passing character strings into functions

I had a quick question on passing a character array into a function for example:

I have an array of image names and i want to iterate through them to edit them all in a certain way. I dont know what command to put in the load function below.

if true

    picturenames = char('IMG_1562' 'IMG_1563' 'IMG_1564' 'IMG_1565');
for i=1:length(picturenames);
imread(% what would go here...);
% ill run my edits here
end

end

Answer 1

[CS Researcher]

You can use a cell array:

picturnames = {'IMG_1562' 'IMG_1563' 'IMG_1564' 'IMG_1565'};

Pass picturnames to the function like you are and do

imread(picturenames{1,i});

Answer 2

[Image Analyst]

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F for the best way(s).

In your case you have a character array, so you need to extract one row like this:

picturenames = char('IMG_1562', 'IMG_1563', 'IMG_1564', 'IMG_1565')
for k = 1 : size(picturenames, 1)
  thisName = picturenames(k, :)
  if exist(thisName, 'file')
    imread(thisName);
  else
    message = sprintf('%s does not exist', thisName);
    uiwait(warndlg(message));
  end
end

However a more robust way is to use cell arrays which will allow the filenames to have different lengths.

picturenames = {'IMG_1562', 'IMG_1563', 'IMG_1564', 'IMG_1565'}
for k = 1 : length(picturenames)
  thisName = picturenames{k}
  if exist(thisName, 'file')
    imread(thisName);
  else
    message = sprintf('%s does not exist', thisName);
    uiwait(warndlg(message));
  end
end

One thing I worry about is that you might want to add the extension to the filenames - it's always good to have one so the imread() function can automatically tell what kind of image format it is. And you can use dir() so that you don't have to check inside the loop if the file exists. Again, it's all in the FAQ.