用matlab对简单数字图像进行数字聚类处理代码，最好附上解释说明。谢个大神了。

答案：wave2gray.m

function w = wave2gray(c,  s,  scale,  border)
%WAVE2GRAY Display wavelet decomposition coefficients.
% W = WAVE2GRAY(C, S, SCALE, BORDER) displays and returns a
% wavelet coefficient image.
%  EXAMPLES:
%   wave2gray(c, s);      Display w/defaults.
%   foo = wave2gray(c,   s);    Display and return.
%   foo = wave2gray(c,   s, 4);    Magnify the details.
%   foo = wave2gray(c,   s, -4);   Magnify absolute values.
%   foo = wave2gray(c,   s, 1, 'append'); Keep border values.
%
%  INPUTS/OUTPUTS:
%   [C, S] is a wavelet decomposition vector and bookkeeping
%   matrix.
%
%  SCALE    Detail coefficient scaling
%--------------------------------------------------------------------
%  0 or 1      Maximum range (default)
%  2, 3...     Magnify default by the scale factor
%  -1, -2...   Magnify absolute values by abs(scale)
%
%  BORDER   Border between wavelet decompositions
%--------------------------------------------------------------------
%  'absorb'  Border replaces image (default)
%  'append'  Border increases width of image
%
%  Image W: ------- ------ -------------- -------------------
%     |      |      |              |
%     | a(n) | h(n) |              |
%     |      |      |              |
%     ------- ------     h(n-1)    |
%     |      |      |              |
%     | v(n) | d(n) |              |      h(n-2)
%     |      |      |              |
%     ------- ------ --------------
%     |             |              |
%     |    v(n-1)   |    d(n-1)    |
%     |             |              |
%     -------------- -------------- -------------------
%     |                            |
%     |           v(n-2)           |      d(n-2)
%     |                            |
%
%  Here,  n denotes the decomposition step scale and a, h, v, d are
%  approximation,  horizontal,  vertical, and diagonal detail
%  coefficients,  respectively.

% Check input arguments for  reasonableness.

error(nargchk(2,   4,   nargin));

if (ndims(c) ~= 2)   |   (size(c, 1) ~= 1)
 error('C must be a row vector.'); end

if (ndims(s) ~= 2)   | ~isreal(s)   | ~isnumeric(s)   |   (size(s, 2) ~= 2)
 error('S must be a real, numeric two-column array.'); end

elements = prod(s, 2);

if (length(c) < elements(end))   |   ...
  ~(elements(1) + 3 * sum(elements(2:end - 1)) >= elements(end))
 error(['[C S] must be a standard wavelet ' ...
    'decomposition structure.']);
end

if (nargin > 2) & (~isreal(scale) | ~isnumeric(scale))
 error('SCALE must be a real, numeric scalar.');
end

if (nargin > 3) & (~ischar(border))
 error('BORDER must be character string.');
end

if  nargin == 2
 scale =1;    % Default scale.
end

if nargin < 4
 border = 'absorb'; % Default border.
end

% Scale coefficients and determine pad fill.
absflag = scale < 0;
scale = abs(scale);
if scale == 0
 scale = 1;
end

[cd, w] = wavecut('a', c, s);  w = mat2gray(w);
cdx = max(abs(cd(:))) / scale;
if absflag
 cd = mat2gray(abs(cd), [0, cdx]); fill = 0;
else
 cd = mat2gray(cd, [-cdx, cdx]); fill = 0.5;
end

% Build gray image one decomposition at a time.
for i = size(s, 1) - 2:-1:1
 ws = size(w);
 h = wavecopy('h', cd, s, i);
 pad = ws - size(h);    frontporch = round(pad / 2);
 h = padarray(h, frontporch, fill, 'pre');
 h = padarray(h, pad - frontporch, fill, 'post');
 v = wavecopy('v',   cd,   s,   i);
 pad = ws - size(v);            frontporch = round(pad  /  2);
 v = padarray(v,   frontporch,   fill,   'pre');
 v = padarray(v,  pad - frontporch,  fill,   'post');
 d = wavecopy('d',   cd,   s,   i);
 pad = ws - size(d);            frontporch = round(pad  /  2);
 d = padarray(d,   frontporch,   fill,   'pre');
 d = padarray(d,   pad - frontporch,   fill,   'post');
% Add  1   pixel white border.
 switch  lower(border)
  case   'append'
   w =  padarray(w,   [1   1],   1,   'post');
   h = padarray(h,   [1   0],   1,   'post');
   v = padarray(v,   [0  1],   1,   'post');
  case   'absorb'
   w(:,   end)   =  1;         w(end,   :)   =  1;
   h(end,   :)   =  1;          v(:,   end)   =  1;
  otherwise
   error('Unrecognized BORDER parameter.');
  end
 w = [w h; v d];                                          % Concatenate coefs.
end

if nargout   == 0
 imshow(w);                                               % Display  result.
end ...

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