How to read multiple jpg images in a loop?

hello, i am a novice user in matlab my question is: i have stored some 100s of images in some folder and i want to read it one-by-one.how can i do this?

[Xylo]

You can do this easily..... before doing this program, you have to keep all of your image in a folder and rename them by any common char+number concatenation form (like a1.jpg, a2.jpg,a3.jpg....). after that you just use strcat() function for reading the path name, and then read the images.

for i=1:10 %suppose there are 10 image
file_name=dir(strcat('J:\multimedia\photo\')); % the path tht u hv imges
  im=imread(strcat('J:\multimedia\photo\',file_name(i).name));
  imtool(im);
end

[anish m r]

hi while doing this i am getting an error like Error using imread (line 366) Can't open file "E:\Image." for reading; you may not have read permission.

Error in Untitled (line 3) im=imread(strcat('E:\Image',file_name(i).name));

pls help me to solve this

Thanke

[Walter Roberson]

im=imread( fullfile('E:\Image', file_name(i).name ) );

[Yogesh Bhandari]

Hi, I am trying to implement similar code of reading images and later try to randomly select one of the images. However, while performing the reading of images, I am getting an error :Cannot open file "\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS." for reading. You might not have read permission.

Code Snippet

for i=1:15
    file_name=dir(strcat('\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS'));
    im=imread(strcat('\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS',file_name(i).name));

    imtool(im)  
end

if possible could you please guide me through this.

[Walter Roberson]

Do not use strcat to create your file name. Use fullfile().

[Image Analyst]

Yogesh, perhaps this but I'm getting zero files found there:

folder = '//ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS'
files = dir(fullfile(folder, '*.*'))
for k=1:length(files)
  thisFileName = files(k).name
  im=imread(thisFileName);
  imshow(im);
  drawnow;
end

[Yogesh Bhandari]

Thank you for your comments. However, I slightly modified my code and have attached the updated code.

 images=imageSet('\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Rese  archdata\Test case for image extraction\ImaGES_FOR_QUESTIONS');
 n=numel(images.ImageLocation);
 idx=randi(n);
 im=imread(images.ImageLocation(idx).jpg);

But, it still am giving the following error

    Struct contents reference from a non-struct array object.

   Error in codeResearch2 (line 8)
   im=imread(images.ImageLocation(idx).jpg);

could you please help me through this.

[Walter Roberson]

im = read(images(1), idx);

[Yogesh Bhandari]

Dear Walter, Thank you it works. However could you please explain the reason for this.

Is it something related to the fact that its 1-D array having row fixed and the number of columns would be changing

[Walter Roberson]

The ImageLocation property is not the list of images: it is the list of directories in which the images are to be found.

Indexing the imageset at (1) talks about the first directory out of the list. read() with an index is what is used to imread() in the individual images from the directory.

[Yogesh Bhandari]

Thank You Walter, for your writing detailed response. However based on your previous comments I prepared another code

images='\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS';
    jpgfiles=dir(fullfile(images,'\*.jpg*'))
    n=numel(jpgfiles);
   idx=randi(n); 
   im=imread(jpgfiles(idx).name)

However, I am receiving the error

Error using imread (line 349)
File "a1.jpg" does not exist

Error in codeResearch2 (line 6)
im=imread(jpgfiles(idx).name)

[Yogesh Bhandari]

I guess I resolve the query following reference from your other post. (PS:thanks) Following is the code snippet.

images ='\\ad.uillinois.edu\engr\instructional\yogeshb2\Desktop\Researchdata\Test case for image extraction\ImaGES_FOR_QUESTIONS';
jpgfiles=dir(fullfile(images,'\*.jpg*'))
n=numel(jpgfiles);
idx=randi(n);
im=jpgfiles(idx).name
im1=imread(fullfile(images,im))
imshow(im1)

[Gebra maryam Alehegn]

Question Please everyone how to extract color and texture features from multiple image and prepare for as traning?

[Walter Roberson]

We have given a few links above on how to process sets of files. So you just have to take your existing functions that extract color and texture features and put a loop around them.

[SHUBHDEEP KAUR]

the following code shows single image at a time ..how to display all the jpg images at once

[Anil Varma]

showing error

Error using randi

First input must be a positive scalar integer value IMAX, or two integer values [IMIN IMAX] with IMIN

less than or equal to IMAX.

Error in test (line 9)

idx=randi(n);

[shweta banait]

how to display five images in matlab

Answer 1

[Dishant Arora]

Here it is How can I process a sequence of files?

[archana]

thank you sir...! now can you please tell me how can i convert all these images to gray and make all of them of same sizes for further purpose..

[Dishant Arora]

use imresize and rgb2gray.

[archana]

sir, i wrote this code for reading images

myFolder = 'C:\Users\shree\Desktop\final data\1'; if ~isdir(myFolder) errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder); uiwait(warndlg(errorMessage)); return; end filePattern = fullfile(myFolder, '*.jpg'); jpegFiles = dir(filePattern); for k = 1:length(jpegFiles) baseFileName = jpegFiles(k).name; fullFileName = fullfile(myFolder, baseFileName); %fprintf(1, 'Now reading %s\n', fullFileName); imageArray = imread(fullFileName); imshow(imageArray); % Display image. drawnow; % Force display to update immediately. end

      now i want to convert it to gray and then make them of same size by compressing them.i also want to ask you what should i do 1st should i compress 1st and then convert to gray or what i must not lose any features of images..

[Dishant Arora]

What do you want to do?? compression or resizing?? The two are completely different things. If you want to resize you are definitely going to loose some data, whereas compression can be both lossless or lossy depending upon the algorithm. I guess what you want is resize not compression. And convert it to grayscale first.

[archana]

sir,actually i want to obtain the covarience matrix of all these read images...for same i wrote a code but there i worked on each image seperatly (i.e. reading convrting to gray and the resized it) because of which code became verry bulky ,now with your guidlines i modified sem for loop reading. now what i supposed to do is 1st i should convert it to gray and then resize all..but fact is yet i didnot reached to covarience matrix stage...:( apologize me for mistake if any

[Dishant Arora]

Use the builtin cov to get the covariance matrix.

Answer 2

[Karthik Karri]

You can rename all images like..im1,im2,im3.....im100. To read 100 images one by one, run a loop 100 times with i as variable from 1 to 100 and in imread, m=imread(['folder_path\im' num2str(i) '.jpg']). I hope I answered your question.

[archana]

thanks its working.....:)

Answer 3

[chaitra naveen]

can you please help me out to read 100's of images from folder to matlab and resize them to 100x100.

[Image Analyst]

Use imresize in a loop like the loops given in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Answer 4

[Muhammad Sohail]

filelist = dir('Training data');
for i=1 : length(filelist)
for i=1 : length(filelist)
  filename = filelist(i);
  if ~strcmp(filename.name , '.') && ~strcmp(filename.name , '..')
      filename.name
  end
end

[Haseeb Hassan]

Simple and easy

Answer 5

[Haseeb Hassan]

for i=1:16; % we have 16 images we have in or folder
clc;clear;
images ='C:\Users\Haseeb\Desktop\input\for_loop_input';
jpgfiles=dir(fullfile(images,'\*.jpg*'));
n=numel(jpgfiles(i));
im=jpgfiles(i).name
im1=imread(fullfile(images,im));
imshow(im1);
end

Here is the simple and short code, which will acces your images from your folder in a sequence.

[shital shinde]

Actually it gives error as

Array indices must be positive integers or logical values.

n=numel(jpgfiles(i)); // for this line.

will you tell me why ?

Answer 6

[Xylo]

You can do this easily..... before doing this program, you have to keep all of your image in a folder and rename them by any common char+number concatenation form (like a1.jpg, a2.jpg,a3.jpg....). after that you just use strcat() function for reading the path name, and then read the images.

for i=1:10 %suppose there are 10 image
file_name=dir(strcat('J:\multimedia\photo\')); % the path tht u hv imges
  im=imread(strcat('J:\multimedia\photo\',file_name(i).name));
  imtool(im);
end

[archana]

heyy thanks for answering now can you please tell me how can i store the image immidiatly after reading it by some name like g1,g2,g3,jpg.....as i want to do some operation on these all images..... regards....:)

[Xylo]

ya..... offcrse u can. just use imwrite function to save. like this:- imwrite(im,'your path address','name1','jpg'); here name1:-name of the that you want to save

[Xylo]

and use this code in the for loop, that is after im=imread(...) code

[Omar Ahmad]

Xylo sir,

I pasted the path very correctly in the im=imread.... code but it gives me an error saying you may not have read permission. I even changed the path to another drive..but same error.. why does that occur? plz help

[Omar Ahmad]

I got the above problem right. I have one more:

How can I subtract and find the image difference one from another. e.g. from gray_2.jpg and gray_1.jpg? I mean once reading these, how can we separate them into individual images?

[Walter Roberson]

Isha Pandya comments to Omar Ahmad:

I am not able to solve this problem. Please help.

[Walter Roberson]

Isha Pandya, please show your current code and describe what difficulty you are observing.

[Zahoor abbas]

How I can access the images from two folders by using one for loop