MATLAB: How to read .png image from a folder iteratively

imreadpngread image

I have a folder with multiple images. The format of all images is .png. When I try to read all those images in a cell array I am getting following error.
Error:
Error using imread>get_format_info (line 543)
Unable to determine the file format.
Error in imread/call_format_specific_reader (line 464)
fmt_s = get_format_info(fullname);
Error in imread (line 440)
[X, map] = call_format_specific_reader();111.png
%Specify training and test folders
train_fold  = ['..',filesep,'Train_Set',filesep];  
test_fold   = ['..',filesep,'Test_Set',filesep];
%Read train and test set images folder information
train_ims = dir(train_fold);
test_ims = dir(test_fold);
%Remove all the train folders that do not contain images
for i = 1:length(train_ims) 
    if (length(train_ims(i).name)<10)
        train_ims(i).name = [];
    end
end
train_ims = train_ims(~cellfun('isempty',{train_ims.name}));
% Remove all the test folders that do not contain images
for i = 1:length(test_ims) 
    if (length(test_ims(i).name)<10)
        test_ims(i).name = [];
    end
end
test_ims = test_ims(~cellfun('isempty',{test_ims.name}));
for i = 1:length(train_ims) 
    ims{i} = imread([train_fold,filesep,'compositeImage', num2str(i), '.png']);  
end

Best Answer

The problem is obvious once you've seen the code in your other question that you've used to create these images. These images are not images at all but mat files. Sticking a png extension onto a mat file does not make it a png image.
The files could be read back into matlab with:
matcontent = load(fullfile(train_fold, sprintf('CompositeImage%d.png', i));   %read all the variables in the mat file
ims{i} = matcontent.CompositeImage; %ang get the CompositeImage variable out of it.
But no program will ever recognise these files as png images.
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