source: trunk/src/series/sub_background.m @ 1180

Last change on this file since 1180 was 1180, checked in by sommeria, 3 weeks ago

various bugs repaired,Relabeling frames installed for multitif

File size: 22.8 KB
Line 
1%'sub_background': substract a sliding background to an image series
2%------------------------------------------------------------------------
3% Method:
4    %calculate the background image by sorting the luminosity of each point
5    % over a sliding sub-sequence of 'nbaver_ima' images.
6    % The luminosity value of rank 'rank' is selected as the
7    % 'background'. rank=nbimages/2 gives the median value.  Smaller values are appropriate
8    % for a dense set of particles. The extrem value rank=1 gives the true minimum
9    % luminosity, but it can be polluted by noise.
10% Organization of image indices:
11    % The program is working on a series of images,
12    % In the mode 'volume', nbfield2=1 (1 image at each level)and NbSlice (=NbField_j)
13    % Else nbfield2=NbField_j =nbre of images in a burst (j index)
14   
15% function GUI_config=sub_background(Param)
16%
17%%%%%%%%%%% GENERAL TO ALL SERIES ACTION FCTS %%%%%%%%%%%%%%%%%%%%%%%%%%%
18%
19%OUTPUT
20% ParamOut: sets options in the GUI series.fig needed for the function
21%
22%INPUT:
23% In run mode, the input parameters are given as a Matlab structure Param copied from the GUI series.
24% In batch mode, Param is the name of the corresponding xml file containing the same information
25% when Param.Action.RUN=0 (as activated when the current Action is selected
26% in series), the function ouput paramOut set the activation of the needed GUI elements
27%
28% Param contains the elements:(use the menu bar command 'export/GUI config' in series to
29% see the current structure Param)
30%    .InputTable: cell of input file names, (several lines for multiple input)
31%                      each line decomposed as {RootPath,SubDir,Rootfile,NomType,Extension}
32%    .OutputSubDir: name of the subdirectory for data outputs
33%    .OutputDirExt: directory extension for data outputs
34%    .Action: .ActionName: name of the current activated function
35%             .ActionPath:   path of the current activated function
36%             .ActionExt: fct extension ('.m', Matlab fct, '.sh', compiled   Matlab fct
37%             .RUN =0 for GUI input, =1 for function activation
38%             .RunMode='local','background', 'cluster': type of function  use
39%             
40%    .IndexRange: set the file or frame indices on which the action must be performed
41%    .FieldTransform: .TransformName: name of the selected transform function
42%                     .TransformPath:   path  of the selected transform function
43%    .InputFields: sub structure describing the input fields withfields
44%              .FieldName: name(s) of the field
45%              .VelType: velocity type
46%              .FieldName_1: name of the second field in case of two input series
47%              .VelType_1: velocity type of the second field in case of two input series
48%              .Coord_y: name of y coordinate variable
49%              .Coord_x: name of x coordinate variable
50%    .ProjObject: %sub structure describing a projection object (read from ancillary GUI set_object)
51%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
52
53%=======================================================================
54% Copyright 2008-2024, LEGI UMR 5519 / CNRS UGA G-INP, Grenoble, France
55%   http://www.legi.grenoble-inp.fr
56%   Joel.Sommeria - Joel.Sommeria (A) univ-grenoble-alpes.fr
57%
58%     This file is part of the toolbox UVMAT.
59%
60%     UVMAT is free software; you can redistribute it and/or modify
61%     it under the terms of the GNU General Public License as published
62%     by the Free Software Foundation; either version 2 of the license,
63%     or (at your option) any later version.
64%
65%     UVMAT is distributed in the hope that it will be useful,
66%     but WITHOUT ANY WARRANTY; without even the implied warranty of
67%     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
68%     GNU General Public License (see LICENSE.txt) for more details.
69%=======================================================================
70
71function ParamOut=sub_background (Param)
72
73%%%%%%%%%%%%%%%%%    INPUT PREPARATION MODE (no RUN)    %%%%%%%%%%%%%%%%%
74if isstruct(Param) && isequal(Param.Action.RUN,0)
75    ParamOut.AllowInputSort='off';% allow alphabetic sorting of the list of input file SubDir (options 'off'/'on', 'off' by default)
76    ParamOut.WholeIndexRange='on';% prescribes the file index ranges from min to max (options 'off'/'on', 'off' by default)
77    ParamOut.NbSlice='on'; % edit box nbre of slices made active
78    ParamOut.VelType='off';% menu for selecting the velocity type (options 'off'/'one'/'two',  'off' by default)
79    ParamOut.FieldName='off';% menu for selecting the field (s) in the input file(options 'off'/'one'/'two', 'off' by default)
80    ParamOut.FieldTransform = 'off';%can use a transform function (option 'off'/'on','off' by default)
81    ParamOut.ProjObject='off';%cannot use projection object(option 'off'/'on','off' by default)
82    ParamOut.Mask='off';%cannot use mask option   (option 'off'/'on', 'off' by default)
83    ParamOut.OutputDirExt='.sback';%set the output dir extension
84    ParamOut.OutputFileMode='NbInput';% '=NbInput': 1 output file per input file index, '=NbInput_i': 1 file per input file index i, '=NbSlice': 1 file per slice
85
86    %% check the validity of  input file types
87    if isfield(Param,'SeriesData')&& isfield(Param.SeriesData,'FileInfo')
88    if ~strcmp(Param.SeriesData.FileInfo{1}.FieldType,'image')
89        msgbox_uvmat('ERROR','invalid file type input: not an image series')
90        return
91    end
92    end
93
94    %% numbers of fields
95    NbSlice_i=1;%default
96    if isfield(Param.IndexRange,'NbSlice')&&~isempty(Param.IndexRange.NbSlice)
97        NbSlice_i=Param.IndexRange.NbSlice;
98    end
99    incr_j=1;%default
100    if isfield(Param.IndexRange,'incr_j')&&~isempty(Param.IndexRange.incr_j)
101        incr_j=Param.IndexRange.incr_j;
102    end
103    if isfield(Param.IndexRange,'first_j')&&~isempty(Param.IndexRange.first_j)
104        NbField_j=numel(Param.IndexRange.first_j:incr_j:Param.IndexRange.last_j);%nb of fields for the j index (bursts or volume slices)
105    else
106        NbField_j=1;
107    end
108    first_i=1;last_i=1;incr_i=1;%default
109    if isfield(Param.IndexRange,'MinIndex_i'); first_i=Param.IndexRange.MinIndex_i; end   
110    if isfield(Param.IndexRange,'MaxIndex_i'); last_i=Param.IndexRange.MaxIndex_i; end
111    if isfield(Param.IndexRange,'incr_i')&&~isempty(Param.IndexRange.incr_i)
112        incr_i=Param.IndexRange.incr_i;
113    end
114    nbfield_i=numel(first_i:incr_i:last_i);%nb of fields for the i index (bursts or volume slices)
115    nbfield=NbField_j*nbfield_i; %total number of fields
116    nbfield_i=floor(nbfield/NbSlice_i);%total number of  indexes in a slice (adjusted to an integer number of slices)
117   
118    %% setting of  parameters specific to sub_background
119    CheckVolume='No';
120    nbaver_init=23; %default number of images used for the sliding background: to be adjusted later to include an integer number of bursts
121    SaturationValue=0;
122     if nbfield_i~=1 && NbField_j<=nbaver_init
123        nbaver=floor(nbaver_init/NbField_j); % number of bursts used for the sliding background,
124        if isequal(mod(nbaver,2),0)% if nbaver is even
125            nbaver=nbaver+1;%put the number of burst to an odd number (so the middle burst is defined)
126        end
127        nbaver_init=nbaver*NbField_j;%propose by default an integer number of bursts
128    end
129    BrightnessRankThreshold=0.1;
130    if isfield(Param,'ActionInput')
131        if isfield(Param.ActionInput,'CheckVolume') && Param.ActionInput.CheckVolume
132            CheckVolume='Yes';
133        end
134        if isfield(Param.ActionInput,'SlidingSequenceLength')
135         nbaver_init=Param.ActionInput.SlidingSequenceLength;
136        end
137        if isfield(Param.ActionInput,'BrightnessRankThreshold')
138          BrightnessRankThreshold=Param.ActionInput.BrightnessRankThreshold;
139        end
140        if isfield(Param.ActionInput,'SaturationValue')
141            SaturationValue=Param.ActionInput.SaturationValue;
142        end
143    end   
144    prompt = {'volume scan mode (Yes/No)';...
145        'Number of images for the sliding background (MUST FIT IN COMPUTER MEMORY)';...
146        'the luminosity rank chosen to define the background (0.1=for dense particle seeding, 0.5 (median) for sparse particles';...
147        'image saturation level for rescaling( reduce the influence of particles brighter than this value), =0 for no rescaling' };
148    dlg_title = 'get (slice by slice) a sliding background and substract to each image';
149    num_lines= 4;
150    def     = { CheckVolume;num2str(nbaver_init);num2str(BrightnessRankThreshold);num2str(SaturationValue)};
151    answer = inputdlg(prompt,dlg_title,num_lines,def);
152    if isempty(answer)
153        return
154    end
155    %check input consistency
156    if strcmp(answer{1},'No') && ~isequal(NbSlice_i,1)
157        check=msgbox_uvmat('INPUT_Y-N',['confirm the multi-level splitting into ' num2str(NbSlice_i) ' slices']);
158        if ~strcmp(check,'Yes')
159            return
160        end
161    end
162    if strcmp(answer{1},'Yes')
163        step=2;%the sliding background is shifted by the length of one burst, assumed =2 for volume
164        ParamOut.NbSlice=1; %nbre of slices displayed
165    else
166        step=NbField_j;%case of bursts: the sliding background is shifted by the length of one burst
167    end
168    ParamOut.ActionInput.SlidingSequenceLength=adjust_slidinglength(str2double(answer{2}),step);
169    ParamOut.ActionInput.CheckVolume=strcmp(answer{1},'Yes');
170    ParamOut.ActionInput.BrightnessRankThreshold=str2double(answer{3});
171%     ParamOut.ActionInput.CheckSubmedian=strcmp(answer{4},'Yes');
172    ParamOut.ActionInput.SaturationValue=str2double(answer{4});
173    % apply the image rescaling function 'level' (avoid the blinking effects of bright particles)
174%     answer=msgbox_uvmat('INPUT_Y-N','apply image rescaling function levels.m after sub_background');
175%     ParamOut.ActionInput.CheckLevelTransform=strcmp(answer,'Yes');
176    return
177end
178%%%%%%%%%%%%%%%%%    STOP HERE FOR PAMETER INPUT MODE   %%%%%%%%%%%%%%%%%
179
180%% read input parameters from an xml file if input is a file name (batch mode)
181% checkrun=1;
182RUNHandle=[];
183% WaitbarHandle=[];
184if ischar(Param)
185    Param=xml2struct(Param);% read Param as input file (batch case)
186else
187 hseries=findobj(allchild(0),'Tag','series');
188RUNHandle=findobj(hseries,'Tag','RUN');%handle of RUN button in GUI series
189% WaitbarHandle=findobj(hseries,'Tag','Waitbar');%handle of waitbar in GUI series
190end
191
192%% input preparation
193NbSlice_i=Param.IndexRange.NbSlice;
194if ~isequal(NbSlice_i,1)
195    disp(['multi-level splitting into ' num2str(NbSlice_i) ' slices']);
196end
197RootPath=Param.InputTable{1,1};
198RootFile=Param.InputTable{1,3};
199SubDir=Param.InputTable{1,2};
200NomType=Param.InputTable{1,4};
201FileExt=Param.InputTable{1,5};
202%[filecell,i1_series,i2_series,j1_series]=get_file_series(Param);%series of file names organised as a single array
203
204
205%% file index parameters
206% NbSlice_i: nbre of slices for i index in multi-level mode: equal to 1 for a single level
207% the function sub_background is then relaunched by the GUI series for each
208%      slice, incrementing the first index i by 1
209% NbSlice_j: nbre of slices in volume mode
210% nbfield : total number of images treated per slice
211% step: shift of image index at each step of the sliding background (corresponding to the nbre of images in a burst)
212% nbaver_ima: nbre of the images in the sliding sequence used for the background
213% nbaver=nbaver_ima/step: nbre of bursts corresponding to nbaver_ima images. It has been adjusted so that nbaver is an odd integer
214i_indices=Param.IndexRange.first_i:Param.IndexRange.incr_i:Param.IndexRange.last_i;
215if isfield(Param.IndexRange,'first_j')
216j_indices=Param.IndexRange.first_j:Param.IndexRange.incr_j:Param.IndexRange.last_j;
217else
218    j_indices=1;
219end
220nbfield_i=numel(i_indices); %nb of fields for the i index (bursts or volume slices)
221NbField_j=numel(j_indices); %nb of fields for the j index
222j_indices=j_indices'*ones(1,nbfield_i);
223i_indices=ones(NbField_j,1)*i_indices;
224
225if Param.ActionInput.CheckVolume% case of volume scan: the background images must be determined for each index j
226    step=2;% we assume the burst contains only one image pair
227    NbSlice_j=NbField_j;
228    nbfield_series=nbfield_i;
229else
230    if Param.ActionInput.SlidingSequenceLength<NbField_j
231        step=1;
232    else
233    step=NbField_j;%case of bursts: the sliding background is shifted by the length of one burst
234    end
235    NbSlice_j=1;
236    nbfield_series=nbfield_i*NbField_j;
237end
238nbfield=NbField_j*nbfield_i; %total number of fields
239[nbaver_ima,nbaver,step]=adjust_slidinglength(Param.ActionInput.SlidingSequenceLength,step);
240if nbaver_ima > nbfield
241    disp('number of images in a slice smaller than the proposed number of images for the sliding average')
242    return
243end
244halfnbaver=floor(nbaver/2); % half width (in unit of bursts) of the sliding background
245
246
247%% File relabeling documented by the xml file
248CheckRelabel=isfield(Param,'FileSeries' );
249
250%% Input file info
251if CheckRelabel
252    [RootFileOut,frame_index]=index2filename(Param.FileSeries,Param.IndexRange.first_i,j_indices(1),NbField_j);
253    FirstFileName=fullfile(RootPath,SubDir,RootFileOut);
254else
255    FirstFileName=fullfile_uvmat(RootPath,SubDir,RootFile,FileExt,NomType,Param.IndexRange.first_i,[],j_indices(1));%get first file name
256    RootFileOut=RootFile;
257end
258[FileInfo,MovieObject]=get_file_info(FirstFileName);
259FileType=FileInfo.FileType;
260if ~CheckRelabel
261    if isfield(FileInfo,'NumberOfFrames') && FileInfo.NumberOfFrames >1
262        if isempty(regexp(NomType,'1$', 'once'))% no file indexing
263            frame_index=i_indices;% the index i denotes the frame number in a movie, no index j
264        else
265            frame_index=j_indices;% the index j denotes the frame number in a movie
266            MovieObject=[]; %not a single video object
267        end
268    else
269        frame_index=ones(1,nbfield);
270    end
271end
272
273%% output file naming
274FileExtOut='.png'; % write result as .png images for image inputsFileInfo.FileType='image'
275if strcmp(FileInfo.FileType,'image')
276    NomTypeOut=NomType;
277elseif NbField_j==1
278    NomTypeOut='_1';
279else
280    NomTypeOut='_1_1';% case of purely numerical indexing
281end
282OutputDir=[Param.OutputSubDir Param.OutputDirExt];
283OutputPath=fullfile(Param.OutputPath,Param.Experiment,Param.Device);
284
285%% calculate absolute brightness rank
286rank=floor(Param.ActionInput.BrightnessRankThreshold*nbaver_ima);
287if rank==0
288    rank=1;%rank selected in the sorted image series
289end
290
291%% prealocate memory for the sliding background
292Ak=zeros(FileInfo.Height,FileInfo.Width,nbaver_ima,['uint' num2str(FileInfo.BitDepth)]); %prealocate memory
293
294%% selection of frame indices
295if Param.ActionInput.CheckVolume
296    nbfield=floor(nbfield/NbSlice_j)*NbSlice_j;% truncate the total number of frames in case of incomplete series
297    indselect=1:nbfield;
298    indselect=reshape(indselect,NbSlice_j,[]);
299    NbSlice=NbSlice_j;
300else
301    NbSlice=NbSlice_i;
302    nbfield=floor(nbfield/NbSlice)*NbSlice;% truncate the total number of frames in case of incomplete series
303    indselect=reshape(1:nbfield,NbSlice,[]);
304    for j_slice=1:NbSlice
305        indselect(j_slice,:)=j_slice:NbSlice:nbfield;% select file indices of the slice
306    end
307end
308
309%%%%%%%  LOOP ON SLICES %%%%%%%
310for j_slice=1:NbSlice
311
312    %% read the first series of nbaver_ima images and sort by luminosity at each pixel
313    for ifield = 1:nbaver_ima
314        ifile=indselect(j_slice,ifield);
315        %filename=filecell{1,ifile};
316        if CheckRelabel
317            [filename,FrameIndex]=index2filename(Param.FileSeries,i_indices(ifile),j_indices(ifile),NbField_j);
318             filename=fullfile(RootPath,SubDir,filename);
319        else
320            filename=fullfile_uvmat(RootPath,SubDir,RootFile,FileExt,NomType,i_indices(ifile),[],j_indices(ifile));
321            FrameIndex=frame_index(ifile);
322        end
323        Aread=read_image(filename,FileType,MovieObject,FrameIndex);
324        if ndims(Aread)==3%color images
325            Aread=sum(double(Aread),3);% take the sum of color components
326        end
327        Ak(:,:,ifield)=Aread;
328    end
329    Asort=sort(Ak,3);%sort the luminosity of images at each point
330    B=Asort(:,:,rank);%background image
331
332    %% substract the first background image to the first images
333    disp( 'first background image will be substracted')
334    for ifield=1:step*(halfnbaver+1)% nbre of images treated by the first background image
335        Acor=double(Ak(:,:,ifield))-double(B);%substract background to the current image
336        Acor=(Acor>0).*Acor; % put to 0 the negative elements in Acor
337        ifile=indselect(j_slice,ifield);
338        newname=fullfile_uvmat(OutputPath,OutputDir,RootFileOut,FileExtOut,NomTypeOut,i_indices(ifile),[],j_indices(ifile));
339
340        %write result file
341        if ~isequal(Param.ActionInput.SaturationValue,0)
342            C=levels(Acor,Param.ActionInput.SaturationValue);
343            imwrite(C,newname,'BitDepth',16); % save the new image
344        else
345            if isequal(FileInfo.BitDepth,16)
346                C=uint16(Acor);
347                imwrite(C,newname,'BitDepth',16); % save the new image
348            else
349                C=uint8(Acor);
350                imwrite(C,newname,'BitDepth',8); % save the new image
351            end
352        end
353        disp([newname ' written'])
354    end
355
356    %% repeat the operation on a sliding series of images
357    disp('sliding background image will be substracted')
358    if nbfield_series > nbaver_ima
359        for ifield = step*(halfnbaver+1):step:nbfield_series-step*(halfnbaver+1)% ifield +iburst=index of the current processed image
360            %             update_waitbar(WaitbarHandle,ifield/nbfield_series)
361            if  ~isempty(RUNHandle)&&~strcmp(get(RUNHandle,'BusyAction'),'queue')
362                disp('program stopped by user')
363                return
364            end
365            if nbaver_ima>step
366                Ak(:,:,1:nbaver_ima-step)=Ak(:,:,1+step:nbaver_ima);% shift the current image series by one burst (step)
367            end
368            %incorporate next burst in the current image series
369            for iburst=1:step
370                ifile=indselect(j_slice,ifield+iburst+step*halfnbaver);
371                if CheckRelabel
372                    [filename,FrameIndex]=index2filename(Param.FileSeries,i_indices(ifile),j_indices(ifile),NbField_j);
373                    filename=fullfile(RootPath,SubDir,filename);
374                else
375                    filename=fullfile_uvmat(RootPath,SubDir,RootFile,FileExt,NomType,i_indices(ifile),[],j_indices(ifile));
376                    FrameIndex=frame_index(ifile);
377                end
378                Aread=read_image(filename,FileType,MovieObject,FrameIndex);
379                if ndims(Aread)==3%case of color images
380                    Aread=sum(double(Aread),3);% take the sum of color components
381                end
382                Ak(:,:,nbaver_ima-step+iburst)=Aread;% fill the last burst of the current image series by the new image
383            end
384            Asort=sort(Ak,3);%sort the new current image series by luminosity
385            B=Asort(:,:,rank);%current background image
386            %substract the background for the current burst
387            for iburst=1:step
388                Acor=double(Ak(:,:,step*halfnbaver+iburst))-double(B); %the current image has been already read ans stored as index step*halfnbaver+iburst in the current series
389                Acor=(Acor>0).*Acor; % put to 0 the negative elements in Acor
390                ifile=indselect(j_slice,ifield+iburst);
391                newname=fullfile_uvmat(OutputPath,OutputDir,RootFileOut,FileExtOut,NomTypeOut,i_indices(ifile),[],j_indices(ifile));
392                %write result file
393                if ~isequal(Param.ActionInput.SaturationValue,0)
394                    C=levels(Acor,Param.ActionInput.SaturationValue);
395                    imwrite(C,newname,'BitDepth',16); % save the new image
396                else
397                    if isequal(FileInfo.BitDepth,16)
398                        C=uint16(Acor);
399                        imwrite(C,newname,'BitDepth',16); % save the new image
400                    else
401                        C=uint8(Acor);
402                        imwrite(C,newname,'BitDepth',8); % save the new image
403                    end
404                end
405                disp([newname ' written'])
406            end
407        end
408    end
409
410    %% substract the background from the last images
411    disp('last background image will be substracted')
412    for  ifield=nbfield_series-step*halfnbaver+1:nbfield_series
413        Acor=double(Ak(:,:,ifield-nbfield_series+step*(2*halfnbaver+1)))-double(B);
414        Acor=(Acor>0).*Acor; % put to 0 the negative elements in Acor
415        ifile=indselect(j_slice,ifield);
416        newname=fullfile_uvmat(OutputPath,OutputDir,RootFileOut,FileExtOut,NomTypeOut,i_indices(ifile),[],j_indices(ifile));
417        %write result file
418        if ~isequal(Param.ActionInput.SaturationValue,0)
419            C=levels(Acor,Param.ActionInput.SaturationValue);
420            imwrite(C,newname,'BitDepth',16); % save the new image
421        else
422            if isequal(FileInfo.BitDepth,16)
423                C=uint16(Acor);
424                imwrite(C,newname,'BitDepth',16); % save the new image
425            else
426                C=uint8(Acor);
427                imwrite(C,newname,'BitDepth',8); % save the new image
428            end
429        end
430        disp([newname ' written'])
431    end
432end
433
434function C=levels(A,Coeff)
435
436% nblock_y=100;%2*Param.TransformInput.BlockSize;
437% nblock_x=100;%2*Param.TransformInput.BlockSize;
438% [npy,npx]=size(A);
439% [X,Y]=meshgrid(1:npx,1:npy);
440%
441% %Backg=zeros(size(A));
442% %Aflagmin=sparse(imregionalmin(A));%Amin=1 for local image minima
443% %Amin=A.*Aflagmin;%values of A at local minima
444% % local background: find all the local minima in image subblocks
445% if CheckSubmedian
446%     fctblock= inline('median(x(:))');
447%     Backg=blkproc(A,[nblock_y nblock_x],fctblock);% take the median in  blocks
448%     %B=imresize(Backg,size(A),'bilinear');% interpolate to the initial size image
449%     A=A-imresize(Backg,size(A),'bilinear');% substract background interpolated to the initial size image
450% end
451% fctblock= inline('mean(x(:))');
452% AMean=blkproc(A,[nblock_y nblock_x],fctblock);% take the mean in  blocks
453% fctblock= inline('var(x(:))');
454% AVar=blkproc(A,[nblock_y nblock_x],fctblock);% take the mean in  blocks
455% Avalue=AVar./AMean;% typical value of particle luminosity
456% Avalue=imresize(Avalue,size(A),'bilinear');% interpolate to the initial size image
457%C=uint16(1000*tanh(A./(Coeff*Avalue)));
458C=uint16(Coeff*tanh(A./Coeff));
459%------------------------------------------
460% adjust the number of images used for the sliding average
461function [nbaver_ima,nbaver,step_out]=adjust_slidinglength(nb_aver_in,step)
462%nbaver_ima=str2double(nb_aver_in);%number of images for the sliding background
463nbaver=ceil(nb_aver_in/step);%number of bursts for the sliding background
464if isequal(mod(nbaver,2),0)% if nbaver is even
465    nbaver=nbaver+1;%set the number of bursts to an odd number (so the middle burst is defined)
466end
467step_out=step;
468if nbaver>1
469    nbaver_ima=nbaver*step;% correct the nbre of images corresponding to nbaver
470else
471    nbaver_ima=nb_aver_in;
472    if isequal(mod(nbaver_ima,2),0)% if nbaver_ima is even
473        nbaver_ima=nbaver_ima+1;%set the number of bursts to an odd number (so the middle burst is defined)
474    end
475    step_out=1;
476end
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