How to read and store greyscaleimage into single matrix?

i have 2429 images in pgm format. each is in 19*19 size. Now i need to read all the images one by one and store in single matrix. With the help of previous mathworks available examples i read my file. now how to store in single matrix.

myFolder = 'C:\Users\smanohar\Documents\MATLAB\RBMimplementation\Gaussian    RBM\gdrbm\greyscsalegdrbm\face';
if ~isdir(myFolder)
errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
uiwait(warndlg(errorMessage));
return;
end
filePattern = fullfile(myFolder, '*.pgm');
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);
end

Answer 1

[Geoff Hayes]

Subha - if all images are of the same dimension, 19x19, then you can save all of them to a single array of size 19x19x2429. Try something like the following

 % pre-size the image array
 imageArray = zeros(19,19,2429);

 filePattern = fullfile(myFolder, '*.pgm');
 pgmFiles = dir(filePattern);
 for k = 1:length(pgmFiles)
     baseFileName = pgmFiles(k).name;
     fullFileName = fullfile(myFolder, baseFileName);
     fprintf(1, 'Now reading %s\n', fullFileName);
     imageArray(:,:,k) = imread(fullFileName);
 end

Note how the kth image is stored in the imageArray. You may want to cast the imageArray to the appropriate data type before or after you have copied the images into it. (The appropriate data type being that of the pgm images.)

[subha]

I want my image file to be stored in the size of 2429*361. so i reshaped as,

imageArray= reshape(imageArray,19*19,k);

Then i transposed as below.

    imageArray= transpose(imageArray,19*19,k); 
but values are only 0 insteadgreyscale range. Some thing goes wrong?

[subha]

when isee the value of matrix, everything zero.

[Geoff Hayes]

Subha - why are you doing the following

 imageArray= reshape(imageArray,19*19,k);

so that it is dependent upon k? Is this during each iteration or once finished and so outside the for loop?

If you want a matrix that is 2429x361, then why not do the following

 % pre-size the image array
 imageArray = zeros(2429,19*19);

 filePattern = fullfile(myFolder, '*.pgm');
 pgmFiles = dir(filePattern);
 for k = 1:length(pgmFiles)
     baseFileName = pgmFiles(k).name;
     fullFileName = fullfile(myFolder, baseFileName);
     fprintf(1, 'Now reading %s\n', fullFileName);
     imageArray(k,:) = reshape(imread(fullFileName),1,361);
 end

The above does the reshape on the image as it is read from the file, converting it from the 19x19 matrix to one that is 1x361.

[subha]

thanks Geoff.

Answer 2

[Image Analyst]

Why not try the montage() function?