pyramid.m

这是一个基于MATLAB的机器视觉工具箱,里面用很多非常有价值的的程序

%PYRAMID	Pyramidal image decomposition
%
%	p = pyramid(im)
%	p = pyramid(im, sigma)
%	p = pyramid(im, sigma, N)
%
%	Compute pyramid decomposition of input image, IM, using Gaussian
%	smoothing of SIGMA (default 1) prior to each decimation.  If N 
%	is specified compute only that number of steps.
%
% SEE ALSO:	igauss
%
%	Copyright (c) Peter Corke, 1999  Machine Vision Toolbox for Matlab

% 1995 Peter Corke

function p = pyramid(im, sigma, N)
	if nargin < 2,
		sigma = 1;
	elseif nargin < 3,
		N = floor(log2(min(size(im))));
	end
	N

	[height,width] = size(im);
	% figure the width of the pyramids (sum of a power series)
	w = width * (1 - (1/2)^(N-1));
	p = zeros(height/2, w);		% make a blank image
	mask = igauss(2, sigma);
	w = 0;

	for k = 1:N,
		[nrows,ncols] = size(im);

		% smooth
		im = conv2(im, mask, 'same');

		% sub sample
		im = im(1:2:nrows,1:2:ncols);

		% place it
		p(1:numrows(im),w+1:w+numcols(im)) = im;
		w = w + numcols(im);
		w
	end