function sk = pick_curves(mask)% pick_curves - ask for the user to build a set of curves%%   sk = pick_curves(mask);%%   mask is a background image (should be in [0,1] approx).%%   The user right-click on a set of point which create a curve.%   Left click stop a curve.%   Another left click stop the process.%%   Copyright (c) 2007 Gabriel Peyr?n = size(mask,1);sk = zeros(n);b = 1;while b(end)==1    % draw a line    clf;    imagesc(mask+sk); axis image; axis off;    colormap gray(256);    [y1,x1,b] = ginput(1);    while b==1        clf;        imagesc(mask+sk); axis image; axis off;        [y2,x2,c] = ginput(1);        if c~=1            break;        end        t = linspace(0,1,1000);        x = round( x1*t+x2*(1-t) );        y = round( y1*t+y2*(1-t) );        sk( x+(y-1)*n ) = 1;        x1 = x2; y1 = y2;    endend