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rotating and saving images to folder: error during loop

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Hi folks,
I'm trying to read all files in a folder, rotatet them 90 degrees, then save them to the same folder. I need to do this 3 times (90, 180, 270 degrees).
The following is my code.
folder = "C:\Users\ME\Pictures\Filler\";
S = dir(fullfile(folder,'*.png'));
for k = 1:250
currentfilename = fullfile(folder,S(k).name);
I = imread(currentfilename);
I2 = imrotate(I, 90);
I2Name = sprintf('%d -1.png', k);
I2Path = fullfile(folder, I2Name);
imwrite(I2, I2Path);
I3 = imrotate(I, 180);
I3Name = sprintf('%d -2.png', k);
I3Path = fullfile(folder, I3Name);
imwrite(I3, I3Path);
I4 = imrotate(I, 270);
I4Name = sprintf('%d -3.png', k);
I4Path = fullfile(folder, I4Name);
imwrite(I4, I4Path);
Running it seems to throw up some errors. Some of the files are repeated or rotated incorrectly. Can anyone spot the reason please? I don't really know enough about matlab to see what I've done wrong!


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Accepted Answer

Image Analyst
Image Analyst on 15 Jan 2020
I believe the problem comes about because you are, in subsequent runs, processing images from a prior run. You should either skip those images, like I did in my code below, or write those images to a folder different than your input folder.
folder = pwd;
S = dir(fullfile(folder,'*.png'));
fprintf('Found %d PNG files.\n', length(S));
hFig = figure;
hFig.WindowState = 'maximized';
angles = [90, 180, 270];
for k = 1 : 3
originalFilename = fullfile(folder, S(k).name);
[~, baseFileNameNoExt, ~] = fileparts(lower(originalFilename))
originalImage = imread(originalFilename);
fprintf('\nRead in %s.\n', originalFilename);
subplot(2, 2, 1);
title(['Original image : ', S(k).name], 'FontSize', 15);
% Skip files that are the outputs from prior runs.
% They will contain '-n.png'
if endsWith(baseFileNameNoExt, ' -1') || ...
endsWith(baseFileNameNoExt, ' -2') || ...
endsWith(baseFileNameNoExt, ' -3')
continue; % Skip this image.
for angleIndex = 1 : 3
thisAngle = angles(angleIndex);
rotatedImage = imrotate(originalImage, thisAngle);
subplot(2, 2, angleIndex + 1);
% Create new name with -1, -2, or -3 appended to the original base file name.
rotatedName = sprintf('%s -%d.png', baseFileNameNoExt, angleIndex);
title(rotatedName, 'FontSize', 15);
fullFileName = fullfile(folder, rotatedName);
imwrite(rotatedImage, fullFileName);
fprintf(' Wrote out %s.\n', fullFileName);
promptMessage = sprintf('Do you want to Continue processing,\nor Quit processing?');
titleBarCaption = 'Continue?';
buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
if contains(buttonText, 'Quit')


Teshan Rezel
Teshan Rezel on 15 Jan 2020
Thanks for this! The only thing is that it works for images 1, 10 and 100 only. Apologies for this, but is there a way to make it work for all 250 images please?
Image Analyst
Image Analyst on 15 Jan 2020
Sorry, for testing I just did the first 3. Change
for k = 1 : 3
for k = 1 : length(S)

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More Answers (1)

Matt J
Matt J on 14 Jan 2020
The code works fine for me. If I had to guess, I would say it is because you ran the code previously while debugging and never cleaned the folder of the results of previous runs.


Show 4 older comments
Matt J
Matt J on 14 Jan 2020
Is this meant to hold the name of my ".m" file?
Teshan Rezel
Teshan Rezel on 14 Jan 2020
right, I've tried that but it still says it can't be found. Not sure what I'm doing wrong
Matt J
Matt J on 14 Jan 2020
That seems to say that it is not on your path. I.e., it will only be detected and run if your current Matlab folder is the folder where your mfile actually resides.

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