Conversion of 100 jpg images to PGM

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');
       imwrite(I,'myImage7.pgm');

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

Answer 1

[Image Analyst]

See the FAQ http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Use the second code sample block.

[shawin]

I used the code which you direct me to :

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);
  uiwait(warndlg(errorMessage));
  return;
end
% 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.
  imageArray2=imwrite(imageArray,'myImg(k).name.pgm');
end

it does not work ?

[Image Analyst]

That's because you constructed the filename incorrectly. Try this:

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 ~isfolder(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
% 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.
  baseOutputFileName = strrep(baseFileName, '.jpg', '.pgm');
  outputFullFileName = fullfile(myFolder, baseOutputFileName);
  fprintf(1, 'Now writing to %s\n', outputFullFileName);
  imwrite(imageArray,outputFullFileName);
end

[shawin]

 I am receiving an error which is:

• Undefined function or variable 'isfolder'.*

I change it to isdir();

then I have the error below:

Error using imwrite
  Too many output arguments.

    Error in ImageConversion (line 51)
      imageArray2=imwrite(imageArray,outputFullFileName);

[Image Analyst]

Try

imwrite(imageArray, outputFullFileName);

[shawin]

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]

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]

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.

Answer 2

[John D'Errico]

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.

[shawin]

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);
  uiwait(warndlg(errorMessage));
  return;
end
% 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.
  imageArray2=imwrite(imageArray,'myImg(k).name.pgm');
end

it does not work?

Answer 3

[Guillaume]

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]

I like ACDSee, which has a similar feature.

[Guillaume]

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.

Answer 4

[kalai selvi]

how to convert the scatter plot fig into pgm

[Image Analyst]

Try exportgraphics() if using r2020a or later. Otherwise try export_fig.