imcontour.m

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function [c,h] = imcontour(x,y,a,n)
%IMCONTOUR Create contour plot of image data.
%   IMCONTOUR(I,N) draws a contour plot of the intensity image I,
%   automatically setting up the axes so their orientation and
%   aspect ratio match the image. N is the number of equally
%   spaced contour levels in the plot; if you omit the argument,
%   the number of levels and the values of the levels are chosen
%   automatically.
%
%   IMCONTOUR(I,V) draws a contour plot of I with contour lines
%   at the data values specified in vector V. The number of
%   contour levels is equal to length(V).
%
%   IMCONTOUR(X,Y,...) uses the vectors X and Y to specify the x-
%   and y-axis limits.
%
%   IMCONTOUR(...,LINESPEC) draws the contours using the line
%   type and color specified by LINESPEC. Marker symbols are
%   ignored.
%
%   [C,H] = IMCONTOUR(...) returns the contour matrix C and a
%   vector of handles to the objects in the plot. (The objects
%   are actually patches, and the lines are the edges of the
%   patches.) You can use the CLABEL function with the contour
%   matrix C to add contour labels to the plot.
%
%   Class Support
%   -------------
%   The input image can be of class uint8 or double.
%
%   Example
%   -------
%       I = imread('ic.tif');
%       imcontour(I,3)
%
%   See also CLABEL, CONTOUR.

%   Clay M. Thompson 10-6-92
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 5.6 $  $Date: 1997/11/24 15:35:20 $

if nargin==1, % imcontour(a)
  a = x;
  x = 1:size(a,2); y = 1:size(a,1);

elseif nargin==2, % imcontour(a,n) or imcontour(a,v)
  a = x;
  n = y;
  x = 1:size(a,2); y = 1:size(a,1);
end

% Make sure x,y are vectors.
if all(size(x)==size(a)), x = x(1,:); end
if all(size(y)==size(a)), y = y(:,1); end

% If x and y are two-element vectors, make them be the
% same size as a.
x = x(:);
y = y(:);
if (length(x) ~= size(a,2))
    if (length(x) ~= 2)
        error('Invalid size of X');
    end
    x = linspace(x(1), x(end), size(a,2));
end
if (length(y) ~= size(a,1))
    if (length(y) ~= 2)
        error('Invalid size of Y');
    end
    y = linspace(y(1), y(end), size(a,1));
end

if nargout==0,
  if nargin==1 | nargin==3,
    contour(x,y,a)
  else
    contour(x,y,a,n)
  end
else
  if nargin==1 | nargin==3,
    [c,h] = contour(x,y,a);
  else
    [c,h] = contour(x,y,a,n);
  end
end

if ~ishold,
  axis ij
  axis image
end