Finding the mean of a group of images?

Hello everyone,

So I am trying to find the mean of a group of images so I can compare their mean before and after the filter.

for l = 1:numel(bmpFiles)
    %applying the filter
    
    bflt_img1{l} = bfilter2(img1{l},w,sigma);
    
    %finding the average of the images
    I0 = imread(img1{l});
    sumImage = double (I0)
    grayImage = imread(img1{l+1});
    sumImage = sumImage + double(grayImage);
    meanImage = sumImage / numel(bmpFiles);
    
end

However, I get this error message:

Error using imread>parse_inputs (line 504)
The file name or URL argument must be a character vector or string scalar.

Error in imread (line 342)
[source, fmt_s, extraArgs, was_cached_fmt_used] = parse_inputs(cached_fmt, varargin{:});

Error in bil1_MH (line 21)
    I0 = imread(img1{l});

Is there a problem with using img1{L} as a format to refer to the image?

Thanks in advance.

Answer 1

[Walter Roberson]

bfilter2() is not part of MATLAB, so we do not know what it does. There is a File Exchange contribution https://www.mathworks.com/matlabcentral/fileexchange/12191-bilateral-filtering but it would give an error if img1{l} were not floating point. Either you are using a different bfilter2() or else img1{l} is floating point.

If img1{l} is floating point, that would explain the error message when you tried to imread() it. If you have already read the data into img1 then just

I0 = img1{l};

[Walter Roberson]

Your logic for taking mean is suspect. Are you wanting to take the mean of each pair of adjacent images? If so then do not divide by the number of files. If you are wanting to take the mean of all of the images, then initialize the sum image to 0 before the loop instead of I0 = img1{l}

[Walter Roberson]

If you have a group of images that are all the same size in a cell array img1 then skip the loop and do

nd = ndims(img1{1});
mean_image = mean(cat(nd+1, img1{:}), nd+1);

[Mohammed Hammouda]

Thank you very much for your answers. Apologies for not making my question clear enough and suspect to multiple assumptions. My images were already read so I just used your suggestion to go with

I0 = img1{l};

Thank you very much!! I hope I did not keep you waiting long for replying!