MATLAB图像处理：基于熵的特征提取

function stats = graycoprops(varargin)
%GRAYCOPROPS Properties of a gray-level co-occurrence matrix.  
%   STATS = GRAYCOPROPS(GLCM,PROPERTIES) normalizes the gray-level
%   co-occurrence matrix (GLCM) so that the sum of its elements is one. Each
%   element in the normalized GLCM, (r,c), is the joint probability occurrence
%   of pixel pairs with a defined spatial relationship having gray level
%   values r and c in the image. GRAYCOPROPS uses the normalized GLCM to
%   calculate PROPERTIES.
%
%   GLCM can be an m x n x p array of valid gray-level co-occurrence
%   matrices. Each gray-level co-occurrence matrix is normalized so that its
%   sum is one.
%
%   PROPERTIES can be a comma-separated list of strings, a cell array
%   containing strings, the string 'all', or a space separated string. They
%   can be abbreviated, and case does not matter.
%
%   Properties include:
%  
%   'Contrast'      the intensity contrast between a pixel and its neighbor 
%                   over the whole image. Range = [0 (size(GLCM,1)-1)^2]. 
%                   Contrast is 0 for a constant image.
%
%   'Correlation'   statistical measure of how correlated a pixel is to its 
%                   neighbor over the whole image. Range = [-1 1]. 
%                   Correlation is 1 or -1 for a perfectly positively or
%                   negatively correlated image. Correlation is NaN for a 
%                   constant image.
%
%   'Energy'        summation of squared elements in the GLCM. Range = [0 1].

%                   Energy is 1 for a constant image.
%  
%   'Homogeneity'   closeness of the distribution of elements in the GLCM to
%                   the GLCM diagonal. Range = [0 1]. Homogeneity is 1 for
%                   a diagonal GLCM.
%  
%   If PROPERTIES is the string 'all', then all of the above properties are
%   calculated. This is the default behavior. Please refer to the
%   Documentation for more information on these properties.
%  
%   STATS is a structure with fields that are specified by PROPERTIES. Each
%   field contains a 1 x p array, where p is the number of gray-level
%   co-occurrence matrices in GLCM. For example, if GLCM is an 8 x 8 x 3 array
%   and PROPERTIES is 'Energy', then STATS is a structure containing the
%   field 'Energy'. This field contains a 1 x 3 array.
%
%   Notes
%   -----  
%   Energy is also known as uniformity, uniformity of energy, and angular second
%   moment.
%
%   Contrast is also known as variance and inertia.
%
%   Class Support
%   -------------  
%   GLCM can be logical or numeric, and it must contain real, non-negative, finite,
%   integers. STATS is a structure.
%
%   Examples
%   --------