)/2)*pi/2);
%Mfiltre=(ones(5,5)/5^2);
Mfiltre=fct2_y'*fct2_x;
Mfiltre=Mfiltre/(sum(sum(Mfiltre)));%normalize filter

Atype=class(DataIn.A);% detect integer 8 or 16 bits
if numel(size(DataIn.A))==3
    DataOut.A=filter2(Mfiltre,sum(DataIn.A,3));%filter the input image, after summation on the color component (for color images)
    DataOut.A=uint16(DataOut.A); %transform to 16 bit images
else
    DataOut.A=filter2(Mfiltre,DataIn.A);
    DataOut.A=feval(Atype,DataOut.A);%transform to the initial image format
end
%reduce the size of the image
[npy,npx]=size(DataOut.A);
ind_y=ceil(by/2):by:npy-ceil(by/2);
ind_x=ceil(bx/2):bx:npx-ceil(bx/2);
B=DataOut.A(ind_y,ind_x);
DataOut.A=B;

