Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

Hi,

I am working on character recogntiion and my images are in gray images.

here in the code on read all images but I am facing error.

function [images, labels, imageFiles] = readDataset(dirPath)
    imageFiles = '';
    % Get a list of all files and folders in this folder.
    files = dir(dirPath);
    % Get a logical vector that tells which is a directory.
    dirFlags = [files.isdir];
    % Extract only those that are directories.
    subFolders = files(dirFlags);
    % add all image file name
    for i = 1 : length(subFolders)
      subDir = subFolders(i).name;
      if subDir == '.' | strcmp(subDir, '..') == 1
          continue;
      end
      
      files = dir(strcat(dirPath, '/', subDir));
      fileFlags = ~[files.isdir];
      files = files(fileFlags);
      for j = 1: length(files)
          filename = strcat(subDir, '/', files(j).name);
          imageFiles = strvcat(imageFiles, filename);
      end
    end
    
    % shuffle file list
    idx = randperm(length(imageFiles));
    imageFiles = imageFiles(idx, :);
    
    % read images and labels
    images = [];
    labels = [];
    for j = 1: length(imageFiles)
      filenames = strsplit(imageFiles(j, :), '/');
      a = str2num(filenames{1});
      labels = [labels, str2num(filenames{1})];

      img = imread(strcat(dirPath, '/', imageFiles(j, :)));
      %img = rgb2gray(img);
      img = imresize(img, [32, 32]);
      img = double(img) / 255;
      images(:, :, length(labels)) = img;          
    end
    
    labels = reshape(labels, [length(labels), 1]);
    images = reshape(images, [32, 32, 1, length(labels)]);
end

Answer 1

[Jan]

Use the debugger to find the cause of the problem. Type e.g. this in the command window:

dbstop if error

Run the code again. When Matlab stops at the error, check the currently used variables:

size(img)
size(images)

Maybe the rgb2gray is important?

Some hints:

• fullfile(a,b) is smarter than [a, '/', b], because it considers the fileseparators of the platform.
• The names of the variables look confusing: "filenames" is not a list of file names, "a" is meaningless,
• labels = reshape(labels, [length(labels), 1]) can be written as labels = labels(:).
• The condition if subDir == '.' | strcmp(subDir, '..') == 1 can be simplified. Remember that == is the elementwise operation and subDir is a char vector. If subDir is '..', the comparison replied [true, true]. Because if requires a scalar condition, Matlab inserts an all implicitly. Then this is suffcient actually: if subDir == '.', because it catchs '..' also. Writing this explicitly is nicer to read: if all(subDir == '.'). This would trigger also for '...', but this is not an allowed file name under Windows, but maybe under Linux (?). Therefore I prefer the explicit: if strcmp(subDir, '.') || strcmp(subDir, '..')

Prefer to work with cell strings (or strings) instead of CHAR matrices. Replace:

imageFiles = '';
...
      files = dir(strcat(dirPath, '/', subDir));
      fileFlags = ~[files.isdir];
      files = files(fileFlags);
      for j = 1: length(files)
          filename = strcat(subDir, '/', files(j).name);
          imageFiles = strvcat(imageFiles, filename);
      end

by

      imageFiles = {};
      ...
      files      = dir(fullfile(dirPath, subDir));
      fileNames  = {files(~[files.isdir]).name};
      imageFiles = cat(2, imageFiles, fileNames);
      ...
      % Instead of imageFiles(j, :) use imageFiles{j} afterwards

[neha gautam]

images(:, :, length(labels)) = img;

end

labels = reshape(labels, [length(labels), 1]);

images = reshape(images, [32, 32, 1, length(labels)]);

this line has error (mentioned in bold color)

[neha gautam]

Index in position 1 exceeds array bounds (must not exceed 1).

Error in readDataset (line 23)

imageFiles = imageFiles(idx, :);

Error in run (line 9)

[train_images, train_labels] = readDataset('dataset/train');

this is the error

[Jan]

I've mentioned already, that you can use the debugger to find the reasons of the errors. I've suggested several improvements of your code. Now you post two different errors. How can we help you?

Answer 2

[KSSV]

function [images, labels, imageFiles] = readDataset(dirPath)
imageFiles = '';
% Get a list of all files and folders in this folder.
files = dir(dirPath);
% Get a logical vector that tells which is a directory.
dirFlags = [files.isdir];
% Extract only those that are directories.
subFolders = files(dirFlags);
% add all image file name
for i = 1 : length(subFolders)
    subDir = subFolders(i).name;
    if subDir == '.' | strcmp(subDir, '..') == 1
        continue;
    end
    
    files = dir(strcat(dirPath, '/', subDir));
    fileFlags = ~[files.isdir];
    files = files(fileFlags);
    for j = 1: length(files)
        filename = strcat(subDir, '/', files(j).name);
        imageFiles = strvcat(imageFiles, filename);
    end
end

% shuffle file list
idx = randperm(length(imageFiles));
imageFiles = imageFiles(idx, :);

% read images and labels
images = cell(length(imageFiles),1);
labels = [];
for j = 1: length(imageFiles)
    filenames = strsplit(imageFiles(j, :), '/');
    a = str2num(filenames{1});
    labels = [labels, str2num(filenames{1})];
    img = imread(strcat(dirPath, '/', imageFiles(j, :)));
    %img = rgb2gray(img);
    img = imresize(img, [32, 32]);
    img = double(img) / 255;
    images{j} = img;
end

% labels = reshape(labels, [length(labels), 1]);
% images = reshape(images, [32, 32, 1, length(labels)]);
end

[neha gautam]

Error using imread>get_format_info (line 543)

Unable to determine the file format.

Error in imread (line 391)

fmt_s = get_format_info(fullname);

Error in readDataset (line 35)

img = imread(strcat(dirPath, '/', imageFiles(j, :)));

This is the errors