I am working on to pre process my ultrasound images using loop.But i couldnt save the output of the preprocessed images from the loop.

myDir = uigetdir('*.m'); %gets directory
myFiles = dir(fullfile(myDir,'*.png')); %gets all png files in struct
for k = 1:length(myFiles)
  baseFileName = myFiles(k).name;
  fullFileName = fullfile(myDir, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  %[imData, Fs] = imread(fullFileName);
  myFiles.name;
 filename = myFiles.name;
img = imread(filename);
img = im2gray(img); % need to work on the right image
% use the actual image dimensions

[nrows,ncols,~] = size(img);
for row = 1:nrows
    for col = 1:ncols
        % image origin is NW corner, so a line which points from SW to NE
        % actually has negative slope!
        if row < (-0.77*col + 253.64)
            img(row,col) = 0; % i'm using gray so it's easy to see 
        end
    end
end
%imshow(img)
%filename = '181.png';
%img = imread(filename);
%img = im2gray(img); % need to work on the right image
% use the actual image dimensions
[nrows,ncols,~] = size(img);
for row = 1:nrows
    for col = 1:ncols
        % image origin is NW corner, so a line which points from SW to NE
        % actually has negative slope!
        if row < (0.77*col - 238.31)
            img(row,col) = 0; % i'm using gray so it's easy to see 
        end
    end
end

cropped=img(5:370,31:609);
imshow(img)
 imwrite(cropped, filename, 'png') ;
end

Answer 1

[Sulaymon Eshkabilov]

The code is overwriting the already existing file with a changed size and recalling it again. Thuis, the file name change was necessary. Here is the corrected code:

clearvars
myDir = uigetdir('*.m'); %gets directory
myFiles = dir(fullfile(myDir,'*.png')); %gets all png files in struct
for k = 1:length(myFiles)
  baseFileName = myFiles(k).name;
  fullFileName = fullfile(myDir, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  %[imData, Fs] = imread(fullFileName);
 FName= myFiles.name;
img = imread(FName);
img = im2gray(img); % need to work on the right image
% use the actual image dimensions

[nrows,ncols,~] = size(img);
for row = 1:nrows
    for col = 1:ncols
        % image origin is NW corner, so a line which points from SW to NE
        % actually has negative slope!
        if row < (-0.77*col + 253.64)
            img(row,col) = 0; % i'm using gray so it's easy to see 
        end
    end
end
%imshow(img)
%filename = '181.png';
%img = imread(filename);
%img = im2gray(img); % need to work on the right image
% use the actual image dimensions
[nrows,ncols,~] = size(img);
for row = 1:nrows
    for col = 1:ncols
        % image origin is NW corner, so a line which points from SW to NE
        % actually has negative slope!
        if row < (0.77*col - 238.31)
            img(row,col) = 0; % i'm using gray so it's easy to see 
        end
    end
end
% New and corrected images aer writtedn under different file names, e.g.
% NEW1.png from 181.png, NEW2.png from 182.png, NEW3.png from 183.png
 FName =  strcat(['NEW', num2str(k), '.png']);
 cropped=img(5:370,31:609);
 imshow(img)
 imwrite(cropped, FName) ;
end