⤵️ A MATLAB program converts image type.

ImageConverter.m

folderName = 'D:\Images\IMAGES_FOR_PROCESSING\lfwcrop_grey\faces';
imagefiles = dir(strcat(folderName, '\*.pgm'));      
nfiles = length(imagefiles);

for i=1:nfiles
    currentfilename=imagefiles(i).name;
    I = imread(strcat(folderName, '\', currentfilename));
    
    [pathstr,name,ext] = fileparts(currentfilename);
    currentfilename = name;
    
    imwrite(I, strcat(folderName, '\', currentfilename , '.png'));
    
    fprintf('%d image processed \n', i);
end

fprintf('\n\n## operation successful!!');