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    filename: imDirectionalFilter.m
    path of file: ./repos/matImage/matImage/imFilters
    
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%IMDIRECTIONALFILTER Apply and combine several directional filters
%
%   Applies a directional filter, with linear structural element, and 
%   computes min or max of results. Result is the same type as the input
%   image.
%
%   Classical uses of such filters is max of opening, which performs
%   good enhancement of lines.
%
%   For the use of median or mean filters, the functions "imMedianFilter"
%   and "imMeanFilter" are also provided, with a syntax similar to imopen
%   or imclose.
%
%   Usage
%   RES = imDirectionalFilter(SRC, 'imMeanFilter', 'max', 20, 8);
%   computes the mean in each 8 directions, with linear structuring element
%   of length 20, and keep the max value over all directions.
%   
%   RES = imDirectionalFilter(SRC, 'imMeanFilter', 20, 8); 
%   uses 'max' as default for second operator.
%
%   RES = imDirectionalFilter(SRC, 20, 8); also work, the
%   uses 'imopen' as default operator for first transform.
%

    
function res = imDirectionalFilter(img, varargin)
%IMDIRECTIONALFILTER Apply and combine several directional filters
%
%   Applies a directional filter, with linear structural element, and 
%   computes min or max of results. Result is the same type as the input
%   image.
%
%   Classical uses of such filters is max of opening, which performs
%   good enhancement of lines.
%
%   For the use of median or mean filters, the functions "imMedianFilter"
%   and "imMeanFilter" are also provided, with a syntax similar to imopen
%   or imclose.
%
%   Usage
%   RES = imDirectionalFilter(SRC, 'imMeanFilter', 'max', 20, 8);
%   computes the mean in each 8 directions, with linear structuring element
%   of length 20, and keep the max value over all directions.
%   
%   RES = imDirectionalFilter(SRC, 'imMeanFilter', 20, 8); 
%   uses 'max' as default for second operator.
%
%   RES = imDirectionalFilter(SRC, 20, 8); also work, the
%   uses 'imopen' as default operator for first transform.
%
%   RES = imDirectionalFilter(SRC, 'imMeanFilter', 'max', 20, 8, 3);
%   Specifies width of the line (obtained by dilation).
%
%
%   See also
%   imopen, imclose, imMeanFilter, imMedianFilter

%   ---------
%   author : David Legland 
%   INRA - TPV URPOI - BIA IMASTE
%   created the 16/02/2004.
%

%   HISTORY
%   17/02/2004 debug, added some doc, manage different types of images
%   26/02/2007 cleanup code
%   03/10/2007 update doc
%   19/08/2009 fix bug in parsing arguments
%   18/06/2010 fix initialization for 'min' operator, update doc
%   02/12/2011 rename to "imDirectionalFilter", update doc


%% Default values

% operators
op1 = 'imopen';
op2 = 'max';

% parameters for structuring element
Nd = 32;
N = 65;
w = 1;


%% Process input parameters

% first operation
if ~isempty(varargin)
    op1 = varargin{1};
end