zigzag.rar_The Handle_zigzag

function seq = zigzag(SI) % % Description: % ------------ % This function is used to build the corresponding sequences of a given % scaled gray level image matrix from 45' degree direction. The whole process is using zigzag method % It can handle nonsquare image matrix % % Author: % ------- % (C)Xunkai Wei <xunkai.wei@gmail.com> % Beijing Aeronautical Technology Research Center % Beijing %9203-12,10076 % % History: % ------- % Creation: beta Date: 01/11/2007 % Revision: 1.0 Date: 12/11/2007 % % Trick: all the sequence starts or ends lie on the boundary. % initializing the variables %---------------------------------- c = 1; % initialize colum indicator r = 1; % initialize row indicator rmin = 1; % row boundary checker cmin = 1; % colum boundary checker rmax = size(SI, 1); % get row numbers cmax = size(SI, 2); % get colum numbers % i = 1; % counter for current ith element j = 1; % indicator for determining sequence interval % intialize sequence mark sq_up_begin=1; sq_down_begin=1; % % Output contain value and its flag status % the first row contain value % the second row contain its flag output = zeros(1, rmax * cmax); % sequence counter % % % Position Matrix % position =zeros(1, rmax * cmax); %---------------------------------- while ((r <= rmax) && (c <= cmax)) % for current point, judge its zigzag direction up 45, or down 45, or % 0,or down 90 if (mod(c + r, 2) == 0) % up 45 direction % if we currently walk to the left first colum if (r == rmin) % First, record current point output(i) = SI(r, c); % if we walk to right last colum if (c == cmax) % add row number move straight down 90 r = r + 1; sq_up_end = i; sq_down_begin = i+1; seq{j}=output(sq_up_begin:sq_up_end); j = j + 1; % else % Continue to move to next (1,c+1) point % This next point should be the begin point of next sequence c = c + 1; sq_up_end = i; sq_down_begin = i+1; seq{j}=output(sq_up_begin:sq_up_end); j = j + 1; end; % add couter i = i + 1; % if we currently walk to the last column elseif ((c == cmax) && (r < rmax)) % first record the point output(i) = SI(r, c); % then move straight down to next row r = r + 1; sq_up_end = i; seq{j}=output(sq_up_begin:sq_up_end); sq_down_begin =i+1; j=j+1; % add counter i = i + 1; % all other cases i.e. nonboundary points elseif ((r > rmin) && (c < cmax)) output(i) = SI(r, c); % move to next up 45 point r = r - 1; c = c + 1; % add counter i = i + 1; end; % down 45 direction else % if we walk to the last row if ((r == rmax) && (c <= cmax)) % firstly record current point output(i) = SI(r, c); % move right to next point c = c + 1; sq_down_end = i; seq{j}=output(sq_down_begin:sq_down_end); sq_up_begin =i+1; j = j + 1; % add counter i = i + 1; % if we walk to the first column elseif (c == cmin) %first record current point output(i) = SI(r, c); % if (r == rmax) c = c + 1; sq_down_end = i; seq{j}=output(sq_down_begin:sq_down_end); sq_up_begin =i+1; j = j + 1; else r = r + 1; % record sequence end sq_down_end = i; seq{j}=output(sq_down_begin:sq_down_end); sq_up_begin =i+1; j = j + 1; end; i = i + 1; % all other cases without boundary point elseif ((r < rmax) && (c > cmin)) % output(i) = SI(r, c); % position(i) = sub2ind(SI,r,c); r = r + 1; c = c - 1; % keep down_info i = i + 1; end; end; if ((r == rmax) && (c == cmax)) % bottom right element output(i) = SI(r, c); sq_end = i; seq{j}=output(sq_end); % position(i) = sub2ind(SI,r,c); break end; end;