MATLAB Answers

Conversion of 100 jpg images to PGM

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shawin on 1 Oct 2018
Commented: Image Analyst on 3 Oct 2018

Kindly how can we convert 100 images which are jpg to PGM format?

the Matlab code for one image conversion is:

I = imread('myImage.jpg');

then if we have 100 jpg images how we can convert them to pgm format?


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Accepted Answer

Image Analyst
Image Analyst on 1 Oct 2018


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shawin on 3 Oct 2018
The code is running, but there is a problem with output, I could not see the output?
I used opensleeit to view the output)
Guillaume on 3 Oct 2018
Seriously, use a better image viewer, one that includes batch format conversion. A few were already suggested. You would have solved your problem in a matter of minutes.
Image Analyst
Image Analyst on 3 Oct 2018
I don't know what "opensleeit" is.
When you run the program, imshow() shows/displays each image as it's loaded. Are you saying imshow() does not work for you?
Why do you want PGM format images anyway? Isn't that some obsolete format from the 90's? Why not just leave them as they are, or use PNG format, which has become the defacto standard?
Since the images have already been ruined by saving in JPG format, converting to another format won't gain you anything. Plus nearly every program that "sees" PGM images will also see JPG images.

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More Answers (2)

John D'Errico
John D'Errico on 1 Oct 2018
Use a loop? Surely you can get the directory contents, so the names of all images in a directory, using a tool like dir. Now just loop over the images that dir returns.

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shawin on 2 Oct 2018
myFolder = 'C:\Users\shawin\Desktop\FR_Matlab\FR_Test7\Database_2';
% Check to make sure that folder actually exists. Warn user if it doesn't.
if ~isdir(myFolder)
errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
% Get a list of all files in the folder with the desired file name pattern.
filePattern = fullfile(myFolder, '*.jpg'); % Change to whatever pattern you need.
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
baseFileName = theFiles(k).name;
fullFileName = fullfile(myFolder, baseFileName);
fprintf(1, 'Now reading %s\n', fullFileName);
% Now do whatever you want with this file name,
% such as reading it in as an image array with imread()
imageArray = imread(fullFileName);
imshow(imageArray); % Display image.
drawnow; % Force display to update immediately.
it does not work?

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Guillaume on 2 Oct 2018
Even simpler, particularly if you don't have the knowledge to write the code is to download any decent image viewer program that will surely include batch image conversion as one of its feature.
My favorite, which is free for personal and academic use is IrfanView. Start the program, press B (for batch conversion), select the images to convert, select PGM in output format, Press Start Batch. Done!


Image Analyst
Image Analyst on 2 Oct 2018
I like ACDSee, which has a similar feature.
Guillaume on 2 Oct 2018
ACDSee is still around! I remember using that in the 90s. There's also XnView which is also free and probably many more that can do this in a few clicks. And if you prefer command line, there's always ImageMagick, which again, can do the job in just one command.
The point is, you don't always have to use matlab to solve your problems.

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