rotating and saving images to folder: error during loop

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!

Answer 1

[Image Analyst]

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);

[Teshan Rezel]

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]

Sorry, for testing I just did the first 3. Change

for k = 1 : 3

to

    for k = 1 : length(S)

[Teshan Rezel]

thank you very much, that's solved it!

Answer 2

[Matt J]

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.

[Teshan Rezel]

Hi Matt, the code itself works fine and runs without a problem but the outputs are wrong. I've cleaned the folder, clc + clear the console line, closed matlab and restarted again and ran it. The outputs are still wrong.

The first image is rotated and labelled fine. The 2-250th images are labelled wrong.

Hope that clarifies the issue

[Matt J]

As I said, the problem is not reproducible with the code you've posted. It has to be something about your environment. Perhaps you have a buggy version of your script higher up on the Matlab path? Try,

>>which -all myScript

[Teshan Rezel]

Hi Matt, it returns "myScript not found"

Is this meant to hold the name of my ".m" file?

[Teshan Rezel]

If it helps, my array of numbers seems to be really weird:

Columns 1 through 22

   104    97    91    95    88    84    94    91    93    92    89    85    82    87    96   105   113   103   116   113   116   113
   101    96    93   115   132   126   113    95   114   105    94    84    82    88    95   101   101   102   115   111   115   121
   103    93    85    96   110   114   119   109   108   103    94    90    89    88    89    87    98   120   129   124   113   115
   101    94    81    75    77    91   103    91    88    92    94    90    85    85    90    96   113   131   119   114   107   108
    98    93    86    92    99   100   100    98    94    89    85    86    93    98   103   104   112   110    93    95   101   107
    97    96    93    96   101   106   107    96    97    94    93    92    97   101   106   109   105    96    93    96   104   109
    95    93    98   106   110   115   113    98   104    99    95    94    95    99   100   101   106    99   101   102   107   110
    95    96   101   108   111   110   107   105   101   100    98    98    98    98    98    97    90    97   101   108   108   107
    98    93    95   107   113   110   107    98   105   104   102    99   100    98    95    93    97    99   102   105   109   112
    95    95   105   108   110   110   101    99   104   102    99   100   102   104   104   107   106   105   105   106   105   106
    90    94   105   100   102   106   100    99   101    94    94    97    95    97   104   104   104   107   106   105   106   108
    90    92    98   100    96    98    97    90    90    80    78    82    86    91    94    96    99    99    98    98    98   101
    92    91   101   101    88    82    78    67    60    52    44    48    58    65    71    76    85    94    97    91    88    92
    87    82    90    79    58    51    42    39    36    29    30    30    28    43    64    70    76    80    81    82    84    86
    89    84    82    60    41    38    31    34    33    28    35    38    36    58    83    86    73    57    52    66    77    76
    84    85    72    48    39    39    34    36    35    32    29    33    50    71    81    78    51    45    41    49    65    77
    82    77    71    47    41    35    32    28    33    34    27    28    52    54    41    35    41    39    37    39    50    60
    77    74    74    52    37    32    24    20    31    31    29    25    37    44    53    57    50    45    39    37    38    44
    72    77    53    38    33    28    25    22    30    30    30    27    39    50    62    69    75    67    56    45    37    34
    77    75    49    39    30    29    28    30    28    29    26    24    41    50    60    70    75    70    61    48    39    33
    84    75    41    38    32    33    31    35    27    27    27    32    50    58    62    66    74    73    68    59    46    36
    85    82    50    57    59    50    40    34    34    31    42    52    64    68    73    71    81    85    77    58    46    49
    92    85    72    70    59    57    48    40    40    44    60    69    72    72    81    84    85    81    78    75    67    52
    93    93    77    73    68    68    63    53    48    57    74    83    90    82    83    86    86    87    88    87    82    76
    96    95    95    85    85    78    79    73    70    73    79    82    83    84    84    84    80    85    84    87    80    86
    98    94   100    89    91    91    84    84    79    78    74    73    75    80    79    76    78    77    83    85    83    80
    93    88    96    88    88    87    81    79    77    75    73    71    73    75    74    73    78    80    81    72    77    79
    91    85   103    93    93    89    87    82    80    74    70    69    70    69    68    71    74    81    83    82    81    73
    88    75   112   100    98    96    92    90   101    85    72    70    71    67    67    71    76    83    82    83    78    73
    80    69   106   100    95    88    86    79    72    64    63    71    75    73    76    81    88    81    77    78    75    74
    77    74    99   103    97    88    77    70    56    55    57    60    58    52    49    52    58    66    65    53    51    52
    78    77    98   105   102    98    76    73    55    52    45    40    37    41    43    44    45    55    47    36    40    30
    67    60    98   105    95    77    61    60    47    39    34    34    37    44    47    42    37    44    38    29    30    29
    65    44   107    84    61    47    48    42    33    36    40    60    80    71    55    50    55    55    51    48    47    36
    66    52    76    52    53    53    48    53    60    66    89   112   119   117   109   100    96    97    83    63    55    54
    65    66    75    75    62    59    69    82    98   112   126   131   131   133   134   130   131   125   110    86    65    56
    78    73    74    78    80    79    87   103   118   127   131   131   135   131   128   130   126   116   111    99    75    56
    80    76    84    86    86    89   104   117   122   121   125   128   125   123   120   116   110   103    94    74    52    43
    87    84    87    84    85    87    97   108   114   120   124   124   122   118   111   103    84    66    46    33    31    36
    85    88   108   102   102    90    94   104   126   131   130   125   113    94    73    56    39    40    35    29    28    33
    91    93   114    88    96    99    98   110   134   134   126   103    72    50    35    27    26    36    43    33    32    31
    96    96    87    74    69    84    95   110   125   121    92    57    45    36    31    30    25    27    30    30    27    26
    96    81    47    62    60    77    87   100   105    81    58    57    50    40    39    49    33    29    23    30    28    29
    90    84    30    31    37    50    61    78    72    49    43    44    47    48    61    58    41    41    36    34    28    29
    84    85    33    27    27    30    40    48    42    35    30    41    46    54    52    49    41    45    45    35    27    24
    89    89    35    31    31    32    39    39    34    31    29    32    48    53    52    45    44    40    41    33    33    28
    83   100    55    36    32    33    31    34    30    28    26    30    41    54    56    55    55    48    45    46    46    40
    88    92    78    56    36    32    30    31    29    34    31    27    38    54    65    70    63    64    65    67    57    47
    72    67   105    70    47    34    25    27    32    38    27    24    33    45    60    64    68    72    74    74    73    65
    65    66   110    77    52    28    27    17    22    24    19    20    25    41    60    63    67    70    70    66    64    62
    75    75    97    93    56    39    26    23    17    19    19    23    29    44    62    65    73    75    78    78    71    58
    81    85    90    77    67    42    30    29    23    24    20    24    33    49    65    73    81    77    74    69    58    45
    88    91    82    84    62    47    42    40    34    28    29    35    48    65    77    86    88    83    75    66    58    52
    86   106    81    74    68    63    66    60    51    36    38    50    63    83    97    98    92    81    69    65    68    69
    71    81    69    64    67    67    77    76    72    48    48    58    73    91   100    97    77    69    66    74    84    87
    45    49    63    64    58    68    74    84    80    61    64    78    95   101    91    82    65    69    75    84    89    91
    44    45    60    50    50    63    66    66    72    73    81    95    98    81    59    50    60    65    73    81    78    66
    47    42    66    61    61    67    73    65    66    83    86    76    56    34    36    42    63    68    63    45    40    45
    51    40    70    72    73    81    90    79    77    87    83    56    41    40    37    39    61    62    51    41    38    36
    70    54    87    89    85   100   109   101    83    69    52    45    42    38    41    49    64    59    46    41    41    47
    86    84    86    86   105   117   104    95    81    77    62    49    46    47    53    62    60    57    53    44    52    68
    82    91    86    94   105   109    94    77    66    65    66    63    62    59    53    57    51    61    67    73    81    84
    85    91    94   102   111   108    84    61    40    42    48    64    71    62    58    62    61    78    85    91    92    86
    90    88   101   105   112   104    71    49    39    34    34    46    63    72    75    83    78    85    97    98    92    92
    84    84    93    91   105    94    66    45    36    29    43    50    58    55    60    56    76    91    95    92    90    95
    84    78    90    94    99    95    63    43    35    32    51    75    79    59    48    40    68    94   103    96    88    95

[Matt J]

Is this meant to hold the name of my ".m" file?

Yes.

[Teshan Rezel]

right, I've tried that but it still says it can't be found. Not sure what I'm doing wrong

[Matt J]

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.