swt.m

% Max Jaderberg 10/11/12

% Computes the Stroke Width Transform (SWT) of an image using CCV.
% Need to specify bright to dark or dark to bright. Most applications do
% both. direction should be 0 (dark to bright) or 1 (bright to dark).

function im_swt = swt(im, direction, size, low_thresh, high_thresh, visualize)
    % default direction is dark to bright (direction=0)

    
    options = [
        direction;
        size;
        low_thresh;
        high_thresh;
        visualize;
    ];

    opt_flags = 'rslhv';
    opt_hasarg = [0 1 1 1 0];
    opts_args = ' ';
    for i=1:length(options)
        if options(i)
            if opt_hasarg(i)
                opts_args = [opts_args '-' opt_flags(i) ' ' num2str(options(i)) ' '];
            else
                opts_args = [opts_args '-' opt_flags(i) ' '];
            end
        end
    end
    
    n = 5;
    LetterStore = char(97:122);
    rand_string = LetterStore(ceil(length(LetterStore).*rand(1,n)));
    [path name ext] = fileparts(mfilename('fullpath'));
    temp_file = fullfile(path,[rand_string 'swt.jpg']);
    imwrite(im, temp_file);
    
    
    
    % call swt
    system(['swt ' opts_args temp_file ' ' temp_file]);
    
    
    im_swt = imread(temp_file);
    system(['rm -f ' temp_file]);