MATLAB: Rotating and saving images to folder: error during loop

MATLABrotatesave

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);
end

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!

Best Answer

Teshan:

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);
	imshow(originalImage);
	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.
	end
	
	for angleIndex = 1 : 3
		thisAngle = angles(angleIndex);
		rotatedImage = imrotate(originalImage, thisAngle);
		subplot(2, 2, angleIndex + 1);
		imshow(rotatedImage);
		% 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);
	end
	
	promptMessage = sprintf('Do you want to Continue processing,\nor Quit processing?');
	titleBarCaption = 'Continue?';
	buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
	if contains(buttonText, 'Quit')
		break;
	end
end
close(hFig);

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failCount = sum(x < 50)
failRatio = failCount / numel(x)

I see

failCount =
    63
failRatio =
        0.0648815653964985

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