GVF.rar_GVF_梯度matlab

function [xi,yi] = snakeinterp(x,y,dmax,dmin) %插值函数，实现向量差 d(i,i+1)>dmax, then a new point is added between i and i+1 % d(i,i+1)<dmin, then either i or i+1 is removed %SNAKEINTERP Interpolate the snake adaptively % [xi,yi] = snakeinterp(x,y,dmax,dmin) % % dmax: the maximum distance between two snake points % dmin: the maximum distance between two snake points % d(i,i+1)>dmax, then a new point is added between i and i+1 % d(i,i+1)<dmin, then either i or i+1 is removed % % NOTE: the spacing of original curve must be close to the % range defined by dmax and dmin. For arbitrary spacing, % try snakeinterp1. % % See also SNAKEINTERP1 % there is a bug in the program for points removal % Chenyang Xu and Jerry L. Prince, 4/1/95, 6/17/97 % Copyright (c) 1995-97 by Chenyang Xu and Jerry L. Prince % Image Analysis and Communications Lab, Johns Hopkins University % convert to column vector x = x(:); y = y(:); N = length(x); d = abs(x([2:N 1])- x(:)) + abs(y([2:N 1])- y(:)); % x([2:N 1]表示[X的第2到第N个元素，第1个元素] % remove the points which distance to neighbor points is shorter than dmin IDX = (d<dmin); % 某一个元素比相邻下一个元素的差大于dmin，则此处为0 idx = find(IDX==0); x = x(idx); % x，y 剩下那些相邻差大于dmin的元素，那些小于dmin的元素被移除了 y = y(idx); N = length(x); d = abs(x([2:N 1])- x(:)) + abs(y([2:N 1])- y(:)); IDX = (d>dmax); z = snakeindex(IDX);%这个函数是生成一个向量，其大小是2N-M，N为矩阵（向量）X的所有元素个数，M为X中所有元素相邻差小于dmax的元素个 %数，这个向量Z的元素值是1:0.5:N+0.5，其中，在2i位置（i为元素相邻差小于dmax的元素在原向量X中的第i个） p = 1:N+1; xi = interp1(p,[x;x(1)],z'); % 一维数据插值 [x;x(1)]其中的分号应该是逗号？ Z'应该改成Z ? yi = interp1(p,[y;y(1)],z'); %得到一个插值了的向量xi和yi % d(i,i+1)>dmax, then a new point is added between i and i+1 % d(i,i+1)<dmin, then either i or i+1 is removed N = length(xi); d = abs(xi([2:N 1])- xi(:)) + abs(yi([2:N 1])- yi(:)); while (max(d)>dmax),%直到生成的向量xi和yi元素之间的间隔d<dmax IDX = (d>dmax); z = snakeindex(IDX); p = 1:N+1; xi = interp1(p,[xi;xi(1)],z'); yi = interp1(p,[yi;yi(1)],z'); N = length(xi); d = abs(xi([2:N 1])- xi(:)) + abs(yi([2:N 1])- yi(:)); end