MATLAB: Overwritting problem in for loop

overwrite

I simply crop images and save them with a number.For example i have Grain #1,Grain #2,Grain #3.If i move to another image and crop further images i cannot create images Grain #4 ,Grain #5 etc and instead there are overwritten images…Here is my code.Where is my mistake??
clear all;
clc;
addpath(genpath('C:\Users\User\Desktop\TEI'));
imtool close all; 
k=input('How many times do you want to repeat the cropping?');
IMAGE = uigetfile('*.jpg','Pick an image');
A=imread(IMAGE);
figure,imshow(IMAGE);
folder=('C:\Users\User\Desktop\TEI\BEE_POLLEN _PROJECT\Scripts');
for i=1:k
  f = sprintf('Select a ROI and double click to crop #%d',i);
  uiwait(warndlg(f));
  [B, rect] = imcrop(A);
  baseFileName = sprintf('Grain #%d.jpg',i);
  fullFileName = fullfile(folder, baseFileName);
  baseFileName2 = sprintf('Grain #%d .jpg', (i+1));
  fullFileName2 = fullfile(folder, baseFileName2);
  if exist(fullFileName)     
    imwrite(B, fullFileName2);
  else
    imwrite(B, fullFileName);
  end
  if i==k
    f=sprintf('FINISHED!!');
    uiwait(warndlg(f));
  end
end

Best Answer

nExisting = numel(dir(fullfile(folder, 'Grain #*.jpg')));
for i = 1:k
  f = sprintf('Select a ROI and double click to crop #%d',i);
  uiwait(warndlg(f));
  [B, rect] = imcrop(A);
  baseFileName = sprintf('Grain #%d.jpg', i + nExisting);
  fullFileName = fullfile(folder, baseFileName);
  if exist(fullFileName, 'file')  % with 'file' !!!

      error('Collision with filename: %s', fullFileName);
  end
  imwrite(B, fullFileName);
end
f = 'FINISHED!!';  % without sprintf
uiwait(warndlg(f));
Or use https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort (link) tofind the largest index in the file names and start counting there. (I'd prefer this.)
Another idea is to check the existence of a file name dynamically:
count = 1;
for i = 1:k
  ...
  isFree = false;
  while ~isFree
    baseFileName = sprintf('Grain #%d.jpg', count);
    fullFileName = fullfile(folder, baseFileName);
    if ~exist(fullFileName, 'file')  % with 'file' !!!
       isFree = true;
    end
    count = count + 1;
  end
end
It is not tricky, as you can see.
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