Explain the working of commands..

Please explain what is the function of following command lines..??

 if (size(im1,1)<=1000 && size(im1,2)<=1000)
          status1 = system([sift_bin ' -x -o ' desc_file ' ' filename]);
      else
          status1 = system([sift_bin ' -d -x -o ' desc_file ' ' filename]);
      end
 if status1 ~=0
        error('error calling executables');
    end

Where,

 sift_bin = fullfile('lib','sift','bin','siftfeat');   % e.g. 'lib/sift/bin/siftfeat' in linux
    [pf,nf,ef] = fileparts(filename);
    desc_file = [fullfile(pf,nf) '.txt'];
    im1=imread(filename);

Answer 1

[Geoff Hayes]

harpreet - which commands in particular? All of them? Presumably you have a file (image) that you want to analyze using the SIFT algorithms and so you first

 % determine the path, name and extension of the file
 [pf,nf,ef] = fileparts(filename);

 % create a path to a text file using the path and name from filename
 desc_file = [fullfile(pf,nf) '.txt'];

 % read the file
 im1=imread(filename);

 % analyze given the size of the image
 if (size(im1,1)<=1000 && size(im1,2)<=1000)
     status1 = system([sift_bin ' -x -o ' desc_file ' ' filename]);
 else
     status1 = system([sift_bin ' -d -x -o ' desc_file ' ' filename]);
 end
 if status1 ~=0
     error('error calling executables');
 end

where system calls the SIFT feature executable at

 lib/sift/bin/siftfeat

(which may or may not be a valid path to the exe on your workstation).

[harpreet kaur]

thanks geoff hayes. I particulary didn'd get

status1 = system([sift_bin ' -x -o ' desc_file ' ' filename]);

what are '-x -o' basically for..?

[Walter Roberson]

The -x and -o have nothing to do with MATLAB. They are options being passed into the siftfeat executable.

I tracked down one version of the source to here

Scanning through it starting at line 90, we can see that -o followed by a filename outputs the keypoints to that file, and -x turns off the display of keypoints.