Reading image save as matrix and store filename information

Hi,

I have X number of images I need to upload and obtain the data stored in the file name for later operations. For example a file name would be:

image_TM_pos13p72_exp2p456.jpg

or

image_TE_pos12p56_exp2p800.jpg

I need to upload and save the image as a matrix with pixel intensities and I need to obtain the data from the corresponding image (matrix) the filename TE or TM, position XX.XX and exposure time X.XXX.

How do I do this?

[Guillaume]

What do you mean by 'upload'? From your description it sounds like you just want to open and read some files.

Are you trying to open all the files in a directory, or just some files that follow a specific pattern? If the latter what exactly is the pattern?

[Lizan]

I have some X number of images. These images I want to read in matlab and save the pixel map (intensity counts (1 to 255)) into a matrix for each image.

I guess I would have to upload the image matrix into an array?

Answer 1

[Image Analyst]

You need to parse the filename with strfind() and str2double. Try this:

function test
clc;    % Clear the command window.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
[imageType, pos, exposure] = ParseFileName('image_TM_pos13p72_exp2p456.jpg')
[imageType, pos, exposure] = ParseFileName('image_TE_pos12p56_exp2p800.jpg')

function [imageType, pos, exposure] = ParseFileName(filename)
  imageType = filename(7:8); % Extract TM or TE
  % Parse pos
  posLocation = strfind(filename, '_pos') + 4;
  posString = filename(posLocation:posLocation + 4);
  posString = strrep(posString, 'p', '.'); % Convert p to dot
  pos = str2double(posString);
  % Parse exposure
  expLocation = strfind(filename, '_exp') + 4;
  expString = filename(expLocation:expLocation + 4);
  expString = strrep(expString, 'p', '.'); % Convert p to dot
  exposure = str2double(expString);

[Lizan]

Thank you, this solves the reading the filename and saving the data into variables I need.

How can I save all images as matrix in array?

[Guillaume]

dir does work. You probably need to use an absolute path:

urlImage = 'C:/Users/me/Desktop/folder/';
for file = dir(fullfile(ulrImage, '*.jpg'))'
  img = imread(file.name);
  ...
end

[Guillaume]

What are the possible patterns for imagetype, position and exposure?

• Is imagetype just one of: {TM, TE}
• Is position always integer digits + p + integer digits
• Is exposure always integer digits + p + integer digits

[Lizan]

Yes, that is the possible patterns for the filenames that I give the images to be uploaded.

Answer 2

[Guillaume]

   ...
   jpegFiles = dir(filePattern);
   for jpegFile = jpegFile'
     baseFileName = jpegFile.name;
     parts = regexp(baseFileName, 'image_(..)_pos(\d+p\d+)_exp(\d+p\d+)', 'tokens', 'once')
     if isempty(parts)
      error('%s does not follow pattern', baseFileName);
     else
      imagetype = parts{1};
      pstring = parts{2}; pstring(pstring == 'p') = '.';
      position = str2num(pstring);
      %same with exposure

decodes any pattern with image_ followed by any two characters (imagetype) followed by _pos followed by 1 or more digit + p + 1 or more digit (position) followed by _exp followed by 1 or more digit + p + 1 or more digit (exposure).

Answer 3

[Lizan]

Follow-up question 2:

I am not to familiar with arrays or cells in MATLAB. I would like to make an array that contains in one cell;

Image Matrix (Pixel value (size x size) matrix of image) - M
string - imageType
double value - pos
double value - exposure

How do I do this?

[Guillaume]

Please start another question for this. (so that it can be searched and so that whoever answers it gets the credit for it)

[Image Analyst]

http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F