reading multiple images from a folder in Matlab

I want to read many images from a folder in the Matlab directory using imread() and then make different operations in every image individually , i wrote this code but it disagrees about (+k+):

num_file=1;  

file = dir('image.orig');

num_file = numel(file);

NF=num_file;

Y=1;Z=1;

images = cell(1,NF,T);

T=cell(Y,Z,3); 

for k = 1:NF

      images{1,k}(Y,Z,3) = imread('C:Work\image.orig\'+k-1+'.JPEG');

end

also, i want to save the matrix of each image in a cell array and i don't if what i wrote is right or not and i cannot have a permission to read from the folder, i checked the folder and found that it is read only, what do you think?

Thank you in advance

Answer 1

[Walter Roberson]

file = dir('image.orig');
NF = length(file);
images = cell(NF,1);
for k = 1 : NF
  images{k} = imread(fullfile('image.orig', file(k).name));
end

[yasmine]

Thank you but it still gives me this error:

Can't open file "image.orig\." for reading;

you may not have read permission.

Error in ==> fg1 at 10

images{k} = imread(fullfile('image.orig', file(k).name));

[Walter Roberson]

Ah yes, you took the dir of a directory and need to throw out the subdirectories...

file = dir('image.orig');

file = file(~[file.isdir]);

NF = length(file);

images = cell(NF,1);

for k = 1 : NF

images{k} = imread(fullfile('image.orig', file(k).name));

end

[yasmine]

Thank you so much for help

isn't imread supporting the JPEG format ?

so, why it gives me this error:

Unable to determine the file format.

Error in ==> fg2 at 8

images{k}=imread(fullfile('image.orig', file(k).name));

[Walter Roberson]

Perhaps you have non-jpeg files in the directory as well.

You may wish to change the first line to

file = dir(fullfile('image.orig', '*.jpg'));

[yasmine]

yes i realized that not all the files are jpg

now i want to handle all image types

i tried this, is that right?

file = dir(fullfile('image.orig','*');

Thank you alot

[Walter Roberson]

You cannot handle all image types: there are an infinite number of image types that imread() is not able to handle.

Using file = dir(fullfile('image.orig','*'); will not make any difference compared to file = dir('image.orig');

If you have files that imread() is not able to handle (because the file is not an image file, or because the image format details are private and hacked up or proprietary and unpublished), or because the image format is simply not one that imread() knows how to handle, then you are advised to use a try/catch block:

for K = 1 : NF

thisfile = fullfile('image.orig', file(k).name);

try

images{k} = imread(thisfile);

catch

images{k} = [];

fprintf('Unreadable file: %s\n', thisfile);

end

end

[yasmine]

This code was running the other day very good but now it gives no output and no errors , i changed the name of the folder but no good

is there anything in matlab i have to update or something, here is the code:

file = dir('image');

file = file(~[file.isdir]);

NF = length(file);

images = cell(NF,1);

for k = 1 : NF

disp(file(k).name);

images{k} = imread(fullfile('image', file(k).name));

end

Thank you

[Walter Roberson]

I would put a breakpoint in and check each step -- for example, does file come out empty?

Check to be sure that you have not accidentally created your own dir.m or imread files:

which -all dir

which -all imread

Answer 2

[Image Analyst]

It's always worth throwing in a plug for the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Answer 3

[yasmine]

Would you please help me : i'm dividing an image into blocks then making some analysis on each block i divided the image using mat2cell

now i want to convert each block into a numeric array but this error appears to me:

 Assignment has more non-singleton rhs dimensions than non-singleton
subscripts

Here is the code:

nb(1) = ceil(256/ b(1)); % number of blocks in each dimension

nb(2) = ceil(384/ b(2)); % number of blocks in each dimension

C=mat2cell(images,ones(256/ b(1),1)*b(1),ones(384/ b(2),1)*b(2),3);% dividing the Image into blocks.

 A= size(C);

      m=1;
      while (m < ((nb(1)*nb(2))+1))
           for i=1:nb(1)%256
              for j=1:nb(2)%384
                  A(i,j)=cell2mat(C{i,j});% here is the error
                  figure(1),subplot(nb(1),nb(2),m), image(A(i,j));
                  m=m+1;
              end 
           end 
      end

[Walter Roberson]

That is an unrelated matter and should have been posted to a distinct Question.

Count the number of dimensions you have provided in mat2cell: ones-this, ones-that, and 3. So each cell stored will contain a 3D array whose final dimension is 3.

When you go through the de-referencing and cell2mat, you would be coming out with a 3D array. And you try to store that full 3D array in to a single element of the numeric array A -- an array that you initialized to just contain size(C) . One has to wonder what you think you are doing?

Remember too: the result of mat2cell applied to numeric data is going to be a cell array each entry of which contains numeric data. De-referencing that cell array using {} is going to give you a numeric array. You then try to apply cell2mat() to that numeric array even though it is not a cell by that point.

cell2mat is for converting a _group_ of cell entries back in to a single array, and is not called for at all in accessing the contents of a single cell entry.

[yasmine]

ya i know cell2mat is used to convert a group of blocks into a single array but i used this:

A(i,j)=C{i,j};

and gave me this error:

Assignment has more non-singleton rhs dimensions than non-singleton

subscripts

would you explain using code example, i didn't get what you mean in your first point.

[yasmine]

i got what you mean but can't translate it into matlab code

i want to make an array of 3D arrays to store in it the values of each block,so how to declare an array of arrays in matlab?

Thank you

[Walter Roberson]

There is no way to make a nested numeric array. The closest MATLAB equivalent is the cell array whose elements are numeric arrays, and you have already created that (it is your "C")

[yasmine]

yes i understand what you mean but i want to make a histogram for each block and when i did so :

for i=1:nb(1)%256

for j=1:nb(2)%384

[counts(i,j), x(i,j)] = imhist(C{i,j});

end

end

this error occurred:

??? Error using ==> iptcheckinput

Function IMHIST expected its first input, I or X, to be two-dimensional.

Error in ==> imhist>parse_inputs at 281

iptcheckinput(a,

{'double','uint8','int8','logical','uint16','int16','single','uint32', 'int32'}, ...

Error in ==> imhist at 59

[a, n, isScaled, top, map] = parse_inputs(varargin{:});

Error in ==> fll1 at 26

[counts(i,j), x(i,j)] = imhist(C{i,j});

so what do you think?

[Walter Roberson]

I think this should definitely have gone in its own thread ;-)

You are trying to apply imhist() to a (subsection of) a truecolor image (which is thus a 3D matrix). imhist() is only for grayscale images. You should convert your whole image to grayscale before you break it up in to blocks; or you should convert each block to grayscale and imhist that as you go; or you should imhist() each of the three color planes separately.

Answer 4

[Shaveta Arora]

If I have .tiff images and .tif images that I want to read, how they can be read ? I know how to read one type of images but how to read two types of images.

[Walter Roberson]

dstats1 = dir('*.tiff');
dstats2 = dir('*.tif');
dstats = [dstats1; dstats2];
filenames = {dstats.name};
for K = 1 : length(filenames)
  load_images{K} = imread(filenames{K});
end

[Emily Leung]

Hi this doesnt work for me, filenames comes up empty. Do you know what might be the issue?

[Walter Roberson]

@Emily LeungIn the code I posted here, the filenames would come up empty if you do not have any .tif or .tiff files in the current directory.

In some cases, depending upon operating system configuration, files ending with extension .TIF or .TIFF might not be treated as if they ended in .tif or .tiff -- sometimes files are case sensitive.

The code I posted is not designed to look for files in a different directory; the changes to look in a different directory are not difficult though.

[Emily Leung]

@Walter Roberson i solved the issue, thank you very much this approach saved me many an if loop!

Answer 5

[Kumar Vaibhav]

 I=imread(sprintf('C:/Users/kumar.vaibhav/Documents/MATLAB/Visually Similar Images/%d.jpeg',i));

[Walter Roberson]

Kumar, is there a question associated with that?