getFeaturesFromImg.m

function [features,values] = getFeaturesFromImg( n, varargin )
  % features = getFeaturesFromImg( n [, scale ] )
  %
  % Inputs:
  % n - the number of features to select
  % scale - the scale of the displayed image (default is 1)
  %
  % Output:
  % features - a 2 column array.  The first column are the x (or
  % horizontal) coordinates, and the second column are the y (or
  % vertical coordinates).
  %
  % Written by Nicholas Dwork - Copyright 2018
  %
  % This software is offered under the GNU General Public License 3.0.  It
  % is offered without any warranty expressed or implied, including the
  % implied warranties of merchantability or fitness for a particular
  % purpose.

  p = inputParser;
  p.addRequired( 'n', @(x) isnumeric(x) && x>0 );
  p.addOptional( 'scale', 1, @isnumeric );
  p.parse( n, varargin{:} );
  scale = p.Results.scale;

  scaledFeatures = ginput(n);
  features = round( scaledFeatures / scale );

  if nargout > 1
    img = getimage;
    values = zeros( n, 1 );
    scaledFeatures = round( scaledFeatures );
    for fIndx = 1:n
      values(fIndx) = img( scaledFeatures(fIndx,2), scaledFeatures(fIndx,1) );
    end
  end
end